National Food Institute - Technical University of Denmark (DTU) Danish Food Composition Databank - ed. 7.01
 

 

About the food data - Vitamins

Vitamin A

For vitamin A, values are given for the vitamin A active components retinol and β-carotene. The total vitamin A effect is calculated and expressed as retinol equivalents, RE (after Nordic Nutrition Recommendations NNR 2004 [1] and National Academy of Science, Food and Nutrition Board (2001) [2]), where

1 retinol equivalent = 1 µg retinol
= 12 µg β-carotene
= 24 µg other provitamin A carotenoids

The total vitamin A effect, expressed as retinol equivalents (RE), is the sum of the food's retinol content and carotene multiplied by an activity factor, which is a measure for the relative completeness the carotenes and carotenoids are metabolised to retinol in the human body.

The factors shown above are averaged values, approximations for an average diet. It is not completely correct to use the same factors on all foods, as the activity varies between foods. Resent research show, that the activity of β-carotene and provitamin A carotenoids is lower than previously accepted. Therefore, since version 6.0 of the Danish Food Composition Databank activity factors have been half of earlier used factors for these components.

By recalculation of values given in the original reference in international units (IU) the following conversion is used

1 IU vitamin A = 0.3 µg retinol

If the reference has only indicated one value for the content of carotene, this value is assumed to represent the content of β-carotene. The error thus introduced is small as the values indicated in the reference in most cases can be considered as the content of β carotene.

Some choose to give the total vitamin A effect calculated with the above mentioned low factors (1/12 and 1/24, respectively) as Retinol Activity Equivalents (RAE), but the Danish Food Composition Databank follow the Nordic Nutrition Recommendations and therefore use Retinol Equivalents (RE) as unit for total vitamin A effect. The content of retinol and β-carotene are given with the unit µg/100 g edible part.

Vitamin D

The content of vitamin D can be determined by use of a biological method, where the results is given as vitamin D, or by use of a chemical method, where the content of vitamin D3, D2, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D is determined.

The following activity factors are used:

1 µg vitamin D3 = 1 µg vitamin D2
= 0.2 µg 25-hydroxyvitamin D

There is not full agreement between data determined by the biological and the chemical method, when the above mentioned factors are used. One reason is, that the biological method include other vitamin active compounds, which is not yet included in the chemical method. Other reasons are, that the conversion factors may not be accurate, and that the results for the biological method, which used rats as model, does not give the vitamin D activity in foods for a human being.

Furthermore, the following conversion factor exist:

1 IU vitamin D = 0.025 µg vitamin D3

The vitamin D content of foods is given with the unit µg/100 g edible part.

Vitamin E

Newer findings has shown that it is only the d-α-tocopherol form that contributes to the vitamin E activity. Other forms of vitamin E ((β tocopherol, γ-tocopherol, α-tocotrienol, etc.), which earlier were attributed vitamin E activity, do not contribute to the vitamin E activity, although absorbed (after Nordic Nutrition Recommendations NNR 2004 [1] and National Academy of Science, Food and Nutrition Board (2001) [4])).

Note that calculation of the total vitamin E activity is only valid for an average diet. Therefore, the total vitamin E activity should be regarded with reservations in the judgement of a single food.

The vitamin E activity is expressed as d-α-tocopherol equivalents, αTE, unit mg/100 g edible part.

Vitamin K

The major form of vitamin K in the diet is vitamin K1 (phylloquinone). In this databank the vitamin K content is represented by the vitamin K1 form.

Vitamin K1 is expressed as µg/100 g edible part.

Thiamin (vitamin B1)

The thiamin content of food is determined as thiamin hydrochloride, and expressed in mg/100 g edible part.

Riboflavin (B2 vitamin)

Riboflavin values are expressed as mg/100 g edible part.

Niacin

The term niacin refers to nicotinamide (nicotinic acid amide), nicotinic acid and derivatives that exhibit the biological activity of nicotinamide. For niacin, values are given for niacin as well as contribution from tryptophan, which can be converted into niacin. The values are expressed as nicotinic acid.

The total niacin activity is expressed as niacin equivalents (NE) (from National Academy of Science, Food and Nutrition Board: Recommended Dietary Allowances. 9th ed.), where

1 niacin equivalent (NE) = 1 mg niacin
= 60 mg tryptophan

The calculation of niacin equivalents is only valid for an average diet, not for the single food. Therefore, the values given in the data tables should only be regarded as indicative when judging the single food.

For cereals and cereal products, only tryptophan's contribution is used in the calculation of the niacin equivalents, as niacin in these foods most probably is not available for the human body. Although recent studies have shown that about 30% of the niacin in cereal grains is available, the traditional interpretation of 0 percent availability of niacin in cereals has been chosen until further studies support the new findings.

The total niacin activity is expressed as niacin equivalents (NE), whereas niacin and tryptophan's contribution is expressed in mg/100 g edible part.

Vitamin B6

The term vitamin B6 refers to the sum of the three naturally occurring vitamin B6 active compounds: pyridoxal, pyridoxine, and pyridoxamine and their respective phosphates and other compounds, expressed as pyridoxinehydrochloride.

The content of vitamin B6 has since approx. year 2000 been determined by use of a chemical method. Before that, a microbiological assay was used. The different vitamin B6 active components in the have different vitamin B6 activity. Therefore, older vitamin B6 values should be used with careful consideration.

The vitamin B6 content is expressed as mg/100 g edible part.

Pantothenic acid

The content of panthothenic acid is expressed as mg/100 g edible part.

Biotin

Biotin contents are expressed as mg/100 g edible part.

Folate

The folate content of foods is determined by microbiological assay. The different folate active components in foods have different folate activity, and as the present analytical methods are neither very precise nor reliable. The newest surveys carried out by the Danish Institute for Food and Veterinary Research have shown that older Danish folate values are too low.

The folate values should be used with careful consideration.

Folate content is expressed as µg/100 g edible part.

Vitamin B12

Vitamin B12 is determined as cyanocobalamin, the most stable of the cobalamins.

The vitamin B12 content is expressed as µg/100 g edible part.

Vitamin C

The term vitamin C refers to the two vitamin C active components: ascorbic acid and dehydroascorbic acid. The total vitamin C activity is the sum of the two forms. The isomers, isoascorbic acid and dehydroisoascorbic acid show little or no vitamin C activity.

Until now, only little data are available on the dehydroascorbic acid content of foods. In the older Danish vitamin C surveys only ascorbic acid has been determined. From more recent studies, it is assumed that the dehydroascorbic acid content of foods is of little significance. In some cases, though, amounts of dehydroascorbic acid corresponding to 10-30% of the ascorbic acid content can be present in foods, like it can be the case for physically handled (i.e. grated or sliced/carved) vegetables or fruits.

The vitamin C content is expressed as mg/100 g edible part.

References

[1] Nordic Nutrition Recommendations NNR 2004 - integrating nutrition and physical activity. Nord 2004:013. ISBN 92-893-1062-6 URL: http://www.norden.org/sv/publikationer/publikationer/2004-013 and in a short version

[2] National Academy of Science, Food and Nutrition Board: Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). URL: http://www.nap.edu/openbook.php?isbn=0309072794

[3] National Academy of Science, Food and Nutrition Board: Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1999). URL: http://www.nap.edu/openbook.php?record_id=5776

[4] National Academy of Science, Food and Nutrition Board: Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000). URL: http://www.nap.edu/openbook.php?record_id=9810&page=1

 

 
Department of Nutrition  -   Mørkhøj Bygade 19  -  DK-2860 Søborg, Denmark  -  Phone +45 35 88 70 00 Updated 2009-03-16