The latest trend in natural foods marketing—combining soy and flaxseed—is so ubiquitous you could dine on the combo at every meal. You could start with a breakfast of Zoe's Flax & Soy Granola with a side of Van's Soy-Flax Waffles, then snazz up your lunch with a handful of Trader Joe's Soy & Flaxseed Tortilla Chips. For an afternoon treat, you could munch on Real Foods' flax and soy Corn Thins and later have a midnight snack of a bowl of Back to Nature Flax & Fiber Crunch (with soy grits).
Of course, both foods are moving just fine on their own—sales of soy foods have increased 44 percent since 2001, and flax has become known as the richest vegetarian source of omega-3 essential fatty acids, prompting even mainstream bakers like Oroweat, U.S. Mills, and Roman Meal to sell flaxseed-enriched breads. So, why the sudden urge to combine these two in so many products?
The answer is that both soy and flaxseed contain phytoestrogens (plant estrogens), which can mimic human estrogen. There has been a lot of talk that this capacity could help relieve menopausal symptoms, like hot flashes.
Since soy and flaxseed are cousins but not identical twins—the phytoestrogens in flaxseed, called lignans, have a significantly different structure from the soy phytoestrogens—they may work differently in the body, says Lilian Thompson, professor of nutritional sciences at the University of Toronto and the queen of flaxseed research. Combining soy and flax in foods like protein bars or waffles may offer two sources of health protection; however, there's no hard evidence yet to suggest that their combined effect is greater than that of each alone.
Of course, just about the time menopausal women were hearing the news, research was showing that slurping down vast quantities of soymilk or soybean chili might actually increase your risk of breast cancer. As so often happens with modern medical dilemmas, newspaper headlines tilted back and forth, one week trumpeting the benefits of taking in ample amounts of phytoestrogens, and the next week decrying the risks.
It's tricky to figure out whether to stock up on soy-and-flax cereal or avoid the aisles brimming with snacks touting the duo. Will the pair tame your hot flashes and restless sleep? Will they lower your breast cancer risk or bump it up?
The truth is that both flaxseed and soy reduce menopausal symptoms, a boon to any woman who's spent even one night thrashing through hot flashes—the closest experience to life as a strobe light. Studies show that just one serving of soy each day (a half cup of tofu) reduces hot flashes by 10 to 20 percent. (Hormone replacement therapy reduces hot flashes by 60 percent.) Such studies have led both the American Menopause Foundation and the North American Menopause Society to recommend soy's use.
And soy does not affect hormone levels. In 30 studies, soy didn't raise estrogen levels. Theoretically that's a good thing, since increased estrogen may stimulate tumor growth, increasing the risk of breast cancer. Soy may also increase the length of the menstrual cycle by one day, says Mark Messina, adjunct associate professor of nutrition at Loma Linda University in Loma Linda, California. Which is also a good thing, since longer cycles are associated with decreased risk of breast cancer. And flaxseed may block prostaglandins, hormone-like substances that, when released in excess during menstruation, can cause heavy bleeding.
Meanwhile, the jury is still out on the effect of soy protein and phytoestrogens on bone density. Some studies show that for postmenopausal women, eating soy slightly reduces bone loss; others show it brings about no improvement.
Fears about soy intake increasing the risk of breast cancer have arisen largely in the past five years. William Helferich, a professor of nutrition at the University of Illinois, demonstrated that soy protein (isoflavones) appears to promote breast cancer. However, Harvard researchers found that isoflavones prevented tumor growth. Finally, a 2004 study showed that when women between the ages of 49 and 65 ate soy for one year, breast density (which is associated with cancer risk) did not increase. "The study suggests that the soy wasn't beneficial, but it wasn't harmful either," says Messina.
Perhaps the most certain data, which comes largely from population studies, suggests that those of us who ate tofu scrambles and soybean stews as children are the best protected. Soy eaten during childhood likely alters the structure of the developing breast, lessening the risk of cancer—a possible explanation for low breast cancer rates in Asia.
"But if that's the case," says Mindy Kurzer, soy researcher and professor of nutrition at the University of Minnesota in St. Paul, "then we know much less about whether an adult woman should consume soy. It may have no [additional] benefit or there may be a small possibility that it's stimulating cancer cells to grow."
Still, there is no research that suggests a greater risk of breast cancer in people who eat soy than those who do not. And studies of large populations associate soy with lowered risk. "It's theoretically possible that soy phytoestrogens stimulate tumor cells that have estrogen receptors, but that's not been proven," says Kurzer.
She tells friends who've had breast cancer, or who are at risk for it, to continue eating soy if they always have—but not to start if they haven't. She does not recommend supplements, since little is known about them. Messina takes this recommendation a bit further: "You need to be aware of the controversy, and you can live happily without eating soy. But the evidence suggests that soy is safe for everyone, including breast cancer survivors."
The flaxseed story is simpler: Some research shows that flaxseed reduces the risk of breast cancer and slows tumor growth, says Thompson. And evidence points to a possible long-term boon for flax lovers: It may have some protective effect in children as well, a fabulous inheritance to leave to your kids.
The central gift of flaxseed is the heart-healthy omega-3 fatty acids that help lower cholesterol and reduce clogging in the arteries. Those acids may also help fight inflammation in the prostate gland, keep sperm healthy, and improve penile blood flow, which in turn checks impotence. And the body simply needs those fatty acids—often difficult for vegetarians to come by—to help cell membranes best accept nutrients while barring harm.
Experts recommend eating about 1/4 cup of ground flaxseed (whole flax seeds aren't generally digested), or 1 to 3 tablespoons of flaxseed oil each day. If you haven't succumbed to one of those soy-and-flax products, you may want to sprinkle ground flaxseed on yogurt, cereal, soup, or salads.
Although ground flaxseed looks a bit like flour, if you bake with it, substitute it for the oil or eggs, not the flour. (For 1/3 cup of oil, substitute 1 cup of ground flaxseed. For one egg, substitute 1 tablespoon of ground flaxseed plus 3 tablespoons of water.)
To sum up: Despite the ever-changing news stories, the best evidence suggests that when you grab a flax-and-soy snack, you're benefiting your hormonal health —or at the least doing it no harm. Soy is a terrific low-fat protein and both it and flaxseed are great for your heart and your cholesterol levels. So don't skimp on these fabulous foods.
Dorothy Foltz-Gray writes often about food and fitness and is a contributing editor at Health, Alternative Medicine, and Arthritis Today.