Vitamin A in new food composition tables from Japan

Standard Tables of Food Composition in Japan--Fourth Revised Edition--were issued to the public in October 1982. The data for vitamin A include chemically determined preformed vitamin A and provitamin A. Vitamin A values in the tables are shown as micrograms of retinol and/or micrograms of carotene and also as international units of retinol potency per 100 g edible portion of the foods. The term "carotene" is used for the total mixed carotenoids with vitamin A activity analyzed. In fact, the carotenes analyzed consisted of a large portion of beta-carotene and a small portion of alpha-carotene. One retinol potency (IU) is equivalent to 0.3 micrograms of retinol or 1.8 micrograms (0.6 micrograms X 3) of carotene, which means that the biologic activity of carotenoids is considered to be one-third that of retinol, mainly due to the inferior absorption of carotene. However, as an exception, in milk and dairy products 1 IU is considered to be equivalent to 0.6 micrograms of carotene. As for the foods for which both retinol and carotene contents are given in the table, the retinol potency is calculated by addition of values derived from both retinol and carotene. There are considerable differences in vitamin A values of some foods between the third revised edition and the fourth revised edition of the Standard Tables of Food Composition in Japan. The mean daily vitamin A intake of Japanese people as determined by the recent national nutrition survey was 2,120 IU when the calculation was made from the data in the fourth revised edition and 1,762 IU when the calculation was made from the data in the third revised edition, indicating approximately a 20% larger value in the former than the latter. This fact has to be taken into consideration in the comparison between new data and previous data from nutrition surveys.