We suggest that olive oil does have independent protective affects

Dr Michael Goldacre, University of Oxford

But the Oxford researchers have also confirmed that intake of meat and vegetables can affect the risk factors.

They studied bowel cancer rates in 28 countries across the world, most of which were in Europe. However, rates of the disease in the UK, the USA, Brazil, Colombia, Canada and China were also examined.

The researchers found that three dietary factors could affect a person's risks of developing the disease.

They suggested that people who ate a lot of meat and fish, as opposed to those who ate mostly vegetables and cereals, were at increased risk.

They also found that a diet rich in olive oil was associated with a decreased risk.

This is because a high meat intake can increase the amount of a bile acid called deoxycyclic acid, which reduced the activity of an enzyme called diamine oxidase (DAO).

DAO is thought to regulate the cell turnover in the bowel lining and reduced levels of this enzyme could be responsible for abnormal cell turnover.

But the Oxford researchers found the olive oil seemed to reduce the amount of bile acid and to increase DAO levels, thus protecting against abnormal cell growth and cancer.

Confirmation

Dr Michael Goldacre, one of the authors of the report, said their findings backed up previous studies.

"A lot of the major effects we have found are really confirmation of what is by and large already known.

"What our findings suggest is that countries with high intakes of olive oil have relatively lower incidence rates of colorectal cancer than would be suggested considering other aspects of their diet.

"We suggest that olive oil does have independent protective affects."

Speaking to BBC News Online he added: "We have suggested that the findings on olive oil need to be tested, confirmed and refuted in other studies before being accepted."

A spokeswoman for the British Nutrition Foundation said more people were using olive oil because of its health benefits.

"The main benefit of olive oil has always been in terms of coronary heart disease.

"Since those benefits have been publicised people have been using olive oil more and more.

"I think consumption is increasing all the time. The messages of health benefits have certainly been getting out."