Soy is an excellent source of low calorie, highquality protein, a nutrient we need more of as we grow older. Protein builds and repairs tissue and makes infection fighting antibodies. But unlike the protein in animal foods, suchas meat, eggs, and milk, soy protein contains zero heart damaging saturated fat and cholesterol. Soy is packed with other nutrients that older bodies need, such as iron, calcium, and B vitamins like thiamin, riboflavin, and niacin.
But that's not all. Nestled in the heart of soybeans are substances called isoflavones, which are part of a group of plant substances known as phytochernicals. The isoflavones in soy, called phytoestrogens, may be the key to soy's diseasefighting powers, says Gregory Burke, M.D., professor and interim chairperson in the department of public health sciences at Wake Forest University School of Medicine in WinstonSalem, North Carolina.
The average Asian consumes 50 milligrams of isoflavones a day the amount in 2 to 3 ounces of soy, says Dr. Burke. Consuming these minuscule amounts may afford you the protection that many Asians enjoy from many of the illnesses of aging, including the ones below.
Cancer. In animal and test tube studies, the phytoestrogen genistein slows the growth of cancer cells. How? Researchers don't know. But they do know that genistein and another phytoestrogen, daidzein, act as weaker versions of the estrogen that women produce naturally.
It is well known that estrogen can fuel so called hormone dependent cancers of the breast and uterus. Dr. Burke says it may be that soy phytoestrogens compete with natural estrogen for molecules on the surfaces of cells that recognize and bind to estrogen. If soy phytoestrogens fill these receptors, the more potent natural estrogen can't, thereby helping to prevent cancer.
High cholesterol Soy may lower both "bad" low density lipoprotein (LDL) and total cholesterol levels without reducing "good" high density lipoprotein (HDL) cholesterol. In one large study conducted at the University of Kentucky, the LDL cholesterol of people who consumed about 2 ounces of soy protein a day plunged 12.9 percent, and their total cholesterol dropped 9.3 percent. Their levels of "good" HDL cholesterol stayed steady.
No one knows exactly how soy might lower cholesterol. But one theory is that soy phytoestrogens
help transport LDL cholesterol from the bloodstream to the liver, where it's broken down and excreted. Phytoestrogens may also keep LDL from turning rancid (a process known as oxidation), making it less likely to clog the walls of your arteries.
Osteoporosis. Soy phytoestrogens appear not only to repair bone but actually to build it. In one study, women who consumed 40 grams of soy protein (containing high concentrations of isoflavones) a day for 6 months significantly increased the thickness of the bone in their lower spines. And there's another reason to bone up on soy: Animal protein seems to speed up the body's excretion of calcium. Apparently, soy protein doesn't, says Dr. Burke.
Menopausal symptoms. Sometimes isoflavones block a woman's natural supply of estrogen, and sometimes, they actually supplement it. This is a boon for women in menopause, when declining levels of estrogen and progesterone can trigger hot flashes and night sweats. In one study, women who consumed 60 grams of soy protein a day for 12 weeks cut their rate of hot flashes by nearly half.
