Problems with bioavailability and a lack of efficacy are surprisingly common with health food supplements and hydroxycitric acid products are not exceptions. Today, the vast preponderance of commercial products being sold as containing or supplying HCA are stabilized using calcium or a mixture of calcium and potassium to yield HCA salts. There are several reasons for creating HCA salts rather than using liquid HCA as either a free acid or an acid/lactone mixture. For one thing, powders typically are easier to store, transport and work with than are liquids. In the case of HCA, other reasons include the fact that the HCA free acid and its lactone exhibit limited bioavailability and limited interaction with the ATP:citrate-lyase enzyme, one of the primary targets of HCA’s actions. On the positive side, HCA calcium and calcium-potassium salts are cheap to make. On the negative side, many major researchers have determined that HCA salts that contain calcium just are not effective for reducing appetite and food intake or reducing body weight.
All the original pharmaceutical work with HCA was performed with the pure synthesized HCA sodium salt, technically trisodium (–)-hydroxycitrate. This material yielded consistent results in the animal trials and step-wise dose responses for food intake and weight control as the dosage level was increased. Reductions in both food intake and bodyweight appeared within days in the Roche trials testing the HCA sodium salt.
In contrast to the HCA sodium salt, an animal trial using the leading commercial potassium-calcium salt found no such step-wise progression in either food restriction or weight results. For both genders of animals, the leading CaKHCA salt caused no significant changes in food intake until approximately 90 days into the trial and no significant changes in bodyweight until approximately 60 days into the trial. This was true regardless of the dosage used, i.e., whether the dose was 100 mg/kg/bodyweight/day or 2,500 mg/kg/bodyweight/day. (Food Chem Toxicol. 2004 Sep;42(9):1513-29.) Surprising as it might seem, especially to those who have read the original research publications based on trisodium HCA, there was little difference in results with the CaKHCA whether the dose used was 100 mg/kg bodyweight/day or at 25 times that dose.
Other researchers similarly have noticed that the calcium and calcium-potassium HCA salts do not deliver results. A Japanese – Korean scientific team working with HCA published in one of its reviews that the team could not use available commercial HCA salts, all of which contain some amount of calcium or calcium plus potassium as ligands, and had to return to synthesizing the pure trisodium HCA salt in order to achieve significant and consistent results. (J Nutr Sci Vitaminol (Tokyo). 2005 Feb;51(1):1-7.)
Several direct comparisons of HCA salts with and without calcium bear out the observation that non-calcium salts are more active. In one such trial, a Dutch group (Louter-van de Haar et al., Nutr Metab (Lond). 2005 Sep 13;2:23.) performed a rodent study in which it compared three products—the first was 97% potassium salt, the second was 50% potassium salt, and the third was a 1:1 mixture of a potassium and a calcium salt. All animals were gavaged at set intervals. The results were that the mostly potassium easily performed the best, the calcium-potassium salt performed least well, and the 50% salt was somewhere in between. In analyzing the HCA clinical trial data, Frank Greenway at the Pennington Biomedical Center (“Garcinia,” Encyclopedia of Dietary Supplements, 2010) remarks, “if is possible that some, if not all, of the negative studies of HCA may be due to the poor bioavailability of the calcium salt.” He further concludes, “future trials should consider using the monovalent salts of HCA acid.)
Indeed, comparisons of the leading commercial calcium-potassium HCA salt with HCA monovalent potassium and near monovalent potassium-magnesium salts have confirmed the findings and conclusions of Louter-van de Haar and Greenway. Whether in terms of blood pressure support, insulin sensitivity or healthy inflammatory responses, it is consistently the case that, as is true of the trisodium hydroxycitric acid salts, monovalent potassium and near monovalent potassium-magnesium salts in animal trials have proven to be more active and efficacious than any tested salt containing calcium. (Current Topics in Nutraceutical Research 2008;6(4): 201-210.) (Journal of the American College of Nutrition 2005;24:429 Abstract.)
So, do calcium-containing HCA salts “work?” There is an answer that disinterested third parties are able to agree on. That answer, according to comparative trials and analyses, is “yes, sometimes,” but not as well or as consistently as monovalent potassium and near monovalent potassium-magnesium salts.