More evidence that soy foods may be good for the heart comes from a large observational study published in March 2020 in Circulation.
The Harvard investigators analyzed data from the long-running Nurses’ Health Study and Health Professionals Follow-Up Study, involving a total of 168,474 women and 42,226 men and spanning almost three decades. Those whose diets included the most isoflavones—plant compounds that weakly mimic the effects of estrogen and are abundant in soy foods—were moderately less likely to have a heart attack or die from coronary heart disease (CHD) than those who consumed the least isoflavones.
In addition, consuming tofu regularly—at least one serving per week—was linked with a lower risk of heart attack or CHD death compared to eating tofu once a month or less. (The same effect was not seen with soy milk, however, which is also high in isoflavones. This may be due in part to the foods’ different nutritional profiles; as the authors noted, “unlike tofu, soy milk may contain added sugar, emulsifiers, and other constituents which may mask the protective effects of isoflavones on CHD risk, to a certain extent.”)
Interestingly, the apparent benefit from isoflavones was more pronounced in premenopausal women and postmenopausal women who did not take hormones, vs. postmenopausal women on hormone therapy. The results don’t prove that soy foods prevent heart disease; intake of isoflavones and tofu may be markers for healthier lifestyles overall, though the researchers attempted to control for this by adjusting the results for factors such as diet, exercise, body weight, and use of alcohol or tobacco.
While more research is needed, the findings “suggest that soy products such as tofu can be integrated into healthy plant-based diets as an important source of plant proteins and aid in the prevention of CHD,” the authors concluded. The study looked at intake of isoflavones from foods, not supplements. We don’t recommend supplements because they have potential health risks.
Also see Is Soy Still Good for You?