Questions Popular CLA Supplement
By Marcia Wood
July 31, 2001
A popular nutritional supplement called
conjugated linoleic acid, or CLA, may provide more health benefits
for animals than for humans. Thats according to findings from a study by
scientists with the Agricultural Research
Service, the U.S. Department of
Agricultures chief scientific research agency.
ARS research chemist Darshan S. Kelley at the
ARS Western Human Nutrition Research
Center at Davis, Calif., and colleagues were unable to find any
significant, positive benefits of CLA supplements in their three-month-long
test of 17 healthy, nonsmoking women, age 20 to 41.
During the test, the volunteers lived at the research center, formerly
located in San Francisco. They ate familiar, everyday foods at mealtimes and
for their evening snack. For the first month of the study, all volunteers took
sunflower oil capsules with meals. The sunflower oil capsules served as a
control--that is, a basis from which a comparison to CLA capsules could be
For the second and third months of the study, 10 volunteers ate capsules
that provided a daily total of 3.9 grams of CLA. Thats more than 10 times
the amount most Americans consume every day from foods like beef and some other
meats, or dairy products. The other seven volunteers continued taking the
sunflower oil capsules.
In animal studies conducted elsewhere, CLA stimulated the animals
immune systems, protected against some kinds of cancer, reduced body fat and
improved cardiovascular health. In the ARS study, however, Kelley found no
significant change in more than a dozen indicators of volunteers immune
system activity. Colleagues Nancy L. Keim and Marta D. Van Loan of the center
found that CLA didnt reduce volunteers body fat or help them build
In addition, CLA didnt lower blood-fat levels or improve any of the
other health indicators the research team examined.
Kelley suggests that the results might have been different if volunteers had
consumed more CLA over a longer period of time. Also, a different mixture of
CLA components, called isomers, might have led to a different outcome.