Dr. Weaver reports that a 4 oz. serving of calcium-set tofu provides as much calcium as an 8 oz. Soyfoods may be better sources of dietary calcium than dairy products because soy protein causes the body to excrete much less calcium in the urine than animal protein. This is true even though those same countries tend to exhibit a correspondingly high calcium intake. Isoflavones also seem to play a role in the prevention of osteoporosis. The women who ate the high-isoflavone soy protein gained significantly more bone mass over 6 months than either of the other two groups.
Researchers are unsure exactly how isoflavones influence bone mass.
Soyfoods seem to assist in the prevention of kidney disease largely because they replace animal protein, which stresses the kidneys, with healthful plant protein. Soy helps to dissolve gallstones after they have formed, and may even prevent their formation. The research on the relationships between soy consumption and heart disease, prostate cancer, and osteoporosis demonstrates a link between soy consumption and a decreased risk of succumbing to those diseases. Researchers are less sure of the connection between soyfoods and other cancers, menopausal symptoms, diabetes, kidney problems, gallstones, and high blood pressure, but the research appears promising. It may be that scientists merely have not figured out the amounts or forms of soy necessary to impact those diseases.