More women may want to develop a taste for seaweed, if animal research is any indication of the food’s potential cancer-fighting ability.

In experiments with a group of female rats, scientists found that sprinkling some brown kelp seaweed on the animals’ apple wedges lowered the rats’ estrogen levels and lengthened their reproductive cycles.

The findings, according to lead author Christine F. Skibola, support an earlier pilot study involving women with abnormal menstrual cycles. In that study, brown kelp seaweed lowered the women’s estrogen levels and increased the number of days between their menstrual periods.

This research lays the groundwork for studying whether seaweed can help fight hormone-related cancers, according to Skibola, a toxicologist at the University of California, Berkeley. A majority of breast cancers are estrogen-dependent; meaning the hormone helps fuel tumor growth, and estrogen is thought to act similarly in ovarian and endometrial cancers.

If further research can uncover the anti-estrogen compounds in brown kelp, Skibola told Reuters Health, it could yield new ways to treat these cancers. “A lot of work needs to be done,” she said, “but hopefully this opens the door.”

The findings, published in the current issue of the Journal of Nutrition, also suggest that including seaweed in the diet could lower a woman’s risk of developing cancer in the first place.

Research has found that estrogen-dependent cancers are less common in women who have fewer menstrual periods throughout their lives, due to factors such as pregnancy, longer menstrual cycles and early menopause. In Japan, where the traditional diet is rich in seaweed, women tend to have lower blood levels of estrogen and more days between menstrual periods than women in Western countries. Moreover, their rates of estrogen-dependent cancers are lower.

“We’ve always assumed it was soy,” Skibola said, referring to the tofu and other soybean products that are common in many Asian diets. “But seaweed may play a role.”

Though the research is still in its early stages, Skibola said that women may want to add seaweed to their diets, since it’s believed to be healthful for a number of reasons. Seaweed contains antioxidant compounds, which help clear the body of potentially disease-promoting substances called oxygen free radicals.

“Adding seaweed to the diet is probably going to be beneficial,” Skibola said.

However, she offered a word of caution about the kelp supplements sold at health food stores. Kelp contains high amounts of iodine, as well as low levels of heavy metals, and taking the seaweed in supplement form makes it easier to get too much of these potentially toxic substances.

According to Skibola, kelp is not recommended for women who are pregnant or nursing, or for people with an overactive thyroid gland.

SOURCE: Journal of Nutrition, February 2, 2005.