This document discusses Dietary Reference Intakes (DRIs), which are nutrient-based reference values used to assess dietary needs. DRIs include the Estimated Average Requirement, Recommended Dietary Allowance, Adequate Intake, Tolerable Upper Intake Level, and Acceptable Macronutrient Distribution Ranges. The Recommended Dietary Allowance is set at the EAR plus two standard deviations to cover 98% of the population's needs. Examples of vitamin C and calcium DRIs are provided to illustrate how the values are determined based on scientific studies and potential for toxicity.

1. Dietary
Reference
Intakes
Dr CSN Vittal

2. DRI Process
• North American Initiative from Institute of Medicine
and Health Canada
• Introduced in 1967
• Intended to replace 1989 RDAs and 1990 RNIs

3. WHAT ARE DIETARY REFERENCE INTAKES
• Dietary Reference Intakes (DRIs) comprise a set of
nutrient-based reference values, each of which has
special uses.

4. Components of the DRIs
1. EAR: Estimated Average
Requirement
2. RDA: Recommended Dietary
Allowance
3. AI: Adequate Intake
4. UL: Tolerable Upper Intake Level
5. AMDR: Acceptable Macronutrient
Distribution Ranges

6. EAR and RDA values
• EAR
– obtain scientific data to estimate the
average requirement for a nutrient
– Add 2 SD to this value so that 98% of
popn has their requirement met
– Resulting value is RDA
• RDA = EAR + 2 SD

8. Use of DRIs
• Apply to healthy people
• RDA is generous: covers 98% of popn
• Compare to usual (average) intake, not
intake on any given day
• RDA is goal for an individual
• EAR used to assess groups

9. RDA
• RDA is the average daily dietary intake
level that is sufficient to meet the
nutrient requirement of nearly all (97 to
98 percent) healthy individuals in a
particular gender and life stage group
(life stage considers age and, when
applicable, pregnancy or lactation).

10. RDA
• The RDA for a nutrient is a value to be
used as a goal for dietary intake by
healthy individuals.
• The RDA is not intended to be used to
assess the diets of either individuals or
groups or to plan diets for groups.

11. Adequate Intake
• Nutrients Without an EAR – Do Not Have RDA
Need scientific studies to determine EAR
• The AI is based on observed or experimentally
determined estimates of nutrient intake by a
group (or groups) of healthy people.
• The main intended use of the AI is as a goal
for the nutrient intake of individuals.
• Calcium, Vitamin D, Fluoride, Biotin, Pantothenic acid (and all
infant values)

12. Tolerable Upper Intake Level
• For nutrients Recognized as Toxic
• Often based on case reports, not
studies
• ULs are useful because of the increased
interest in and availability of fortified
foods and the increased use of dietary
supplements.

13. Examples to Illustrate DRIs
• Vitamin C
• Has an EAR
• Has an RDA
• Has a UL
• Important yet not
much is known
• Calcium
• No EAR
• Has an AI
• Has a UL
• Important but
controversial

14. Vitamin C
• In cells Enzyme cofactor for collagen synthesis
• Involved in synthesis of hormones,
neurotransmittors
• Now recognized as important anti-oxidant
• Increases Fe absorption
•   plasma  urine excretion
•  in specialized tissues: WBCs

15. EAR and RDA for Vitamin C
• EAR = 75 mg for adult men
60 mg for women
• Based on following study:
– 7 healthy men lived in for 6 months
– Fed low C diet (5 mg/d) until depleted
– Given graded doses until steady state reached
– Measured serum, neutrophil, and urine ascorbate

16. EAR for Vitamin C
• At 100 mg, neutrophils were saturated with
acorbate in 4/7 subjects, but urine excretion
was high (25% of dose)
• At 60 mg, neutrophils were not quite saturated,
but urine excretion 0 %
• Panel chose value between 60 and 100 => 75
mg, as level of “adequate” vitamin C levels in
WBCs

17. RDA for Vitamin C
• Use RDA as a goal for an individual
• RDA = EAR + 2 SD
• Men: RDA = 75 + 2(7.5) = 90 mg
• Women: RDA = 60 + 2 (6) = 75 mg (rounded)
• Smokers – need more
– Add 35 mg to RDA

18. Toxicity of Vitamin C
• Many “problems” attributed to vitamin C
– Excess urinary oxalate excretion, increased uric acid
excretion in urine  kidney stones
– Pro-oxidant
–  Fe absorption  iron overload
–  serum B12
– Rebound scurvy
• DRI panel found no evidence for anything
except GI disturbances (osmotic diarrhea)

19. UL for Vitamin C
• Uncontrolled cases and several controlled
studies show that some people get GI
disturbances at >3 g
• 3 g = LOAEL
• Since UL is set so no risk of adverse effects,
Then UL = 3/1.5 = 2 g (~ NOAEL)

20. Thank You
• Dr CSN Vittal