Soy foods, dairy products may affect breast cancer risk

A study in Nutrition and Cancer suggests that eating soy foods like tofu can reduce the risk of brea…

A study in Nutrition and Cancer suggests that eating soy foods like tofu can reduce the risk of breast cancer. T he study did not directly link eating soy to reduced
risk of breast cancer; rather it found intake of the food was associated with lower levels of a biomarker that may be involved in the carcinogenesis of breast cancer and other cancers.

The study led by Y . Takata and colleagues from Cancer Research Center of Hawaii in Honolulu, HI, USA shows women eating the highest amounts of soy foods had lower serum levels of insulin-like growth factor -I (IGF-I), which has been linked to elevated risk for breast cancer and other malignancies.

For the study, the researchers analyzed dietary intake of soy collected through a validated food frequency questionnaire from 611 pre- and postmenopausal women including Japanese women in Japan and women in Hawaii who also provided blood samples for the analysis of IGF-I and IGF binding protein -3. 

It was found "Tofu intake was higher in Japan than among Japanese and Caucasians in Hawaii." and "Mean IGF-I levels were 11% lower among women in the highest tofu intake category compared with the lowest, but the difference in IGF-I levels between the highest and lowest tofu category was only significant among women in Japan." Japanese women are known to have a lower risk for breast cancer.

The researchers concluded "These findings suggest that a diet rich in soy foods and low in meats may be related to lower IGF-I levels."

Earlier, L. Francesca from University of Oxford and colleagues conducted another large study based on data from the European Prospective Investigation into Cancer and Nutrition to examine if some foods may affect serum levels of IGF-I, which has been found associated with some cancers including breast cancer.

They found a positive association between consumption of dairy products and elevated serum levels of IGF-1. T hey also found serum calcium levels positively associated with increased levels of IGF-I.

In their report published in Cancer Epidemiology, Biomarkers & Prevention, the researchers suggested that it is likely dairy products but not calcium that may increase serum IGF-I. In Western countries, dairy products are a major calcium source, meaning that calcium and dairy products are not two independent factors and suggesting that both indicate the same thing - dairy foods.

The authors said that high levels of IGF-I have been linked to breast cancer, prostate cancer and colorectal cancer in other observational studies.