October 10, 2007
Medical News Today

Reduced Risk Of Ovarian Cancer Linked To Low Fat Diet

A new US study has suggested that reduced risk of ovarian cancer in postmenopausal women could be linked to a low fat diet high in fruit and vegetables and grains. The 8 year study also suggested the risk probably gets lower the longer the diet is sustained. However, the study found no significant link between a low fat diet and reduction in overall cancer risk.

The study is published in the October 9th issue of the Journal of the National Cancer Institute and is the work of Dr Ross Prentice, of Fred Hutchison Cancer Research Center in Seattle, Washington, and colleagues.

The results came from the Women's Health Initiative (WHI) Dietary Modification Randomized Controlled Trial and cover 8.1 years of the intervention phase where researchers found there were fewer new cases of ovarian cancer among the participants in the intervention group (who changed their diet) than among the comparison group (did not change their diet).

Other studies have used data from the WHI trial but they were looking at incidence of breast and colorectal cancer in postmenopausal women and until now had not shown any results on ovarian cancer risk.

The researchers discovered no link between diet and ovarian cancer in the first four years of the trial, which was no surprise since it can take years for diet changes, which are preventive measures, to have an effect on disease. However, after the first four years, there was a small but statistically significant drop of 40 per cent in the risk of ovarian cancer among the women in the low fat intervention group compared to those in the unchanged diet group.

The researchers examined the data to see if dietary changes were linked to changes in risk of ovarian and endometrial cancer, and of invasive cancers overall. However, the only statistically significant results were in the links to ovarian cancer.

The WHI assigned nearly 20,000 women to the diet change group while nearly 30,000 women did not change their diet. The diet change group was asked to limit their fat intake to no more than 20 per cent of their total calorie intake, and to eat 5 or more daily servings of vegetables and fruit, and 6 or more daily servings of grains.

Significant changes of food intake were observed in the diet change group compared to the no change group which remained relatively unchanged. By the end of the first year of the study the diet change group had significantly reduced their total fat intake from 35 to 24.3 per cent of total calories. This was 10.7 per cent lower than the no change group. They also increased their intake of vegetables and fruits from 3.6 to 5.1 portions a day (1.2 portions more than the comparison group), and their grain intake went up from 4.8 to 5.1 portions a day (0.9 portions more than the comparison group). Some of the diet change group members reverted back to previous habits but the vast majority kept up the changes.

Women who had the highest fat intake at the start of the trial showed the greatest reduction in ovarian cancer risk. There was no difference in the endometrial cancer risk between the intervention and the comparison group, but a slight insignificant trend toward reduction in overall invasive cancers was visible in the intervention group.

The researchers concluded that "A low-fat dietary pattern may reduce the incidence of ovarian cancer among postmenopausal women." They suggested it was worth continuing to track the participants to see if longer term effects emerge between a sustained low fat diet and incidence of cancers.

According to the American Cancer Society (ACS), ovarian cancer is the 8th most common cancer among women in the US, excluding non-melanoma skin cancers.

The ACS estimates that nearly 22,500 American women will be diagnosed with ovarian cancer this year and nearly 15,300 will die from it.

A woman has a lifetime risk of developing ovarian cancer of about 1.5 per cent, or 1 in 67, and her risk of dying from ovarian cancer is just over 1 in 100. In both cases the risk is higher for white than for black women.

Ovarian cancer mostly occurs in older women; two thirds of cases are seen in women aged 55 and above.