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.
[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.nal.usda.gov/fnic/etext/000105.html
[3] National Academy of Science, Food and Nutrition Board:
Dietary Reference Intakes for Calcium, Phosphorus, Magnesium,
Vitamin D, and Fluoride (1999). URL: http://www.nal.usda.gov/fnic/etext/000105.html
[4] National Academy of Science, Food and Nutrition Board:
Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and
Carotenoids (2000). URL: http://www.nal.usda.gov/fnic/etext/000105.html
Department of Nutrition - Mørkhøj Bygade 19 - DK-2860 Søborg, Denmark - Phone +45 35 88 70 00
