A recent meta-analysis (i.e. a review of multiple previous studies, in this case 23) published in the September 2019 issue of the Journal of the Academy of Nutrition and Dietetics identified a possible relationship between soy intake and decreased mortality.
The studies totaled 330,826 participants who consumed both soy ‘products,’ such as tofu, bean curd, soymilk and soy ‘cheese,’ as well as soy ‘specific’ foods, which included natto, tofu and miso. After reviewing the studies, it appears that soy consumption is inversely associated with death from all causes, and specifically deaths from cancer and cardiovascular diseases. For example, those with higher intakes of soy were less likely to die from gastric, colorectal and lung cancers. Additionally, those with the highest intakes of soy isoflavones had a 10% lower risk of all-cause death.
Soy isoflavones (more specifically diadzein, genistein, and glycitein) are compounds found in plants that have ‘estrogenic’ activity, which means they bind to estrogen receptors in the body. This action may inhibit cell transformation, change, and growth or even induce cell death, which would have significant effects on tumor growth and/or proliferation.
The review of studies found that a 10mg/day increase in soy isoflavone intake was associated with a 7% decrease in death from cancer, and a 9% decrease in death from breast cancer, specifically. Additionally, breast cancer survivors who consumed at least 10mg/day of soy isoflavones saw a 25% less risk of tumor recurrence. Additionally, a 5mg/day intake of soy protein was associated with a 12% reduction in death from breast cancer.
According to the meta-analysis, “available evidence suggests that intake of non-protein soy constituents favorably affect the markers of cardiovascular health.”
Bottom Line: Soy is no stranger to the ‘on-again, off-again’ fad diet craze. For years, people have either loved or hated it, myself included. After seeing these results, however, it’s clear some forms of soy do indeed have beneficial properties. At the very least, soy is anti-inflammatory, and inflammation is related to disease recurrence. It’s worth noting that these studies looked at soy intakes from food, not supplementation, and that supplementation is often not as effective food. In order to get the most from your soy intake, focus on minimally processed soy foods, such as soymilk, soy beans (edamame) and tofu. For reference, you can get 6.2 mg of soy isoflavones in one cup of soymilk, 21.3 mg in ½ cup of tofu yogurt, and 16.1 mg in ½ cup of edamame.
Nachvak, S.M., Moradi, S., Anjom-shoae, J., Rahmani, J., Nasiri, M., Maleki, V., & Sadeghi, O. (2019). Soy, Soy Isoflavones, and Protein Intake in Relation to Mortality from All Causes, Cancers, and Cardiovascular Diseases: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Journal of the Academy of Nutrition and Dietetics, 119(9), 1483-1500.
Holly R. Layer is a Registered Dietitian and a freelance writer. She teaches fitness classes at the Southtowns YMCA and leads nutrition tours at the East Aurora Cooperative Market. She lives in the village with her husband, Andrew, an East Aurora native. She blogs at www.thehealthypineapple.com. Questions can be emailed to Holly at firstname.lastname@example.org.