Which is the Best Type of Beta-Carotene?

Why was this study done?

Differing shapes of identical chemicals (called isomers) can have differing effects on humans. The “cis” isomer of beta-carotene have shown in animal studies to have lower vitamin A activity, but humans have different physiology than animals. This study was designed to investigate how different isomers of beta-carotene act in humans.

What did the study find?

Participants supplemented with all “trans” beta-carotene had better absorption than the “cis” isomer.

Jensen CD, et al. Observations on the Effects of Ingesting Cis- and Trans-Beta-Carotene Isomers on Human Serum Concentrations Nutr Rep Int, 1987. 35(2): p. 413-422.PDF Manuscript: Nutr Rep Int, 1987.

Earlier Paper:

Jensen CD, et al. Observations on the Effects in Humans of Cis- and Trans-b-Carotene Isomers. Am J Clin Nutr, 1986. 43(4): p. 689.PDF Abstract: Am J Clin Nutr, 1986.