Conjugated Linoleic Acid or CLA is an essential fatty acid found mainly in beef, lamb, and milk, in trace amounts. While CLA is best known for its ability to reduce the risk of diabetes and reduce the risk of certain cancers, it has also been synthesised and made available as a supplement intended to reduce body fat in overweight people. Research on CLA has generally shown that it is effective, but some studies show no effect and that it may have some side effects of concern.
The first major study, published in the Journal of Nutrition in 2001, found that CLA reduced body fat by an average of six pounds (as compared to a placebo group) and preserved muscle tissue. Interestingly, it seemed to have the greatest effect on abdominal fat. Dr. Michael Pariza, who conducted research on CLA with the University of Wisconsin-Madison, reported in August 2000 to the American Chemical Society that, "It doesn't make a big fat cell get little. What it rather does is keep a little fat cell from getting big." Dr. Pariza found that when dieters stop dieting, those taking CLA were less likely to gain the fat back. Instead, they gained muscle. A later study from Purdue University in Indiana showed that CLA improved insulin levels in two-thirds of diabetic patients, and reduced blood glucose levels somewhat.
Some of the qualities that have beeen attributed to CLA include:
- Acts as an antioxidant
- Increases metabolic rate
- Reduces abdominal fat
- Enhances muscle tissue growth
- Lowers cholesterol and triglycerides
- Lowers insulin resistance
- Enhances the immune system
Two later studies, published in the Journal of Lipid Research and the Journal of Nutritional Biochemistry, again showed that CLA reduced body fat. However, it might have the dangerous side effect of causing fat to accumulate in the liver, which is a common side effect of rapid weight loss. Fat accumulation in the liver can result in increased insulin resistance, which is associated with the development of diabetes. Interestingly, one study was done with rats and the other with mice, and each had very different results. The mouse study revealed an accumulation of fat in the liver, while the rat study showed a decrease in liver fat after CLA supplementation.
“Many people take CLA as a supplement in hopes of trimming body fat, and it seems to work,” said Martha Belury, the lead author of both studies and an associate professor of human nutrition at Ohio State University. “But we're not sure what else it does to the body. Studying CLA's effects in two different animal models may help us to better understand any additional effects in humans. It seems that these mice and rats represent a continuum of possible side effects induced by CLA,” she continued. “The question is, are humans more like mice or rats? We're probably somewhere in between.”
More clinical trials are needed to determine exactly how humans respond to CLA supplementation. Martha Belury is currently working with researchers from Ohio State's medical center who are conducting a clinical trial of the effects of CLA on women with diabetes.
If you are interested in taking CLA for weight loss, keep in mind that it is not a “magic pill” and a program of diet and exercise are essential to ensure weight loss. The initial studies done on CLA indicate that a dose of 3.4 grams per day is adequate to stimulate weight loss and muscle preservation. It is recommended that you use a patented name brand, as some brands contain inconsistent amounts of CLA. You can also get CLA from the dietary sources mentioned earlier, namely beef, lamb, milk. Interestingly, a University of Western Australia and CSIRO sponsored PhD student discovered that the meat of Australia's bush kangaroo may be the highest known source of CLA. Grass-fed meats contain 300%-500% more CLA than other meats. CLA is also found in eggs and some species of mushrooms.
Side effects from taking the recommended amount of CLA are minimal and gastrointestinal in nature. Mild nausea or diarrhoea have been reported and are reduced if CLA is taken with some form of protein such as milk. After about two weeks on CLA, most side effects seem to disappear completely.
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