soy--breast-cancerThe association between consuming soy and developing or experiencing a recurrence of breast cancer is probably one of the most debated of all food and health connections. In the past, there was conflicting advice as women were encouraged to eat large amounts of soy, no soy, or something in between—recommendations that have been frustrating, to say the least.

Countless studies have been done on the subject, which in some ways increases the confusion. But we’ll share with you the latest research so you can make the best choice for your needs. 

So what should you do if you’re at high risk for or have a history of breast cancer, or if you simply want to ensure that you’re eating in the most healthful way? First, some interesting facts about soy and breast cancer:
  • In a review of 19 countries, China had the lowest rate of deaths from breast cancer and the second lowest rates of breast cancer diagnoses. The Chinese also had the highest intake of soy at about 20 to 50 milligrams per day.
  • European nations had the highest rates of breast cancer and the lowest intakes of soy at 0.5 to 0.7 milligrams per day.
  • Americans are in the middle of the road for breast cancer rates but on the low end for soy intake at about 1 to 6 milligrams per day.
From this information, it would seem obvious that the solution is to eat more soy, right? When word got out about China’s soy intake and breast cancer rates, everyone began recommending that we consume megadoses of soy. Food companies began adding it to cereals, desserts, snack bars, and more. But did it help?

According to Leena Hilakivi-Clarke, PhD, a professor of oncology at Georgetown University, “There’s no evidence that consumption of soy products in adult life reduces breast cancer risk in non-Asian women in America, and the reason is probably because women start consuming soy products as adults. Only 6% of adults older than 19 and 2% of individuals younger than 19 consume soy products in the United States.”

What’s important to note is that studies show Asian, Asian American, and Caucasian American women who regularly ate soy as children and teens have at least a 50% lower risk of developing breast cancer.

In addition, there’s a difference in how women in China and America eat soy foods. In China, they eat primarily traditional soy foods such as mature soybeans; edamame, which are green, immature soybeans; soy milk, which is made from soybeans; and tofu, which is made from soy milk.

In America, only 18% of adults and 7% of children who eat soy consume traditional soy foods. The majority of the soy foods eaten in America comes from processed foods made primarily from soy protein isolate and/or concentrate vs. whole soybeans—for example, soy ice cream, hot dogs, crumbles, drinks, cheese, and packaged meals such as pizza and lasagna. These soy isolates and concentrates contain large amounts of a phytochemical similar to estrogen that is linked to an increased risk of breast cancer.

Based on the research, I’d tend to agree with the American Cancer Society’s guidelines for women with a history of breast cancer and suggest they take in only moderate amounts of soy foods as part of a healthy, plant-based diet. They should not take concentrated sources such as soy-containing pills or powders or supplements containing high amounts of isoflavones.

For women without breast cancer, the same guidelines can apply. Whether you’re pre- or postmenopausal, don’t think of soy as a “magic bullet” you should begin loading up on the minute you hit menopause, getting it from as many foods as possible.

If you’re premenopausal, begin to incorporate moderate amounts of whole soy foods into your diet, and if you’ve just reached or are beyond menopause, enjoy these foods as well. Consider alternating cow’s milk with soy milk in cooking and for drinking. Add a tofu-based entree to your dinner rotation. Try munching on edamame or soy nuts (roasted soybeans) or sprinkling them on your salads.