Garcinia cambogia - Uses and Evidence

Uses and Evidence

The prevalence of overweight and obesity has skyrocketed in North America over recent years, and weight management strategies employed have had little widespread success. Both science and the public have been interested in natural and synthetic weight loss aids for decades, the most recent slimming agent being Garcinia cambogia (G. cambogia) and its extract (−)‑hydroxycitric acid (HCA). This extract can be found in the Garcinia family of plants native to South Asia, India, and parts of Africa, and is marketed in hundreds of products, both alone and in combination with other ingredients. HCA is thought to work as both a weight-loss agent, by inhibiting an enzyme responsible for converting carbohydrates into fats, and as an appetite suppressant, by increasing a hormone called serotonin in the brain.^[1]

Whether or not these benefits hold true in human trials, HCA and G. cambogia supplements have become one of the hottest products in the multibillion dollar weight-loss industry. Is G. cambogia really the magic bullet we are looking for? Let’s look at the evidence behind some of these health claims, and see if this trend has lasted for a reason other than promotion by Dr. Oz.

Weight Loss and Appetite Suppression

Weight management is one of the most common health concerns on our minds, and for good reason. Overweight and obesity are important underlying causes to conditions like diabetes, heart disease, and even types of cancer. The natural-health industry has not been blind to this trend, and it’s easy to walk into any supplement dispensary and find a section dedicated to weight loss. G. cambogia and HCA have recently become available on Canadian markets and can now be found among these supplements, although many products were previously accessible through the USA and online. The human evidence investigating the weight-management effect of G. cambogia and HCA have been mixed, and results from different studies may depend on the extract or product used, study design and duration, potential bias through sponsorship, and other confounding factors like diet changes of the participants. Several rigorous reviews exist on the use of G. cambogia and weight loss or appetite that summarize these trials, the most recent of which was published in 2013.

This report identified five human trials using G. cambogia or HCA, each involving over 20 overweight or obese participants, for longer than two weeks, that met multiple other requirements for inclusion. Although five trials may not sound like many, this herb has the most available research among any of the popular natural weight-management supplements that were studied. Most trials looked at both appetite and weight change over the duration of study, and only one reported a positive effect on appetite control in the group taking G. cambogia.^[2] In this study, participants took a highly absorbable calcium–potassium supplement containing 2.8 g of HCA, at least 30 minutes before meals, for eight weeks. Unfortunately, most of the products available on our market are in a calcium salt form, which decreases absorption of HCA, thus likely impacting effectiveness. Two of these studies also reported a significant decrease in body weight at the end of their trials, although neither of them reported the content of HCA in their supplements. One administered 2.4 g of G. cambogia daily for 12 weeks, while the other used a combination product containing G. cambogia, caffeine, and ephedra for 39 weeks. It is difficult to determine the value of the G. cambogia when used in a combination product with other known weight-loss agents like in this trial. A previous review published in 2011 considered nine trials in their analysis, several of which overlap with the 2013 review, and concluded G. cambogia has a short-term and small magnitude of effect, if any.^[3] Further rigorous trials isolating G. cambogia are needed to establish impact on weight management.

Cholesterol Control

High cholesterol is a clinical finding often associated with overweight and obesity, and is an important predictor of long-term health consequences like heart attack and stroke. Although effective medications are marketed to target this issue, many people look for alternative solutions due to risk of side effects, cost, or personal preference. Interest in the use of G. cambogia to lower cholesterol is currently mounting in the research world regarding the potential effect of HCA on cholesterol production.

HCA seems to act by inhibiting an enzyme called ATP-citrate lyase, which is involved in the production of fatty acids.^[4] One trial published in 2014 examined the use of 2.4 g of G. cambogia (50% HCA) taken for 60 days before meals by 30 overweight subjects. Authors reported that while this treatment had no effect on LDL (“bad” cholesterol) or HDL (“good” cholesterol), it did significantly lower triglyceride levels by 28%; triglycerides are a type of fat that have been correlated with an increased risk of stroke.^[4] Another trial published in 2008 has also examined this effect, dosing a combination product of G. cambogia (2.4 g, 52% HCA) and a fibre-like compound called glucomannan to 32 subjects for a 12 week period. Authors reported a positive lowering effect on total cholesterol and LDL levels in the treatment group, even though there was no effect on triglyceride levels or weight.^[5] It is again hard to isolate the effect of G. cambogia from these results, due to the inclusion of an additional ingredient that may lower cholesterol levels. A third intervention previously described also measured several cholesterol parameters during their eight-week trial, reporting a significant decrease in total cholesterol, LDL, and triglycerides.^[2] Interestingly, HDL also increased in their treatment group, which is a marker of decreased cardiovascular risk. Although these results seem promising, further human study is necessary before conclusions are drawn on the effect of G. cambogia and HCA on cholesterol levels.

Blood Sugar Balance

Several trials have also examined blood sugar control as an outcome during treatment with G. cambogia or HCA, which is important for both long-term health and weight management. Results have unfortunately been less than promising. Two studies previously described measured glucose levels and insulin levels, respectively, in their trials, but both reported no significant changes after their treatment periods.^{[4, 5]} Interestingly, one additional study has been completed in eight athletes, demonstrating that 500 mg of HCA after exercise lowered blood sugar levels and enhanced fuel recovery in muscle tissue.^[9] Although this small study may indicate that HCA does have some situational influence on blood sugar regulation, these are clearly not the conditions under which it is often used. G. cambogia has been promoted as a blood sugar–lowering agent, possibly due to more positive results in animal trials, but the obvious lack of clinical support for these conclusions makes this marketing questionable. Blood sugar levels are an important parameter that will hopefully be measured in future weight-management trials using HCA, especially those involving exercise.

 Side Effects and Safety

An important consideration in the marketing of any over-the-counter supplement is safety for the general public. G. cambogia and its isolated ingredient HCA are relatively new to the supplement market in North America, although this fruit has been historically consumed as a flavouring for certain dishes in its native environments. Clinical trials of G. cambogia have not highlighted any significant adverse effects that seem to arise, and both animal and human trials have demonstrated relative safety with regards to mortality, toxicity, and liver health at reasonable doses of 2.8 mg HCA per day.^{[6, 7]} One clinical trial did, however, report twice the amount of GI effects in their treatment group of 135 individuals taking 1.5 g HCA per day.^[8] One issue in drawing conclusions about safety is the duration and size of the studies. Most studies still have a relatively small treatment group, and the longest trial duration has been 12 weeks, which does not necessarily indicate safety with long-term use. There have been several case reports of toxicity involving combination products containing HCA as an ingredient, such as Hydroxycut, but it is impossible to identify HCA as the offending ingredient in these cases. Hydroxycut and HCA do not seem to present any significant risk of interactions with medications, although theoretical interactions exist with drugs that lower blood sugar due to a potential additive effect. There has also been one case report involving a condition called rhabodmylosis (muscle breakdown) after the use of a combination product containing Garcinia in conjunction with a statin medication.^[9] Again, direct causation due to G. cambogia is difficult to establish.

G. cambogia and HCA have had massive success in the market of weight-management supplements, and are only becoming more widespread through inclusion into many combination products. Although results seem to be mixed when it comes to weight loss in human trials, the debate continues and ongoing research will narrow down the value of HCA and its infamous “fat-burning” abilities in the near future. Preliminary research investigating effects on cholesterol levels has been promising, although results are far from conclusive. The exact effect HCA has on the different types of cholesterol is yet to be elucidated. Treatment seems to be generally well-tolerated, and no concerns regarding toxicity have been raised, making it a relatively safe product for the general public. Time will tell if Garcinia cambogia and HCA are the panacea the Western world is searching for to alleviate the rising epidemic of obesity and diseases of lifestyle.