Conjugated linoleic acid (CLA) is a group of fatty acids found naturally in some foods, mainly beef and dairy products. The various forms of CLA serve different functions. The best known forms, and usually the ones found in dietary supplements, are “cis-9, trans-11” and “trans-10, cis-12.” The CLA in dietary supplements is often produced from linoleic acid found in safflower or sunflower oils.

CLA has been studied for potential health benefits such as preventing cancer and reducing the risk of atherosclerosis (a disease of the arteries), but most of the interest in it as a dietary supplement has been as an aid for weight loss and fat loss. Research with animals suggests that CLA might help decrease body fat and weight while increasing lean muscle mass, and some studies with humans have found that CLA can lead to small decreases in body weight, body fat, and waist circumference. However, many studies have found no such effects. Bottom line: More research is needed to determine its effects in humans for weight or fat loss.

CLA in certain foods—including milk, yogurt, meal-replacement shakes, nutritional bars, fruit juices, and soy milk—is “generally recognized as safe” (GRAS) up to 1.5 grams per serving. Supplemental CLA is considered safe, but common side effects include gastrointestinal upset such as constipation, diarrhea, and stomach pain. In addition, CLA supplements have been associated with 3 cases of liver toxicity. However, it’s unknown whether these cases were caused by CLA or a possible contaminant. Still, more research is needed on the long-term health effects of CLA supplements in humans.

Updated 08 June 2018

References

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