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Recommended Daily Allowance vs Optimal Daily Intake


Recommended Daily Allowance (RDA)

The RDA is defined as, "the daily dietary intake level of a nutrient considered sufficient to meet the requirements of nearly all (97–98%) healthy individuals in each life-stage and gender group." So in plain english, this is the amount of nutrients any healthy person requires, on a daily basis, to survive. NOTE: HEALTHY PERSON

Optimal Daily Intake (ODI)

This is a level of intake that takes into consideration a person's genetic background, their environment - both in their home and their place of employment (or where they spend the majority of the day) - as well as their daily habits such as smoking, drinking, stress levels, prescription medications, and other factors unique to them. In considering all of these factors, the ODI would reveal an optimal level of intake for an individual. Each person has individual optimal requirements which depend on his or her unique biological makeup and living situation. Because of the uniqueness in requirements among people, establishing an average intake level can be very difficult. It thus becomes more useful for individuals rather than for the general population. So, this is the amount of nutrients, an individual with unique circumstances and health issues, requires to suvive.

For example: the RDA for vitamin B6 is 2mg. Vitamin B6 is used for a number of functions in the body and the general population will survive on that RDA. Now take a person who works in a stressful environment, possibly drinks a bit too much and tends towards depression due to the stress. 2mg is never going to be enough to help the body cope with stress, let alone cope with the depression, drinking and other ailments that WILL eventually crop up. The ODI of 10-25mg would be more appropriate to help the person and their body cope with their lifestyle and instead of just surviving, they'll correct the deficiency and begin to thrive.

RDA vs ODI table


An international unit (IU) is a measurement used to calculate the amount of Vitamin A, Vitamin D or Vitamin E. The following table shows the amount of each of these vitamins in milligrams (mg) or micrograms (µg) that is equivalent to 1 international unit.

Vitamin A: 1 IU = 0.3µg retinol or 3.6 µg beta-carotene
Vitamin D: 1 IU = 0.025µg
Vitamin E: 1 IU = 0.67 mg

So for example if a vitamin label quotes that a product contains 40 IU vitamin D, this is equivalent to 1µg vitamin D.
(40 x .025 = 1µg vitamin D)

Vit A 100 IU = 30 mcg = 0.03 mg
Vit D 100 IU = 2.5 mcg
Vit E 100 IU = 66.67 mg

For Vitamin A,

1 IU = 0.3µg retinol,
3.6µg b-carotene, or
7.2µg other vitamin A carotenoids

For Vitamin D,

1 IU = 0.025µg cholecalciferol

For Vitamin E,

1 IU = 0.67µg natural alpha – tocopherol (different conversion factors are used for different forms of vitamin E)

Vitamin A Conversions:

1 IU = 0.3 mcg all-trans retinal = 0.3 mcg retinol = 0.344 mcg retinyl acetate = 0.55 mcg retinyl palmitate = 3.6 mcg Beta-Carotene
1 mcg Retinol = 3.34 IU of vitamin A activity
1 mg of all-trans Beta-Carotene = 1667 IU of Vitamin A activity
1 mcg Beta-Carotene = 1.67 IU of Vitamin A activity
1 mcg dietary Beta-Carotene = 0.167 mcg retinal

Retinol Equivalents (RE) = the Vitamin A activity in foods

1 RE = 1 mcg all-trans retinal = 1 mcg retinal = 3.33 IU Retinol
1 RE = 6 mcg all-trans Beta-Carotene = 6 mcg Beta-Carotene
1 RE = 12 mcg other provitamin A carotenoids

Vitamin D Conversion:

1 IU = 0.025 mcg of cholecalciferol (Vitamin D3)
1 mcg Vitamin D (cholecalciferol) = 40 IU
1 mcg 25-hydroxyvitamin D = 80 IU
1 mcg 1,25-dihydroxyvitamin D = 200 IU

Vitamin E Conversion:

1 IU = 0.67 mg of d-alpha-tocopherol or 0.45 dl-alpha-tocopherol
1 mg = 1.49 IU d-alpha-tocopherol (natural vitamin E; RRR-alpha-tocopherol)
1 mg = 1.10 dl-alpha-tocopherol (synthetic vitamin E; all-rac-alpha-tocopherol)


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