Soy Protein Reduces Breast Cancer Risk

Summary
A recent study from Korea assessed the impact of soy protein intake on the occurrence of breast cancer. For the study, the researchers compared consumption patterns of tofu and other soy products of 362 women with breast cancer with 362 women of the same age who had never been diagnosed with breast cancer. The study reports that “high soy protein intake was associated with reduced breast cancer risk” in premenopausal as well as postmenopausal women. The breast cancer preventive effect was more evident in premenopausal women for whom the cancer risk decreased as tofu consumption increased.

Introduction
All women do not have similar chances of suffering from breast cancer. Researchers are making an effort to identify which factors, including dietary factors, that might help in reducing or increasing the incidence of cancer. Studies have shown that Japanese women are at a higher risk of breast cancer if they migrate to the U.S., compared to those who continue to live in Japan. To account for this difference in breast cancer occurrence between migrant and non-migrant Japanese women, researchers have looked at the role of dietary patterns in the development of breast cancer. Soy is well known for its antioxidant and anticancer properties. In the present study, the researchers compared tofu and other soy protein consumption patterns of Korean women with breast cancer with those who had never had breast cancer.

Methodology
* In the hospital-based study, researchers selected 362 women with breast cancer and matched them with control participant women by menopausal status and age.
* Trained people interviewed these women on age, education, marital status, reproductive and menstrual history, family history of cancer, physical activity and dietary habits.
* With the help of food questionnaires, the women were specifically asked about intake of tofu and other soy products.
* The researchers measured the total soy protein intake and its association with breast cancer risk.

Results
* Breast cancer patients were more likely to have a high carbohydrate diets in the past; less likely to have breastfed their children; and less likely to drink alcohol or take a vitamin supplement. Compared to the controls, breast cancer patients had a lesser average number of children.
* Women with breast cancer had consumed 27 grams of tofu per day, while others had consumed an average of 36 grams in a day.
* Regarding soy proteins, the breast cancer patients had been using 7.4 grams per day while others had used 8.5 grams in a day.
* Tofu consumption helped both premenopausal and postmenopausal women. However, in the case of premenopausal women, it showed a proportional relationship with cancer risk reducing with every increase in tofu consumption.

Shortcomings/Next steps
All the participants recalled their eating habits after a gap of more than three years, which might have affected the accuracy of reporting. Moreover, different soy foods may have varying soy protein content. The study was conducted in one country only. The need is to conduct such studies in more countries so that universally applicable conclusions can be reached.

Conclusion
Compounds called isoflavones present in soy are biologically active and proposed to impact the development of breast cancer. Some studies have reported that the use of soy products can help in cancer prevention, while other research has failed to confirm these findings. For the present study, the researchers assessed the impact of past consumption of tofu and other soy foods on the chances of developing cancer. They report that women using more tofu and other soy proteins had less chances of developing breast cancer when compared with those who used less of these nutritious foods. For the premenopausal women, the advantages were evident with every incremental increase in use. The positive impact of a soy-rich diet, if confirmed, can help lower the risk of breast cancer.

For More Information:
Dietary Intake of Soy Protein and Tofu in Association With Breast Cancer Risk Based on a Case-Control Study
Publication Journal: Nutrition and Cancer, 2008
By Mi Kyung Kim; Jin Hee Kim; Hanyang University, Seoul, Korea

*FYI Living Lab Reports Are Summaries of the Original Research.


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