Description
(-) - Hydroxycitric acid, commonly called hydroxycitric acid, is found in the fruits of the genus Garcinia. Supplemental hydroxycitric acid is typically an extract of the rinds of Garcinia cambogia fruit, also called Brindle berry. Fruit of this plant has long been used in India as a condiment, and the dried rind is used as a flavoring agent. The dried fruit rind is also used in Indian folk medicine for gastrointestinal complaints and rheumatism. Hydroxycitric acid is the principal acid in the fruits of Garcinia cambogia and makes up to 16% of the content of the dried fruit.
Hydroxycitric acid, in addition to being called (-)- hydroxycitric acid, is also known as hydroxycitrate, (-) — threo-hydroxycitric acid and 4S-hydroxycitric acid. It is abbreviated as (-)-HCA and sometimes as HCA. It is a different substance than either citric acid or isocitric acid, which are key intermediates in the tricarboxylic acid or Krebs cycle. The terms for the acid and anion forms, hydroxycitric acid and hydroxycitrate, respectively, are used interchangeably. However, the anion form is the form that occurs under biological conditions.
Actions & Pharmacology
Actions
Hydroxycitric acid is a putative antiobesity agent.
Mechanism of Action
Hydroxycitric acid is a competitive inhibitor of the enzyme adenosine triphosphate-citrate (pro-3S) — lyase or ATP citrate lyase. In the cytosol, ATP citrate lyase catalyzes the conversion of citrate and coenzyme A to oxaloacetate and acetyl coenzyme A (acetyl CoA). Acetyl CoA is used in the synthesis of fatty acids, cholesterol and triglycerides and also in the synthesis of acetylcholine in the central nervous system.
Oxaloacetate may enter the gluconeogenic pathway, which can lead to the production of glucose and glycogen. It is believed that the putative antiobesity effect of hydroxycitric acid is due to suppression of fatty acid and fat synthesis. In addition, hydroxycitric acid is thought to suppress food intake via an anorectic effect. This is believed to be accounted for by hydroxycitric acid's stimulation of liver gluconeogenesis.
Pharmacokinetics
There is little reported on the pharmacokinetics of hydroxycitric acid in humans. Animal studies indicate that it is absorbed via the gastrointestinal tract and transported to the liver and other body tissues. There are no reports indicating if the marketed hydroxycitric acid is transported into liver cells in humans.
Indications & Usage
Claims are made that hydroxycitric acid is an effective weight-loss agent. These claims are not presently supported by well-controlled studies.
Overdosage
There are no reports of overdosage.
Dosage
Hydroxycitric acid is available in Garcinia cambogia extracts. Some products contain hydroxycitric acid in the lactone form, which has not shown activity in animal models. There are products available that are free of the lactone form. Typical doses are about 1500 milligrams (as hydroxycitric acid) daily.
Literature
Conte AA. A non-prescription alternative in weight reduction therapy. Am J Bariatr Med. 1993; Summer:17-19.Greenwood MR, Cleary MP, Gruen R, et al. Effect of (-)-hydroxycitrate on development of obesity in the Zucker obese rat. Am J Physiol. 1981; 240:E72-E78.Heymsfield SB, Allison DB, Vasseli JR, et al. Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial. JAMA. 1998; 280:1596-1600.Kriketos AD, Thompson HR, Greene H, Hill JO. (-)-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; 23:867-873.Research & Summary
A suggestion from animal work that hydroxycitric acid might be an effective antiobesity agent has not been confirmed in human studies. A recent well-controlled trial of hydroxycitric acid failed to produce any significant weight loss compared with placebo. This was a 12-week double-blind study in which overweight subjects were randomized to receive 1500 milligrams of hydroxycitric acid daily or placebo.
In another recent study, also conducted double-blind, placebo-controlled and randomized, researchers sought to see whether hydroxycitric acid supplementation could increase fat oxidation in human subject. The researchers found no significant effect.
Contraindications, Precautions & Adverse Reactions
Contraindications
Known hypersensitivity to a hydroxycitric acid-containing product.
Precautions
Pregnant women and nursing mothers should avoid hydroxycitric acid supplements. Because of the theoretical possibility that hydroxycitric acid might affect the formation of acetylcholine in the brain, those with dementia syndromes, including Alzheimer's disease, should avoid hydroxycitric acid. Those with diabetes should be cautious about using hydroxycitric acid.
Adverse Reactions
In a 12-week weight loss study comparing hydroxycitric acid, 1500 milligrams daily, against a placebo, the number of reported adverse reactions was not significantly different between the placebo group and hydroxycitric acid groups.
