Soybean and Breast Cancer

By Assoc. Prof. Dr. Youwanush Kongdan

Soybeans have properties that contain a substance called Isoflavones, a hormonal agent which act similarly to estrogens. These female hormones stimulate growth of cancerous cells; therefore, people may shy away from consuming soy based products as it may reinforce cancer. According to research, soybean can both increase and decrease the risk of breast cancer either way.

We must understand the mechanism behind estrogen and breast cancer. In breast cancer, there are ones that have estrogen receptors and ones that does not have estrogen receptors. Therefore, we will be addressing the cancer type that have estrogen receptors only.  What makes this topic even more complicated is how the binding of estrogen hormone with receptors in each organ reacts differently, or the fact that how an environment plays a role in carrying different levels of estrogen in the body. It may not always be the case in stimulating breast cancer cells but sometimes it also inhibits breast cancer cells as well.

Back to the topic on whether soybeans reduce or increase the risk of breast cancer. Studies show that there is a significantly lower rate of breast cancer among the population of Japan and China in comparison to the western countries. Further studies also show that these people consume more foods that are lower in fat and soybeans; therefore, people start believing that eating soybeans can help reduce the risk of breast cancer. Another study shows that within the 70,000 Chinese female population; between the groups who ingest 13 grams and 5 grams per day respectively, there is an 11% reduced risk of breast cancer in groups who ingested 13 grams per day. In addition, some research also states that soybeans will compete to help separate estrogen hormone from binding with cancerous cell which in a way prevents cancer.
However, some research also mention that soybean has an interfering affects on patients who are receiving an anti-hormonal drug, lowering the estrogen level in the body.

On the contrary, studies by Sloan Kettering Cancer Center and Weill Cornell Medical College states that soybeans stimulate cancer cells, where they conducted a randomized trial in 140 randomly selected Stage 1 and 2 breast cancer patients. The first group consumes approximately 52 grams of soy based protein (equivalent to four cups of soymilk) for two to three weeks before operation; while the latter refrains from eating soy. It is found that there is cancer growth with the first group to be consuming soy based protein than those who did not. However, this study has not been followed through long enough to really conclude its validity. Dr. Youwanush Kongdan (Chief Executive Officer of Namarak Hospital, Specializing in Breast Health Care) concludes that eating soybeans is not a restriction for breast cancer patients nor does it induce more risk of cancer, Just follow these steps:

     1. Both general healthy public and breast cancer patients can eat soybeans and soy based products; but in the right amount that is not too much. 

     2. One to two servings of soybeans can reduce the risk of breast cancer.

     3. Soybeans should be consumed in its organic form found in regular menu items, rather than in supplementary diets or soy extracts as the concentration level can be too excessive.

     4. In the case of breast cancer group with positive hormone receptors, patients should avoid eating excessive amount of soy and monitor their soy intake during their                 treatment period, for instance, before surgery to one serving such as: 

         - ½ cup of Tofu

         - ½ cup of Boiled Soybeans

         - 1 tablespoon of Miso

         - 1 cup of Soymilk

         - ½ cup of Soy Yogurt

         - ½ cup of Soybean Flour