OSU – CLA, or conjugated linoleic acid, is a supplement that some people use for weight loss. Two new animal studies, however, show that CLA may have some previously unknown, unhealthy side effects, but the issue is not resolved with regard to risk for people.

Scientists studied how mice and rats reacted to the supplement conjugated linoleic acid (CLA), a fatty acid found in trace amounts primarily in beef, lamb and milk. Synthetic forms of CLA are marketed as supplements to help reduce body fat, and some manufacturers also promote CLA for reducing the risk of diabetes and certain types of cancer.

Indeed a prior study in humans had positive results for weight loss. A 2003 study (Belury) found that CLA supplements lowered body mass and blood sugar levels of diabetics. The study participants took CLA supplements for two months.

In the recent animal studies, however, the mice and rats responded in very different ways to CLA, said Martha Belury, the lead author of both studies and an associate professor of human nutrition at Ohio State University.

Mice fed a CLA-supplemented diet lost weight very fast, but also accumulated excessive amounts of fat in their livers – a common side effect of rapid weight loss. Excessive fat accumulation in the liver is linked to insulin resistance, a hallmark of Type 2 diabetes.

As for the rats? The CLA did not help rats lose weight they had gained prior to taking the supplement. But it effectively decreased the amount of fat that had accumulated in the animals’ livers due to the weight gain. In turn, the rats were more sensitive to insulin.

“Many people take CLA as a supplement in hopes of trimming body fat, and it seems to work,” Belury said. “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.” For more information on these two animal studies, visit the OSU news story at this link:

Question of fatty liver side effect from weight loss supplement CLA

Belury noted that up to 75 percent of people with diabetes and obesity develop an illness called non-alcoholic fatty liver disease, in which fat accumulates in the liver and which is associated with insulin resistance.

CLA may or may not have a similar effect on people, and it will take time to learn how the human body responds to the CLA supplement. But clinical trials with the weight loss supplement CLA are underway – Belury is currently working with researchers from Ohio State’s medical center who are beginning a clinical trial of the effects of CLA on diabetic women.