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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #161939
Title: BETA-CAROTENE-VITAMIN A EQUIVALENCE IN CHINESE ADULTS ASSESSED BY AN ISOTOPE DILUTION TECHNIQUE

Author
item WANG, ZHIXU - QINGDAO UNIV MED, CHINA
item YIN, SHIAN - NTL INST NUTRI FOOD SFTY
item ZHAO, XIANFENG - IBID
item RUSSELL, ROBERT - TUFTS-HNRCA
item TANG, GUANGWEN - TUFTS-HNRCA

Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2003
Publication Date: 1/1/2004
Citation: Wang, Z., Yin, S., Zhao, X., Russell, R.M., Tang, G. 2004. Beta-carotene-vitamin a equivalence in chinese adults assessed by an isotope dilution technique. British Journal of Nutrition. 91(1):121-31.

Interpretive Summary: Beta-carotene, a substance that is converted to vitamin A, is a major dietary component. To determine the efficiency of the conversion of beta-carotene to vitamin A, approximately 6 mg of pure beta-carotene, an amount comparable to that found in a meal rich in fruits and vegetables, was given to 15 healthy Chinese adult volunteers aged 50~60 years. The beta-carotene was labeled so that the efficiency of its breakdown in the body to vitamin A could be exactly determined. In addition, a reference dose of pure vitamin A (labeled differently) was given on the fourth day of the study. Serum samples were collected at multiple time points on the first and the fourth days of study, daily for 10 days, and then weekly during days 14 to 56. Blood samples were then collected over 56 days. Four of the subjects exhibited beta-carotene to vitamin A conversion factors of greater than 29.0 to 1 by mole and were termed 'poor converters'. In the 11 normal converters the calculated conversion factor of beta-carotene to retinol ranged from 2.0~12.2 to 1 with an average of 4.8+/-2.8 to 1 on a molar basis, or 3.8~22.8 to 1 with an average of 9.1 +/- 5.3 to 1 on a weight basis. The 52-day post-intestinal absorption conversion was estimated to be ~ 30% of the total converted retinol.

Technical Abstract: This study was done to determine the conversion ratio of synthetic deuterium labelled beta-carotene to vitamin A in Chinese adults by using a stable isotope dilution technique. Fifteen healthy volunteers aged 50~60 years were recruited for a 55 day experiment. The volunteers (9 males and 6 females) were each given a physiological dose of **2H8 beta-carotene (6 mg) in oil on the first day of the experiment, and a reference dose of **2H8 retinyl acetate (3 mg) in oil was given on the fourth day. Serum samples were collected at 0, 3, 5, 7, 9, 11, 13 hours on the first and the fourth days of study, daily for 10 days, and then weekly from days 14 to 56. beta-carotene and retinol were extracted from serum and isolated by HPLC, and their enrichments were respectively determined by using GC/ECNCI-MS and LC/APCI-MS. Four of the subjects exhibited beta-carotene to vitamin A conversion factors of > 29.0 to 1 by mole and were termed 'poor converters'. In the 11 normal converters (7 males and 4 females), the calculated conversion factor of beta-carotene to retinol ranged from 2.0~12.2 to 1 with an average of 4.8+/-2.8 to 1 on a molar basis, or 3.8~22.8 to 1 with an average of 9.1 +/- 5.3 to 1 on a weight basis. The 52-day post-intestinal absorption conversion was estimated to be ~ 30% of the total converted retinol.