New research on ovarian cancer, one of the five most deadly cancers among women in developed countries, suggests that a balanced plant-based diet may help in its prevention. The National Cancer Institute says this strategy is important since ovarian cancer often produces no clear symptoms until late in its development and is difficult to detect through current tests and screenings. Several different studies now show that a mostly plant-based diet offers multiple ways to lower risk of ovarian cancer.

In four separate studies in the past two years, women who ate more vegetables and fruits slashed their risk of this cancer one-third to two-thirds compared to women who ate the least produce. Vegetables and fruits contain a variety of protective substances that fight a broad range of cancers. In a new report in the Journal of Nutrition, diets high in fiber were linked with 57 percent lower risk of ovarian cancer, and those highest in carotenoids (beta-carotene and its cousins) faced 67 percent lower risk.

In Italy, higher consumption of legumes (dried beans and peas) was linked with 33 percent lower risk, according to a report in the International Journal of Cancer. Protective benefits could come from the fiber and natural phytoestrogens in legumes. Greater use of beans could also reflect more meatless meals; in the same study, higher red meat consumption was linked with more than 50 percent higher ovarian cancer rates.

Dietary fat may have positive or negative influence on risk of ovarian cancer. A summary analysis of studies involving more than 6,000 women published in Nutrition and Cancer found that those with higher fat consumption faced greater risk; in particular, eating more animal fat was linked with a 70 percent increase in risk.

Yet not all fat is bad. A new study in the International Journal of Cancer reports 40 percent lower ovarian cancer in women with diets highest in omega-3 fat (the type found in salmon and certain other fish, flaxseed and walnuts). Olive oil and certain seed-derived oils may also offer some protection, since an Italian study in Cancer Causes and Control noted women consuming the most faced 32 percent less ovarian cancer than those who ate the least. However, more olive oil consumption may be a marker for diets with more cooked vegetables and salads (especially in Italy), and it could be the higher vegetable consumption truly offering protection.

A study of more than 62,000 women showed that body fat may also affect risk. Published in the American Journal of Epidemiology, women with enough excess weight to be classified as obese were almost 70 percent more likely to develop ovarian cancer than those in a healthy weight range. The same study noted earlier that linked greater vegetable, fruit, fiber, and carotenoids with lower risk also reported 25 percent greater risk among those who consumed the most calories. Results like these can be hard to interpret, since such links could reflect the hormonal changes from high caloric intake or excess body fat, or could be a reflection of diets low in fruits and vegetables.

More research is needed, but for now, the mostly plant-based diet recommended by the American Institute for Cancer Research to lower overall cancer risk 30 to 40 percent is a good way to help protect against ovarian cancer. But since ovarian cancer can be difficult to detect, talk with your doctor about risk factors and possible ways to help protect yourself.