Updated: Dec 12, 2019
The soya bean or soybean is a legume that is native to East Asia where it has been human food for thousands of years. Now, the United States produces 32% of the world total, Brazil grows 31% and Argentina grows 18%, making it widely available in the modern Western diet as an protein alternative, ingredient or supplement.
The soybean it self can be eaten whole, but there are also different ways in which it is processed so that it can be transformed into a wide variety of products such as:
Soybean protein or meat alternative
Textured vegetable protein (TVP)
In addition to its uses in food, soy is available as dietary supplements in the form of powders, capsules and tablets.
Benefits of Soy on Health
Consuming soy protein is shown to lower blood levels of LDL (bad) cholesterol and reduce hypertension, making it important for heart health. The presence of isoflavones (a phyto-estrogen) in soy is known to reduce menopausal symptoms. (Cheng, et,al, 2007). For women it has also been shown to relieve breast pain, premenstrual syndrome (PMS), migraine headaches during menstruation and disorders of the ovaries such as polycystic ovary syndrome.
There are also several other body systems that may have a positive benefit from the consumption of soy or soy products. Studies have shown that soy may:
serve as a safe alternative in infant formula for babies that are allergic to dairy
prevent osteoporosis and relieve joint pain and stiffness
help normalize type 2 diabetes and pregnancy-related diabetes
slow down the development of kidney disease
improve memory and mental function
prevent certain type of inflammatory functions
relieve constipation, diarrhea, and irritable bowel syndrome
help with weight loss, improves muscle strength and relieves muscle soreness caused by exercise
Possible Dangers of Soy
While soy is a good source of (complete) protein and shows to be beneficial for several body systems, there are also a number of dangers that may actually outweigh the benefits.
Soy is the number 1 genetically modified organism (GMO) with 82% adoption by farmers in the West. (Non-GMO). No one knows for sure "allegedly" how GMOs affect our health and the corporations that are behind the GMO soy do not sponsor any research that might reveal negative properties of their product. However, potential effects of consuming GMO based foods may include alteration in DNA, if there is continued consumption over time.
The isoflavones, which are phytoestrogens, act like normal estrogen, causing changes in gene expression that interfere with certain body processes. (Morito, et, al, 2001). For example, they can reduce or increase estrogen activity in the body which can lead to hormonal imbalances . (Hwang, et, al, 2006).
Animal studies (Allred, et, al, 2001) and human studies have shown that the use of soy may cause breast cancer. In one study, 24 women consumed soy protein supplements and 7 women were found to have an increased number of breast epithelial cells (cells that are likely to turn cancerous). (Petrakis, et, al, 1996).
Because of isoflavones, soy is believed to affect male fertility. In male animal studies, exposure to soy isoflavones in the womb was found to cause adverse effects on sexual development. (Levy, et, al, 1995). Studies on human males have not been conclusive and more studies are needed.
Soy may affect thyroid health by inhibiting the function of the enzyme called thyroid peroxidase, which is necessary for the production of thyroid hormones (4). In a 3-month study, 37 adults consumed 30g of soy supplements daily. At the end of the study, scientists found raised levels of thyroid stimulating hormone, a marker for diminished thyroid function. Some participants developed symptoms of hypothyroidism, which succeeded after stopping taking the supplements. (Ishizuki & others, 1991)
Female children who are fed soy infant formula have been found: to have more breast tissue at 2 years old (Zung & others, 2008), to experience early puberty, and to have a longer and more painful menstrual cycle (Strom & others, 2001).
Children who are given soy-based infant formula may be at risk of developing neurological and behavioral conditions (i.e ADHD) due to high levels of manganese and aluminum present in certain soy products. (Cockell & others, 2004).
Most of the soy grown in the West is genetically modified and people are consuming a variety of soy products without understanding of the possible consequences. With many studies being initiated on the effects of soy, we are starting to recognize trends of negative effects. In order to ensure safety and reduce risk of adverse effects, it is advisable to prioritize other legumes, such as chickpeas, alfalfa, non-soy beans, peas, and lentils. If you plan to have a child, or if you are pregnant, try to avoid soy as it may potentially affect your health and the health of your child. Mothers, the best food for your infant is breast milk so consider breast feeding and then supplement with formula if needed. If you are unable to nutrify your child with breast milk or formula, seek professional guidance from an expert.
Allred, et, al, . (2001, July). Cancer Research. Soy diets containing varying amounts of genistein stimulate growth of estrogen-dependent (MCF-7) tumors in a dose-dependent manner.
Cheng, et, al, . (2007, May-June). Menopause. Isoflavone treatment for acute menopausal symptoms.
Cockell, KA & others. (2004, April). Journal of the American College of Nutrition. Manganese content of soy or rice beverages is high in comparison to infant formulas.
Divi, RL, et, al, . (1994, November). Biochemical Pharmacology. Anti-thyroid isoflavones from soybean: isolation, characterization, and mechanisms of action.
Hwang, CS, et, al, (2006, November). The Journal of Steroid Biochemistry and Molecular Biology. Isoflavone metabolites and their in vitro dual functions: they can act as an estrogenic agonist or antagonist depending on the estrogen concentration.
Ishizuki, Y & others. (1991, May). Nihon Naibunpi Gakkai Zasshi. The effects on the thyroid gland of soybeans administered experimentally in healthy subjects. (article is in Japanese).
Levy, JR & others. (1995, January). Society for Experimental Biology and Medicine, NY. The effect of prenatal exposure to the phytoestrogen genistein on sexual differentiation in rats.
Morito, K & others. (2001, April). Biological and Pharmaceutical Bulletin. Interaction of phytoestrogens with estrogen receptors alpha and beta.
NCCIH. National Center for Complementary and Integrative Health. Soy.
Non-GMO Project. Soy.
Petrakis, NL and others. (1996, October). Cancer Epidemiology, Biomarkers & Prevention. Stimulatory influence of soy protein isolate on breast secretion in pre- and postmenopausal women.
Strom B & others. (2001, August 15). JAMA. Exposure to Soy-Based Formula in Infancy and Endocrinological and Reproductive Outcomes in Young Adulthood.
Zung, A & others. (2008, February). Journal of Pediatric Gastroenterology and Nutrition. Breast development in the first 2 years of life: an association with soy-based infant formulas.