Safety profile of conjugated linoleic acid in a 12-month trial in obese humans

Conjugated linoleic acid (CLA) is marketed in numerous commercially available dietary supplements, but few studies have looked at the long-term safety of this product. The current study evaluated the safety of one CLA product (Clarinol™) over a one-year period in obese humans who were generally healthy. This was a randomized, double-blind study consisting of three phases in which subjects were given 6 g/day of CLA or placebo. Phase 1 was a low calorie diet (13 kcal/kg desirable weight) for 12 weeks or until 10–20% of initial body weight was lost. In phase 2, from weeks 12 to 28, subjects were re-fed a diet providing 25–30 kcal/kg of desirable body weight. Phase 3 was open label, with subjects from both groups taking CLA from weeks 28 to 52. At biweekly visits, subjects completed a questionnaire evaluating side effects and adverse events. Blood was taken for assay of liver function, glucose, insulin, serum lipids, blood counts, and general chemistry. Overall, body composition did not differ between groups. Laboratory tests showed no adverse effects of CLA. Adverse events and side effects were less in the CLA group compared to placebo. We conclude that CLA as Clarinol™ is safe for use in obese humans for at least one year.