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United States Department of Agriculture

Agricultural Research Service


item Hickenbottom, Sabrina
item Follet, Jennifer
item Lin, Yumei
item Dueker, Stephen
item Burri, Betty
item Neidlinger, Terry
item Clifford, Andrew

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2002
Publication Date: 7/13/2002
Citation: Hickenbottom, S.J., Follet, J.R., Lin, Y., Dueker, S.R., Burri, B.J., Neidlinger, T.R., Clifford, A.J. 2002. Variability in conversion of b-carotene to vitamin a in men as measured by using a double-tracer study design. American Journal of Clinical Nutrition. American Journal of Clinical Nutrition. 75:900-907.

Interpretive Summary: Vitamin A deficiency is the most common cause of nutritional blindness in the world, and a leading cause of death in young children. Fruits and vegetables containing beta-carotene (such as carrots, mangos, and sweet potatoes) are the major sources of vitamin A for all people who cannot afford or do not wish to eat large amounts of meat and milk. However, results from studies that have tried to correct vitamin A deficiency with beta-carotene rich fruits and vegetables have been disappointing. There are many reasons why these programs have been disappointing; including the possibilities that they were given to children who were already sick, or that they used the wrong type of vegetables. We measured how well pure beta-carotene is converted to vitamin A in healthy men using advanced scientific techniques. We found that even when we fed beta-carotene to healthy adult men under ideal conditions, beta-carotene absorption was poor and variable. Once beta-carotene was absorbed,it converted to vitamin A well. So, these experiments proved that beta-carotene absorption is the problem (instead of its metabolism). They also showed that beta-carotene absorption is poor and variable even under ideal conditions, which is an important finding that will be used in public health programs that seek to correct vitamin A deficiency.

Technical Abstract: The vitamin A activity of B-carotene is variable and surprisingly low in women. The reasons for this are not well understood. The vitamin A activity of B-carotene in men is still uncertain. Contributions of dietary factors compared with individual traits are largely unknown. Objective: Our objective was to measure the intrinsic variablility in the vitamin A activity of B-carotene among healthy, well-fed men living in a controlled environment. Design: We used a double-tracer test retest design. We dosed 11 healthy men orally with 30 umol hexadeuterated (D6) retinylacetate(all-trans-19, 19,19,19,20,20,20-[2H6]retinyl acetate) and then with 37 umol D6 B-carotene (19,19,19,19',19',19'-[2H6]B-carotene) 1 wk later. Doses were taken with breakfasts containing 16g fat. We measured D6 retinol, D6 B-carotene, and trideuterated (D3)retinol (derived from D6 B-carotene) concentration in plasma. Areas under the plasma concentration X time since dosing curves (AUCs) were determined for D6 B-carotene, and D3 retinol. Results: All men had detectable D6 retinol concentrations in plasma. The mean (+SE) absorption of D6 B-carotene in all subjects was 2.235, and the mean conversion ratio was 0.0296+0.0108 mol retinol to 1 mol B-carotene. Only 6 of 11 men had sufficient plasma concentrations of D6 B-carotene and D3 retino that we could measure. The mean absorption of D6 B-carotene in these 6 subjects was 4.097 + 1.208%, and the mean conversion ratio was 0.0540+0.0128 mol retional to 1 mol B-carotene. Conclusion: The vitamin A activity of B-carotene, even when masured under controlled conditions, can be surprisingly low and variable.

Last Modified: 10/18/2017
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