Breast Cancer Benefits of Soy – Early Intake Appears Best
Posted Dec 03 2010 8:50am
Soy and breast cancer – it’s one of the most debated topics related to the impact of dietary habits on breast cancer. In spite of all the debate, current human research studies have been reporting that soy appears to be safe for breast cancer survivors and reduces breast cancer risk and the risk for breast cancer recurrence. In fact, one Johns Hopkins’ breast cancer expert recently stated, “I don’t think that women necessarily need to be afraid of consuming soy products, but they shouldn’t take the message that this is going to make a dramatic difference in the treatment of their breast cancer. Maybe it will in terms of prevention in the future but again, we need to do the more definitive studies to figure that out. Hopefully what we’ll take away from it is that soy is not a bad thing for breast cancer.” 
Many soy and breast cancer research studies have started looking at the potential benefits of soy for breast cancer in regards to specifics like the timing of soy consumption, effects of menopausal status, and breast cancer hormone receptor status. While the research is still in the early stages, each of the population-based studies that have looked at the timing of soy consumption in regards to breast cancer risk have reported that consumption of soy starting early in life appears to have the greatest benefit [2-5].
One study of over 3,000 Chinese women reported that increasing levels of dietary soyfood intake between ages 13 – 15 years was inversely linked with breast cancer risk later in life with the highest quarter of soyfood intake linked to a 49% reduction in breast cancer risk . The beneficial link between adolescent soyfood consumption and later breast cancer risk in this study was seen in both premenopausal and postmenopausal women. A smaller study of Asian-American women showed that breast cancer risk as an adult was reduced with higher dietary intakes of soy as a teen . Furthermore, this study reported that high soy consumption as both a teen and an adult provided greater protection (47% reduction in breast cancer risk) than low consumption at both times of life, while intermediate protection was provided by consuming high amounts as a teen and low amounts as an adult (33% reduction in breast cancer risk). This latter study suggests that lifetime soy consumption starting during our teen years might offer the greatest breast cancer risk reduction benefits. In addition to these two initial studies, two more recent studies continue to confirm the possible benefits of adolescent soyfood consumption. A study of more than 6,000 Canadian women who responded to questions about their adolescent soyfood consumption habits as a teen reported that higher intakes of both soy isoflavones and lignans (common in flaxseed) were both associated with a reduction in breast cancer risk (29% reduction in the highest intake group) . A second study of Asian-American women reported that breast cancer risk was reduced by about 60% with childhood soy intake , 20% by adolescent soy intake, and 24% by adult soy intake . While much more research is needed to confirm these studies and explore the mechanisms involved, these first few studies clearly suggest that regular soy consumption starting early in life appears to confer the greatest breast cancer protection benefits.
An ever-growing body of science suggests that regular dietary soy consumption, particularly starting early in life, as part of a healthy, well balanced diet, can be an important part of our fight against breast cancer. Future research studies will likely continue to explore this relationship in greater detail to determine how soy consumption provides breast cancer protection and whom might best benefit from regular dietary intake of soy.