Possibility of breast cancer prevention: use of soy isoflavones and fermented soy beverage produced using probiotics

Abstract

The various beneficial effects of soybeans, which are rich in phytochemicals, have received much attention because of increasing health awareness. Soy milk that has been fermented using lactic acid bacteria has been used to prepare cheese-like products, tofu (bean-curd), and yogurt-type products. However, the distinct odor of soybeans has limited the acceptance of such foods, particularly in Western countries. In Japan, while tofu and soy milk have long been habitually consumed, the development of novel, palatable food products has not been easy. The unpleasant odor of soy milk and the absorption efficiency for isoflavones can be improved using a recently developed fermented soy milk beverage. Cancer has been the leading cause of death, and breast cancer is the most common malignancy among women. The most common type of breast cancer is estrogen-dependent, and the anti-estrogenic effects of isoflavones are known. The present review focuses on the characteristics of soy milk fermented using probiotics, an epidemiological study examining the incidence of breast cancer and soy isoflavone consumption, and a non-clinical study examining breast cancer prevention using fermented soy milk beverage.

Keywords: L. casei Shirota; breast cancer; fermented soy milk; isoflavone; probiotics.

Figure 1

Serum concentration of total isoflavones in healthy adult subjects after the ingestion of soy milk or fermented soy milk beverage [23]. White circle, soy milk; black circle, fermented soy milk beverage. Data were expressed as the mean ± SD (n = 12) and were evaluated using a paired t-test. * p < 0.05. Data from Kano M. et al., J. Nutr. 2006 [23].

Figure 2

Time course changes in palpable mammary tumors in PhIP-exposed rats in 12th, 14th and 16th week after the start of the experiment. (A) Tumor incidence; (B) multiplicity; and (C) tumor volume. White bar, control; gray bar, soy milk and black bar, fermented soy milk beverage. All the data were expressed as the mean ± SE. The tumor incidence was analyzed using the χ² test. The tumor multiplicity and volume were analyzed using the Dunnett test relative to the control group [52]. * p < 0.05; ** p < 0.01. Kaga C. et al. Unpublished data [52].

Figure 2

Time course changes in palpable mammary tumors in PhIP-exposed rats in 12th, 14th and 16th week after the start of the experiment. (A) Tumor incidence; (B) multiplicity; and (C) tumor volume. White bar, control; gray bar, soy milk and black bar, fermented soy milk beverage. All the data were expressed as the mean ± SE. The tumor incidence was analyzed using the χ² test. The tumor multiplicity and volume were analyzed using the Dunnett test relative to the control group [52]. * p < 0.05; ** p < 0.01. Kaga C. et al. Unpublished data [52].