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NATIONAL NUTRITION & PUBLIC HEALTH POLICIES:

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.

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NATIONAL NUTRITION & PUBLIC HEALTH POLICIES:

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  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 Allowances1989 • Energy • Protein • 7 minerals (Ca, Fe, P, Mg, Zn, I, Se) • 11 vitamins (A, C, D, B1, B2, niacin, E, K, B6, B12, folate) • Safe and adequate daily dietary intakes (biotin, pantothenate, Cu, Mn, F, Cr, Mo) 160-01

  5. Dietary Reference Intakes Standing Committee on the Scientific Evaluation of Dietary Reference Intakes Panels Calcium, Vitamin D, Phosphorus, Mg, F--1997 Folate, B12, Other B Vitamins, Choline--1998 Interpretation and Uses of DRIs Subcommittee Upper Reference Levels Subcommittee Vitamins C and E, Se, ß-carotene and Other Carotenoids--2000 Vitamins A and K, B, Cr, Cu, Fe, I2, Mn, Mo, Ni, Si, V, Zn--2000 Energy and Macronutrients--2001 Electrolytes Other Food Components Alcohol ? 149-04

  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 EAR UL RDA AI Risk of excess Risk of inadequacy 0.5 0.5 Observed level of intake Increase 196-02

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

  9. Dietary Reference Intakes EAR UL RDA AI Risk of excess Risk of inadequacy 0.5 0.5 Observed level of intake 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 B12 DRI Recommended Intakes • Normal gastric, pancreatic, ileal function • 50% average absorption of all forms of B12 • 10–30% of those > 50 y have atrophic gastritis

  13. Percent Absorption of B12 from Foods, Healthy Adults 353-01

  14. Requirements for Normal Absorption of Vitamin B12 • Intact stomach • Intrinsic factor • Pancreatic sufficiency • Functioning terminal ileum 354-01

  15. Effect of Oral Intake of B12 on Absorption 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. 355-01

  16. Derivation of EAR for B12 Requirement normal person for absorbed B12 = 1.0 µg/day Correct for bioavailability  0.50 = 2.0µg/day EAR: Average requirement for normal person for B12 from food - 2 µg/day

  17. RDA for Vitamin B 12 (g/day) Men and Women, 19 y + 2.4 g* Pregnancy 2.6 g Lactation 2.8 g *For those over age 50 y, needs to come primarily from fortified foods or supplements

  18. Distribution of Reported Vitamin B12 Intake for Men and Women Aged 19+ Years EAR Percent Vitamin B12 (µg) Source: NHANES III, 1988–1994 (J. Wright) 389-01

  19. SUMMARYBioavailability Assumptions for B12 DRI Recommended Intakes • Normal gastric, pancreatic, ileal function • 50% average absorption of all forms of B12 • 10–30% of those > 50 y have atrophic gastritis

  20. Bioavailability Assumptions for FolateDRI 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 ofDietary 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 EAR Percent Folate (µg) 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 EARC EARF Percent Folate (µg) Source: NHANES III, 1988–1994 (J. Wright) 388-01

  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 EAR Unmodified Data NHANES III Percentage of Population µg EAR Modified Data NHANES III µg DFE Lewis et al., 1999, AJCN, 70:198-207 403-01

  26. SUMMARYBioavailability Assumptions for FolateDRI 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 MenWomen • Need: Absorbed iron 1.3 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 CAdjustment of Iron RDA MenWomen 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. SUMMARYBioavailability 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 Proteinfor 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. SUMMARYBioavailability 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 Boardhttp://www.nas.edu/iom/fnbPublications: http://www.nap.edu 111-02

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