The soybean has been considered one of the five sacred grains of China dating back to 2900 BC. Currently, the soybean has been cultivated extensively and is now the United State’s second largest export crop. The bean is widely known for its high protein (40%) and oil (20%) content. The soybean was one of first genetically engineered crops, and as of 2012, 97% of soybeans grown in the U.S. are GE crops. The main purpose for cultivation of the soybean is to extract soybean oil for export. The leftover part of the bean is then used to make animal feed. A small percentage is used for food products such as tofu, tempeh, textured vegetable protein, miso, soy sauce, and soy lecithin.
There has been much debate over the past decade about the constituents of soy. One of these components is soy isoflavone, a phytoestrogen (phyto means plant). When absorbed, phytoestrogens act like very weak estrogens in the body. These are the molecules that have caused great controversy in the efficacy of the safety of soy products. Many experts consider them useful in the prevention of cancer, while other experts see them as endocrine disruptors and carcinogenic. After several years of reviewing the research, recent studies have shown that consuming soy leads to moderate beneficial effects in the reduction in risk of breast and prostate cancer, menopausal symptoms, and cardiovascular disease. Additionally, soy offers essential vitamins and minerals, complete protein, and high antioxidant properties.
What’s in it for me?
Soy contains a number of significant compounds, including vitamins, alpha-linolenic acid, and isoflavones.
Vitamins: Soy has a higher concentration of calcium, folate, and choline in comparison to other common grains such as corn, wheat, and rice.
- Calcium is essential for bone growth and repair. The National Institutes of Health list soy products as a source for calcium intake. This is an important note for those who are dairy-free. Soy supplements are not recommended as a source for calcium, as there is not enough evidence to show this is beneficial.
- Folate is a B vitamin essential for DNA replication and repair. Soy offers approximately 165mcg in 2/3 cup serving. The CDC recommends 400mcg of folate daily, especially among young women whom could become pregnant.
- Choline is an essential B-complex vitamin and is the precursor needed for the important neurotransmitter acetylcholine. Choline is found in the highest amounts in eggs and fatty meats. For those on a vegetarian diet or avoiding eggs and red meat, soy is a great alternate source for choline as 2/3 cup contains 116 mg.
Alpha-linolenic acid: ALA is an omega-3 essential fatty acid, which means it is necessary to consume ALA through the diet. ALA is an important molecule found in the cell membrane and used to make EPA and DHA, which are important for brain and nerve health and help the body make anti-inflammatory factors. Soybeans contain 8% ALA of the oil content.
Soy Isoflavones: Some of the most researched components of soy are the phytoestrogens called Diadein and Genistein. The most recent research to date has revealed:
- A recent study that will be published Mar 2014 reviewed the effects of soy isoflavones and prostate cancer. They found chemo protective mechanisms and also suggested that additional molecules in whole soy products are contributing beneficial effects by working synergistically with isoflavones.
- A study published Jan 2014 in Japan Journal of Clinical Oncology did a review on soy intake and risk of breast cancer in Japanese woman. They found, “There is some evidence that supports the biological plausibility of a protective effect of isoflavones on breast cancer risk.”
- Lastly, a review study published in Alternative Therapies in Health and Medicine in Jan 2014 states, “This literature review revealed that soy foods and isoflavones may provide relief from menopausal symptoms and protect against breast cancer and heart disease. Soy does not appear to offer protection against osteoporosis.”
- Choose whole soy foods when possible. Studies show that it is more beneficial to consume the whole soybean than processed soy such as soybean oil or textured vegetable protein. Tofu, tempeh, edamame, and miso are examples.
- Choose organic soy products. Any soy products that are not labeled organic are likely to be made from genetically modified soybeans. You can also look for the label ‘GMO Free’.
- Choose fermented whole soy. Research has shown increased benefits from fermented soy beans verses non-fermented. The fermentation process breaks down some of the phytates in soy making it easier to digest. It also adds in beneficial probiotics. Examples are tempeh, miso, natto, soy sauce, or tamari.
- Up to three servings a day is a conservative safe limit for soy products even if you have a family history of breast or prostate cancer.
- Soy supplements such as soy isoflavones are not recommended. Research has not shown a benefit.
Diet Recommendations
- Choose whole soy foods when possible. Studies show that it is more beneficial to consume the whole soybean than processed soy such as soybean oil or textured vegetable protein. Tofu, tempeh, edamame, and miso are examples.
- Choose organic soy products. Any soy products that are not labeled organic are likely to be made from genetically modified soybeans. You can also look for the label ‘GMO Free’.
- Choose fermented whole soy. Research has shown increased benefits from fermented soy beans verses non-fermented. The fermentation process breaks down some of the phytates in soy making it easier to digest. It also adds in beneficial probiotics. Examples are tempeh, miso, natto, soy sauce, or tamari.
- Up to three servings a day is a conservative safe limit for soy products even if you have a family history of breast or prostate cancer.
- Soy supplements such as soy isoflavones are not recommended. Research has not shown a benefit.
By Haylee Nye NCNM Naturopathic Medicine program Edited by Dr Elise Schroeder
References
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“Choline.” Micronutrient Information Center. Linus Pauling Institute at Oregon State University, n.d. Web. 24 Feb. 2014.
D’Adamo, CR, and A. Sahin. “Soy Foods and Supplementation: A Review of Commonly Perceived Health Benefits and Risks.” Alternative Therapies in Health and Medicine 20.1 (2014): 39-51. PubMed.gov. Web. 22 Feb. 2014
Evert, Alison. “Calcium in the Diet.” MedlinePlus. National Institute of Health, 18 Feb. 2013. Web. 22 Feb. 2014.
“Facts about Folic Acid.” Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 13 Jan. 2012. Web. 24 Feb. 2014.
“Full Report (All Nutrients): 16108, Soybeans, Mature Seeds, Raw.” Agricultural Research Service United States Department of Agriculture. National Nutrient Database for Standard Reference, n.d. Web. 22 Feb. 2014.
Mahmoud, AM, W. Yang, and MC Bosland. “Soy Isoflavones and Prostate Cancer: A Review of Molecular Mechanisms.” The Journal of Steroid Biochemistry and Molecular Biology 140.Mar (2014): 116-32. PubMed.gov. Web. 22 Feb. 2014.
Nagata, C. et al. “Soy Intake and Breast Cancer Risk: An Evaluation Based on a Systematic Review of Epidemiologic Evidence among the Japanese Population.” Japanese Journal of Clinical Oncology Jan (2014): n. pag. PubMed.gov. Web. 22 Feb. 2014.
Pedersen, Palle. “Soy Isoflavones.” Soybean Extension and Research Program. Iowa State University, 17 July 2007. Web. 24 Feb. 2014.
Shurtleff, William, and Akiko Aoyagi. “SoyInfo Center.” The Soybean Plant: Botany, Nomenclature, Taxonomy, Domestication, and Dissemination. Soyinfo Center, Lafayette, California, 2007. Web. 24 Feb. 2014.
“Soybeans.” Soybeans. The George Mateljan Foundation, n.d. Web. 22 Feb. 2014. <http://www.whfoods.com/genpage.php?tname=foodspice&dbid=79>.