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It's not fish oil, but....

It's not fish oil, but ...

Preliminary research suggests the body can convert vegetable-derived linolenic acid -- an omega-3 fatty acid -- into the same fatty acids found in marine fish oils. This findings suggests people may reap the fish oil's beneefits from natural constituents of soybeans and other, less costly plants, says Edward A. Emken, the Peoria, III.-based Agricultural Research Service chemist who directed the study.

Emken fed four healthy men 10.7-ounce milkshakes whose fats had been tagged with nonradioactive deuterium labels. Then he periodically sampled blood from these volunteers over two days and studied changes in its fatty acid profiles. The tests showed that the two men whose shakes contained linolenic acid converted it through a cascade of reactions into a family of new molecules.

EPA and DHA -- the primary omega-3 fatty acids in fish oils--were the main end-products. This transformation, "undoubtedly occurring in the liver," required lengthening linolenic's 18-carbon chain by two or four carbons and adding two or three more double bonds, Emken says.

Although the transformation has been documented in rodents, many researchers suspected the conversion by humans was negligible, largely because tissues sampled from people consuming linolenic-rich diets showed no excess EPA or DHA. Emken's new data offer an alternative explanation for this observation: Humans use newly formed EPA and DHA primarily to replace those same fatty acids already in their tissues, not as a substitute for other fatty acids. In fact, Emken's data show that the turnover of omega-3 fatty acids in human tissue occurs at a rate many times faster than that of the omega-6 fatty acids more typical of vegetable fats.

Emken is now exploring how the presence of other fats affects the linolenic-acid conversion. His provocative findings hint that increasing saturated-fat consumption actually enhances the activity of linolenic-transforming liver enzymes.
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Title Annotation:Chemistry; vegetable-derived linolenic acid
Publication:Science News
Date:Apr 15, 1989
Words:299
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