Could eating oily fish increase the risk of diabetes?

Scientists believe that cocktails of manmade chemicals which pollute our sea and soil could be one of key factors which in trigger the disease.

Until now, obesity was thought to be the most important factor in the development of type 2 diabetes, which as the most common form of the condition affects more than one million Britons.

But new research suggests that toxic chemicals may also play a role.

Studies have shown that people whose bodies are polluted by high levels of chemicals including the pesticide DDT and industrial coolants called PCBs are more likely to have diabetes than those with lower amounts in their bodies.

Despite being long-banned, DDT and PCBs persist in our soil and seas and enter our bodies through the food we eat.

Oily fish, such as salmon, have been praised by dieticians as being particularly beneficial for health.

But they also tend to contain particularly high levels of PCBs.

Scientists have also shown a link between the chemicals and insulin resistance, a condition which often leads to diabetes.

The South Korean research showed that fat people with the chemicals in their blood were more likely to suffer from insulin resistance that thin people whose blood was polluted.

However, those who were overweight but did not have the chemicals in their blood were no more likely to have been insulin resistant.

The findings, reported in this week's New Scientist, suggest that it is the chemicals, which are stored in fatty tissue, and not obesity itself, that is crucial in the development of diabetes.

Other evidence for the link includes the observation that US air force pilots who sprayed the PCB-based herbicide Agent Orange during the Vietnam War are more likely to develop diabetes.

Professor David Jacobs, who supervised the latest research, said described the possibility that levels of chemicals found in our everyday environment could trigger diabetes as 'shocking'.

Other experts said the link between pollution and diabetes could go as far back as the first days of life.

Dr Robert Lustig, an obesity expert from the University of California in San Francisco, said animal studies have shown environmental toxins in the womb may cause obesity in later life - which could then lead to diabetes.

He added: "We just don't know. But is there reason to be concerned? You bet."

However, others urged caution, saying that the researchers had yet to prove the chemicals trigger diabetes.

Other explanations for the findings include diabetics, or those prone to the condition, finding it harder to clear the pollutants from their bodies.

Type 2 diabetes accounts for up to 85 per cent of the 1.4million or so cases of diabetes in the UK.

Sufferers do not make enough insulin, a hormone key in converting sugar into energy, or make insulin that doesn't work properly.

It is usually kept in check through a tightly-contolled diet. However, worsening of the condition over time does need to some sufferers needing insulin injections as they get older.

Type 1 diabetes usually comes on during childhood or adolescence. Sufferers of this type of diabetes are unable to produce any insulin and need regular injections of the hormone.