Transcript Define

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
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
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Nutrition and Public Health Policy
Formulation: Outline
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DRI Framework/Process
Development of DRIs
Examples of Impact of Changes in
Bioavailability on Reference Values and
Evaluation of Diets
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Recommended Dietary Allowances
1989
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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)
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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
Upper Reference Levels
Subcommittee
Vitamins C and E, Se, ß-carotene and Other
Carotenoids--2000
Interpretation and Uses
of DRIs
Subcommittee
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 ?
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Major Points of DRI Framework
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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
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Dietary Reference Intakes
UL
RDA
AI
0.5
0.5
Risk of excess
Risk of inadequacy
EAR
Observed level of intake
Increase
196-02
Dietary Reference Intakes
Frequency Distribution
of Individual Requirements
EAR
2 s.d.
RDA
Increasing Intake
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Dietary Reference Intakes
UL
RDA
AI
0.5
0.5
Risk of excess
Risk of inadequacy
EAR
Observed level of intake
Increase
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To Provide a Quantitative
Recommendation You Need:
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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
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Bioavailability
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Form of nutrient or food component
Factors that affect absorption/utilization
Assumptions for “typical” diet
Special considerations
Bioavailability Assumptions for B12
DRI Recommended Intakes
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Normal gastric, pancreatic, ileal function
50% average absorption of all forms of B12
10–30% of those > 50 y have atrophic
gastritis
Percent Absorption of B12 from
Foods, Healthy Adults
Foods
Absorption (%)
Eggs
24 to 36
Chicken
60
Trout
25 to 47
Mutton
65
Liver
9
Source: Doscherholmen et al., 1975, 1978, 1981;
Heyssel et al., 1966
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Requirements for Normal Absorption
of Vitamin B12
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Intact stomach
Intrinsic factor
Pancreatic sufficiency
Functioning terminal ileum
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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.
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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
RDA for Vitamin B 12 (g/day)
Men and Women, 19 y +
Pregnancy
Lactation
2.4 g*
2.6 g
2.8 g
*For those over age 50 y, needs to come
primarily from fortified foods or
supplements
Percent
Distribution of Reported Vitamin B12
Intake for Men and Women Aged 19+
Years
50
45
40
35
30
25
20
15
10
5
0
EAR
Males
Females
0
2
4
6
8
10 12 14 16 18 20 22 24
Vitamin B12 (µg)
Source: NHANES III, 1988–1994 (J. Wright)
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SUMMARY
Bioavailability Assumptions for B12
DRI Recommended Intakes
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Normal gastric, pancreatic, ileal function
50% average absorption of all forms of B12
10–30% of those > 50 y have atrophic gastritis
Bioavailability Assumptions for Folate
DRI Recommended Intakes
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Absorption of synthetic folate  1.7 - 2.0 x food folate
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Folate supplements taken w/water
 90% absorption
Folate added to food or taken w/food  85% absorption
Folate naturally found in food
 50% absorption
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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)
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Distribution of Reported Folate Intake
for Men and Women Aged 19+ Years
40
EAR
35
Percent
30
25
Males
Females
20
15
10
5
0
0
200
400
600
800
1000
Folate (µg)
Source: NHANES III, 1988–1994 (J. Wright)
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Distribution of Reported Folate Intake
for Men and Women Aged 19+
Years, with Higher Bioavailability
40
EARC
35
EARF
Percent
30
25
Males
Females
20
15
10
5
0
0
200
400
600
800
1000
Folate (µg)
Source: NHANES III, 1988–1994 (J. Wright)
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Importance of Data on Food
Composition and Dietary Intake
Folate intakes in surveys underestimated due to:
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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
Estimated Folate Intakes, 19-30 Years
45
40
35
30
25
20
15
10
5
0
35
10
00
11
00
12
00
13
00
14
00
15
00
90
0
80
0
70
0
60
0
µg
45
40
Unmodified Data
NHANES III
50
0
40
0
30
0
20
0
10
0
0
EAR
EAR
Men
Women
Modified Data
NHANES III
30
25
20
15
10
5
0
µg DFE
Lewis et al., 1999, AJCN, 70:198-207
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SUMMARY
Bioavailability Assumptions for Folate
DRI Recommended Intakes
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Absorption of synthetic folate  1.7 - 2.0 x food folate
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Folate supplements taken w/ water
 90% absorption
Folate added to food or taken w/food  85% absorption
Folate naturally found in food
 50% absorption
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Bioavailability Assumptions for Iron
1989 RDA
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Increased absorption with increased need
Form of iron: heme vs non-heme
Other food components
— Ascorbic acid
— Polyphenols
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— Phytate
— Fiber
Typical diet “relatively highly available”, 10–15%
Prevalence of Inadequate Intakes
1989 Iron RDA
Men
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Need:
Absorbed iron
Intake: 10% absorption
15% absorption
Women
1.3 mg
13 mg
8.7 mg
1.8 mg
18 mg
12 mg
RDA (12.5 %)
10 mg
NHANES III 19-30 y, inadequate <5%
15 mg
< 25%
Plant-based Diet, low in Vitamin C
Adjustment of Iron RDA
Need:
Intake:
Men Women
Absorbed iron
1.3 mg 1.8 mg
Assume 4% absorption 32 mg 45 mg
NHANES III 19-30 y, inadequate
92%
>95%
SUMMARY
Bioavailability Assumptions for Iron
1989 RDA
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Increased absorption with increased need
Form of iron: heme vs non-heme
Other food components
— Ascorbic acid
— Polyphenols
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— Phytate
— Fiber
Typical diet “relatively highly available”, 10–15%
Derivation of 1989 RDA for Protein
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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
Bioavailability Assumptions for Protein
1989 RDA
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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
Adjusting the 1989 RDA for Protein
for a Primarily Plant-Based Diet, Adult
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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
Impact of 1/3 Animal, 2/3 PlantBased Protein Diet, 3 yr Old
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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
SUMMARY
Bioavailability Assumptions for Protein
1989 RDA
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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
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
Food and Nutrition Board
http://www.nas.edu/iom/fnb
Publications: http://www.nap.edu
111-02