Soy-based diets reduce blood pressure in spontaneously hypertensive rats, but apparently not in hypertensive humans. In the present study, the antihypertensive potential of soy milk (500 mL twice daily) compared with cow’s milk was investigated in a 3-mo double-blind randomized study of 40 men and women with mild-to-moderate hypertension. Before initiation of the study, urinary isoflavonoids (measured by HPLC) were undetectable in most cases (for genistein, they were always