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.