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United States Department of Agriculture

Agricultural Research Service

Title: Variability in Conversion of Beta-Carotene to Vitamin a in Men As Measured by Using a Double-Tracer Study Design

Authors
item Hickenbottom, S - UNIV OF CALIF DAVIS
item Follett, J - UNIV OF CALIF DAVIS
item Lin, Y - UNIV OF CALIF DAVIS
item Dueker, S - UNIV OF CALIF DAVIS
item BURRI, BETTY
item Neidlinger, Terry
item Clifford, A - UNIV OF CALIF DAVIS

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2002
Publication Date: May 1, 2002
Citation: Hickenbottom, S.J., Follett, J.R., Lin, Y., Dueker, S.R., Burri, B.J., Neidlinger, T.R., Clifford, A.J. 2002. VARIABILITY IN CONVERSION OF BETA-CAROTENE TO VITAMIN A IN MEN AS MEASURED BY USING A DOUBLE-TRACER STUDY DESIGN. American Journal of Clinical Nutrition. 75 (5): 900, 2002.

Interpretive Summary: Vitamin A is an essential nutrient, necessary for normal growth and eyesight. Beta-carotene, the pigment that makes carrots and sweet potatoes organge, from vitamin A in the human body. Americans get about 50% of their vitamin A from beta-carotene by this conversion process. Beta-carotene should form vitamin A easily and efficiently, but we have known for many years that it did not. What we did not know until now is just how bad the conversion ratio really was. We used advanced new technology to accurately measure the amounts of vitamin A formed beta-carotene. We found that the conversion ratio in healthy well-fed men was about 3 times less than previously believed. Furthermore, the converstion ratio varied from person to person, so that some men found much less vitamin A than others. Our results show that it is difficult to get enough vitamin A from eating beta-carotene rich vegetables.

Technical Abstract: Background: The vitamin A activity of beta-carotene is variable and surprisingly low in women. The reasons for htis are not well understood. The vitamin A activity of beta-carotene in men is still uncertain. Contributions of dietary factors compared with individuals traits are largely unknown. Objective: Our objective was to measure the intrinsic variability in the vitamin A activity of beta-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) retinyl acetate (all trans-19,19,19,20,20,20-[2H6]retinyl acetate) and then with 30 umol D6 beta-carotene (19,19,19,19',19'-[2H6]beta-carotene) 1 wk later. Doses were taken with breakfasts containing 16 g fat. We measured D6 retinol, D6 beta-carotene, and trideuterated (D3) retinol (derived from D6 beta-carotene) concentrations in plasma. Areas under the plasma concentration x time since dosing curves (AUCs) were determined for D6 retinol, D6 beta-carotene, and D3 retinol. Conclusion: The vitamin A activity of beta-carotene, even when measured under controlled conditions, can be surprisingly low and variable.

Last Modified: 9/10/2014
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