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NCC Home > Food and Nutrient Database > Foods, Nutrients, Food Groups > Nutrients, Nutrient Ratios, and Other Food Components > Vitamins

Vitamins

Vitamin A includes preformed vitamin A (retinol) and provitamin A carotenoids expressed as beta-carotene activity. International Units (IU) or Retinol Equivalents (RE) have been traditionally used to describe total vitamin A activity. A more recent definition, Retinol Activity Equivalents (RAE), reduces by half the vitamin A activity of the carotenoids.

Vitamin A values are analyzed or are calculated from the following:
RE Vitamin A = mcg retinol + (mcg beta-carotene equivalents/6)
IU Vitamin A = (mcg retinol/0.3) + (mcg beta-carotene equivalents/0.6)
RAE Vitamin A = mcg retinol + (mcg beta-carotene equivalents/12)
Beta carotene equivalents include vitamin A activity from the provitamin A carotenoids: beta-carotene, alpha-carotene, and beta-cryptoxanthin. Beta-carotene equivalents are calculated from the following:
mcg beta-carotene equivalents = mcg beta-carotene + (mcg alpha-carotene + mcg beta-cryptoxanthin)
Values are expressed in micrograms. 6 mcg beta-carotene equivalents provide 0.5 RAE vitamin A, 1 RE vitamin A, or 10 I.U. vitamin A.

Retinol is preformed vitamin A found only in animal products. Values are given in micrograms. 1 mcg retinol provides 1 RE (or RAE) vitamin A or 3.33 I.U. vitamin A.

Vitamin D includes calciferol (Vitamin D2) and cholecalciferol (Vitamin D3). Values are expressed in micrograms.
0.025 mcg vitamin D = 1 I.U.
Vitamin E (total alpha-tocopherol) has recently been redefined as limited to the following forms of alpha-tocopherol:
  • RRR-alpha-tocopherol, the form of alpha-tocopherol that occurs naturally in food, and
  • 2-R-stereoisomeric forms of alpha-tocopherol that occur in fortified foods and supplements

(Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, 2000).

Synthetic alpha-tocopherol used in fortified foods and supplements provides less than half of the vitamin E activity as the natural form of alpha-tocopherol. Vitamin E currently is expressed in milligrams.
mg vitamin E (total alpha-tocopherol) = mg natural alpha-tocopherol + (mg synthetic alpha-tocopherol x 0.45)
Many fortified foods and supplements continue to label vitamin E in international units (IU), where 0.67 mg of natural alpha-tocopherol or 1.0 mg of synthetic alpha-tocopherol equals 1 IU of vitamin E.
vitamin E (IU) = (mg natural alpha-tocopherol/0.67) + (mg synthetic alpha-tocopherol/1.0)
Natural alpha-tocopherol, also called d-α-tocopherol or RRR-α-tocopherol, is the form of alpha-tocopherol that occurs naturally in foods. It is expressed in milligrams.
mg natural alpha-tocopherol = IU vitamin E x 0.67
Synthetic alpha-tocopherol, also called dl-α-tocopherol or all-rac-α-tocopherol, includes eight stereoisomers of alpha-tocopherol in equal amounts. Only four of these isomers are in the 2-R-stereoisomeric form and are biologically active as vitamin E. Synthetic vitamin E also may be listed on the label of fortified foods or supplements as dl-α-tocopheryl acetate or dl-α-tocopheryl succinate. In the NDSR, values for synthetic alpha-tocopherol are as milligrams.
1 mg synthetic alpha-tocopherol = 1 IU vitamin E = 0.45 mg vitamin E
Total alpha-tocopherol equivalents (α-TE) are determined from alpha-, beta-, gamma-, and delta-tocopherols and previously was used as the measure of vitamin E activity. Currently only alpha-tocopherol is recognized as contributing to vitamin E. Because the other naturally occurring tocopherols are not converted to alpha-tocopherol in humans, they are no longer used to determine vitamin E activity. α-TE values continue to be maintained in the database for studies that still want to use them as a vitamin E measure or want to compare current data with α-TE values used in the past. α-TE values are expressed in milligrams.
mg α-TE = mg natural alpha-tocopherol + (0.4 x mg beta-tocopherol) + (0.1 x mg gamma-tocopherol) + (0.01 x mg delta-tocopherol) + mg synthetic alpha-tocopherol
The Third National Health and Examination Survey (NHANES III) estimated that 80 percent of the α-TE from foods in the survey was alpha-tocopherol (Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, 2000). Therefore to estimate the milligrams of vitamin E (total alpha-tocopherol) from α-TE values of daily diets typical in the United States, the following factor may be used:
mg vitamin E (total alpha-tocopherol) in a meal = mg α-TE in a meal x 0
Vitamin K values are for vitamin K1 (phylloquinone) which is found in natural food sources, but do not include vitamin K2 (menaquinone), the form synthesized by bacteria in the human intestines. Generally, values are those derived by high-performance liquid chromatography and are reported in micrograms.

Vitamin C represents total vitamin C expressed as the activity of reduced ascorbic acid. Values are in milligrams.

Thiamin (also known as vitamin B1) includes both bound and free forms and is expressed in milligrams.

Riboflavin (also known as vitamin B2) includes both bound and free forms. Values are in milligrams.

Niacin includes bound and free forms. Values do not include amounts that could be contributed by the precursor, tryptophan. Amounts are given in milligrams.

Niacin Equivalents (NE) include the amount of niacin provided by the conversion of tryptophan to niacin, and also are expressed in milligrams. Niacin equivalents are calculated by the following:
mg NE = mg niacin + (mg tryptophan/60)
Pantothenic acid values include both free and bound forms which have been determined by microbial assay or radioimmunoassay. They are expressed in milligrams.

Vitamin B6 includes three forms, pyridoxine, pyridoxal and pyridoxamine. Values are determined microbiologically or by liquid chromatography and are expressed in milligrams.

Total Folate consists of a group of biologically active compounds, pteroylglutamic acid (PGA) and its derivatives. Values include all forms of natural PGA, both bound and free, as well as synthetic folic acid. Values selected are those measured with L. casei using conjugase treatment for release of bound forms and ascorbic acid for protection from oxidation. Amounts are given in micrograms.

Dietary Folate Equivalents (DFE) are units that account for differences in absorption between natural folate and synthetic folate and are calculated as follows:

For folate occurring in food:
mcg DFE = mcg natural folate + (1.7 x mcg synthetic folate)
For folate occurring in dietary supplements:
mcg DFE = 2 x mcg synthetic folate
Natural Folate is that which occurs naturally in foods, usually as pteroylpolyglutamates.

Synthetic Folate is in the form of folic acid (pteroylmonoglutamic acid) and is used in fortified foods and vitamin supplements.

Vitamin B12 occurs in several forms designated as cobalamin. Values are generally those obtained by assay with L. leichmanni. Vitamin B12 is found only in animal products. Values are expressed in micrograms.

 
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