Synthetic Beta-Carotene

Could Synthetic Beta-Carotene
Be the Real Problem?

This section is compiled by Frank M. Painter, D.C.
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September 1996 issue of The Nutrition Reporter™ newsletter

by Jack Challem

Smokers who took beta-carotene supplements in recent experiments may have faced a greater risk of lung cancer because they took the synthetic form of the nutrient, a new study suggests. The subtle differences between synthetic and natural beta-carotene do appear to influence how the body uses the nutrient.

Synthetic beta-carotene consists of just the "all-trans" isomer of the nutrient, whereas natural beta-carotene consists of two different isomers, "9-cis" and "all-trans." Isomers have the same molecular formula, but a different arrangement of atoms. They're a little like anagrams, in which the letters of one word can be rearranged to form another, such as "star" and "rats."

It turns out that the natural 9-cis isomer is a more potent antioxidant than the all-trans, according to Ami Ben-Amotz, Ph.D., and Yishai Levy, Ph.D., in the American Journal of Clinical Nutrition (May 1996;63:729-34). That means the natural form has something the synthetic does not.

In experiments at Israel's National Institute of Oceanography, the researchers gave young, healthy men supplements of either natural beta-carotene from Dunaliella algae or synthetic beta-carotene. Blood analyses showed the presence of the all-trans isomer of beta-carotene, but not the 9-cis form found in natural beta-carotene. However, the researchers looked for‹and found‹9-cis metabolic byproducts, indicating the presence and activity of the natural isomer.

Ben-Amotz and Levy reported experiments showing that the natural 9-cis isomer was rapidly used up in quenching free radicals and preventing oxidative damage to cell fats. In contrast, much of the all-trans isomer was converted to vitamin A, which is a very weak antioxidant.

Ben-Amotz and Levy wrote that the differences between natural and synthetic beta-carotene "should provoke a shift in scientific attention to natural sources of carotenoids and their role in cancer prevention." They urged that researchers pay more attention to the different isomers of beta-carotene.

An earlier study, in Free Radical Biology & Medicine (1994;17:77-82) also showed that the natural 9-cis isomer is a more potent antioxidant than the all-trans form.

The information provided by Jack Challem and The Nutrition Reporter™ newsletter is strictly educational and not intended as medical advice. For diagnosis and treatment, consult your physician.

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