WEDNESDAY, Aug. 29, 2001 (HealthDayNews) -- Women who add flaxseed to their diet may reduce their risk of breast cancer, says a study presented today at the 222nd national meeting of the American Chemical Society.
The researchers say flaxseed appears to affect hormone levels specifically linked to breast cancer.
"We found that flax consumption altered urinary estrogen 2/16 -- alpha estrone -- which is thought to be a risk factor for breast cancer," says lead investigator Joanne Slavin, a nutritionist at the University of Minnesota at St. Paul. The "2/16" refers to the ratio between two types of "daughter" estrogens; 2 hydroxy estrone generally is called the "good estrogen," and 16 alpha-hydroxy estrone is called "bad estrogen;" as the ratio fluctuates so does a woman's tendency to get cancer, say experts.
Although flaxseed is considered a phytoestrogen, a hormone-like plant substance that acts like a weak estrogen in humans, it doesn't behave exactly like other phytoestrogens. Instead, flaxseed is thought to interfere with hormone production, affecting natural levels of estrogen.
"It is thought to offer protection against hormone-sensitive cancers of the breast, uterus and prostate by interfering with the actual metabolism of the sex hormones," says Cindy Moore, spokeswoman for the American Dietetic Association and director of Nutrition Therapy at The Cleveland Clinic Foundation in Ohio.
The new study is said to be the first to prove the ability of flaxseed to alter hormone levels linked directly to breast cancer in humans.
"Flax contains, besides phytoestrogens, omega-3 fatty acids and soluble fiber," Slavin says. Combined with the fact that flaxseed also is a powerful antioxidant, this may all work together to achieve the desired protective effects, she says.
Moore says, "Flaxseed is rich in dietary fiber, lignins [a source of plant estrogen and fiber], vitamins, minerals and essential fatty acids, all of which have been shown in a number of studies to have anti-cancer properties."
The study involved 28 postmenopausal nuns in a convent in Minnesota, chosen partly because of their strict dietary practices.
"All the sisters ate in a centralized cafeteria where the same diet was fed to all. They had some food choices, but with one basic entrée, starch, vegetable and dessert in a diet that was about 30 percent fat, 50 percent carbohydrate and 20 percent protein," says Slavin.
In addition, Slavin says the diets fluctuated on a rotating schedule, so every seven weeks the identical meal plans came around again.
To this plan, each nun added a dietary supplement containing either zero, five or 10 grams of ground flaxseed, alternating within the seven-week cycles.
At the conclusion of the year-long study, levels of two forms of estrogen were measured in each nun and compared with readings taken before the study began.
The result: All the nuns who ingested the five- or 10-gram doses of flaxseed had a decrease in estradiol and an increase in a type of alpha estrone. Both changes are thought to help prevent breast cancer.
In addition, Slavin says the higher the dose of flaxseed, the greater the change in hormone levels.
While no one knows for certain if making and maintaining the hormonal changes over time will affect breast cancer rates, experts say documenting the changes alone is an encouraging start.
"The alterations in hormone levels achieved by flaxseed are similar to what we also see with soy isoflavones. Hopefully studies will continue to prove they have a true protective effect against breast cancer. It would be a wonderful and safe way to gain that protection," says Moore.
In addition to breast cancer, Moore reports that flaxseed also is being studied in the prevention of heart disease, hypertension and inflammatory and immune disorders. The health benefits are thought to be primarily the result of the seed's fatty-acid content and fiber profile.
What To Do
If you are considering adding flaxseed to your diet, it's important to note that whole flaxseeds, in their natural state, cannot be digested. And munching on flaxseeds won't give you the lignins or the omega-3 fatty acids.
Moore says flaxseeds must be ground to obtain all the benefits. "Or, you can use flaxseed oil, as well," she says.
Flaxseeds can be ground into a meal or a flour, then sprinkled on cereal, salad and yogurt or added to baked goods, soups or casseroles.
"To ensure a longer shelf life, you should also refrigerate flaxseed," says Moore.
To learn more about the health benefits of flaxseed, click here. Or check the Flax Council.
To find recipes on everything from flaxseed salad dressing to crackers to flaxseed fried rice, click here.
