According to researchers it has been found that postmenopausal women who adhere to a low-fat diet for at least eight years can reduce their risk of developing ovarian cancer by 40%.

Ovarian cancer usually occurs in women over the age of 50, but it can also affect younger women; it is not known what causes ovarian cancer but the disease is hard to detect in the early stages.

The earlier ovarian cancer is detected and treated, the better the chance for recovery, but often women with ovarian cancer have no symptoms or only mild symptoms until the disease is in an advanced stage and hard to treat.

Symptoms may include a heavy feeling in the pelvis, pain in lower abdomen, bleeding from the vagina, weight gain or loss, abnormal periods, unexplained back pain that gets worse, gas, nausea, vomiting, or loss of appetite.

Treatment usually involves surgery followed by chemotherapy.

In a study led by Dr.Ross Prentice of the Fred Hutchinson Cancer Research Center, a large group of women women age 50 to 79, took part in a randomized, controlled dietary modification trial of chemoprevention.

The study was part of the Women's Health Initiative and for it 19,541 women followed a diet with no more than 20% of energy from fat, at least five servings of fruit and vegetables a day, and at least six servings of grains daily, while the other 29,294 women (the control group) followed their usual diet.

The diet group attended 18 group sessions with nutritionists in the first year and then received quarterly maintenance sessions to help them reach dietary goals.

The sessions included information on the fat content of food, fat budgeting, high-risk food situations, and other nutritional topics as well as dietary self-monitoring, social influences on eating, and relapse prevention.

The study found at the end of the first four years that the two groups had similar cancer rates; however, after the next four years of the study, the intervention group had a rate of 0.38 cases of ovarian cancer per 1,000 women annually, compared with a rate of 0.64 cases per 1,000 women in the control group.

The women in the intervention group also had a 9% lower risk of developing breast cancer, but the researchers say the finding was not large enough to be statistically significant.

Some experts believe that a high fat intake increases the amount of estrogen in the blood, which could play a role in the development of ovarian and breast cancer.

The study found that women in the intervention group had an average 15% reduction in estradiol, a form of estrogen, while the control group had no change.

It was found that the women in the study who cut their fat intake the most experienced the greatest reduction in breast and ovarian cancer risk.

The researchers say postmenopausal patients should be encouraged to change to a low-fat diet to reduce their risk for ovarian cancer risk and also reduce the risk of breast cancer and total invasive cancer.

The research is published online in the Journal of the National Cancer Institute.