Confused about soy? The research on its benefits continues to pile up, including studies on women. A 2016 review of each of the major research areas involving soy concludes that it reduces the risk of breast cancer in women and has the following beneficial characteristics.
10 Benefits of Soy
- It has a high protein content compared to other plant proteins, and is a good substitute for animal protein. The protein in soy is easily digested. Replacing your animal protein with soy, legumes, mushrooms and hemp seeds will have the added benefit of decreasing greenhouse gases responsible for climate change.
- The low carbohydrate content of soybeans means that it is good for people with diabetes. It has a low glycemic index and will not elevate insulin. High insulin levels otherwise increase breast cancer risk threefold.
- Soy is a good source of the minerals potassium, calcium and iron. The absorption of calcium in soymilk is similar to what one would obtain from an equivalent amount of cow’s milk. Thus it is a good replacement for dairy, and source of iron for vegetarians.
- Soy contains isoflavones, such as genistein, which act as weak estrogens that offer protection against breast cancer and selectively bind to certain estrogen receptors to block the body’s stronger estrogens. Isoflavone intake among adults ranges from about 30–50 mg/day in Japan but is less than 3 mg/day in the United States, Canada and Europe. Japan’s breast cancer incidence is about half of that in the US and Europe. Chinese women, who consume a diet higher in isoflavones than western women, have approximately one fifth the breast cancer rate as American women.
- Soy protein significantly lowers LDL-cholesterol by approximately 4% to 6%, when about 25 grams a day are ingested. It also lowers circulating triglyceride levels (~5%) and raises beneficial high-density-lipoprotein (HDL)-cholesterol levels (~1%–3%), thereby reducing the risk of cardiovascular disease.
- Soy intake helps to lower blood pressure by 1.5-2.5 mmHg and helps to reduce stiffness in the walls of the arteries, also reducing the possibility of cardiovascular disease.
- The high-quality protein and well-absorbed calcium provided by many soy foods can contribute to bone health and reduce the risk of osteoporosis.
- Higher soy intake early in life is associated with a 25% to 60% reduction in risk of breast cancer later in life. The protection afforded by isoflavones may be similar to the observed protective effect of early pregnancy against breast cancer.
- In a meta-analysis of five prospective studies, two from the United States and three from China, involving over 11,000 women with breast cancer, it was found that soy consumption after a diagnosis of breast cancer was associated with significant reductions in breast cancer recurrence and mortality. Soy consumption was similarly beneficial in Asian and non-Asian women.
- Higher soy consumption is associated with as much as a 50% reduction in prostate cancer risk.
Soy Intake Reduces the Risk of Breast Cancer Recurrence
A study done in China (published in the Dec. 9, 2009 Journal of the American Medical Association) examined the safety of soy food consumption among 5,042 breast cancer survivors, aged 20 to 75. Women were recruited into the study six months after a breast cancer diagnosis. After four years, women with the highest intake of soy protein had a 29 per cent lower risk of death and were 32 per cent less likely to have a breast cancer recurrence compared with women with the lowest intake. Soy was protective for women with either early or late stage breast cancer and in women with estrogen-receptor (ER) positive and ER negative breast cancer.
Soy intake actually enhanced the effectiveness of the drug, tamoxifen. In fact, women who consumed the most soy and did not take tamoxifen had a lower risk of cancer recurrence and death than tamoxifen users with low soy intakes. In effect, soy food intake performed better than tamoxifen in preventing recurrence! The women who consumed the most soy, whether they used tamoxifen or not, had a 35% reduction in recurrence.
A second study called the Life After Cancer Epidemiology (LACE) study, published in November 2009, followed 1,954 northern California early stage breast cancer survivors for six years and found that postmenopausal women with a high soy intake – compared with none – had a lower risk of their cancer returning. Among postmenopausal women treated with tamoxifen, those who consumed the most soy were 60 per cent less likely to have their breast cancer recur compared with women with the lowest intakes.
In studies on rats, soy inhibits the growth of human-derived breast cancer tumors in a dose-dependent manner and causes cell death (apoptosis) in breast cancer cells.
Soy in Adolescence is Protective
When consumed in childhood, soy substantially decreases the risk of premenopausal breast cancer. Women who consume a high amount of soy foods consistently during adolescence and adulthood (i.e. at least one serving of tofu a day) have a substantially reduced risk of premenopausal breast cancer.
Less or no significant association with soy food consumption is found for postmenopausal breast cancer.
Genistein (from soy), an isoflavone, in combination with capsaicin (from cayenne) exerts anti-inflammatory and anticarcinogenic properties that protect from breast cancer.
When postmenopausal women consumed 20 g of soy protein containing 160 mg of total isoflavones daily, there was a significant improvement in a variety of menopausal symptoms (vasomotor, psychosexual, physical, and sexual) among the women taking isoflavones, while no changes were seen in the placebo group.
However, we recommend you DO NOT take isolated isoflavones – the greatest and safest benefit from soy is from the whole food.
Fermented vs Unfermented
Caution if Allergic
A note of caution though – some people have allergies to soy, with symptoms of gas and bloating. If you are one of them, then minimize or avoid soy and use 2-4 tbsp. daily of freshly ground flaxseed instead.
Soy and Thyroid Function
Use Organic Soy
How Much Do You Need?
So how much do you need? A daily intake of 11 grams of soy protein offered the most benefit, an amount found in about 11/2 cups of soy milk, one soy burger, 1/2 cup of edamame (young green soy beans) or 1/2 cup of firm tofu. Higher intakes did not offer extra protection against breast cancer, although 25 grams daily is required to lower LDL cholesterol.
This chart can help you determine your soy intake.
|Food||Protein Content (Grams)||Quantity Required|
|Tofu, silken||8.1||½ cup|
|Tofu, firm||15.6||½ cup|
|Soybeans, boiled||16.6||½ cup|
|Soybeans, dry-roasted||39.6||½ cup|
|Soy milk||5.6||1 cup|
|Soy protein powder||58.1||1 ounce|
All-in-all, organic soy is a powerful dietary ally in reducing the risk and recurrence of breast cancer.
- Soy food intake and breast cancer survival.
- Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: the Life After Cancer Epidemiology study.
- Anti-inflammatory and anticarcinogenic effect of genistein alone or in combination with capsaicin in TPA-treated rat mammary glands or mammary cancer cell line.
- Adolescent and adult soy food intake and breast cancer risk: results from the Shanghai Women’s Health Study.
- Childhood soy intake and breast cancer risk in Asian American women.
- Dietary intake of soy protein and tofu in association with breast cancer risk based on a case-control study.
- Dietary seaweed modifies estrogen and phytoestrogen metabolism in healthy postmenopausal women.
- Early soy exposure via maternal diet regulates rat mammary epithelial differentiation by paracrine signaling from stromal adipocytes.
- Effect of high-dose isoflavones on cognition, quality of life, androgens, and lipoprotein in post-menopausal women.
- Epidemiology of soy exposures and breast cancer risk.
- Estrogen/isoflavone interactions in cynomolgus macaques (Macaca fascicularis).
- Evidence that low-dose, long-term genistein treatment inhibits oestradiol-stimulated growth in MCF-7 cells by down-regulation of the PI3-kinase/Akt signalling pathway.
- Expression analyses of nuclear receptor genes in breast cancer cell lines exposed to soy phytoestrogens after BRCA2 knockdown by TaqMan Low-Density Array (TLDA).
- Genistein in the Presence of 17beta-Estradiol Inhibits Proliferation of ERbeta Breast Cancer Cells.
- Is equol the key to the efficacy of soy foods?
- Isoflavone-deprived soy peptide suppresses mammary tumorigenesis by inducing apoptosis.
- Perspectives on the soy-breast cancer relation.
- Phytoestrogen-mediated inhibition of proliferation of the human T47D breast cancer cells depends on the ERalpha/ERbeta ratio.
- Soy isoflavones and cancer prevention.
- Soy isoflavones have an antiestrogenic effect and alter mammary promoter hypermethylation in healthy premenopausal women.
- Soy isoflavones, estrogen therapy, and breast cancer risk: analysis and commentary.
- Soya phytonutrients act on a panel of genes implicated with BRCA1 and BRCA2 oncosuppressors in human breast cell lines.
- The effect of genistein aglycone on cancer and cancer risk: a review of in vitro, preclinical, and clinical studies.
- Estrogenic and antiproliferative properties of genistein and other flavonoids in human breast cancer cells in vitro.
- Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature.