β-Carotene–vitamin A equivalence in Chinese adults assessed by an isotope dilution technique

• Published in: British journal of nutrition Vol. 91; no. 1; pp. 121 - 131
• Main Authors: Wang, Zhixu, Yin, Shian, Zhao, Xianfeng, Russell, Robert M., Tang, Guangwen
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.01.2004
• Subjects: Absorption; adults; Antioxidants - metabolism; Area Under Curve; beta Carotene - blood; beta Carotene - metabolism; beta Carotene - pharmacokinetics; beta-carotene; Biological and medical sciences; Biological conversion efficiency; blood serum; Chinese people; Chromatography, High Pressure Liquid - methods; Deuterium; Feeding. Feeding behavior; Female; females; Fundamental and applied biological sciences. Psychology; high performance liquid chromatography; Humans; Indicator Dilution Techniques; intestinal absorption; ionization; Isotope dilution technique; Liver - metabolism; Male; males; Mass Spectrometry - methods; Middle Aged; stable isotopes; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitamin A; Vitamin A - blood; Vitamin A - metabolism; volunteers; β-Carotene; Vitamin A; Biological conversion efficiency; Isotope dilution technique; β-Carotene; Human; Vertebrata; Mammalia; Carotene; Vitamin; β-Carotene: Vitamin A: Biological conversion efficiency: Isotope dilution technique; Isotope dilution; Adult; Chinese; Technique; Retinol
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1079/BJN20031030

The present study was carried out to determine the conversion factor of synthetic 2H-labelled β-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 d experiment. The volunteers (nine males and six females) were each given a physiological dose of [2H8]β-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, and 13 h on the first and the fourth days of the study, daily for 10 d, and then weekly from days 14 to 56. β-Carotene and retinol were extracted from serum and isolated by HPLC, and their enrichments were respectively determined by using GC–electron capture negative chemical ionisation-MS and LC–atmospheric pressure chemical ionisation interface-MS. Four of the subjects exhibited β-carotene to vitamin A conversion factors of >29·0:1 on a molar basis and were termed ‘poor converters’. In the eleven normal converters (seven males and four females), the calculated conversion factors of β-carotene to retinol ranged from 2·0:1 to 12·2:1 with an average of 4·8 (sd 2·8):1 on a molar basis, and from 3·8:1 to 22·8:1 with an average of 9·1 (sd 5·3):1 on a weight basis. The 52 d post-intestinal absorption conversion was estimated to be about 30 % of the total converted retinol.