Research from the Baker Heart and Diabetes Institute in Melbourne suggests exposure to bisphenol A (BPA) used in plastics increases the risk of developing type 2 diabetes.

An article about the research in numerous Fairfax media reported that BPA is the controversial chemical used to make certain plastics. It is so widely used that 95 per cent of people have detectable levels in their urine.

The study by French and Australian researchers, published in Environmental Health Perspectives, tracked 755 healthy people over nine years.

Twice the risk of type 2

The BPA levels of the participants were checked at the start of the study. Those with higher levels of BPA in their urine were at twice the risk of developing type 2 diabetes, compared to those with low levels.

The link held even after the scientists adjusted for food intake, weight and physical activity.

The researchers also tested for BPS, the chemical some companies have been replacing BPA with. Detectable levels of BPS were associated with a doubling of diabetes risk.

Avoid reusing plastic bottles and takeaway containers

The study’s lead author is now urging consumers to avoid re-using takeaway containers, stick to metal water bottles, and avoid BPA plastic.

When you have type 2 diabetes, your cells stop responding to insulin – the hormone that controls how much glucose cells take from your blood. That can leave too much glucose in your blood, which can lead to heart disease, stroke, kidney disease or eye damage.

BPA seems to interfere with blood glucose control by binding to hormone receptors in the liver, changing the way insulin is regulated, says Professor Dianna Magliano, the scientist who led the Baker Institute research.

“It disrupts all those normal pathways … which gives rise to insulin resistance,” she says.

“In all the studies – and there have been lots of studies – most people find some sort of link. The data is building.”

Professor Katherine Samaras, who is head of the Clinical Obesity, Nutrition and Adipose Biology lab at the Garvan Institute of Medical Research and was not involved in the study, said she was unsurprised by the findings.

Link to weight gain

Other evidence strongly linked BPA exposure to weight gain, she said. Therefore, it was not surprising BPA would raise diabetes risk as well.

“I think there is certainly strong evidence between BPA and obesity, early onset of periods and breast developments, and smaller penises in boys. There is good evidence there.”

The study is also in line with a 2018 meta-analysis of 16 studies that included 41,320 people published in BMC Endocrine Disorders. It found a small but consistent link.

But neither study is likely to bring consensus on BPA’s health risks.

Dozens of comprehensive studies have been done, including a $30 million American-government effort that just released its results.

Governments reach different conclusions

Governments and scientists cannot agree on what they mean.

US and Australian safety authorities say it is safe at normal exposure levels.

“The overwhelming weight of scientific opinion,” Australia’s food safety regulator has concluded, “is that there is no health or safety issue at the levels people are exposed to.”

BPA is already banned in France after the country’s food safety agency (who funded the study) classified it as an endocrine disruptor. The EU has banned its use in baby bottles. Some scientists suspect it is responsible for broad declines in human sperm quality.

Much of the debate centres on how you read a core finding: BPA exposure seems to have its greatest effects at extremely low levels. Those effects go away at higher levels.

Food regulators argue that means the studies are likely wrong, and BPA is perfectly safe; some scientists argue BPA mimics hormones which are most-powerful in very low doses.

Those who do believe try everything they can to lower their BPA exposure.

“We cannot completely eliminate BPA. But we can live a bit cleaner,” says Prof Magliano. “Limit your exposure to crappy plastic. Buy decent water bottles. And chuck out your takeaway plastics.”