Wednesday, August 31, 2011

Garcinia may help exercise recovery by Jerry Brainum

Garcina Cambogia, also known as Bridle berry or by the exotic name of Malabar Tamarind, is one of the more popular ingredients in products touted for promoting bodyfat loss, such as Hydroxycut. The active ingredient in Garcina is hydroxycitrate (HCA), a citric acid derivative.The primary mechanism for HCA is that it inhibits an enzyme called citrate lyase, which converts carbohydrates into fat. One problem here is that citrate lyase is far more active in animals compared to humans,thus explaining why the preponderance of studies that have shown effective fat loss with HCA has involved animals. The studies with humans are more equivocal, with some studies showing success, and others abject failure in humans who have supplemented with garcinia extract or HCA.One example of the latter is a 1998 study published in the Journal of the American Medical Association, in which human subjects ingested 1,500 milligrams a day (the suggested effective dose of HCA) of HCA for 12 weeks.In that study, HCA was found to be ineffective for weight or fat loss. Some have criticized  the JAMA study, claiming that the high fiber content of the diet used in that study interfered with the activity of HCA. A recent meta-analysis published in the Journal of Obesity that examined several past studies concluded that HCA is effective for short-term weight loss. HCA is also known to boost levels of the brain neurotransmitter,serotonin, which among other effects, lowers the cravings for carbohydrates. HCA may also lower levels of leptin, which would result in decreased appetite surges.
     The effects of HCA remain controversial. For example, in a study of Zucker rats, which are lab rats  genetically prone to obesity, high doses of Garcinia did suppress fat synthesis, but also caused testicular atrophy and injury in the rodents. This would lead to lower testosterone synthesis. But a follow-up 2008 study that involved human subjects who ingested 1,000 milligrams a day of either HCA or a placebo for 12 weeks found no effects of HCA on testosterone or estrogen.
     The latest study of oral HCA shows an effect that may interest all those engaged in intense exercise. The study consisted of 8 men, average age, 22, who cycled for 60 minutes at an intensity of 70-75% of maximum oxygen intake. The men consumed either 500 milligrams of HCA or a placebo with a high carbohydrate meal containing 80% carbs, 8% fat, and 12% protein. Tests showed that those who consumed the HCA with the carbs showed a significantly greater synthesis of glycogen following the exercise. The HCA also veered energy usage more toward fat oxidation, and increased post-meal insulin sensitivity.The increased glycogen synthesis rate induced by HCA would speed exercise recovery by filling up depleted muscle glycogen levels more rapidly.
Chenga, S et al. Oral hydroxycitrate supplementation enhances glycogen synthesis in  exercised human skeletal muscle.Br J Nut; 2011: in press.


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