Soy Protein Isolate and Breast Cancer

The protein separated from soybeans is known as soy protein. Soy protein isolate is obtained after removing most of the carbohydrates and fats from the soy meal. Proteins serve as building blocks for cells. Soybeans, soy flour, soy concentrate (70% soy protein) and soy isolates (90% soy protein) are the main sources of soy protein. Out of these, soy protein isolate is the richest source of protein.

Soy Protein Isolate

Health Benefits

Soy protein has been used in the food industry for more than 50 years. Soy protein isolate contains 90% or more protein. Proteins are essential for the growth and repair of cells, muscle building, and for proper functioning of bodily systems. Soy protein isolate is added to protein powders which replace milk and dairy products. It is an important ingredient of liquid nutrition meals, infant formula foods, and soy milk. It is used to enrich protein bars, fruit drinks and juices, sauces, salad dressings, soups, breads, breakfast cereals, pet foods, pastas, muscle building foods and dietary supplements. It is mainly present in processed and fortified foods.

Soy protein isolate is a highly refined form of soy protein, and it comes with a neutral flavor. Absence of fats and carbs makes it easy to digest. It does not lead to flatulence or gas. This protein isolate is loaded with all the essential nutrients like omega 3 fatty acids, calcium, protein, folate, choline, magnesium, potassium, phosphorus and iron, which help improve your health. It improves heart health, strengthens the bones, and prevents prostate cancer. It is believed that it helps control problems like mood swings and fluctuating body temperatures in women. It also helps stabilize sugar levels in diabetic postmenopausal women. Several studies have proved that soy protein helps reduce bad cholesterol (LDL) levels, triglycerides levels, and thus helps reduce the risk of heart diseases.

Side Effects

Although soy protein provides complete proteins, excessive consumption of soy protein can affect your health seriously. It has been found that this isolate contains certain harmful substances like MSG (monosodium glutamate); although it is not mentioned on the labels. MSG consumption can lead to rapid heart rate, headache, chest pain, and numbness or tingling sensation in extremities. Studies have shown that phytoestrogens from soy protein may lead to hormonal imbalance. Excessive consumption of soy protein may affect libido and sperm count, and it can even cause erectile dysfunction. Some people may suffer from indigestion, allergy, constipation, diarrhea, nausea and vomiting. But you need not worry about these side effects, as very few people experience them.

Risk of Breast Cancer

The protein isolate contains certain types of enzymes which can affect your health. Depending upon the extrusion process, it may contain high levels of genistein, daidzein and other soy isoflavones. Studies show that soy isoflavones do not lower the symptoms like 'hot flashes' in postmenopausal women. They do not help prevent the growth of cancerous cells in breast, uterus or prostate.

Low rates of breast cancer in Asian women were attributed to high consumption of soy through the diet. But it was noticed that various cultural factors also determine the cancer rates. In fact, no epidemiological evidence was found which could prove the belief that consumption of soy lowers the risk of breast cancer. Experimental studies regarding the effect of soy protein on breast cancer risk have not helped the scientists draw any conclusion. The results produced were very confusing and conflicting. Some studies showed that soy protein isolate containing isoflavones was not as efficient as soy protein concentrate lacking isoflavones; in preventing the progression of cancerous breast tumors. Certain rat studies showed that rats who were fed this protein isolate showed low chances of developing malignancies in breast, but those who developed breast cancer had highly invasive tumors. Results of another study which involved mice whose ovaries were removed, state that the isolate caused development of breast tumor (estrogen positive), and it also led to increased uterine weight.

Some researchers have found out that soy protein consumption can prevent breast cancer while some have stated that it can lead to increased risk of the cancer, especially in premenopausal women. Studies have shown that if soy is consumed early in life, especially in early adolescence, then it protects the girl from breast cancer, later in life. Small doses of the soy isoflavone 'genistein' can lead to abnormal growth of cells, while large doses can inhibit such cell growth. Some scientists have shown that genistein helps prevent abnormal growth of the blood vessels that support tumor growth, and it also helps prevent production of some enzymes that promote abnormal cell growth.

It has not been scientifically proven that consumption of soy protein isolate can lead to the development of breast cancer. Whether women who have been diagnosed with breast cancer should consume soy protein is a controversial topic. It is true that Asian women are at less risk for breast cancer than Western women; but Asian women, especially Chinese and Japanese women, consume soy mostly in the fermented form. Consumption of soybeans in the form of fermented soy products, tofu, soy butter, and soy nuts, is considered as a better way of consuming soy protein.

The above information shows that more studies are required to prove the usefulness of soy protein in preventing breast cancer. The above discussion also shows that it is difficult to draw any conclusion about the relationship between soy protein isolate and breast cancer, at this stage. If you are thinking of taking soy protein supplements, then you should consult your physician first.

Posted in: Breast Cancer, Health Benefits