Adverse effects from Hoodia supplements: new Stellenbosch study

A new Stellenbosch University study into the physiological effects of Hoodia gordonii (the well-known ‘wonder’ weight-loss supplement) on rats, has delivered some disturbing results, including a rise in blood pressure, loss of skeletal muscle mass and bloated stomachs.

The results of the study were published this month in the Journal of Ethnopharmacology. The study is the first to investigate the physiological effect of Hoodia gordonii on both lean and obese rats, as well as the specific tissue types affected.

Prof-Carine-SmithProf Carine Smith (left), head of the Multidisciplinary Stress Biology research group in the Department of Physiological Sciences at SU, says she and her colleague, Dr Annadie Krygsman, embarked on this study because of the lack of scientific data on the physiological effect of Hoodia gordonii on animals and people published in peer-reviewed journals.

“The fact that several prominent pharmaceutical companies that were initially involved in the commercial development of Hoodia have subsequently withdrawn their interest, raises the question of whether this plant may have as yet unreported side-effects,” she says.

Meanwhile Hoodia gordonii is still being marketed worldwide as a weight-loss drug and is present in powder supplements, tea and energy bars.

“Many plant extracts available as supplements today can at best be described as a cocktail of unknowns, and sometimes do not even contain the specified plant at all. It is therefore important to understand what these consumers are being physically exposed to and whether a product actually exerts the effects claimed,” she says.

In the experiment, 12 lean rats and 12 obese rats were given different dosages of Hoodia gordonii extract over a two week period. The control group did not receive any Hoodia.

Smith says they were alarmed by the effect of the Hoodia gordonii extract on both the lean and obese rats.

As expected, both groups showed a striking loss in weight, but this was not only due to a decrease in fat mass. While the obese rats lost weight in accordance with the size of the dosage of Hoodia extract they received, the lean rats were significantly more sensitive to its effects.

The lean rats lost on average 35% of muscle fibre at both doses, while the obese rats had relatively smaller average decreases of only 20% (low dose) and 30% (high dose).

Another alarming observation was the fact that all the rats (except for those in the control group) had swollen or enlarged stomachs with hardened content. According to Smith this suggests that the weight loss of Hoodia gordonii may be as a result of a starvation response (similar to anorexia).

“It seems that Hoodia gordonii inhibits the uptake of food through the digestive system. This means that the body uses muscle fibre for energy production, leading to muscle weakness,” she explains.

The last alarming observation observed in all the rats receiving the extract was a thickening of the heart muscle (in medical terms, left ventricular hypertrophy). This means the heart needs to work harder than normal to pump blood to the rest of your body, manifesting as symptoms such as increase blood pressure and heart rate.

In one of the few clinical trials of which the results were published in an accredited academic journal and which was conducted in 2011, all the patients reported cardiovascular side-effects such as increased blood pressure and heart rate.

Prof Smith says most people currently consuming weight loss products containing Hoodia gordonii are probably experiencing a placebo effect, as the dosage is simply too low to have any effect or, more probable, the product does not even contain Hoodia.

“Above a critical threshold, which still needs to be determined, people will experience appetite suppression and subsequent weight loss. But at the same time they will also start experiencing the negative side effects if they continue with the supplementation. This poses the question of whether it should be consumed at all,” she says.

Smith makes it clear that she is not condemning indigenous knowledge.

“We cannot disregard the wealth of knowledge that is indigenous medicine. Rather, as scientists our contribution should be to use technology to identify and isolate true actives in plants, producing pure substances from which those with no or minimal side-effects may be selected. Only then should we consider using plant-derived products for treatments outside of the context originally described by traditional users,” she concludes.

Some background to the commercialisation of Hoodia

The appetite-suppressing qualities of the cactus-like plant Hoodia gordonii were discovered by the San “bushmen” from Southern Africa centuries ago. On their frequent hunting trips they chewed this plant to reduce feelings of hunger and increase their energy levels. Hoodia enabled them to go without food for days.

In the 1963, the South African Council for Scientific and Industrial Research (CSIR) became aware of the plant’s properties, and in the 1980s isolated its active ingredient, which they called P57. In 1995 they patented the compound. 

Two years later, in 1997, the CSIR licensed P57 to a British company, Phytopharm, which launched a series of trials to test its appetite-suppressing qualities. At the end of 2001, the first clinical study was concluded and the prospects looked good. It showed that the appetite of obese people who ingested P57 was considerably reduced and that they ate on average 1 000 fewer calories per day.

These results are however difficult to verify, as the study was never published or subjected to a peer-review process.

So promising did the studies appear that Pfizer bought the international marketing rights from Phytopharm for $21-million, with the idea of turning P57 into diet pills. These plans did, however, not materialise and in 2002 Pfizer released the rights. According to Jasjit Bindra, who led the research at Pfizer, development of these products were stopped because of difficulties with the synthesizing of P57.

Apparently there were also unwanted effects on the liver, caused by other components which could not be removed from the supplement. According to Bindra: “Clearly, Hoodia has a long way to go before it can earn approval from the FDA. Until safer formulations are developed, dieters should be wary of using it.”

Another consideration is that anything that switches off the brain’s ability to register hunger and thirst cannot ultimately be a good thing. Without this kind of feedback the body may be deprived of food and fluids for too long, which could lead to death from starvation and/or dehydration.

In December 2004 Phytopharm signed an agreement with Unilever to market Hoodia gordonii in the form of shakes and diet bars. Like with Pfizer, their plans did not materialise, and in 2008 Unilever pulled out of their arrangement with Phytopharm. (Unilever found that Hoodia does not stifle hunger and has serious side effects, including headaches, nausea, increases in blood pressure and signs of liver damage.)

Source: www.health24.com; Stellenbosch University

Journal Reference: http://www.sciencedirect.com/science/article/pii/S0378874114004814

Additional reading:

Unravelling Unilever’’s unravelling weight management plans