Highly touted for its health benefits, soy has increasingly entered American diets over the past five years. At the same time, nutritional researchers have raised doubts by demonstrating that not all soy research is positive. While experts generally do agree upon including soy in your diet, as it is full of nutrients and low in saturated fat, evidence for the more therapeutic benefits of soy is debatable, particularly when it comes to women’s health.

The Health Claim on Soy

In 1999, the U.S. Food and Drug Administration (FDA) approved a health claim for soy, allowing manufacturers to label soy as a food that may reduce the risk of heart disease. Legally, a product with a minimum of 6.25 grams of soy protein can have the following label: "25 grams of soy protein a day as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."

Soy’s ability to moderately lower cholesterol, and thus heart disease risk, may indeed be the most proven of soy’s promoted benefits. The greatest reductions seem to occur in people with elevated cholesterol levels to begin with, with benefits only lasting as long as soy is included in the diet. Reductions are also observed when animal proteins in the diet are completely replaced with soy protein.

While this data is certainly promising, there are a couple of things to keep in mind. First, the health claim on soy was based on positive study results of people eating an unusually high amount of soy protein each day: 50g, or the equivalent of eight 8-oz. glasses of soy milk a day, an amount not generally recommended. And second, that soy protein can’t possibly balance out other heart disease risk factors such as a lack of exercise or a diet high in saturated fat.

In the end, the soy health claim has spurred on a whole new world of soy products, consumer enthusiasts and research as well. With manufacturers and the media frequently highlighting the positives, the less than favorable science behind soy has largely slipped between the cracks. A review of some of the latest research reveals a more balanced picture.

Key Components of Soy

Many of the health benefits of soy research is related to compounds called phytoestrogens. The soybean is one of the richest sources of a particular type of phytoestrogen, isoflavones. However, not all soy products contain the same amount of isoflavones due to processing. Isoflavones are essentially removed from products such as soy hot dogs, soy burgers, soy cheeses, soy yogurts and soy isolate powder, while the best sources are relatively unprocessed products such as roasted soy nuts, soy flour, textured soy protein, cooked soybeans, soymilk, tempeh and tofu.

Ironically, while isoflavones may be behind some of the health benefits of soy, they have also been the object of much scientific debate and scrutiny in recent years, particularly as they relate to women’s health. Because these weak, plant-based sources of estrogen can either mimic or block human estrogen, their role in post-menopausal women and breast cancer is being carefully considered and studied.

Soy & Hot Flashes

During post menopause, a time when natural estrogen levels decrease, researchers have been looking into whether soy’s isoflavones in the form of food and supplements can reduce hot flashes by playing the role of such estrogens. While several studies have suggested a reduced number of hot flashes and other menopausal symptoms, more recent research reports no benefits at all. Overall, the scientific evidence does suggest benefits, although better quality studies are needed in this area in order to form a firm conclusion.

Soy & Breast Cancer

Suggestions that increased soy consumption is associated with reduced risk of breast cancer largely come from observations of Asian cultures where women who eat soy have a lower rate of breast cancer. However, because this research has been based on dietary interviews with women, as opposed to controlled human trials, it can only be considered preliminary. In other words, people who choose to eat soy may be making other lifestyle decisions that lower the cancer risk, but which aren’t obvious from the interviews, such as a healthier overall diet, more exercise and lack of smoking.

More worrisome are studies suggesting that soy can cause harm. Evidence indicating that high levels of isoflavones might increase the risk of breast cancer in women who are at high risk for the disease cannot be underestimated. What is not confusing is the impact of soy supplements on women taking tamoxifen for the treatment of breast cancer. It has been shown that this level of isoflavones directly competes with this drug therapy. Therefore, soy supplements should not be taken by women being treated for breast cancer.

To demystify the relationship between soy consumption and breast cancer, more research is necessary, particularly randomized clinical trials in the United States.

How much soy is best?

Most nutritionists recommend eating two to four servings of soy products a day, while more conservative experts suggest stretching this out over a week. Either way, this amount of soy provides the equivalent of about 25 grams of soy protein, the amount recommended by the FDA to see a reduction in heart disease risk.

For women in the midst of menopause or beyond who experience hot flashes or other issues related to estrogen loss, experts suggest increasing soy intake, which they say may help a little in the short term. Given the evidence we have today, this is not encouraged in the long-term, as current studies suggest that women diagnosed with breast cancer probably shouldn’t be eating lots of soy.

Wrapping Up

For better or worse, moderation is still the key in all diets, and variety is best. Experts recommend getting protein from a variety of sources, as well as your vitamins and minerals from a range of foods, especially fruits and vegetables. While soy may be a good alternative to other proteins, remember: It’s not a medication, but a food. The Coop carries a wide variety of both soy food products and supplements. To determine how soy best fits into your diet, be sure to consult a health practitioner and use common sense.

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