NIH eyes potential health benefits of dietary supplement

Conjugated linoleic acid (CLA), a dietary supplement commonly touted for its ability to reduce body fat, may be beneficial in the treatment of cancer, cardiovascular disease, diabetes, osteoporosis, and asthma, according to several new studies.

What is CLA? CLA is the common name of a group of fatty acids. It exists naturally in dairy products as well as in meat from cows, goats, moose, and deer. CLA also exists, to a lesser extent, in fruits and vegetables.

The studies on CLA's potential benefits were recently presented at a workshop held by the National Institutes of Health.

Delbert Dorscheid, M.D., assistant professor of pulmonary critical care medicine at the University of British Columbia, is the lead investigator of a study on CLA and its potential benefits in the treatment of asthma. The study, launched in March, is being conducted for Natural Inc., a Vernon Hills, Ill.-based manufacturer of a CLA supplement called Tonalin.

"Twelve years ago, CLA was found to be an anticancer agent, and when it was studied in animal models, an additional effect was found: Animals who were given CLA had less fat and more lean mass than animals not given CLA," said Dorscheid. Since then, there have been seven clinical trials in humans and, according to five reports published in the past 14 months, the fat-loss effect isn't as profound in humans as in animals. The effect is lost in the heterogeneity of the human population.

However, according to Dorscheid, one of the important findings was that when CLA is taken for eight to 12 weeks, the supplement promotes a fat loss of about 4%, and the fat loss is in the abdominal circumference. This is significant because people who have excessive abdominal fat are at the most risk for Type 2 diabetes, as well as for heart disease, strokes, and high blood pressure, he said.

Dorscheid said the recommended dosage of CLA is 4 gm a day. While CLA has been studied only in consumers who have taken the supplement for 16 weeks, he said that preliminary results of a two-year study in Normandy showed there are no known side effects of long-term use of the substance. Dosages being tested are 3.2, 4, 4.8, and 6 gm a day. In addition to use as a supplement, CLA could be used as an ingredient in foods. He noted that research conducted at the University of Washington in Seattle is studying the benefits of CLA intake in infants.

"The anti-inflammatory benefits of CLA may also benefit people who have osteoporosis," Dorscheid said. Researchers are also studying the potential benefits of CLA in bone density, diabetes, asthma, and allergies.

As far as the supplement's anticancer properties, Dorscheid said, "all the basic science studies for tumors that grow within highly fatty tissue, such as the breast and prostate, will probably show that CLA will have a profound benefit of reducing the incidence of cancer in those organs. The European Union is looking at sponsoring a long-term study to prove that benefit–that CLA supplementation reduces cancer of those two organs."

Commenting on NIH's involvement in the two-and-a-half-day CLA workshop in which 20 investigators presented research to the institute and the Food & Drug Administration, Dorscheid claimed, "That's a sign that down the road they see significant benefits for this molecule. We still need more science to prove that, in the long run, humans will benefit from taking CLA."

Sandra Levy

Sandra Levy. NIH eyes potential health benefits of dietary supplement.

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