Dietary Reference Intakes for Japanese 2010: Fat-Soluble Vitamins

Abstract

S57 Vitamin A Background informationCompounds with potent vitamin A activity in vivo after oral intake include retinol; retinal; carotenoids; and 50 different types of provitamin A carotenoids, including b-carotene, a-carotene, and b-cryptoxanthin. The retinol equivalent (RE) is the vitamin A unit used in Dietary Reference Intakes for Japanese (DRIs-J) 2010, the most current Dietary Reference Intakes (DRIs) for the Japanese. Retinoic acid, a hormone binding to the nuclear receptor, is responsible for the majority of vitamin A activity in vivo, but is not converted to retinal or retinol in vivo, and its content in food is relatively low. Retinylester provitamin A carotenoids are the main forms of vitamin A contained in animal and plant foods, respectively. Retinylester hydrolase in the intestinal brush border catalyzes the hydrolysis of retinylester to retinol, which is then absorbed at a rate that ranges from 70% to 90% (1, 2). Cleavage of carotenoids yields 2 molecules of vitamin A (retinal) from b-carotene (3) and 1 molecule from other provitamin A carotenoids.In the DRIs-J 2010, the absorption rate of b-carotene is 1/6 of its total value, which is in accordance with rate in the DRIs for the United States and Canada (4). Assuming that the conversion rate of b-carotene to retinol is 50%, the bioavailability of b-carotene as vitamin A is 1/12 (1/631/2), such that 12 mg of food-derived b-carotene would correspond to 1 mg in RE units. Thus, the following formula can be used to convert the value of food-derived vitamin A-related compounds into RE units: Retinol equivalent (mg RE) 5 retinol (mg)1b-carotene (mg)31/12 1a-caro tene (mg)31/241b-cryptoxantin (mg) 31/241other provitamin A carotenoids (mg) 31/24. A word of caution is indicated when calculating the value for oil-solubilized b-carotene, as its bioavailability as a form of vitamin A is 1/2 of its total value, such that 2 mg of fat-solubilized b-carotene would correspond to 1 mg of retinol. Determining DRIsClassical vitamin A deficiency leads to corneal xerosis in infants and possibly to blindness and to night blindness in adults. Other deficiency signs include growth retardation; skeletal and neurological development defects; disturbed growth and differentiation of epi- Kobe, 658-8558, Japan (Received October 26, 2012) Summary We have determined the Dietary Reference Intakes for fat-soluble vitamins (vitamin A, vitamin D, vitamin E, and vitamin K) for the Japanese. Regarding vitamin A, the estimated average requirement (EAR) and the recommended dietary allowance (RDA) were defined for those aged 1 y old and over. For vitamin D, vitamin E, and vitamin K, the EAR or RDA was not adopted, because of the insufficient data available. Thus, the adequate intake (AI) was determined for those vitamins based on the food surveillance data and biomarkers for each vitamin. The AI for vitamin D was decided as the median intake of vitamin D in the population with a circulating 25-hydroxy vitamin D level which was high enough for bone health. The basis for the AI for vi...

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“…The World Health Organization and the Food and Agriculture Organization have set the recommended dosages for vitamin K1 at 65 µg/day for men and 55 µg/day for women, on the basis of 1 µg/day/kg body weight [31]. The European Commission has set the recommended daily allowance (RDA) for vitamin K at 75 µg/day [32]. Japan has set the AI of vitamin K at 75 µg/day for adult men and 65 µg/day for adult women by the Ministry of Health, Labor, and Welfare in 2010 [33], with both values being over 1 µg/day/kg body weight.…”

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