Tofu carries two stubborn health myths. The first is that soy raises estrogen in men and feminizes them. The second is that it is bad for the heart.
A large pooled cohort analysis published in the American Heart Association's journal Circulation on March 23, 2020 found the opposite of the second claim. People who ate tofu more than once a week had an 18% lower risk of coronary heart disease compared with those who ate it less than once a month.
The analysis drew on more than 200,000 US adults in the Nurses' Health Study, Nurses' Health Study II, and the Health Professionals Follow-up Study. Researchers tracked 8,359 heart-disease cases across more than 4.8 million person-years of follow-up.
The AHA release notes the association was strongest in younger premenopausal women and in postmenopausal women who were not taking hormone therapy. The authors flagged that the design was observational and shows a relationship, not causality.
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What phytoestrogens actually do
The estrogen concern rests on isoflavones, the plant compounds concentrated in soy foods like tofu, tempeh and edamame. According to the Harvard T.H. Chan School of Public Health's Nutrition Source, soy isoflavones can bind to estrogen receptors in the body and cause either weak estrogenic or anti-estrogenic activity, depending on hormone levels and menopausal status.
In practical terms, they can occupy the same receptor site as human estrogen without triggering the same signal, and in some contexts they blunt rather than mimic estrogen.
LDL cholesterol and blood pressure
The heart-disease signal is partly explained by cholesterol. Harvard's Nutrition Source notes that a 1995 meta-analysis found roughly 50 grams of soy protein a day reduced LDL cholesterol, the harmful fraction, by 12.9%, though later research put the effect closer to 3%. The benefit is real but modest, not a statin replacement.
Blood pressure has been tested more recently. A 4-week randomized controlled trial in 45 healthy adults compared a soy protein food (Kori-tofu, a freeze-dried Japanese tofu) with whey protein in a double-blind crossover design.
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Systolic blood pressure fell by 3.1 mmHg during the soy period, and LDL cholesterol dropped 7.3% from baseline. The authors noted, however, that these changes did not differ significantly from the whey control arm, and concluded there was no clear evidence that Kori-tofu had beneficial effects on cardiometabolic health beyond whey.
What "regular" tofu eating looks like
The Circulation analysis defined the protective threshold as more than one serving of tofu a week, hardly a soy-heavy diet.
For most healthy adults, tofu fits comfortably within dietary patterns the AHA already recommends for the heart, where plant proteins substitute for red and processed meats.
Qi Sun of Harvard T.H. Chan School of Public Health, quoted in the AHA release on the 2020 study, said "overall diet quality is still critical to consider, and tofu can be a very healthy component."
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Anyone taking levothyroxine should discuss timing and portion size with their doctor, because soy can interfere with absorption of the medication.
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This article is made and published by Emil Martesen, who may have used AI in the preparation.