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Fatty acids

For fatty acid values, tagnames are assigned which identify whether the values are expressed per quantity of edible portion of food or per quantity of total fatty acids in the food. The tagnames for values expressed per quantity of edible portion of food are subsidiary to the < comp> structural tag, while the tagnames for values expressed per quantity of total fatty acids are subsidiary to the <drvd-comp> structural tag. If the quantity of total fatty acids appears, it is identified with the <FACID> tagname, subsidiary to <comp>. All fatty acid tagnames are listed below with their respective structural tags.

Fibre

There is no standard definition for dietary fibre. Dietary fibre values are highly dependent on the analytical method used to determine those values and the chemical components included in the measurements. Therefore, before a tagname can be assigned to a dietary fibre value, it is necessary to know exactly how that value was determined. The available tagnames for dietary fibre are listed below. They include a tagname that can be assigned to fibre values when the method of determination is not known. All fibre tagnames are subsidiary to the < comp> structural tag.

Values for the non-starch and non-cellulosic polysaccharide components of dietary fibre should be identified using the following tagnames:

Tagnames also exist for identifying data on the individual components of dietary fibre: algal polysaccharides, cellulose, gums, hemicellulose, lignin, mucilages, pectins, and resistant starch.

Folate

"Folate", "folacin", and "folic acid" are three terms used to describe the same food component. Most frequently, folate values represent total folate and should be assigned the tagname < FOL > . Some food composition tables also include values for free folate; these values are identified by tagname < FOLFRE >.

Glycerides

Values representing the quantity of total glycerides in a food are dependent on whether they were determined by analysis or by calculation from the fatty acid composition using conversion factors. The tagnames for total glyceride values are method-dependent and are listed below, along with a tagname that can be assigned to total glyceride values when the method of determination is not known. All of these tagnames are subsidiary to the <comp> structural tag.

Iron

The iron values in food composition tables usually represent the quantity of total iron in the foods. Tagname <FE> is used to identify such values. Some food tables also contain values for haem and non-haem iron, which should be identified by the tagnames < HARM > and < NHAEM > respectively.

Niacin

Most niacin values in food composition tables include both the nicotinie acid and the nicotinamide found in the food. Historically, however, niacin was synonymous with nicotinic acid, so one must be certain before assigning a tagname to a "niacin" value whether that value includes the quantity of nicotinamide.

Another factor to consider before an appropriate tagname can be assigned to a niacin value is whether that value represents only the preformed niacin in the food or whether it also includes the niacin equivalents derived from tryptophan.

The selection of tagnames for niacin data are listed below. All are subsidiary to the <comp> structural tag.

Nitrogen

Most nitrogen values in food composition tables represent total nitrogen. However, some sources also include data for the protein, non-protein, and amino nitrogen components. Individual tagnames,listed below, are used to identify the particular nitrogen component. All are subsidiary to the <comp> structural tag.

Protein

By far the most popular method of determining the total protein content of a food is by calculation from the total nitrogen value using an appropriate conversion factor (i.e., tagname < PROCNT> is appropriate in most cases). It is also possible to determine a value for total protein by calculation from the amino nitrogen or protein nitrogen components or by direct protein analysis. The tagnames for total protein values, as listed below, reflect these various methods of determination. A tagname is also provided for identifying total protein values for which the method of determination is unknown. All of these tagnames are subsidiary to the <comp> structural tag.

Selenium

The selenium values in food composition tables usually represent the total selenium in a food. Such values should be assigned tagname <SE>. Interest in the distinction between organic and inorganic selenium has also generated data for these two components, which should be identified by the tagnames < SEO > and < SEIO > respectively.

Starch

Most starch values in food composition tables represent the quantity of total starch in a food. These values may be expressed as a quantity of starch or in terms of its monosaccharide equivalents. Values for resistant starch, a measure of the quantity of non-digestible starch (see the section "Fibre" above), also appear in sources of food composition data. The relevant tagnames for starch values are listed below. All are subsidiary to the < comp > structural tag.

Sugar

Data labelled as "sugar" usually represent the quantity of total sugars (free monosaccharides plus disaccharides) in a food. These values may be expressed either as a quantity of sugars or in terms of their monosaccharide equivalents. Data also exist for the quantity of reducing and non-reducing sugars and for the quantity of invert sugar in a food. The appropriate tagnames for all of these data values are listed below. All are subsidiary to the <comp> structural tag.

It is also quite common to find data values in food composition tables for individual sugar components. When not further specified, these values usually include only the free monosaccharide or disaccharide. However, some food tables also contain values for the sugar components found in dietary fibre. Therefore, two tagnames have been created for each sugar component in order to specify this distinction. These tagnames are listed below. All are subsidiary to the <comp> structural tag.

Vitamin A

Nutrient values labelled "vitamin A" in different food composition tables and nutrient data bases may represent different portions of the total vitamin A activity in a food. Therefore, it is essential to know what is included in a particular "vitamin A" value before a tagname is assigned to that value.

Total vitamin A includes both retinol (also called "preformed vitamin A") and carotene (also called "vitamin A precursor"). Total vitamin A is usually calculated as the total vitamin A activity contributed by retinol, beta-carotene, and other active carotenoids. This calculated value is expressed in retinol equivalents (RE) and is sometimes referred to simply as "retinol equivalents". It is calculated according to the following formula:
total vitamin A (RE) = mcg of retinol + 1/6 mcg of beta-carotene + 1/12 mcg of other active carotenoids

Total vitamin A may also be determined directly by bioassay and expressed in international units (IU). The tagnames for identifying total vitamin A values distinguish between those values that were calculated from retinol and the active carotenoids and those determined by bioassay. A tagname is also available for use when the method of vitamin A determination is not known. These three tagnames are listed below. All are subsidiary to the <comp> structural tag.

<VITA> values are usually expressed in retinol equivalents, and <VITAA> values are usually expressed in international units. However, a value expressed in one unit may be converted to the other unit according to the following formulae:

1 mcg retinol = 3.3 IU of retinol
1 RE from beta-carotene = 10 IU of beta-carotene

Beta-carotene equivalents (also called "provitamin A carotenoids") are a measure of the vitamin A activity contributed by the active carotenoids. As indicated in the above formula for calculating vitamin A in retinal equivalents, beta-carotene has twice the vitamin A activity of the other active carotenoids. Therefore, beta-carotene equivalents are calculated according to the following formula:
mcg of beta-carotene equivalents = mcg of betacarotene + 1/2 the mcg of other active carotenoids

The tagname for beta-carotene equivalents is listed below, as are the tagnames for identifying data on the retinol and active carotenoid components that can contribute to the calculated total vitamin A value. All are subsidiary to the <comp> structural tag.

Vitamin B-6

The quantity of vitamin B-6 in a food can be determined either by direct analysis or by summation of the component quantities of pyridoxal, pyridoxamine, and pyridoxine. Since these two methods tend to produce different results, separate tagnames have been created to identify the method used to determine the vitamin B-6 values. These tagnames are listed below, along with a tagname that can be used for vitamin B-6 values when the method of determination is unknown. All are subsidiary to the <comp> structural tag.

Tagnames are also available for data on the pyridoxal, pyridoxamine, and pyridoxine components of vitamin B-6.

Vitamin C

Vitamin C is a measure of the sum of the L-ascorbic acid and the L-dehydroascorbic acid in a food. The tagname < VITC > is used to identify data values which represent this sum, the tagname <ASCL> is used to identify data values which represent only the quantity of L-ascorbic acid, and the tagname <ASCDL> is used to identify data values which represent only the quantity of L-debydroascorbic acid. Some food composition tables commonly label vitamin C values as "ascorbic acid", so it is essential before assigning a tagname to determine whether the values truly represent only L-ascorbic add or whether they are a measure of L-ascorbic acid plus L-dehydroascorbic acid (vitamin C).

Vitamin D

Vitamin D is most commonly determined by calculation as the sum of ergocalciferol (also called vitamin D-2) and cholecalciferol (also called vitamin D-3). Historically, it was determined by bioassay. In some food tables and nutrient data bases, vitamin D is labelled as "calciferol", so it is important not to confuse this name with the ergocalciferol and cholecalciferol components of vitamin D.

Tagnames for vitamin D, based on its method of determination, and the components of vitamin D are listed below. All are subsidiary to the < comp> structural tag.

Vitamin E

Vitamin E is most commonly determined by calculation as the sum of the vitamin E activities of the active tocopherols and tocotrienols in a food. This calculated vitamin E value is expressed as alpha-tocopherol equivalents. It is important not to confuse values for alpha-tocopherol equivalents, a measure of total vitamin E, with values for alpha-tocopherol, one of the tocopherol components contributing to the total vitamin E activity.

Historically, vitamin E has also been determined by bioassay. These values are usually expressed in international units (IU). It is possible to convert between alpha-tocopherol equivalents and international units by using the following equation:

1 mg alpha-tocopheroJ equivalents = 1.49 IU

The tagnames for vitamin E, which are based on its method of determination, and for the tocopherol and tocotrienol components of vitamin E are listed below. All are subsidiary to the < comp > structural tag.

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