Vitamin A equivalence of spirulina beta-carotene in Chinese adults assessed by stable isotope dilution and reference techniques

Authors: WANG, JIE - NIN&FS CHINA CDC; WANG, YIN - INST OF HEALTH FOOD, CH; WANG, ZHIXU - QINGDAO UNIV, CHINA; LI, LEI - JM USDA HNRCA @ TUFTS; QIN, JIAN - JM USAD HNRCA @ TUFTS; LAI, WEIQI - INST OF HEALTH FOOD, CH; FU, YING - INST OF HEALTH FOOD, CH; SUTER, PAOLO - UNIV HOSP SWITZERLAND; Russell, Robert; GRUSAK, MICHAEL - USDA-ARS CNRC TEXAS; Tang, Guang-Wen; YIN, SHIAN - NIN&FS CHINA CDC

Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2008
Publication Date: 6/1/2008
Citation: Wang, J., Wang, Y., Wang, Z., Li, L., Qin, J., Lai, W., Fu, Y., Suter, P., Russell, R., Grusak, M.A., Tang, G., Yin, S. 2008. Vitamin A equivalence of spirulina beta-carotene in Chinese adults assessed by stable isotope dilution and reference techniques. American Journal of Clinical Nutrition. 87:1730-1737.

Interpretive Summary: Spirulina a blue-green algae that has been used as a high-protein food supplement. The algae is rich in carotenoids and the provitamin A carotenoids, beta-carotene, that may convert to vitamin A in human small intestine to provide vitamin A. However, the efficiency of spirulina beta-carotene conversion to vitamin A was not clear. The study aimed at determining the vitamin A equivalence of spirulina beta-carotene in humans using intrinsically labeled spirulina beta-carotene. When spirulina was grown in cultural solution of a 23 atom% heavy water, spirulina beta-carotene showed the labeled 10 units heavier beta-carotene. This labeled beta-carotene was taken by ten healthy Chinese male subjects with normal vitamin A status and Body Mass Index. A known amount of labeled vitamin A was given to the subjects as reference dose. Our results showed that the mean (+/-SD) conversion factor of spirulina beta-carotene to retinol was 4.5 +/- 1.6 (range 2.3–6.9) by weight. It was estimated that 80% of the conversion occurred within the first 24 h after taking spirulina. Therefore, spirulina is one of the plant foods that can provide vitamin A very effectively. This may related to its simple cell matrix.

Technical Abstract: Background: Spirulina is a high-protein food supplement that contains carotenoids. Objective: The study aimed at determining the vitamin A equivalence of spirulina beta-carotene in humans. Design: Spirulina was grown in a 23 atom% 2H2O cultural solution. Spirulina beta-carotene showed the highest abundance of enrichment as [2H10] trans beta-carotene. Ten healthy Chinese male subjects with a mean (+/- SD) serum retinol concentration of 1.7 +/- 0.3 µmol/L and a BMI of 23 +/- 3 kg/m2 consumed 5.8 µmol of [13C10] retinyl acetate in oil as a reference dose with a breakfast containing 13 g of fat. One week later, each subject consumed 7.9 µmol of trans beta-carotene in spirulina with a breakfast containg 22 g of fat. Low carotenoid and vitamin A diets were followed by all the subjects. Forty blood samples were collected from each subject over 56 days. Concentrations and enrichments of retinol and beta-carotene in serum samples were determined by using HPLC and mass spectrometry. Results: The mean (+/-SD) area-under-the-curve (AUC) for the total labeled serum beta-carotene response was 129.7 +/- 112.5 nmol•d/µmol of spirulina beta-carotene. For [13C10]retinyl acetate, the mean (+/-SD) conversion factor of spirulina beta-carotene to retinol was 4.5 +/- 1.6 (range 2.3–6.9) by weight. It was estimated that 80% of the conversion occurred within the first 24 h after taking spirulina. Conclusions: In a group of well-nourished, non-overweight Chinese males following low vitamin A diets, 4.5 mg of beta-carotene in spirulina consumed with 22 g of fat has the same vitamin A activity as 1 mg of retinyl acetate.