In 1999, the Food and Drug Administration (FDA) approved labeling on soy-based products that stated that eating soy-based foods reduced the risk of coronary heart disease. However, since the approval, studies on the health benefits of soy-based foods have shown mixed results.

As a consequence, in 2007, the FDA announced that they would be reviewing the evidence on soy-based foods and heart health. In 2017, they proposed revoking the health claim that soy-based foods reduce heart disease, given the conflicting evidence that their review found.

The present study intervenes in this debate, hoping to provide more information on the relative benefit of soy-based foods for heart health.

Gaining a more detailed understanding of nutrition and heart health is important because, as the Centers for Disease Control and Prevention (CDC) note, “Heart disease is the leading cause of death in the United States.”

The evidence for the value of a plant-based diet that is high in fiber and low in salt, sugar, and saturated and trans-fats is clear. Indeed, the Department of Health & Human Services list primarily plant-based foods in their dietary recommendations.

However, understanding precisely how and why specific food sources contribute to overall health is important so that clinicians can help people develop an eating plan that works best for them.

The study drew on data from three separate studies that included a total of 168,474 women and 42,226 men, and each tracked the participants for more than 20 years. Participants were all free of heart disease and cancer at the beginning of the studies.

Every 2–4 years, the participants received a nutrition survey to complete. The researchers obtained their heart disease information from medical records or from death certificates in the instances where a person died due to heart disease.

The study took into account various confounding factors that may also affect heart disease to try to identify precisely how isoflavones affect heart health.

After analyzing the data, the study found that, in general, a higher intake of isoflavones was associated with a moderate reduction in the risk of heart disease. This link was also true for tofu when the team looked at this food independently.

The study also found that the benefits of eating tofu were particularly apparent for women before menopause. After menopause, the researchers only noted a clear association between tofu consumption and reduced heart disease risk in women who were not taking hormone therapy.

While the study suggests an association between tofu and isoflavones on the one hand and reduced risk of heart disease on the other, it is not clear why or how the relationship between them works.

Dr. Qi Sun, an associate professor in the department of nutrition at Harvard University, MA, and lead author of the study, says: “Despite these findings, I don’t think tofu is by any means a magic bullet. Overall diet quality is still critical to consider, and tofu can be a very healthy component.”

Dr. Sun believes that a person should consider all aspects of their diet when making any changes:

“If their diet is packed with unhealthy foods, such as red meat, sugary beverages, and refined carbohydrates, they should switch to healthier alternatives. Tofu and other isoflavone-rich, plant-based foods are excellent protein sources and alternatives to animal proteins.”

Dr. Sun also makes it clear that although the study controlled for other confounding factors that can affect heart health, more research is necessary to untangle precisely what value isoflavones offer.

“For example, younger women who are more physically active and get more exercise tend to follow healthier, plant-based diets that may include more isoflavone-rich foods like tofu. Although we have controlled for these factors, caution is recommended when interpreting these results.”

— Dr. Qi Sun