Chromium not so therapeutic?

Supplements containing chromodulin may form carcinogens in the body.

Australian researchers have cast some doubts on the health benefits of chromium(III), which had long been branded an essential trace element playing an important role in fat and glucose metabolism.

Cr(III) compounds are reported to have insulin-enhancing properties attributed to specific interactions with cellular insulin receptors. Now, Peter Lay and colleagues at the University of Sydney, Australia, have found that the Cr(III) compound chromodulin, found in many dietary supplements, could be oxidised in the body to form carcinogenic and toxic Cr(V) and Cr(VI) compounds.

It was previously thought that Cr(III) could not be oxidised to Cr(VI) in the body, but Lay’s team thought otherwise. ’Strong oxidants such as H2O2 and ClO- are produced naturally by cells, particularly those involved in the immune response,’ says Lay. It is also known that Cr(V) and Cr(VI) compounds, but not Cr(III) compounds, act as inhibitors of the enzyme protein tyrosine phosphatase, which halts the action of insulin.

The researchers focused on a well understood mimic of chromodulin - [Cr(III)3O(CO2Et)6(OH2)3]+, simplified here as ’Complex A’ - which is considered a safer therapeutic agent than chromodulin. They oxidised the complex using H2O2 and ClO- under conditions similar to those found in the body and monitored the resulting solutions using electronic spectra analysis. This showed clearly that Cr(VI) compounds were being formed, they report.

Tests on rats using Complex A, compared against tests on rats using an alternative treatment [Cr(III)(pyridine-2-carboxylato)3] (’Complex B’), showed that only Complex A worked as an efficient insulin activator. Lay says this adds weight to his argument for Cr(VI) production, as Complex A is more easily oxidised than Complex B. ’The ease of oxidation of [Complex A] to carcinogenic Cr(VI) warrants further research into the safety of using any Cr(III) compound as a nutritional supplement or therapeutic agent,’ he concluded.

Andrew West