1. NATIONAL NUTRITION & PUBLIC HEALTH POLICIES: Issues Related to Bioavailability of Nutrients When Developing & Using Dietary Reference Intakes Allison A. Yates, PhD, RD Food and Nutrition Board Institute of Medicine The National Academies 120-02

2. Examples of Applications of Reference Intakes USERS: Government - Industry - Academia - Health Services USES: Guide for procuring food supplies for groups of healthy persons Basis for planning meals for groups Reference point for evaluating the dietary intake of population subgroups Basis for food and nutrition education programs Reference point for the nutrition labeling of food and dietary supplements 261-01

3. Nutrition and Public Health Policy Formulation: Outline DRI Framework/Process Development of DRIs Examples of Impact of Changes in Bioavailability on Reference Values and Evaluation of Diets 144-01

4. Recommended Dietary Allowances 1989 Energy Protein 7 minerals (Ca, Fe, P, Mg, Zn, I, Se) 11 vitamins (A, C, D, B 1, B 2, niacin, E, K, B 6, B 12, folate) Safe and adequate daily dietary intakes (biotin, pantothenate, Cu, Mn, F, Cr, Mo) 160-01

5. Dietary Reference Intakes Upper Reference Levels Subcommittee Interpretation and Uses of DRIs Subcommittee Standing Committee on the Scientific Evaluation of Dietary Reference Intakes Panels Calcium, Vitamin D, Phosphorus, Mg, F--1997 Folate, B 12, Other B Vitamins, Choline--1998 Vitamins A and K, B, Cr, Cu, Fe, I 2, Mn, Mo, Ni, Si, V, Zn--2000 Energy and Macronutrients--2001 Electrolytes 149-04 Other Food Components Alcohol ? Vitamins C and E, Se, ß-carotene and Other Carotenoids--2000

6. Major Points of DRI Framework Based on estimating an average requirement Criteria used to assess adequacy Coefficient of variation of requirement often extrapolated rather than measured Only use of RDA is as a goal for individual 365-01

7. Dietary Reference Intakes Observed level of intake UL Risk of inadequacy Risk of excess 0.5 RDA AI EAR Increase 196-02

8. Dietary Reference Intakes 2 s.d. Frequency Distribution of Individual Requirements EAR Increasing Intake RDA 193-01

9. Dietary Reference Intakes Observed level of intake UL Risk of inadequacy Risk of excess 0.5 RDA AI EAR Increase 196-02

10. To Provide a Quantitative Recommendation You Need: Data on intakes/food composition Data from studies with multiple intakes and measured indicators of adequacy Indicators which reflect status of individual, therefore not rapidly resolved with increased intake Indicators correlated with health or functional outcome Both half-way point and coefficient of variation of requirements needed to establish EAR and thus RDA 366-01

11. Bioavailability Form of nutrient or food component Factors that affect absorption/utilization Assumptions for “typical” diet Special considerations

12. Bioavailability Assumptions for B 12 DRI Recommended Intakes Normal gastric, pancreatic, ileal function 50% average absorption of all forms of B 12 10–30% of those > 50 y have atrophic gastritis

13. Percent Absorption of B 12 from Foods, Healthy Adults 353-01

14. Requirements for Normal Absorption of Vitamin B 12 Intact stomach Intrinsic factor Pancreatic sufficiency Functioning terminal ileum 354-01

15. Effect of Oral Intake of B 12 on Absorption 355-01 Dose % Absorbed Amount Absorbed 1 µg 50 0.5 µg 5 µg 20 1.0 µg 25 µg 5 1.25 µg Adams et al., Scand. J. Gastroenterol 6:249-252, 1971.

16. Derivation of EAR for B 12 Requirement normal person for absorbed B 12 = 1.0 µg/day Correct for bioavailability  0.50 = 2.0µg/day EAR: Average requirement for normal person for B 12 from food - 2 µg/day

17. RDA for Vitamin B 12 (  g/day) Men and Women, 19 y +2.4  g* Pregnancy2.6  g Lactation2.8  g *For those over age 50 y, needs to come primarily from fortified foods or supplements

18. Distribution of Reported Vitamin B 12 Intake for Men and Women Aged 19+ Years Percent Vitamin B 12 (µg) EAR Source: NHANES III, 1988–1994 (J. Wright) 389-01

19. SUMMARY Bioavailability Assumptions for B 12 DRI Recommended Intakes Normal gastric, pancreatic, ileal function 50% average absorption of all forms of B 12 10–30% of those > 50 y have atrophic gastritis

20. Bioavailability Assumptions for Folate DRI Recommended Intakes Absorption of synthetic folate  1.7 - 2.0 x food folate Folate supplements taken w/water  90% absorption Folate added to food or taken w/food  85% absorption Folate naturally found in food  50% absorption

21. Concept of Dietary Folate Equivalents 1 µg DFE= 0.5 µg folate from supplements (DFE = 2 x weight) = 0.6 µg folate from fortified food (DFE = 1.7 x weight) = 1.0 µg naturally present folate in food (DFE = 1 x weight) 364-02

22. Distribution of Reported Folate Intake for Men and Women Aged 19+ Years Percent Folate (µg) EAR Source: NHANES III, 1988–1994 (J. Wright) 388-01

23. Distribution of Reported Folate Intake for Men and Women Aged 19+ Years, with Higher Bioavailability Percent Folate (µg) EAR F Source: NHANES III, 1988–1994 (J. Wright) 388-01 EAR C

24. Importance of Data on Food Composition and Dietary Intake Folate intakes in surveys underestimated due to: Inadequate enzymatic digestion of food folate when determining food folate content Data on intake based on prefortification values for folate content in foods consumed Folate content of foods not available in DFEs Underreporting errors

25. Estimated Folate Intakes, 19-30 Years Unmodified Data NHANES III Modified Data NHANES III Percentage of Population µg DFE 403-01 Lewis et al., 1999, AJCN, 70:198-207 µg EAR

26. SUMMARY Bioavailability Assumptions for Folate DRI Recommended Intakes Absorption of synthetic folate  1.7 - 2.0 x food folate Folate supplements taken w/ water  90% absorption Folate added to food or taken w/food  85% absorption Folate naturally found in food  50% absorption

27. Bioavailability Assumptions for Iron 1989 RDA Increased absorption with increased need Form of iron: heme vs non-heme Other food components — Ascorbic acid— Phytate — Polyphenols— Fiber Typical diet “relatively highly available”, 10–15%

28. Prevalence of Inadequate Intakes 1989 Iron RDA Men Women Need:Absorbed iron1.3 mg 1.8 mg Intake: 10% absorption 13 mg 18 mg 15% absorption 8.7 mg 12 mg RDA (12.5 %) 10 mg 15 mg NHANES III 19-30 y, inadequate <5% < 25%

29. Plant-based Diet, low in Vitamin C Adjustment of Iron RDA Men Women Need:Absorbed iron 1.3 mg 1.8 mg Intake:Assume 4% absorption 32 mg 45 mg NHANES III 19-30 y, inadequate 92% >95%

30. SUMMARY Bioavailability Assumptions for Iron 1989 RDA Increased absorption with increased need Form of iron: heme vs non-heme Other food components — Ascorbic acid— Phytate — Polyphenols— Fiber Typical diet “relatively highly available”, 10–15%

31. Derivation of 1989 RDA for Protein EAR ~ 0.6 g reference protein/kg/day CV ~ 12.5%  Need 0.75 g reference protein/kg/day U.S. diet amino acid score ~ 100 for adults U.S. digestibility ~ 100% RDA for men and women (rounded)  0.8 g protein/kg/day

32. Bioavailability Assumptions for Protein 1989 RDA U.S. Diet high quality protein, amino acid score of 100 for adults 65% animal origin protein, 35% plant Digestibility  100 (equal to reference proteins) 14–18% of kcal from protein

33. Adjusting the 1989 RDA for Protein for a Primarily Plant-Based Diet, Adult EAR ~ 0.6 g reference protein/kg/day CV ~ 12.5%  Need 0.75 g reference protein/kg/day U.S. diet amino acid score ~ still 100 for adults U.S. digestibility ~ 92% Adjusted RDA for men and women: 0.75  0. 92 = 0.8 g protein/kg/day  no change

34. Impact of 1/3 Animal, 2/3 Plant- Based Protein Diet, 3 yr Old 3 yr old amino acid score ~ 51/58 = 88 (due to low lysine content) Digestibility ~ 92% Adjusted RDA for 3 yr old: 1.1g /kg  0.88 = 1.25 g/kg 1.25g/kg  0.92 = 1.36 g/kg Adjusted RDA = 1.4 g protein/kg/day  27% increase in amount needed

35. SUMMARY Bioavailability Assumptions for Protein 1989 RDA U.S. diet high quality protein, amino acid score of 100 for adults 65% animal origin protein, 35% plant Digestibility  100 (equal to reference proteins) 14–18% of kcal from protein

36. Examples of Applications of RDAs USERS: Government - Industry - Academia - Health Services USES: Guide for procuring food supplies for groups of healthy persons Basis for planning meals for groups Reference point for evaluating the dietary intake of population subgroups Component of food and nutrition education programs Reference point for the nutrition labeling of food and dietary supplements 261-01

37. Food and Nutrition Board http:// www.nas.edu/iom/fnb Publications: http://www.nap.edu 111-02