Soy: good or bad for our health?

Soy is traditionally a part of a typical Asian diet. Researchers at the U.S. National Cancer Institute investigated whether soy consumption can render protection against breast cancer.

According to senior researcher Regina Ziegler

“Historically, breast cancer incidence rates have been four to seven times higher among white women in the U.S. than in women in China or Japan. However, when Asian women migrate to the U.S., their breast cancer risk rises over several generations and reaches that of U.S. white women, suggesting that modifiable factors, rather than genetics, are responsible for the international differences.”

However, the lifestyle factors that predispose Asian women living in the US to breast cancer have never been identified.

The study looked at Asian women (of Chinese, Japanese and Filipino descent) living in California or Hawaii. The researchers interviewed 597 of these women (aged 22 to 55 years old) with breast cancer and case-matched with 966 controls. In addition, whenever possible, the mothers of the women were interviewed regarding the participants’ diet during their childhood.

The results of the study show:

• Consumption of or large amounts of soy during childhood was linked to a 58% reduced risk for breast cancer
• high soy consumption during adolescence and adulthood was linked to a 20 to 25% reduced risk.

The study authors concluded:

Soy intake during childhood, adolescence, and adult life was associated with decreased breast cancer risk, with the strongest, most consistent effect for childhood intake. Soy may be a hormonally related, early-life exposure that influences breast cancer incidence.

Soy is rich with isoflavones. The authors speculate that these compounds may have estrogenic properties that may cause changes in the mammary tissue. Animal studies have shown that soy consumption results in early maturation of breast tissue and increased resistance to carcinogens.

I myself am of Asian descent and therefore found this study rather interesting. We Asians consume soy in the form of tofu (coagulated soy milk) or soya sauce. Soya milk is also used as a substitute formula for lactose-intolerant infants. The food products come from the soya bean plant Glycine max.

Soy used to be considered the wonder superhealthy food but has become somewhat controversial lately as more and more research studies have linked soy consumption to adverse health effects ranging from memory decline to cancer. In 2007, the Cancer Council of New South Wales, Australia issued guidelines that warn cancer patients about the dangers of high-soy diets and soy supplements. The guidelines especially emphasized the dangers for those suffering from hormone-dependent cancers, including prostate and breast cancers.

Clearly there is a need for more studies before we can clearly say whether soy is beneficial or detrimental to our health.

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