A diet rich in red and processed meats appears to put men at a higher risk of developing prostrate cancer, a United States study said.

Researchers at the National Cancer Institute (NCI) found that among more than 175,000 men they followed for nine years, those who ate the most red and processed meats had heightened risks of developing any stage of prostate cancer - and advanced cancer in particular.

The findings, reported in the American Journal Of Epidemiology, add to a conflicting body of research on meat intake and prostate cancer risk. Because studies over the years have come to different conclusions, experts generally consider the evidence linking red and processed meats to the disease to be limited and inconclusive.

These latest findings do not settle the question. However, they do suggest that processed red meats and high-heat cooking methods - namely, grilling and barbecuing - may be particularly linked to prostate cancer risk.

For the study, Dr Rashmi Sinha and her colleagues at the NCI followed 175,343 American men between the ages of 50 and 71 who were surveyed about their diets - including how much and what type of meat they typically ate, as well as the cooking methods they used.

The researchers used that information to estimate the levels of certain potentially cancer-promoting chemicals in the men's diets.

Over the next nine years, 10,313 study participants developed prostate cancer and 419 died from the disease.

Overall, the researchers found that 20 per cent of men with the highest intake of red meats - which in this study included beef and pork - were 12 per cent more likely to develop prostate cancer than those who consumed the least red meats. That was after a range of other factors, like smoking, exercise habits and education, were taken into account.

There was a stronger connection to advanced prostate cancer - with that risk being almost one-third higher among those who ate the most red meat versus those who ate the least.

Similar findings were seen with processed meat. However, when the researchers further broke down the men's diet information, they found that red processed meats - like bacon and sausages - were related to higher prostate cancer risk, while white processed meats, like poultry cold cuts, were not.

When it came to cooking methods, the only one that was linked to prostate cancer was grilling and barbecuing, Dr Sinha's team found.

The finding is in line with the theory that meats cooked at high temperatures may be particularly linked to cancer because the cooking process produces certain chemicals - including polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines - that are known to cause cancer in animals.

Giving further support to that idea, the researchers found that higher dietary levels of a PAH called benzo-alpha-pyrene were related to a higher risk of prostate cancer.

A similar pattern emerged when the investigators looked at men's intake of nitrites and nitrates - chemicals used to preserve and flavour processed and cured meats like ham, bacon and sausage.

In the body, nitrites and nitrates can promote the production of potentially cancer-promoting chemicals called nitrosamines.

Taken together, Dr Sinha's team said the findings point to potential mechanisms by which certain meats could promote prostate cancer. They also said it would be important to study the relationship between specific types of meat and prostate cancer risk.