We are still carrying out this study and are certainly not saying people should stop eating vegetables

Prof Kenneth McColl

Gullet cancer - which occurs around the gastro-oesophaga junction where the oesophagus joins the stomach - kills more than 3,000 people in the UK every year.

It is three times more common in men than women.

Professor McColl said: "We are still carrying out this study and are certainly not saying people should stop eating vegetables.

"But our investigations have shown that there is definitely something happening here."

Further tests

The team found that human saliva plays a vital role in converting nitrates into carcinogens - which operate at the gastro-oesophageal junction.

They believe gullet cancer may be sparked in some people when the saliva they swallow first meets the acidic juices in the stomach.

Prof McColl and his team plan to carry out further tests on humans in an effort to judge the extent of the problem.

People in Scotland seem to be more affected that those in any other part of the UK.

Vegetables could contain high amounts of nitrates, the researchers warn

"Hopefully, with further human tests, we will be able to see exactly how and why this is taking place because at the moment it is a mystery, but one that is having severe consequences," Prof McColl added.

He warns that organic food would not be any healthier as it too contains substantial levels of nitrate, some coming from natural fertilisers such as manure.

Grant

He said this form of gullet cancer was now more common than stomach cancer in the UK - with some victims as young as 30.

And it is more common in countries with less sunlight where the majority of produce is grown under glass - such as the UK.

His team has received a �150,000 grant from the Scottish Executive to carry out the study.

Prof McColl said it was essential to determine if the permitted levels of nitrate fertilisers - which has fallen in recent years - is partly to blame.

Green and root vegetables contained the highest levels of nitrate, he said.

In the last 20 years, the number of people suffering this form of cancer in Scotland alone has risen from 450 to more than 1,100.

But the professor adds: "It is not alone, the rest of the UK is not that far behind."