Scholarly article on topic 'A Critical Assessment of Research Needs Identified by the Dietary Guidelines Committees from 1980 to 2010'

A Critical Assessment of Research Needs Identified by the Dietary Guidelines Committees from 1980 to 2010 Academic research paper on "Health sciences"

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Abstract of research paper on Health sciences, author of scientific article — Esther F. Myers, Chor-San Khoo, William Murphy, Alison Steiber, Sanjiv Agarwal

Abstract The Dietary Goals for the United States were introduced in 1977 and have been followed by the Dietary Guidelines for Americans (DGA) every 5 years from 1980 to 2010. The DGA provide science-based advice to promote health and reduce risk for major chronic diseases through diet and physical activity. The Dietary Guidelines Advisory Committees are charged to provide updates of the DGA topics using the best available science. The Dietary Guidelines Advisory Committees' reports also identified 169 research gaps. To date, these gaps have not been compiled and assessed. We evaluated trends in number, topics, and specificity of research gaps by year by placing them in the following topic categories: general, chronic diseases/conditions, diet/diet pattern, food/ingredient, and nutrient-specific research gaps. Some research topics (eg, sodium and hypertension and appropriate uses of DGA) have been identified consistently across the years, some emerged in later years (eg, increasingly specific research gaps between dietary fatty acids and cardiovascular disease), and others appeared intermittently (eg, relationships between dietary components and cancer). These results are a call to action for all DGA stakeholders to have an immediate dialogue about how the research enterprise can best address critical research needs in a timely way to support public policy.

Academic research paper on topic "A Critical Assessment of Research Needs Identified by the Dietary Guidelines Committees from 1980 to 2010"

A Critical Assessment of Research Needs Identified by the Dietary Guidelines Committees from 1980 to 2010

Esther F. Myers, PhD, RD; Chor-San Khoo, PhD; William Murphy, MS, RD; Alison Steiber, PhD, RD; Sanjiv Agarwal, PhD, FACN

ABSTRACT

The Dietary Goals for the United States were introduced in 1977 and have been followed by the Dietary Guidelines for Americans (DGA) every 5 years from 1980 to 2010. The DGA provide science-based advice to promote health and reduce risk for major chronic diseases through diet and physical activity. The Dietary Guidelines Advisory Committees are charged to provide updates of the DGA topics using the best available science. The Dietary Guidelines Advisory Committees' reports also identified 169 research gaps. To date, these gaps have not been compiled and assessed. We evaluated trends in number, topics, and specificity of research gaps by year by placing them in the following topic categories: general, chronic diseases/conditions, diet/diet pattern, food/ingredient, and nutrient-specific research gaps. Some research topics (eg, sodium and hypertension and appropriate uses of DGA) have been identified consistently across the years, some emerged in later years (eg, increasingly specific research gaps between dietary fatty acids and cardiovascular disease), and others appeared intermittently (eg, relationships between dietary components and cancer). These results are a call to action for all DGA stakeholders to have an immediate dialogue about how the research enterprise can best address critical research needs in a timely way to support public policy.

J Acad Nutr Diet. 2013;113:957-971.

THE DIETARY GOALS FOR THE United States were introduced in 1977 by the US Senate Select Committee on Nutrition and Human Needs. These goals were established from US expert opinions, the 1976 Senate Select Committee hearing on diet and disease relationship, the 1974 National Nutrition Policy hearings, and guidelines from US governmental and professional organizations and eight other countries.1,2

In 1980, the US Department of Agriculture and the US Department of Health, Education, and Welfare, now the Department of Health and Human Services, released the first Dietary Guidelines for Americans (DGA), incorporating findings from the 1977 Dietary Goals, the American Society for Clinical Nutrition's panel on the relationship between dietary practices and health outcomes, and the 1979 Surgeon

Copyright © 2013 by the Academy of Nutrition and Dietetics 2212-2672/$36.00 doi: 10.1016/j.jand.2013.03.023 Available online 23 May 2013

Supplementary materials:

Figures 3 and 6 available at www.andjrnl. org

General's Report on Health Promotion and Disease Prevention.1,3-5

The DGA provide "science-based advice to promote health and to reduce risk for major chronic diseases through diet and physical activity."6 The 19802005 DGA target population was healthy individuals aged 2 years and older. A major change occurred in 2010, when the Dietary Guidelines Advisory Committee addressed topics relevant to unhealthy populations—most importantly, inactive and obese Americans— for the first time since 1980. The DGA form the basis for federal policy and programs on food, nutrition, information, and education initiatives for the public and are updated every 5 years.3

The 1985-2000 DGA updates were built on the 1980 DGA. Beginning in 1985, the Dietary Guidelines Advisory Committees were charged to start with previous guidelines and provide updates on these topics using current research and public comments.7 The exact methodology that each Dietary Guidelines Advisory Committee used to evaluate the science was not well documented for the earlier years. However, the 2005 and 2010 Dietary Guidelines Advisory Committees were charged to use an evidence-based approach to recommend major messages for the Secre-

taries of the US Department of Agriculture and Department of Health and Human Services, who then develop DGA for the general public.6,8

The 2005 Dietary Guidelines Advisory Committee posed approximately 40 specific research questions that were evaluated using an evidence-based approach. The 2010 Dietary Guidelines Advisory Committee developed 180 questions and used the US Department of Agriculture's newly established Nutrition Evidence Library to systematically review the scientific literature. A systematic review process typically includes the following formal steps: articulating a question, usually using the population or patient, intervention, comparator, and outcome format; identifying a formal search plan for identifying the body of evidence available to answer the question; searching the literature and identifying which studies will be included in the review; critically appraising each selected research paper; synthesizing the results; and making recommendations.9 Evidence was evaluated to answer approximately 130 of the 180 scientific questions posed in 2010.6 Availability of all Dietary Reference Intakes reports with recommendations for Recommended Dietary Allowances, Average In-

takes, and Tolerable Upper Intake Levels also influenced the process.10

In addition to summarizing the science for guideline updates, the Dietary Guidelines Advisory Committees consistently identified future research needs; however, this process also changed over time. Research recommendations and gaps were identified throughout the earlier editions and separate sections reported future research needs in subsequent Dietary Guidelines Advisory Committee reports. However, during the 32 years between the 1979 Dietary Goals and seven subsequent DGA editions, there has not been a comprehensive analysis of the types of science evaluated or the research gaps identified.

PURPOSE

This paper aims to identify and assess the commonalities and differences in research gaps identified across the seven DGA reports. We hypothesized that research needs identified throughout the DGA reports have not always been met, leaving substantial research gaps to this day.

DESCRIPTION OF PROCESS TO GATHER AND EVALUATE GUIDELINES AND RESEARCH GAPS

Extracting Data from Dietary Guidelines Advisory Committees' Reports

This retrospective review of the 1977 Dietary Goals and the seven subsequent DGA and Dietary Guidelines Advisory Committees' reports involved three phases.1,3,6-9,11,12 The first phase included locating the seven dietary guidelines, reports, panel members, and supporting documents. An Excel database was created based on extraction of the following data elements from the reports: year (1977, 1980, 1985, 1990, 1995, 2000, 2005, and 2010); DGA report section (aiming to meet nutrient intake recommendations, alcohol, carbohydrates, energy, energy balance and weight management, ethanol); topic category (question being asked, recommendation, or future research needed); and characterization of the target population and/or disease state.

Extracting Guideline Recommendations. Guideline recommendations were extracted from two sources: a summary document published by the Center for Nutrition Policy and Promotion, which included the 1980-2000 recommendations; and the 2005 and 2010 DGA recommendations, which were extracted from the governmental policy documents and were developed based on the Dietary Guidelines Advisory Committees' reports.12

Extracting Research Recommendations and Gaps. Future research recommendations included in the Dietary Guidelines Advisory Committees' reports evolved from incorporation throughout the document to a separate section, along with the movement toward more evidence-based policy and use of evidence-based methodology. For this analysis, we extracted information anywhere limitations in research were identified throughout the early reports and from the future research needs sections (eg, Sections F and D in 2005 and 2010, respectively).6

Evaluating Guideline Recommendations and Research Gaps Using Topic Areas

After reviewing the initial extracted data, we used the following global categories for both guideline recommendations and research gaps, ranging from broadest to most specific topic areas:

1. General, including four topics on uses of guidelines, physical activity, food safety, and other unspecified general research topics;

2. Chronic disease/health condition, including nine topics on chronic diseases (ie, hypertension, dyslipi-demia, weight, diabetes, cancer, bone health, metabolic syndrome), health conditions (eg, pregnancy and lactation), or unspecified health outcomes;

3. Diet, including four topics on overall diet or dietary patterns, variety, breakfast, and energy balance;

4. Food/ingredients, including 15 topics on specific food groups or ingredients in foods, and alcohol and glycemic load; and

5. Nutrients, including 13 specific topics on nutrients (macronutri-ents, vitamins, minerals, other bio-active components).

Evaluating Guideline Recommendations. There is an integral relationship between the guideline recommendations from previous reports, research selected for review by the Dietary Guidelines Advisory Committees, published DGA recommendations, and identified research gaps. The first analysis evaluated the final guideline recommendations included in the DGA for persistent and emerging themes throughout all seven editions. Three researchers coded the guideline recommendations into the five topic areas described here and evaluated the number of recommendations, similarity of topics or clusters of recommendations, and directionality (ie, recommendations to "do something" or "avoid something").

Evaluating Research Gaps. Three researchers coded each of the 169 research gaps extracted from the DGA reports into specific topic areas and applicable major categories, with reviews by two additional researchers. A single research recommendation could be classified in multiple topic areas. For example, a research recommendation to "conduct dose-response trials that test the main and interactive effects of sodium and potassium intake, as well as possible impact of other minerals (eg, calcium, magnesium) on blood pressure and other clinically relevant outcomes" would be reported in five areas: sodium, potassium, calcium, other (nutrients), and hypertension (chronic diseases/health conditions).

We tabulated the number of times the topics were identified as part of a research gap by year. Trends within each topic area were subjectively evaluated. In addition, trends across years within topics were also evaluated.

DESCRIPTION OF TRENDS IN

GUIDELINE

RECOMMENDATIONS

Number and Groups of Recommendations

Both the number and clustering of guideline recommendations evolved over time (Figure 1). There were seven recommendations in the 1980 DGA report related to weight, variety, starch and carbohydrate, fat, saturated fat and cholesterol, sodium, and alcohol. The total number of guideline recommendations expanded from seven in the first editions to 23 in 2010 in the fol-

Goal or Guideline type

Dietary Goals for the United States

Population target

Number of goals or guidelines

Healthy, > 2 y

10 dietary goals

Healthy, > 2 y Healthy, > 2 y Healthy, > 2 y Healthy, > 2 y Healthy, 32 y

7 guidelines 7 guidelines

9 guidelines

11 guidelines

10 guidelines, clustered into 3 groups (aim for fitness, build a healthy base, and choose sensibly)

Healthy, 32 y, sedentary

23 guidelines, clustered into 9 groups (adequate nutrients within calorie needs, weight management, physical activity, food groups to encourage, fats, carbohydrates, sodium and potassium, alcoholic beverages, food safety)

Obesogenic, undernutrition, sedentary

23 guidelines, clustered into 4 groups (balance calories to manage weight, foods and food components to reduce, foods and nutrients to increase, and building healthy eating patterns)

Topic Categorya

Number of guidelines/goals addressed in each topic category

1 General/ Uses of DGAb/ Physical Activity /Food Safety

2 Chronic Disease/ Health Status

3 Diet/Diet Pattern/ Energy Balance

4 Food/ Ingredient

5 Nutrients

Actual Goal or Guideline

Maintain ideal Maintain weight2 desirable

weight2

Maintain healthy weight2

Balance the food you eat with physical activity— maintain or improve your weight2

Aim for a healthy weight2

To maintain body weight in a healthy range, balance calories from foods and beverages with calories expended23

To prevent gradual weight gain over time, make small decreases in food and beverage calories and increase physical activity1-3

Be physically active each day1

Engage in regular physical activity and reduce sedentary activities to promote health, psychological well-being, and a healthy body

weight1,2

Achieve physical fitness by

including cardiovascular conditioning, stretching exercises for flexibility, and resistance exercises or calisthenics for muscle strength and endurance1

Prevent and/or reduce overweight and obesity through improved eating and physical activity behaviors12

Control total calorie intake to manage body weight. For people who are overweight or obese, this will mean consuming fewer calories from foods and beverages2-4

Maintain appropriate calorie balance during each stage of life— childhood, adolescence, adulthood, pregnancy and breastfeeding, and older age23

Increase physical activity and reduce time spent in sedentary behaviors1

(continued)

Figure 1. Description of target population, topic category, and Dietary Goals/Dietary Guidelines for Americans recommendations by year: 1977-2010. aData are from the 1977 Dietary Goals for the United States and the 1980, 1985, 1990, 1995, 2000, 2005, and 2010 Dietary Guidelines for Americans.1,3,6-9,11,12 The numbers in each column indicate the number of guidelines that address the topic category in that year. In the remainder of the table, the superscript numbers at the end of each of the individual goals/guidelines indicate which category each of the goals/guidelines was counted against. Since a goal/guideline can represent more than one topic category, the number of times that a topic category is addressed will exceed the total number of goals/guidelines in any given year. bDGA=Dietary Guidelines for Americans. cSFA=saturated fatty acid. dTFA=irans-fatty acid. eUSDA=US Department of Agriculture. fDASH = Dietary Approaches to Stop Hypertension. gPUFA=polyunsaturated fatty acid. hMUFA=monounsaturated fatty acid.

Goal or Guideline type

Dietary Goals for the United States

Keep food safe to eat1

Eat a variety of foods3

Eat a variety of foods3

Eat a variety of foods3

Eat a variety of foods3

Reduce sugar consumption by about 40% to account for about 15% of total energy intake4

Eat foods with adequate starch and fiber5

Eat foods with adequate starch and fiber5

Choose a diet with plenty of vegetables, fruits, and grain products34

Choose a diet with plenty of grain products, vegetables, and fruits3,4

To avoid microbial foodborne illness: (a) Clean hands, food contact surfaces, and fruits and vegetables. Meat and poultry should not be washed or rinsed. (b) Separate raw, cooked, and ready-to-eat foods while shopping, preparing, or storing foods. (c) Cook foods to a safe temperature to kill microorganisms. (d) Chill (refrigerate) perishable food promptly and defrost foods properly . (e) Avoid raw (unpasteurized) milk or any products made from unpasteurized milk, raw or partially cooked eggs or foods containing raw eggs, raw or undercooked meat and poultry, unpasteurized juices, and raw sprouts1,4

Let the Pyramid guide your food choices3

Choose a variety of fruits and vegetables daily4

Consume a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that limit the intake of SFAc and TFAd, cholesterol, added sugars, salt, and alcohol3-5

Meet recommended intakes within energy needs by adopting a balanced eating pattern, such as the USDAe Food Guide or the DASHf Eating Plan3

Consume a sufficient amount of fruits and vegetables while staying within energy needs. Two cups of fruit and 2 1/2 cups of vegetables per day are recommended for a reference 2,000-calorie intake, with higher or lower amounts depending on the calorie level3,4

Choose a variety of fruits and vegetables each day. In particular, select from all five vegetable subgroups (dark green, orange, legumes, starchy vegetables, and other vegetables) several times a week4

Follow food safety recommendations when preparing and eating foods to reduce the risk of foodborne illnesses1

Select an eating pattern that meets nutrient needs over time at an appropriate calorie level3 Account for all foods and beverages consumed and assess how they fit within a total healthy eating pattern3

Choose foods that provide more potassium, dietary fiber, calcium, and vitamin D, which are nutrients of concern in American diets. These foods include vegetables, fruits, whole grains, and milk and milk

products4,5

Increase vegetable and fruit intake4

Eat a variety of vegetables, especially dark green and red and orange vegetables and beans and peas4

(continued)

Figure 1. (continued) Description of target population, topic category, and Dietary Goals/Dietary Guidelines for Americans recommendations by year: 1977-2010. aData are from the 1977 Dietary Goals for the United States and the 1980,1985,1990,1995, 2000, 2005, and 2010 Dietary Guidelines for Americans.1,3,6-9,11,12 The numbers in each column indicate the number of guidelines that address the topic category in that year. In the remainder of the table, the superscript numbers at the end of each of the individual goals/guidelines indicate which category each of the goals/guidelines was counted against. Since a goal/guideline can represent more than one topic category, the number of times that a topic category is addressed will exceed the total number of goals/guidelines in any given year. bDGA=Dietary Guidelines for Americans. cSFA=saturated fatty acid. dTFA=trans-fatty acid. eUSDA=US Department of Agriculture. fDASH = Dietary Approaches to Stop Hypertension. gPUFA=polyunsaturated fatty acid. hMUFA=monounsaturated fatty acid.

Goal or Guideline type

Dietary Goals for the United States

Choose a variety of grains daily, especially whole grains4

Increase carbohydrate consumption to account for 55% to 60% of the energy (calorie) intake

Avoid too much sugar4

Avoid too much

Use sugars only in moderation4

Choose a diet moderate in sugars3,4

If you drink alcohol, do so in moderation4

If you drink alcoholic beverages, do so in moderation4

If you drink alcoholic beverages, do so in moderation4

If you drink alcoholic beverages, do so in moderation4

If you drink alcoholic beverages, do so in moderation4

Choose fiber-rich fruits, vegetables, and whole grains often4 Consume 3 or more ounce-equivalents of whole-grain products per day, with the rest of the recommended grains coming from enriched or whole-grain products. In general, at least half the grains should come from whole grains4

Consume 3 cups/d of fat-free or low-fat milk or equivalent milk products4

Choose beverages and foods to moderate your intake of sugars4

Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts suggested by the USDA Food Guide and the DASH Eating Plan4

Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and starch-containing foods and beverages less frequently24

Those who choose to drink alcoholic beverages should do so sensibly and in moderation—defined as the consumption of up to one drink per day for women and up to two drinks per day for men4

Alcoholic beverages should not be consumed by some individuals, including those who cannot restrict their alcohol intake, women of childbearing age who may become pregnant, pregnant and lactating women, children and adolescents, individuals taking medications that can interact with alcohol, and those with specific medical conditions2,4

Consume at least half of all grains as whole grains. Increase whole-grain intake by replacing refined grains with whole grains4

Increase intake of fat-free or low-fat milk and milk products, such as milk, yogurt, cheese, or fortified soy beverages4

Choose a variety of protein foods, which include seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds4

Increase the amount and variety of seafood consumed by choosing seafood in place of some meat and poultry4

Reduce the intake of calories from solid fats and

added sugars3,4

Limit the consumption of foods that contain refined grains, especially refined grain foods that contain solid fats, added sugars,

and sodium4,5

If alcohol is consumed, it should be consumed in moderation—up to one drink per day for women and two drinks per day for men—and only by adults of legal drinking age4

(continued)

Figure 1. (continued) Description of target population, topic category, and Dietary Goals/Dietary Guidelines for Americans recommendations by year: 1977-2010. aData are from the 1977 Dietary Goals for the United States and the 1980,1985,1990,1995, 2000, 2005, and 2010 Dietary Guidelines for Americans.1,3,6-9,11,12 The numbers in each column indicate the number of guidelines that address the topic category in that year. In the remainder of the table, the superscript numbers at the end of each of the individual goals/guidelines indicate which category each of the goals/guidelines was counted against. Since a goal/guideline can represent more than one topic category, the number of times that a topic category is addressed will exceed the total number of goals/guidelines in any given year. bDGA=Dietary Guidelines for Americans. cSFA=saturated fatty acid. dTFA=trans-fatty acid. eUSDA=US Department of Agriculture. fDASH = Dietary Approaches to Stop Hypertension. gPUFA=polyunsaturated fatty acid. hMUFA=monounsaturated fatty acid.

Figure 1. (continued) Description of target population, topic category, and Dietary Goals/Dietary Guidelines for Americans recommendations by year: 1977-2010. aData are from the 1977 Dietary Goals for the United States and the 1980,1985,1990,1995, 2000, 2005, and 2010 Dietary Guidelines for Americans.1,3,6-9,11,12 The numbers in each column indicate the number of guidelines that address the topic category in that year. In the remainder of the table, the superscript numbers at the end of each of the individual goals/guidelines indicate which category each of the goals/guidelines was counted against. Since a goal/guideline can represent more than one topic category, the number of times that a topic category is addressed will exceed the total number of goals/guidelines in any given year. bDGA=Dietary Guidelines for Americans. cSFA=saturated fatty acid. dTFA=trans-fatty acid. eUSDA=US Department of Agriculture. fDASH = Dietary Approaches to Stop Hypertension. gPUFA=polyunsaturated fatty acid. hMUFA=monounsaturated fatty acid.

Goal or Guideline type

Dietary Goals for the United States

Reduce salt consumption by about 50% to 85% to approximately 3 g/d4

Reduce overall fat consumption from

approximately 40% to 30% energy intake5

Reduce saturated fat consumption to account for about 10% of total energy intake; and balance that with PUFAg and MUFAh, which should account for about 10% of energy intake each5

Reduce cholesterol consumption to about 300 mg/d5

Avoid too much sodium5

Avoid too much sodium5

Use salt and sodium only in moderation45

Choose a diet moderate in salt and sodium3-5

Choose and prepare foods with less salt4

Avoid too much fat, saturated fat, and cholesterol5

Avoid too much fat, saturated fat, and cholesterol5

Choose a diet low in fat, saturated fat, and cholesterol3,5

Choose a diet low in fat, saturated fat, and cholesterol3,5

Alcoholic beverages should be avoided by individuals engaging in activities that require attention, skill, or coordination, such as driving or operating machinery4

Consume <2,300 mg (approximately 1 tsp of salt) of sodium per day4,5

Choose and prepare foods with little salt. At the same time, consume potassium-rich foods, such as fruits and vegetables4,5

Choose a diet that is low in saturated fat and cholesterol and moderate

in total fat3,5

Consume <10% of calories from SFA and <300 mg/d of cholesterol, and keep TFA consumption as low as possible5

Keep total fat intake between 20% and 35% of calories, with most fats coming from sources of PUFA and MUFA, such as fish, nuts, and vegetable oils45

Reduce daily sodium intake to <2,300 mg and further reduce intake to 1,500 mg among persons who are 51 and older and those of any age who are African American or have hypertension, diabetes, or chronic kidney disease. The 1,500-mg recommendation applies to about half of the US population, including children, and the majority

of adults2,5

Consume <10% of calories from saturated fatty acids by replacing them with monounsaturated and polyunsaturated fatty acids5

Consume <300 mg/d of dietary cholesterol5

When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free4

Limit intake of fats and oils high in SFA and/or TFA, and choose products low in such fats and oils5

Keep TFA consumption as low as possible by limiting foods that contain synthetic sources of TFA, such as partially hydrogenated oils, and by limiting other solid fats4,5

Use oils to replace solid fats where possible4

Replace protein foods that are higher in solid fats with choices that are lower in solid fats and calories and/ or are sources of oils4

lowing groups: manage weight, foods and food components to reduce, food and nutrients to increase, and building healthy eating patterns. The proportion of the guidelines that were positive vs negative remained similar over time. Recommendations for weight shifted

from maintaining a healthy weight to preventing or reducing overweight.

DESCRIPTION OF TRENDS IN RESEARCH GAPS

The 1980s research recommendations were limited, with only four to five being

identified each year addressing 10 different topic areas. However, when the methodology changed to an evidence-based approach that relied on development of questions before identifying and selecting research, the research gaps were more fully articulated, with 78 specific research

gaps were extracted from the 1977 Dietary Goals for the United States and the 1980, 1985, 1990, 1995, 2000, 2005, and 2010 Dietary Guidelines for Americans (DGA).1,3,6-9,11,12 Each was evaluated for which of the five categories they represented: general (including four topics on uses of guidelines, physical activity, food safety, and other unspecified general research topics); chronic disease/health condition (including nine topics related to chronic diseases, health conditions, or unspecified health outcomes); diet/diet pattern (including overall diet or dietary patterns, variety, breakfast, and energy balance); food/ingredients (including specific food groups or ingredients in foods, as well as alcohol and glycemic load); and nutrients (including specific nutrients or other bioactive components).

gaps identified in 2010 addressing 215 different topic areas.

Number of Topics Identified in Research Gaps

The number of identified research gaps has dramatically increased. Figure 2 shows how the number of research recommendations in the five topic categories (general, chronic disease/conditions, diet/diet patterns, food/ingredients, nutrients) shifted and increased from 1980 to 2010. The second stacked bar in Figure 2 shows the identified research gaps organized to match the five topics used to describe the guideline recommendations. Since 1980, the frequency of research gaps in all five topic categories has increased at least 10fold. Figure 3 (available online at www. andjrnl.org) includes the actual wording of the research recommendations and their categorization for this evaluation. In Figure 3, all research gaps coded as research topics by year. Data in Figure 3 were extracted from the Di-

etary Guidelines for Americans Committee reports.6-9,11,12

Evolution of Research Gaps within Topics

Research gaps have consistently been identified in the general (eg, appropriate use of the DGA), chronic diseases/health condition (eg, knowledge between diet and chronic diseases), and nutrient-specific categories. Research gaps in the diet/ diet pattern-specific research and the food/ ingredient-specific research categories only emerged in the last two Dietary Guidelines Advisory Committees reports. The nature of the research gaps also shifted over time from broad questions to very specific questions identified for the systematic review/evidence analysis. The dramatic increase in research gaps since 2000 reflects growing awareness of the lack of understanding of the complexity of nutrient interactions with other nutrients and the food matrix, as well as the mechanisms of action for bioactive substances that are components of known nutrients or might

not have been identified previously as "nutrients."

Specific Examples of Trends in Unmet Research Gaps

The changes in research gaps identified within topic areas were characterized as follows: unmet research gaps, shift in focus of research gaps, increasing complexity of research gaps, increasing specificity of research gaps, and intermittent identification of research gaps. The following examples illustrate the evolution of research gaps over time.

Identifying who is sensitive to salt was consistently identified as a research gap (Figure 4). Most notable is the 2005 Dietary Guidelines Advisory Committee's conclusion that, despite not having met the research gap of developing standardized diagnostic tests to identify who was salt sensitive, "it is possible to make general observations." The complexity and specificity increased over time from a single nutrient-single condition to research gaps address-

At present, there is no good way to predict who will develop high blood pressure (with high sodium intake)

At present there is no good way to predict who will develop high blood pressure (with high sodium intake)

At present, there is no way to predict who might develop high BPa and who will benefit from restricting dietary salt and sodium

...There is evidence that both sodium and chloride may be important in raising blood pressure. In future research, the importance of chloride may become clearer

.Researchers continue to search for ways to predict who will develop high BP and which individuals are sensitive to salt and sodium restriction

There is no way at present to tell who might develop high blood pressure from eating too much sodium

The inability to identify in advance individuals who are sensitive to the blood-pressure-raising effects of a high salt.

Need for research to establish the association of food patterns and health outcomes, electrolyte balance and risk of hypertension

There is no way to tell who might develop high blood pressure from eating too much salt

Conduct studies on the appropriateness of population-wide recommendations related to sodium intake

Also, there are no standardized diagnostic criteria and tests (for salt sensitivity). Despite these limitations, it is possible to make some general observations

Conduct trials that assess the effects of salt intake on clinical outcomes other than blood pressure

Conduct dose-response trials that test the main and interactive effects of sodium and potassium intake on blood pressure and other clinically relevant outcomes

Compare calcium salts that provide equivalent amounts of calcium to that in milk and milk alternatives (ie, calcium-fortified soy products) on bone health, insulin resistance, blood pressure, and weight management

Conduct clinical trials to determine the effect of intake of foods from various commodity food groups (ie, fruits, vegetables, cereals, dairy foods, and meat, fish, or poultry) or whole diets on BMIb, lip id metabolism, cardiovascular disease, type 2 diabetes, cancer, and osteoporosis

Conduct studies, including clinical trials, in children to determine the effects of sodium on blood pressure and the age-related rise in blood pressure

Conduct trials that determine the effects of sodium reduction on clinically relevant non-blood pressure variables, such as left ventricular mass, proteinuria, and bone mineral density

However, such information is less available for catered and restaurant foods, which constitute a major portion of the food intake of most US children and adults. The sodium content of foods is available to professionals in food composition tables, although the extent to which added salt is adequately or consistently estimated from these tables is uncertain

Vitamin D: Conduct high-quality, long-term dose-response studies with relevant health outcomes including bone as well as functional outcomes related to the immune system, autoimmune disorders, and chronic diseases such as coronary heart disease, hypertension, cancer, and diabetes

Conduct clinical trials in children and adults to critically examine the impact of adherence to the 2010 DGAc as a total dietary approach to a healthy lifestyle on body weight change, CVDd, type 2 diabetes, cancer, and osteoporosis and related clinical endpoints

Conduct dose-response trials that test the main and interactive effects of sodium and potassium intake, as well as possible impact of other minerals (eg, calcium, magnesium) on blood pressure and other clinically relevant outcomes

Figure 4. Example of sodium and hypertension research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6-9,11,12 Research gaps identified by authors as those pertaining to sodium, salt, and hypertension were combined in this table. Words were added by authors to clarify the context of the statements included in the actual reports. aBP = blood pressure. bBMI = body mass index. cDGA=Dietary Guidelines for Americans. dCVD=cardiovascular disease.

There is.......SFAa

intake should be reduced <10% calories is an appropriate level. However, the precise level that is best remains unclear

Need for research to establish the relationship between fat consumption during childhood and long-term health outcome

Determine the optimal fatty acid composition of the diet

Need for research to establish a better understanding of the physiological basis for the relationship between consumption of alcoholic beverages and cardiovascular disease

Investigate the effect of various types of fatty acids (ie, SFA, TFAb, a-linolenic acid) on the incidence and prevention of cancer

Determine the optimal ratios between fat and carbohydrate for the American diet

Compare the effects of various sources of TFA on lipid metabolism and health outcomes

Determine the optimal fatty acid composition of the diet

Investigate the effects of stearic acid intake on lipid metabolism and health

Conduct clinical trials to determine the effect of intake of foods from various commodity food groups (ie, fruits, vegetables, cereals, dairy foods, and meat, fish, or poultry) or whole diets on BMIg, lip-id metabolism, cardiovascular disease, T2D, cancer, and osteoporosis

Determine the mechanism by which dietary PUFAc improve serum lipids, glucose metabolism, insulin levels, HOMAd scores, inflammatory markers, and blood pressure in both healthy persons and in persons with T2De. Studies of replacing carbohydrates or other dietary fat with PUFA should include isocaloric substitutions, so as not to be confounded by differences in energy

Determine the benefits

and risks of MUFAf vs PUFA as an isocaloric substitute for SFA. Confirm the metabolic pathways through which dietary SFA affect serum lipids, especially as some SFA (eg, stearic acid) do not appear to affect blood lipid levels

Determine the mechanism by which dietary MUFA improve serum lipids, glucose metabolism, insulin levels, HOMA scores, inflammatory markers, and blood pressure in both healthy persons and in persons with T2D. Studies of replacing carbohydrates or other dietary fat with MUFA should include isocaloric substitutions, so as not to be confounded by differences in energy

Conduct feeding studies using cholesterol from sources other than eggs and funded by non industry sponsors. Conduct research on low and high risk consumers of dietary cholesterol and determine a better definition of hypo- and hyper-responders to dietary cholesterol, with respective underlying genetic polymorphisms. Identify additional subgroups in which dietary cholesterol appears especially harmful with regard to cardiovascular risk

(continued)

Figure 5. Example of dietary fat and dyslipidemia/cardiovascular research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6-9,11,12 aSFA=saturated fatty acid. bTFA=irans-fatty acid. cPUFA=polyunsaturated fatty acid. dHOMA=Homeostatic Model Assessment. eT2D=type 2 diabetes. fMUFA=monounsaturated fatty acid. gBMI=body mass index. hSoFAS=solid fats and added sugars. 'DGA=Dietary Guidelines for Americans. jEPA=eicosapentaenoic acid. kDHA=docosahexaenoic acid. 'CVD=cardiovascular disease.

Research on the impact of SFA consumption in healthy children is lacking

Characterize the difference in metabolic effects and intermediate markers between industrial and ruminant TFA.

Examine stearic acid for its benefits as a solid fat, in contrast to liquid oils high in MUFA and PUFA; include other potential metabolic effects of stearic acid, such as inflammation and coagulation.

Investigate the vitamin E requirements of individuals consuming various types and amounts of dietary fat, the bioavailability of vitamin E from various food sources, and the effect of vitamin E status on the risk of chronic disease. Develop a comprehensive nutrient database for the vitamin E content of foods.

Conduct well-controlled and powered research studies testing interventions that are likely to improve energy balance in children at increased risk of childhood obesity, including dietary approaches that reduce energy density, total energy, dietary fat, and calorically sweetened beverages, and promote greater consumption of fruits and vegetables

Develop and test behavior-based interventions designed to lower dietary intakes of nutrients and dietary components overconsumed, focusing on SoFASh.

Examine stearic acid for its benefits as a solid fat, in contrast to liquid oils high in MUFA and PUFA; include other potential metabolic effects of stearic acid, such as inflammation and coagulation.

Characterize the difference in metabolic effects and intermediate markers between industrial and ruminant TFA.

Conduct well-controlled and powered research studies testing interventions that are likely to improve energy balance in children at increased risk of childhood obesity, including dietary approaches that reduce energy density, total energy, dietary fat, and calorically sweetened beverages, and promote greater consumption of fruits and vegetables.

Conduct clinical trials in children and adults to critically examine the impact of adherence to the 2010 DGA as a total dietary approach to a healthy lifestyle on body weight change, CVD, T2D, cancer, and osteoporosis and related clinical endpoints.

(continued)

Figure 5. (onutiuued) Example of dietary fat and dyslipidemia/cardiovascular research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6-9,11,12 aSFA=saturated fatty acid. bTFA=trans-fatty acid. cPUFA= polyunsaturated fatty acid. dHOMA=Homeostatic Model Assessment. ®T2D=type 2 diabetes. fMUFA=monounsaturated fatty acid. gBMI = body mass index. hSoFAS=solid fats and added sugars. 'DGA=Dietary Guidelines for Americans. jEPA=eicosapentaenoic acid. kDHA=docosahexaenoic acid. 'CVD=cardiovascular disease.

Determine the optimal n-6 to n-3 fatty acid ratio in relationship to health outcomes; investigate the conversion factor of a-linolenic acid to EPA and DHAk and how n-6 intake competes with that conversion rate; compare the effects of EPA and DHA vs fish on lipid metabolism and other health outcomes; and determine the health effects of fish consumption on T2D and cancer.

Investigate further the opposing interactions of high EPA and DHA vs high methyl mercury, especially in dietary patterns in which these consumptions coexist. Investigate high versus low DHA-consuming mothers and infants and the long-term effects on intelligence and other cognitive outcomes.

Conduct randomized controlled trials and prospective observational studies in persons with and without CVDl on plant compared to marine n-3 fatty acids. Examine diets rich in plant n-3 fatty acids in individuals with and without adequate intake of n-3 fatty acids from marine sources. Examine the mechanism of action of marine vs plant n-3 fatty acids for synergies and/or inhibition.

Examine the role of dairy products in lipid profiles, especially through intervention trials in which all types of dairy products, both low and high fat, are fed. Bioactive components that alter serum lipid levels may be contained in milk fat.

Furthermore, three methodologically strong prospective cohort studies warned that egg consumption was associated with increased CVD risk in individuals with T2D (Djousse, 2001; Hu, 1999; Tanasescu, 2004) and this warrants further investigation

Conduct randomized controlled trials comparing different types of nuts on intermediate markers, such as serum lipids, and classify each specific type of nut as more or less associated with CVD risk reduction.

(continued)

Figure 5. (continued Example of dietary fat and dyslipidemia/cardiovascular research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6-9,11,12 aSFA=saturated fatty acid. bTFA=trans-fatty acid. cPUFA= polyunsaturated fatty acid. dHOMA=Homeostatic Model Assessment. ®T2D=type 2 diabetes. fMUFA=monounsaturated fatty acid. gBMl = body mass index. hSoFAS=solid fats and added sugars. 'DGA=Dietary Guidelines for Americans. jEPA=eicosapentaenoic acid. kDHA=docosahexaenoic acid. 'CVD=cardiovascular disease.

Figure 5. (continued) Example of dietary fat and dyslipidemia/cardiovascular research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6"9-11-12 aSFA=saturated fatty acid. bTFA=trans-fatty acid. cPUFA= polyunsaturated fatty acid. dHOMA=Homeostatic Model Assessment. ®T2D=type 2 diabetes. fMUFA=monounsaturated fatty acid. gBMI = body mass index. hSoFAS=solid fats and added sugars. 'DGA=Dietary Guidelines for Americans. jEPA=eicosapentaenoic acid. kDHA=docosahexaenoic acid. 'CVD=cardiovascular disease.

Dietary Guideline Advisory Committee Reports by year

1980 1985 1990 1995 2000 2005 2010

Vitamin D: Conduct high-quality, long-term dose-response studies with relevant health outcomes including bone as well as functional outcomes related to the immune system, autoimmune disorders, and chronic diseases such as coronary heart disease, hypertension, cancer, and diabetes

Thus, limited information is available on this relationship (animal protein and CVD), and risk may depend on type of meat or meat products consumed and the type of CVD

ing interactions of multiple nutrients (eg, chloride, electrolyte balance, potassium, calcium minerals, and vitamin D) and conditions (eg, hypertension, other clinically relevant outcomes, left ventricular mass, proteinuria, and bone mineral density). The research gaps also moved from ingredients (sodium chloride) to nutrients (sodium) to foods and food patterns (milk, milk alternatives, and sources of food in the food supply).

The research gaps related to dietary fat and cardiovascular disease were increasingly complex and specific over time, from needing to determine precise optimal levels of saturated fat to specifying research gaps on the impact of polyunsaturated fatty acid, monounsaturated fatty acid, trans-fatty acid, plant vs marine n-3 fatty acids, stearic acid, eicosapentaenoic acid, and docosahexaenoic acid, and effects of dietary sources such as dairy, nuts, eggs, protein, vitamin D, and behavior-based interventions on one or more chronic diseases (Figure 5).

Analysis of research gaps on fiber and cancer illustrates intermittent interest, with no research gaps identified in 1984, 1995, and 2000 (Figure 6, available online at www.andjrnl.org). This topic also showed a shift in focus from needing to verify that low-fiber diets would increase colon cancer risk in 1980, to including other disease conditions (eg, heart disease and obesity);

specifying food sources (ie, whole-grain, cereals, fruits and/or vegetables, and animal protein); specifying types of fibers, including other nutrients as having potential impact on cancer (eg, saturated fatty acids, trans-fatty acid, a-linolenic acid, and vitamin D); and needing to determine the impact of adherence to 2010 DGA on cancer.

The research gap related to DGA use began with the same gap identified by the 1980 and 1985 Dietary Guidelines Advisory Committees stating that "We do not know enough nutrition to identify the 'ideal diet' for each individual" (Figure 7). In 1990, a research gap emerged about our need to understand how individuals and professionals used the DGA. This theme has continued, with research gaps identified in understanding the barriers to compliance, best communication strategies, and educational strategies and tools for implementation, as well as other factors that will lead to improvement in dietary behaviors. In addition, there has been a repeated call for research to demonstrate the health benefits of DGA adherence.

IMPLICATIONS OF RESEARCH GAPS FOR THOSE USING DGA

Our analysis showed that a substantial number of research gaps have persisted since the first edition of the DGA in 1980. When research gaps persist, they

compromise health professionals' ability to create and apply "evidence-based" guidelines. If a paucity of research exists on critical topics, the guidelines based on less than optimal research might not yield the anticipated results. The dietetics profession is one of the key stakeholders of both the DGA and the resulting implementation tools (eg, MyPlate and school lunch menu planning guidance). With our emphasis on providing evidence-based dietetics practice, it is vital that the dietetics profession has a complete understanding of the state of the science behind the DGA and advocates effectively for research to fill the critical research gaps to support future DGA.13

Long lists of research questions are not helpful unless there is a way to synthesize them into a reasonable short list of high-priority research questions that can be funded, either by the federal government, professional societies, or some combination of public or private research funding. An effort to synthesize identified research gaps from the Dietary Reference Intakes was undertaken by the US Institute of Medicine, resulting in an interactive database and published report.10 The database was originally posted on an Institute of Medicine website and subsequently transferred to the federal government for their use. The Institute of Medicine report was a summary of a workshop that resulted in a chapter on each of the

.......we do not know

enough nutrition to identify "ideal diet" for each individual.

.......we do not know

enough nutrition to identify "ideal diet" for each individual.

Explore the need for additional guidance for special age groups especially infants, children and elderly persons.

The committee has concluded that the state of scientific evidence is insufficient at present to provide quantitative guidelines for most of these nutrients that would be applicable to both sexes and all ages above 2 years.

Conduct prospective studies to evaluate short- and long-term benefits of adherence to the Dietary Guidelines, both as a coherent body of advice and also as specific guidelines.

Conduct research to assess understanding and use of The Third Edition (of Dietary Guidelines) by group of consumers of different demographic and socioeconomic characteristics and by the nutrition educators and health professionals who serve them.)

Need for research to Conduct studies on

establish the best ways the appropriateness

to convey informa- of population wide

tion about the role of recommendations

diet and health to the related to sodium

public. intake.

Investigate the impact of following adult-based dietary guidelines on nutrient intake and health or metabolic effects in children and later in life. Determine the impact of establishing dietary guidelines in childhood on dietary intakes and patterns later in life.

Develop and test both individual-based and population-based interventions designed to implement Dietary Guidelines.

Provide more information about specific users and uses of the Dietary Guidelines to help inform future Dietary Guidelines Advisory Committees about how best to approach the development of specific guidelines.

Conduct intervention studies to guide the development of strategies, educational tools, and programs designed to help change dietary patterns at the individual and population levels.

Investigate what motivates people, on an individual and societal level, to adopt recommended behaviors, such as engaging in physical activity, making healthy food choices, and improving food safety.

Investigate further the health benefits (and risks) of combined nutrition and physical activity interventions.

Improve ways of integrating communication expertise into the Dietary Guidelines Advisory Committee process.

Improve definition of the interrelationship between the Food Guide Pyramid and the Dietary Guidelines.

Conduct studies to determine the barriers for complying with the Dietary Guidelines among children, low-income populations, and various ethnic groups. Identify various mechanisms to motivate individuals to change their eating behaviors and habits.

Establish a system for ongoing systematic reviews on key nutrition and physical activity topics relevant to dietary guidance for the general public.

Conduct clinical trials in children and adults to critically examine the impact of adherence to the 2010 Dietary Guidelines for Americans as a total dietary approach to a healthy lifestyle on body weight change, CVDa, type 2 diabetes, cancer, and osteoporosis and related clinical endpoints.

Develop and test behavior-based interventions designed to lower dietary intakes of nutrients and dietary components overconsumed, focusing on SoFASb.

Conduct considerable new research on other behaviors that might influence eating practices (child feeding practices, family influences, peer influences, etc, and what can improve them).

Conduct research on the influence of snacking behavior and meal frequency on body weight and obesity. Develop better definitions for snacking as the research moves forward.

Figure 7. Example of uses of Dietary Guidelines for Americans research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6,9,11,12 Research gaps identified by authors as those pertaining to sodium, salt, and hypertension were combined in this table. Words were added by authors to clarify the context of the statements included in the actual reports. aCVD=cardiovascular disease. bSoFAS=solid fats and added sugars.

topics identified in the Dietary Reference Intakes research gaps rather than a published manuscript.

The current list of research topics could offer vital input into the Academy's dialogue in which they identify high-priority research topics that serve as the basis of advocacy.14 In addition, opportunity exists for a thoughtful collaborative effort among the multiple stakeholders to identify which topics are most important to practice and future DGA development. Although researchers bring in-depth knowledge and interest in their specific areas of research, the broader perspectives of dietetics practitioners, food scientists, and policy makers are needed to effectively identify the highest-priority future research areas.

As the field of nutrition and dietetics practice has evolved, our recognition of our incomplete understanding of the role of nutrition is reflected in the complexity of the current research gaps compared with the initial research gaps identified. This leads us to question whether our deductive approach to nutrition moving toward increasing specificity of research questions on increasingly smaller bioactive components will ultimately lead to the understanding necessary to create useful dietary guidelines for the general population. We might wonder whether we need to simultaneously build equally robust bodies of research leading to a greater understanding of the impact of food matrices, diet patterns on health outcomes, and effective behavioral change and dissemination strategies. All will be critical to support development of future DGA.

With the shift in focus of the DGA from being created for "healthy" Americans to being created for those with common chronic conditions (eg, overweight/obesity, hypertension, and cardiovascular risk), the concept of population dietary guidance appears to be converging with medical nutrition therapy used as treatment for medical conditions or as preventive therapy for individuals with risk factors. For example, the most relevant research for previous DGA were dietary intakes as they relate to the incidence of a medical condition; however, if the guidelines are intended for populations that already have the condition, the research will more closely align with research gaps

in medical care. This might create a synergy in funding support for critical research priorities.

A CALL TO ACTION FOR STAKEHOLDERS OF DGA

Our findings indicate that, despite an increase in the number, diversity, and specificity of research gaps over the years, some common research gaps remain unaddressed. With the express desire for public policy to be based on explicit systematic reviews and evidence-based policy, these identified research gaps become more apparent and demand our immediate attention. Specifically, we believe the following actions should be considered:

• Convene multidisciplinary stakeholder groups that include the Academy of Nutrition and Dietetics, Society of Nutrition Education and Behavior, Institute of Food Technologists, and American Public Health Association along with federal and other partners. This stakeholder group will help to establish an advisory group or organize workshops to review research recommendations, set priorities for the most critical research needs for DGA development, and develop collaborative funding opportunities supported either through federal research programs or a combination of public and private partnerships.

• Explore new and sustained funding mechanisms and collaborative funding opportunities for critical research topics.

• Describe new or refined research methodologies that might be necessary to address the research gaps related to diet or dietary pattern research or to test outcomes of implementing DGA in their entirety vs individual bioactive components. The relationship between the methodology of conducting evidence-based reviews and the astronomical number of increasingly specific research gaps is apparent, but the unintended consequence might be the creation of a list of research gaps that are not easily trans-

lated into fundable research opportunities.

• Explore the timeline for developing a reasonable body of research to support an evidence-based review on a topic as it relates to the DGA review cycle. It is not unreasonable to have research gaps consistently identified over time until an adequate number and variety of research has been published; however, repeated research gaps without substantial progress should be a red flag and warrant collective actions by researchers and stakeholders.

This is a call to action. We need answers to the persistent research needs that have been identified by the Dietary Guidelines Advisory Committees. Public policy and our nation's health depend on our research enterprise's ability to set priorities and to provide the research to address the critical research gaps.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j. jand.2013.03.023.

References

1. US Senate Select Committee on Nutrition and Human Needs. Dietary Goals for the United States. 2nd ed. Washington, DC: US Government Printing Office; 1977.

2. Dietary Goals for the United States, second edition, 1977: A reaction statement by the American Dietetic Association. Diabetes Care. 1979;2(3):278-282.

3. US Department of Agriculture, US Department of Health and Human Services. Nutrition and Your Health: Dietary Guidelines for Americans. http://www.cnpp. usda.gov/DGAs1980Guidelines.htm. Published 1980. Accessed December 29,2012.

4. Symposium. Report of the Task Force on the evidence relating six dietary factors to the nation's health sponsored by the American Society for Clinical Nutrition, Inc. Proceedings. Am J Clin Nutr. 1979; 32(12 suppl):2621-2748.

5. US Department of Health, Education, and Welfare, Public Health Service. Healthy People: The Surgeon General's Report on Health Promotion and Disease Prevention. Washington, DC: US Department of Health, Education, and Welfare; 1979. http://profiles.nlm.nih.gov/NN/B/B/G/K/. Accessed December 29,2012.

6. US Department of Agriculture. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Ameri-

cans, 2010. http://www.cnpp.usda.gov/ DGAs2010-DGACReport.htm. Published June 15, 2010. Accessed December 29, 2012.

9. US Department of Agriculture, Agricultural Research Service, Dietary Guidelines Committee. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 1995. http:// www.cnpp.usda.gov/Publications/Dietary Guidelines/1995/1995DGCommitteeReport. pdf. Published 1995. Accessed December 29, 2012.

12. Dietary Guidelines Advisory Committee. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 1990. http://www.cnpp.usda. gov/Publications/DietaryGuidelines/1990/ 1990CommitteeReport.pdf. Published 1990. Accessed December 29,2012.

7. Dietary Guidelines Advisory Committee. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 1985. http://www.cnpp.usda. gov/Publications/DietaryGuidelines/1985/ 1985CommitteeReportpdf.Published 1985. Accessed December 29,2012.

10. Otten JJ, Hellwig JP, Meyers LD, eds. Dietary Reference intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press; 2006.

13. Stitzel KF. Position of the American Dietetic Association: The roles of registered dietitians and dietetic technicians, registered in health promotion and disease prevention. J Am Diet Assoc. 2006; 106(11):1875-1884.

8. US Department of Health and Human Services. The Report of the Dietary Guidelines Advisory Committee on Dietary Guidelines for Americans, 2005. http://www.health. gov/dietaryguidelines/dga2005/report/default htm. Published 2005. Accessed December 29, 2012.

11. US Department of Agriculture, Center for Nutrition Policy and Promotion. Dietary Guidelines for Americans, 1980 to 2000. http://www.health.gov/dietaryguidelines/ 1980_2000_chart.pdf. Published 2000. Accessed January 9,2013.

14. Academy of Nutrition and Dietetics. Priorities for Research: Agenda to Support the Future of Dietetics. http://www.eatright. org/Members/content.aspx?id=7188. Accessed February 28, 2013.

AUTHOR INFORMATION

E. F. Myers is senior nutrition and dietetics scientist, W. Murphy is senior project manager, Outcomes Research, and A. Steiber is chief science officer, all at the Academy of Nutrition and Dietetics, Chicago, IL. C.-S. Khoo is senior research fellow, International Life Sciences Institute, North America, Washington, DC. S. Agarwal is a nutrition scientist, East Norriton, PA.

Address correspondence to: Esther F. Myers, PhD, RD, Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Suite 2000, Chicago, IL 60606-6995. E-mail: emyers@eatright.org

STATEMENT OF POTENTIAL CONFLICT OF INTEREST

No potential conflict of interest was reported by the authors.

ACKNOWLEDGEMENTS

We thank Roger A. Clemens, PhD, CNS, FACN, FIFT, University of Southern California (2010 Dietary Guidelines Advisory Committee); Johanna Dwyer, DSc, RD, Tufts University (2000 Dietary Guidelines Advisory Committee); Janet King, PhD, Children's Hospital Oakland Research Institute (2005 Dietary Guidelines Advisory Committee); Joanne Lupton, PhD, Texas A&M University (2005 Dietary Guidelines Advisory Committee); John Milner, PhD, US Department of Agriculture (1990 Dietary Guidelines Advisory Committee); Irwin Rosenberg, MD, Jean Mayer Department of Agriculture Human Nutrition Research Center on Aging, Tufts University (1995 Dietary Guidelines Advisory Committee); Joanne Slavin, PhD, RD, University of Minnesota, St Paul (2010 Dietary Guidelines Advisory Committee), and Eric Hentges, PhD, International Life Sciences Institute, North America, for their review and input on the approach to the manuscript. We also thank Sarah Waybright, MS, RD, formerly with International Life Sciences Institute, North America, for her input in gathering the reports; and Robert Voss, Academy of Nutrition and Dietetics, for reviewing the coding for guidelines and research gaps.

There is concern that low-fiber diets might increase the risk of developing cancer of colon but whether this is true is not known.

Just how dietary fiber None is involved (in reducing risk for heart disease, obesity, and cancer) is not known

Therefore, the overall benefits of whole-grain intake or any of its constituents (such as cereal fiber or fiber per se) and the incidence of colon cancer remain an unresolved issue and further research is needed

Just how dietary fiber relates to specific disease is still under study

Investigate the effect of various types of fatty acids (ie, saturated fatty acids, TFAc, a-linolenic acid) on the incidence and prevention of cancer

Conduct studies on the long-term health impact of folate fortification on NTDsa, CRCb, stroke, cognitive function, and other health outcomes, such as emerging evidence suggesting that high folic acid intakes in some pregnant women may lead to asthma in their offspring (Whitrow, 2009), to fully understand the impact of this ecological experiment. Vitamin D: Conduct high-quality, long-term dose-response studies with relevant health outcomes including bone as well as functional outcomes related to the immune system, autoimmune disorders, and chronic diseases such as coronary heart disease, hypertension, cancer, and diabetes

Conduct clinical trials in children and adults to critically examine the impact of adherence to the 2010 DGAd as a total dietary approach to a healthy lifestyle on body weight change, CVDe, type 2 diabetes, cancer, and osteoporosis and related clinical endpoints

Clinical studies are needed to assess the effectiveness of isolated fibers on satiety as there are no measures of fiber chemistry (solubility, structure, etc) that can predict fiber's effect on satiety

Insufficient evidence is available at present to support the hypothesis that dietary fiber is protective against obesity in children.

Thus, results are conflicting and future research should further investigate the relationship between the intake of animal protein products and breast cancer specifically related to menopausal and receptor status

Figure 6. Example of dietary fiber and oncology research gaps by year. Data were extracted from the Dietary Guidelines for Americans Committee reports.6-9,11,12 aNTD = neural tube defects. bCRC=colorectal cancer. cTFA=trans-fatty acids. dDGA=Dietary Guidelines for Americans. eCVD = cardiovascular disease.