In the last decade, since soy products made their debut in the U.S. and continued to skyrocket to become a competitor against corn as the top agricultural crop, many concerns have arisen concerning soy, including it's controversial link to cancer. However, recent studies have come to light that suggest the consumption of soy products early in life may actually reduce the risk of breast cancer.
There is a wide variety of soy foods, a few including soy milk, tofu, soy flour, edamame, and miso. According to BreastCancer.org soy contains antioxidants and beneficial phytochemicals that normalize cell growth and activity, and regulate cholesterol. Soy also contains isoflavones which are phytoestrogens and similar to estrogen women produce but at a much lower strength in plants.
According to LATimes.com, the link between soy and cancer posits that since soy isoflavones bind to estrogen receptors, they could potentially stimulate cells to divide. On the other hand, isoflavones may also block receptor-activation by estrogen. The benefits and risks of soy seem at odds and truly came to head when researchers began large population studies which showed that Asian women, who traditionally consume more soy, had lower rates of breast cancer until they switched to a Western diet.
CNN.com reports that the large population studies suggested that diets high in phytoestrogens have a preventative effect on breast cancer and even prostate cancer in men. Conversely, animal studies showed that extremely high amounts of phytoestrogens actually encouraged breast and uterine cancer growth. The main takeaway is the amount of soy that is being consumed: a diet with naturally-occurring soy could actually lower cancer risk.
A recent study reported by CBSNews.com show that women who consumed soy products in their adolescence years had 30% less risk of cancer than women who did not consume soy. Furthermore, another recent study released by the American Association for Cancer Research found that the isoflavones found in soy were not a risk for breast cancer survivors, with some evidence that soy could actually reduce the risk or recurrence.
The study followed over 18,000 women between the age 20-83 who were survivors of invasive primary breast cancer, 16,000 of which were assessed over a year after their breast cancer diagnosis. The study spanned women in Shanghai, China and women in the U.S. and found that women who consumed more soy (greater than 23 mg per day) had a 9% reduced risk of mortality and a 15% reduced risk of breast cancer recurrence. Not surprisingly, the study found that women in Shanghai had a significantly higher average daily soy consumption at 45.9 mg while women in the U.S. averaged at 3.2 mg per day.
Due to the vast differences in diets between countries and other lifestyle differences, scientists could not conclusively call the results of the study statistical significant but the lead researcher of the study, Xiao Ou Shu, M.D., Ph.D., professor of medicine at Vanderbilt Epidemiology Center, Vanderbilt University Medical Center believes that the inclusion of soy foods to a diet is healthy for patients recovering from breast cancer. This does not include soy supplements as the amount of isoflavones can differ dramatically vs. that found in natural soy food.
As with most things in life, moderation is key. Consuming moderate amounts of soy may even be beneficial to your health by offering a different type of protein. A healthy diet that consists of lean protein and fresh vegetables paired with regular exercise is the best way to fight disease.