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Hydroxycitric Acid (HCA): The Questionable Diet Compound

Posted in: Articles by ProSource, Supplement Articles, Hydroxycitric Acid (HCA)
By Alan Lewis | Feb 21, 2007

HCA: The Great White Hope of the 90s
Hydroxycitric acid (HCA) -- a natural extract from the Garcinia fruit -- is coming of age as a diet compound. Introduced in the early 1990s, it has been through the cycle of initial super-hype, followed by disappointment, followed (at last) by a matured understanding of its role. In a nutshell, it has a role, but it is modest. It does not appear to work as well as the initial claims for it, but that does not mean it is of no value. HCA is said to curb appetite, burn fat and result in significant weight loss without side effects, reducing the Body Mass Index, while at the same time promoting healthy blood lipid levels. Does it, really? 

Mechanisms of Action
HCA does have interesting biochemical effects of potential value in the fight against bodyfat.
FIRST: By inhibiting ATP citrate lyase, HCA might inhibit the supply of fuels that go to make fatty acids and cholesterol; i.e. it "inhibits fat production". This action specifically inhibits the conversion of carbohydrate to fat, even though the extent to which this actually happens in the body is questionable.

There is preliminary evidence that HCA, by inhibiting malonyl CoA, can promote fatty acid oxidation, or the rate at which fats are made available to meet energy (calorie) requirements.

HCA might also promote glycogen synthesis in the liver and possibly in other tissues -- obviously a beneficial action for athletes by increasing the available energy during workouts.

There is suggestive evidence that HCA can promote serotonin synthesis in the brain. If it really does, then HCA would be very useful for controlling carb cravings -- since that is what serotonin unquestionably does.
Does it Really Work?
There have been a few human and animal studies with HCA supplements, showing inhibited appetite, loss of bodyweight, and fat loss. But most of the studies have been questionable in their design: small study groups, lack of placebo controls, and other flaws. The stuff looks promising, but serious scientific proof has been elusive. Not only that, but a few of the most-recent studies have shown lackluster results, at best. For example, a trial at the Obesity Research Center at St Luke's-Roosevelt Hospital in New York set out to assess the efficacy of HCA in overweight humans. This was a serious trial: randomized, double-blind, placebo-controlled, and lasting 12 weeks -- easily long enough to demonstrate significant effects, if any. 135 subjects received either 1500 mg of hydroxycitric acid per day or placebo, while on a high-fiber, low-calorie diet. All participants lost a significant amount of weight, but the difference between the groups was not statistically significant. Further, there were no significant differences in percent body fat mass loss between the groups. The researchers concluded that HCA "failed to produce significant weight loss and fat mass loss beyond that observed with placebo." For another example, a research group at the Center for Human Nutrition at the University of Colorado evaluated the effect of HCA on fat metabolism and energy expenditure (calorie burning) in human subjects. The initial hypothesis was that HCA supplementation would increase fat oxidation and metabolic rate, helping to burn fat and calories. Ten adult males participated in this double blind, placebo controlled, randomized, crossover study, which found that metabolic rate or fat-burning were not affected by HCA supplementation. The researchers concluded that
"these results do not support the hypothesis that HCA alters the short-term rate of fat oxidation in the fasting state during rest or moderate exercise, with doses likely to be achieved in humans while subjects maintain a typical Western diet (approx 30-35% total calories as fat)."
Last, a recent item in the Obesity Research Update relates a story of how HCA researchers at drug-maker Hoffman-La Roche gave up on the project when potential toxicities became evident. "We dropped [HCA] when we saw toxicities in animals", said one researcher. "We never got as far as testing it in humans." Among other problems with HCA, they observed testicular atrophy and zinc deficiency, because of HCA's ability to bind with zinc. Testicular atrophy can mean drastically reduced testosterone levels so this caution should be of particular concern to bodybuilders. Hey, no one is claiming that HCA is going to make your nuts shrivel-up and fall off! The doses they used in those animals were much larger than anything you or I might use. But obviously, caution is in order. If you use HCA, by all means supplement with zinc (not a bad idea, anyway).

The Bottom Line
Clearly, HCA has not lived-up to its promise. Far too much ink has been spilled on the "wonders" of HCA -- while too little convincing scientific evidence has been produced. The ball is in the HCA promoter's court -- to demonstrate that their products do work as billed.

Bibliography Hayamizu K, et al. Effect of Garcinia cambogia extract on serum leptin and insulin in mice. Fitoterapia. 2003 Apr;74(3):267-73. Heymsfield SB, et al. Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial. JAMA 1998 Nov 11;280(18):1596-600. Kovacs EM, et al. Effects of 2-week ingestion of (-)-hydroxycitrate and (-)-hydroxycitrate combined with medium-chain triglycerides on satiety and food intake. Physiol Behav. 2001 Nov-Dec;74(4-5):543-9. Kriketos AD, et al. (-)-Hydroxycitric acid does not affect energy expenditure and substrate oxidation in adult males in a post-absorptive state. Int J Obes Relat Metab Disord 1999 Aug;23(8):867-73 Leonhardt M, Langhans W. Hydroxycitrate has long-term effects on feeding behavior, body weight regain and metabolism after body weight loss in male rats. J Nutr. 2002 Jul;132(7):1977-82 Lim K, et al. (-)-Hydroxycitric acid ingestion increases fat utilization during exercise in untrained women. J Nutr Sci Vitaminol (Tokyo). 2003 Jun;49(3):163-7. Lim K, et al. Short-term (-)-hydroxycitrate ingestion increases fat oxidation during exercise in athletes. J Nutr Sci Vitaminol (Tokyo). 2002 Apr;48(2):128-33. Ohia SE, et al. Safety and Mechanism of Appetite Suppression by a Novel Hydroxycitric Acid Extract (HCA-SX), Molecular and Cellular Biochemistry, 238:89-103, 2002. Preuss HG, et al. Efficacy of a Novel, Natural Extract of (-)Hydroxycitric Acid(HCA-SX) and a Combination of HCA-SX, Niacin-Bound Chromium and Gymnema sylvestre Extract in Weight Management in Human Volunteers: A Pilot Study, Nutrition Research, 24:45-58, 2004. Preuss HG, et al. Effects of a Natural Extract of (-)Hydroxycitric Acid(HCA-SX) and a Combination of HCA-SX plus Niacin-Bound Chromium and Gymnema sylvestre Extract on Weight Loss, Diabetes, Obesity and Metabolism, 6:171-180, 2004. Sullivan AC, et al. Effect of (-)Hydroxycitrate Upon the Accumulation of Lipid in the Rat. 1. Lipogenesis, Lipids, 9:121-128, 1974. Sullivan AC, et al. Effect of (-)Hydroxycitrate Upon the Accumulation of Lipid in the Rat. II. Appetite, Lipids, 9:129-134, 1974. van Loon LJ, et al. Effects of acute (-)-hydroxycitrate supplementation on substrate metabolism at rest and during exercise in humans. Am J Clin Nutr. 2000 Dec;72(6):1445-50.


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