Men who eat their veggies may be less likely than others to develop prostate cancer, a new study suggests.

Among more than 1,700 men with and without prostate cancer, those who ate the most fiber - particularly from vegetable sources - had a lower risk of developing the disease, Italian researchers found.

The benefit was “moderate,” they report in the International Journal of Cancer, but the findings suggest that at least some forms of fiber offer prostate cancer protection.

A number of studies have suggested that eating plenty of fruits and vegetables may help ward off prostate cancer, while “Western”-style diets heavy in animal fat and dairy products may increase a man’s risk of the disease. But not all studies have reached these conclusions, and the importance of diet in prostate cancer risk is still unclear.

There is evidence that fiber-rich foods may lower the risk of heart disease, diabetes and possibly certain cancers. However, studies looking at fiber and prostate cancer have generally yielded “null” findings, said Dr. Claudio Pelucchi, a researcher at the Mario Negri Institute for Pharmacological Research in Milan and lead author of the new study.

The difference in his team’s study, Pelucchi told Reuters Health, is that it broke down men’s fiber intake according to the type and source of fiber.

Fiber comes in two main forms, soluble and insoluble. Soluble fiber partially dissolves in water, and its food sources include vegetables, fruit, oatmeal and legumes. Insoluble fiber, which passes through the digestive system largely intact, is found in foods like whole grains, seeds and the skin on fruit.

For the study, Pelucchi and his colleagues surveyed 1,745 men between the ages of 46 and 74 about their diet and lifestyle habits. All of the men were surveyed while being treated in Milan-area hospitals between 1991 and 2002; nearly 1,300 had prostate cancer, while the rest were treated for conditions unrelated to cancer. Those with prostate cancer were asked about their eating habits during the two years before being diagnosed.

Pelucchi’s team found that men with the highest overall fiber intake had a slightly lower risk of prostate cancer than men with the lowest intake.

When the researchers looked at specific types of fiber, vegetable fiber emerged as most protective. Men who got the most fiber from vegetables were 18 percent less likely than those who ate the least to develop prostate cancer.

Fiber from fruit or grain products, specifically, was not related to a lower prostate cancer risk, but soluble fiber did appear to protect against the disease.

Pelucchi pointed out that because vegetables and fruit were the chief sources of soluble fiber, it’s possible that the fiber, per se, did not bestow the benefit. Other nutrients found in produce - or the generally healthy diet and lifestyle of fiber enthusiasts - could be at work, he said.

International Journal of Cancer, March 2004.