Slimming agents could pose major health risk

Commonly used nutritional supplements and body-building agents for elite athletes could pose an increased risk of cancer according to a study undertaken at the University of Sydney.

Research by Professor Peter Lay, Dr Aviva Levina (senior research associate) and Dr Irma Mulyani (PhD student) from Sydney University's Centre for Heavy Metals Research in conjunction with the recently established International Centre for Excellence in sports Science and Management, has shown that widely used chromium nutritional supplements and prescription drugs could lead to an elevated risk of cancer, particularly for heavy users such as elite athletes.

Research published in the most recent issue of the prestigious international chemistry journal Angewandte Chemie, shows that the in vitro reactions of the dietary chromium(III) dietary supplements with enzymes result in the formation of the human carcinogen chromium(VI). These results provide strong evidence that the dietary supplements may be converted from chromium(III) into carcinogenic chromium(VI) by our bodies.

The project, which was funded by the Australian Research Council, also developed a novel explanation for the mechanism by which Cr is involved in glucose metabolism and anti-diabetic effects, which also supported the proposal that carcinogenic chromium(VI) is generated in the body from the dietary supplements. Identifying these process has become all the more important as the special complexes of chromium(III) demonstrate an insulin-intensifying effect, and are therefore currently under consideration as potential drugs for diabetes.

Under normal metabolic processes, a range of enzymes produce common oxidants, such as hydrogen peroxide and hypochlorite. The team demonstrated that these biological oxidants convert harmless chromium(III) supplements to chromium(VI) in vitro, either directly or when generated in situ by the enzymes.'

'These processes are the same as those that occur when these agents are used to bleach hair or as household bleaching agents. The chromium(VI) compounds that are generated are well established as both occupational carcinogens and more recently as environmental pollutants that cause cancer. This was popularised by the film Erin Brockovitch, based on one of many such USA class lawsuits involving Cr,'said Professor Lay.

'Moreover, we have also established that only chromium(VI) (and another oxidation product, chromium(V)) and not the chromium(III) dietary supplements themselves interfere with the enzymes that result in the insulin intensifying processes that lead to the anti-diabetic and glucose metabolism effects of the supplements. The supplements that are most readily oxidised to chromium(VI) are also the most active in animal studies. This structure-activity relationship, together with the other evidence, strongly points to the in vitro studies being relevant to processes that occur in humans.'

'In the light of our new findings, the safety of chromium(III) compounds as nutritional supplements or drugs should be re-examined very carefully, particularly for heavy users of the supplements, such as elite athletes,' said Professor Lay. 'In even more recent studies, we have shown that the body may have specific Cr(VI) detoxifying processes in human cells, but these are rapidly overtaken if the concentrations are too high, which could be the case for heavy users of the supplements.'