October 7, 2009 (Newswise) - An international team of scientists, led by Monash University researchers, has found that anti-oxidants commonly touted for their health-promoting benefits, could contribute to the early onset of Type 2 diabetes.The team, led by Professor Tony Tiganis from the Monash Department of Biochemistry and Molecular Biology, has found that molecules known as Reactive Oxygen Species (ROS) may play a protective role in the early stages of Type 2 diabetes by enhancing insulin action. Anti-oxidants prevent the beneficial effects of ROS.

The team showed that when ROS levels were elevated in muscles of genetically-modified mice they could prevent the onset of insulin resistance and diabetes that is induced by a high-fat diet.

However when these animals received anti-oxidants, which 'mop up' ROS, the improved insulin response was lost and the mice became more 'diabetic'.

The findings, published today in the prestigious journal Cell Metabolism, challenge the widely-held view that ROS are always harmful and that anti-oxidants are always beneficial.

"ROS molecules, such as hydrogen peroxide, are important for normal cell function. We have shown that ROS present in muscle enhance insulin action and help lower blood sugar levels," Professor Tiganis said.

"However, our studies do not negate the role of ROS in late-stage disease. There's a 'yin and yang' relationship that takes place, wherein ROS are beneficial in the early stages of Type 2 diabetes and shift to being harmful at later stages of the disease. We are now trying to find out when ROS make the switch from being 'good' to 'bad'.

"Although we need to undertake further studies in humans, our results indicate that the widespread use of anti-oxidants by the general public as a preventative measure is something that should be discouraged, particularly if you are otherwise healthy," Professor Tiganis said.

"Eat healthy and exercise as this is a natural source of ROS that promotes insulin action."

Diabetes is Australia's fastest growing disease, with an estimated 275 people developing the disorder each day. Type 2 diabetes, which is linked to genetic and lifestyle factors including obesity, low physical activity and poor diet, costs our health care system an estimated $3 billion dollars annually.

Professor Tiganis led a team of 12 Monash researchers, scientists from the Baker IDI Heart and Diabetes Institute, University of Melbourne, and Cold Spring Harbor Laboratory in the US.