Wednesday, March 30, 2011

What is Hydroxycitrate?

Hydroxycitrate: Controversial Weight-Loss Ingredient

Hydroxycitrate is a generic name for any salt of (-)-hydroxycitric acid (HCA), which occurs naturally in fruits from the genus Garcinia. HCA is found in particularly high concentrations in Garcinia cambogia, commonly called brindleberry or Malabar tamarind.

Hydroxycitrate is the active ingredient in a number of over-the-counter weight-loss products. Among the many dietary supplements that are advertised to aid in weight management, hydroxycitrate is distinguished by the large body of research examining its effectiveness, safety and mechanism of action. However, hydroxycitrate is also distinguishable by the conflicting and inconsistent nature of the studies, and by the controversy generated by these studies.

HCA is a competitive inhibitor of the enzyme ATP citrate lyase, which has a major role in synthesizing fatty acids in the body. HCA is also believed to reduce malonyl-CoA concentrations, leading to increased fatty acid oxidation. Therefore, it is believed that HCA promotes weight loss by interfering with fatty acid synthesis, promoting fat oxidation and reducing appetite.

A recent systematic review and meta-analysis showed a small but statistically significant weight-loss effect of HCA compared to placebo. However, gastrointestinal adverse effects were also twice as common in subjects taking HCA than in those taking placebo.

Several animal and human studies have supported the effectiveness of HCA for weight loss. Of these, the vast majority were funded or conducted by pharmaceutical companies, with one or more authors affiliated with a major supplier of HCA-based products.

Other studies have shown no effects of HCA on weight loss parameters (such as body weight reduction, blood/serum profiles, or satiety). One study, conducted at Columbia University and published in 1998 in the leading medical publication Journal of the American Medical Association, is considered to be strong evidence against the effectiveness of hydroxycitrate or HCA for weight loss.

However, proponents of HCA say that the high-fiber, low-calorie diet that was used in this study may have prevented the anti-obesity effects of hydroxycitrate.

Animal studies have shown that HCA may have toxic effects, such as testicular shrinkage and toxicity. However, the HCA used some of these studies reportedly contained large amounts of HCA lactone. In the free acid or lactone forms, HCA can potentially cause have negative effects on testicular development by chelating zinc, which can lead to zinc deficiency. Many commercial HCA products contain fully reacted calcium or potassium salts of HCA, so should have little or no free HCA acid or HCA lactone. Hydroxycitrate has been determined to be safe in several studies, and has been determined to be GRAS by an independent team of experts for use as a flavoring agent. Acidic conditions may promote lactone formation, even of fully reacted acid salts. Therefore, it should be cautioned that free HCA acid or HCA lactone may accumulate over time in acidic products.

Taken together, the research thus far does not provide conclusive evidence that hydroxycitrate effectively promotes weight loss, either through metabolic processes or by inducing satiety. More research is needed to determine the safety and effectiveness of HCA-containing products.

For more information about HCA, please visit Natural Standard's Foods, Herbs & Supplements database.


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