Whole Grains and Health: Does the evidence support current guidelines?

Transcription

1 Whole Grains and Health: Does the evidence support current guidelines? Joanne Slavin Professor Department of Food Science and Nutrition December 6, 2013

2 Disclosures for Joanne Slavin AFFILIATION/FINANCIAL INTERESTS CORPORATE ORGANIZATION Grants/Research Support: Scientific Advisory Board/Consultant: MN Beef Council, USAPears, MN Wild Rice Council, Novartis Consumer Health, Egg Board (graduate student support) Tate and Lyle, Adkins, Kelloggs Speakers Bureau: Stock Shareholder: NA NA Other NA

3 From the Science to Me The Science Policy Me

4 Nutrient Adequacy - Meet nutrient needs without exceeding calorie needs - Dietary Reference Intakes (DRIs) - Acceptable Macronutrient Distribution Ranges (AMDR) - Protein 10-35% of kcal - Carbohydrates 45 65% of kcal - Fat 20 35% of kcal - Recommended Dietary Allowance (RDA) - Adequate Intake (AI) - Tolerable Upper Limit (UL)

5 USDA grain guidance over time 1916 Cereals and starchy foods 20% of kcal 1940s Basic 7 Bread, flour, and cereal every day 1950s Basic 4 bread, cereal 4 or more servings 1984 Food Guide Pyramid 6 11 servings whole grain, enriched 2005 DGA make half of your grain whole 5

6 Nutritional science nutrients/deficiency diseases 1941: National Academy of Sciences began issuing Recommended Dietary Allowances quantity of nutrients a person needed to consume daily to ensure basic good health, proper growth and reproductive success, and to prevent nutrient deficiency diseases Nutritional deficiency diseases have been virtually eliminated in the US, thanks to enrichment of refined grains (thiamin, riboflavin, niacin, iron), fortification (folate) and other fortification strategies Grains are source of B vitamins, Fe, Ca, Mg, P, and fiber

7 There is no perfect diet! Humans are omnivores, like pigs, and are adaptable to a wide range of foods Humans have survived and prospered on all kinds of diets, mostly reflecting access to food supply Traditional Arctic diet: 80% of kcals from fat Traditional African diet: 80% of kcals from carbohydrate Grains are low in lysine and legumes are low in methionine so vegan diets combine grains and legumes to provide high quality protein most cultures have grains as the base of the diet bread, rice, pasta, tortillas, etc.

8 Dietary Fiber = Whole Grain Deficient intake of both whole grains & dietary fiber Dietary fiber not synonymous with whole grain Both being encouraged, creates consumer confusion Whole grains contain vitamins, minerals, phytochemicals above and beyond fiber Foods with dietary fiber are more than just whole grains; also legumes, fruits, vegetables; and foods with functional fibers Whole grains contain more nutrition than just dietary fiber (not on Nutrition Facts food, not nutrient)

9 Dietary fiber intake is low in U.S. 1 Usual intake only 15 g/day recommended intakes g/day 14 g/1000 kcal Most fiber-containing foods: 1 3 g Apple 3 grams Lettuce 1 gram WW bread 2 grams Oatmeal 3 grams White flour and white potatoes provide the most fiber in the U.S. diet Not b/c concentrated fiber sources, but because widely consumed There s a need to add functional fiber to foods to reach the recommended dietary fiber goals. 1. Slavin J. Position of the American Dietetic Association: Health Implications of Dietary Fiber Dietary Fiber, J Am Diet Assoc. 2008;108:

10 What is a Whole Grain? Bran Outer shell protects seed Fiber B vitamins Trace minerals Phytochemicals Germ Nourishment for the seed B vitamins Vitamin E Trace minerals Phytochemicals, antioxidants Lipids Aleurone Endosperm Provides energy Carbohydrate Protein Some B vitamins

11 Whole grains Grains and grain products made from the entire grain seed, usually called the kernel, which consists of the bran, germ, and endosperm. If the kernel has been cracked, crushed, or flaked, it must retain nearly the same relative proportions of bran, germ, and endosperm as the original grain in order to be called whole grain. Many, but not all, whole grains are also a source of dietary fiber (Appendix E-2, 2010 DGAC Report)

12 Whole Grains Dietary Guidance NAS Diet and Health links whole grains to reduced risk for heart disease and some cancers Dietary Guidelines (5th ed.) separate grain guideline emphasis on whole grain 2005 Dietary Guidelines recommend 3 servings of whole grains per day Whole Grains promoted as a source of fiber FDA permits whole grain health claim 2010 Healthy People objective to whole grain consumption

13 Whole Grains and health 2010 Dietary Guidelines Recommends consuming 3 or more servings of whole grains/day as part of your total grain servings to reduce the risk of CHD and help with weight maintenance. IOM and WHO/FAO reports reinforce importance of whole grains in healthy diets Countries around the world now have WG recommendations

14 Whole grains in the US Whole wheat Whole oats/oatmeal Whole-grain corn Popcorn Brown rice Whole rye Whole-grain barley Wild rice Buckwheat Triticale Bulgur (cracked wheat) Millet Quinoa Sorghum

15 Grain Refining Endosperm Milling Removal of bran and germ layers. Bran Nutrients lost: Vitamins Minerals Phenolics Fiber Enhance desirability. Improve texture, flavor, appearance. Increase shelf life. Germ

16 Comparison of 100 g of WG flour and enriched, white flour WG flour 339 kcal 12.2 g dietary fiber 34 g calcium 138 mg magnesium 420 mg potassium 44 mcg folate White flour 364 kcal 2.7 g dietary fiber 15 g calcium 22 mg magnesium 107 mg potassium 291 mcg folate

17 Whole grains and CHD Trowell (1972) diets rich in whole grains protect against CHD interpreted as fiber hypothesis Morris (1977) cereal fiber (mostly wheat) intake associated with significantly lower rates of CHD in British men DeGroot et al (1963) - oats lower serum cholesterol 5-8%

18 WG and Obesity Epidemiological Studies Harvard Nurses Health Study (75,000 women) Women who consumed more whole grains consistently weighed less than women who consumed fewer whole grains At baseline, women in highest quintile of whole grain intake weighed less than did women in the lowest quintile Increases in whole grain intake associated with significantly less weight gain over time Refined grain intake was linked to increased risk of weight gain Liu et al., 2003

19 Dietary Guidelines for Americans

20 Dietary Guidelines - always controversial Dr. Alfred Harper University of Wisconsin 1988 paper Killer French Fries The model used to learn about nutrient deficiency diseases does not work for chronic diseases such as heart disease and cancer You can cure scurvy with Vitamin C, but you won t prevent or cure heart disease with a low fat diet

21 Indexing/Search Topics Available at:

22 NEL Process Formulate Systematic Review Questions Exploratory searches Public comment Dialogue with experts Analytical Framework PICO Literature Search and Sort Identify study eligibility criteria Determine search strategy Search for relevant studies List included studies List excluded studies and rationale Extract Evidence From Studies Create evidence worksheets Summarize and Synthesize the Evidence Assess quality of individual studies Assess applicability Summarize and synthesize evidence Develop and Grade Conclusion Statements Define Research Recommendations

23 Hierarchy of Evidence Stronger Evidence Weaker Evidence RCT Double Blinded Clinical Study Prospective, cohort study Cross-sectional study Case-control study Case Report Expert Opinion

24 What is the relationship between whole grain intake and selected health outcomes? A moderate body of evidence from large prospective cohort studies shows that whole grain intake, which includes cereal fiber, protects against cardiovascular disease. Limited evidence shows that consumption of whole grains is associated with a reduced incidence of type 2 diabetes in large prospective cohort studies. Moderate evidence shows that intake of whole grains and grain fiber is associated with lower body weight

25 Chapter 4 Foods and Nutrients to Increase

26 The Whole Grain Consumption Gap Recommendations The 2010 Dietary Guidelines recommends at least 3 servings of whole grains per day Healthy People 2010 objectives aim for 3 servings/day Average whole grain intake in US is less than 1 serving/day

27 ASN Scientific Statement Consumption of foods rich in cereal or mixtures of whole grains, and bran is modestly associated with a reduced risk of obesity, T2D, and CVD. The data for whole grain alone are limited primarily because of varying definitions among epidemiological studies what, and how much, was included in that food category Cho et al. Am J Clin Nutr 2013;98:

28 WGs have benefits beyond fiber? Traditional Nutrients, Vitamins, & Minerals Sphingolipids Resistant Starch Lignan WHOLE GRAIN Antioxidants Plant Stanols and Sterols Phytate Inulin and Fructooligosaccharides

29 Whole grain and body weight changes Meta-analysis assessed the effects of whole-grain compared with non-whole grain food on changes in body weight, percentage of body fat, and waist circumference 2516 articles screened for eligibility and relevant data were extracted from 26 studies (# participants=2060) Whole grain intake did not affect body weight, but a small effect on percentage of body fat was found Poi et al Am J Clin Nutr 2013;98:

30 Whole grains and markers of subclinical inflammation Reviewed 13 epidemiological studies and 5 intervention studies Epidemiological studies found an association between diet high in whole grains and lower C- reactive protein (CRP) concentrations In contrast, intervention studies saw no effect of whole grain intake and CRP or other markers of inflammation Lefevre & Jonnalagadda. Nutr Rev 2012;70:

31 Fiber Content Varies by Grain Dietary fiber in various types of grains Brown Rice Whole Grain Corn Meal Whole Oats Whole Grain Wheat 100g 1.8g 7.3g 10.3g 12.2g 55g 1.0g 3.7g 5.7g 6.7g 30g 0.5g 2.2g 3.1g 3.7g USDA National Nutrient Database for Standard Reference

32 Dietary Fiber = Whole Grain DG make ½ grain svgs whole/16 g (epi), wheat, oats, corn, rice, barley, Current food labeling difficult to find whole grains, not on Nutrition Facts. Ingredients don t clearly indicate the amount of whole grain present. Whole Grains Council stamp program Health claim for whole grain: Contains all portions of the grain kernel At least 51% whole grain by weight Meet fat, saturated fat, and cholesterol restrictions

33 Labeling & Identifying Whole Grain Foods Product Name Amount of Whole Grain Grams or Ounce Equivalents Factual Statements Symbols Whole Grains Council Stamp FDA Approved Whole Grain Health Claim Diets rich in whole grain foods and other plant foods, and low in total fat, saturated fat and cholesterol may reduce the risks of heart disease and certain cancers. Product must conform to claim criteria (at least 51% of product weight is whole grain & meets other composition criteria) Ingredients Look for whole grain ingredients as first or predominant in ingredients list

34 Three Levels of Whole-grain Goodness Good Source At least 8 g whole grain/serving Excellent Source At least 16 g whole grain/serving 100%/Excellent At least 16 g whole grain/serving, no refined grains

35 Diets rich in whole grain foods and other plant foods, and low in saturated fat and cholesterol, may help reduce the risk of heart disease.

36 Developing a standard definition of whole grain food While the term whole grain is well defined, there has been no universal standard to define what constitutes a whole grain food, creating challenges for researchers, the food industry, regulatory authorities, and consumers AACC International recommendation: Whole grain food product must contain 8 grams or more of whole grain per 30 g serving May 2013

37 Whole grain key messages Whole grains provide more than fiber Scientific support for whole grains protecting against CVD and obesity 2010 Dietary Guidelines recommends that at least half of all grains come from whole grains the rest from enriched or whole grains 9 out of 10 Americans don t consume 3 WG servings per day

38 Dietary Guidance A Historical Perspective Dr. Atwater specified amount of protein and total calories in a good diet, but left unspecified the division of calories between fats and carbohydrates evils of overeating may not be felt at once, but sooner or later they are sure to appear perhaps in general debility, perhaps in actual disease ordinary food materials make a fitting diet, and the main question is to use them in the kinds and proportions fitted to the actual needs of the body Recommended variety, proportionality and moderation, measuring calories, and an affordable diet focused on nutrient-rich foods, less fat, sugar and starch.

39 1943: Basic Seven Margaret Mead: People don t eat nutrition they eat food Basic 7 did not specify the number of servings of each food group needed daily

40 Food advice: Evolution of USDA s Food Guidance Moderation and Variety 1950s-1960s 1940s Food for Young Children s

41 MyPlate.gov

42 Toward Healthful Diets, FNB, 1980 The Board expresses its concern over excessive hopes and fears in many current attitudes toward food and nutrition. Sound nutrition is not a panacea. Good food that provides appropriate proportions of nutrients should not be regarded as a poison, a medicine, or a talisman. It should be eaten and enjoyed.

43 Conclusions Efforts to micromanage the diet by imposing strict dietary rules are difficult to support with evidence-based nutrition science we do not have strong evidence-based support for many of our accepted dietary practices We have moved from nutrient-based recommendations to food recommendations historically we have supported whole grains as a source of fiber, rather than whole grains per se Dietary fiber is a short-fall nutrient and most Americans need to replace some refined grains with whole grains, not eat more whole grains Our inability to define whole grains and analytically measure them will continue to add to confusion Solving important nutrition problems will require partnerships based on trust among academics, the government, commodity groups, activists, and food companies