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Put soy on your side
Not too many years ago, tofu and other soy items were the butt of jokes on late-night television talk shows -- the foods Americans most loved to hate. Today, soy burgers and other soy foods have become increasingly popular, and soy has emerged as a food that has the coveted ability to enhance health.
Common Uses - As a food, substituting for or stretching meat and eggs
- To help lower cholesterol
- For the prevention of hot flashes associated with menopause
- For cancer prevention, particularly breast cancer
- For the prevention of osteoporosis
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Medical Research
The beneficial compounds in soy are isoflavones, which are a type of phytoestrogen -- plant substances that mimic the human hormone estrogen. Here's how the various types of soy foods stack up [1]:
Raw soybeans (1/2 cup, or 34 g) -- 176 mg of isoflavones
Roasted soybeans, or soy nuts (1/2 cup, 30 g) -- 167 mg
Tempeh (4 oz, 19 g) -- 61 mg
Soy protein (1 oz, 26 g) -- 57 mg
Soy flour (1/4 cup, 8 g) -- 44 mg
Tofu (4 oz, 18 g) -- 38 mg
Textured soy protein (1/4 cup, 18 g) -- 28 mg
Soy milk (8 fl oz, 10 g)-- 20 mg
Soy sauce is not a source of isoflavones.
Cholesterol reduction: Several studies show that soy protein helps reduce cholesterol. At Wake Forest University in Winston-Salem, North Carolina, researchers placed 156 men and women with high cholesterol on the low-fat diet recommended by the American Heart Association. In addition, they were given one of five different drinks -- a placebo and four beverages containing differing amounts of soy isoflavones. After nine weeks, the placebo group showed no decrease in cholesterol level, but the soy groups all showed reductions, with the greatest decrease in the group that drank the most soy isoflavones. [2]
Based on all the research showing that soy protein helps cut cholesterol levels, the U.S. Food and Drug Administration (FDA) in October 1999 announced it would permit manufacturers of foods containing at least 6.25 grams of soy protein per serving to carry a label that promotes its health benefits and role in reducing the risk of heart disease. [3]
Prevention of hot flashes: Hot flashes, a sudden feeling of heat, rank as the leading cause of menopausal discomfort. Hot flashes occur because menopause brings declining blood levels of estrogen, which affect the body's temperature-control mechanism. Doctors often prescribe estrogen-rich hormone replacement therapy (HRT -- also called estrogen replacement therapy or ERT) to relieve hot flashes by increasing the levels of estrogen in the blood. But HRT brings with it other health risks that some women choose to avoid. (For example, some studies show there is an increased risk of breast cancer.) Soy contains plant compounds called isoflavones that are very similar to human estrogens. Soy isoflavones have a mild estrogen effect that is strong enough to prevent and relieve hot flashes but not strong enough to stimulate the growth of breast tumors. [4]
Italian researchers gave 104 postmenopausal women with hot flashes either a placebo or 76 mg/day of soy isoflavones. After one month, the placebo group experienced 13% fewer hot flashes, but the soy group reported a 33% reduction. [5]
Breast cancer prevention: Human estrogen can stimulate the growth of breast tumors. Weaker soy phytoestrogens attach to estrogen receptors on breast cells, in effect, locking out the woman's own estrogen, and thus reducing breast cancer risk. Australian researchers conducted diet surveys involving 144 women newly diagnosed with breast cancer and 144 demographically similar women who were cancer-free. After eliminating other known risk factors for breast cancer (family history, etc.), the women who were cancer-free were shown to consume significantly more soy isoflavones than the women with breast cancer. [6]
There is also some preliminary evidence that soy foods help prevent cancers of the colon and prostate. [7]
Osteoporosis prevention: Estrogen replacement is used to prevent osteoporosis in postmenopausal women. Animal studies show that soy protein increases bone density. [8] Recently, a human study showed the same result. Researchers at the University of Illinois at Urbana-Champaign gave a group of postmenopausal women 40 grams of protein a day. In one group, the protein came from non-soy sources (meat, dairy). In the second, the protein included moderate levels of soy isoflavones. And in the third, it included high levels of soy isoflavones. After six months, the women consuming the high levels of isoflavones showed significantly increased bone mineral density. [9]
Sources
1 Hudnall, M. "Soy as Superhero," Environmental Nutrition 2-99, p. 4.
2 Jancin, B. "Soy Can Bring Down Cholesterol," Family Practice News 5-15-98.
3 Reuters Health, Oct. 21, 1999.
4 Kaplan, D. "Phytoestrogens: Fact and Fiction," Patient Care 3-30-99. pp. 127-143.
5 Albertazzi, P., et al. "The Effect of Dietary Soy Supplementation on Hot Flushes," Obstetrics and Gynecology (1008) 91:6.
6 Ingram, D., et al. "Case-Control Study of Phytoestrogens and Breast Cancer," The Lancet (1997) 350:990.
7 Helmuth, L. "Nutritionists Debate Soy's Health Benefits," Science News 4-24-99.
8 Arjmandi, B.H., et al. "Bone-Sparing Effect of Soy Protein in Ovarian Hormone-Deficient Rats is Related to its Isoflavone Content," American Journal of Clinical Nutrition (1998) 68(6 Suppl):1364S.
9 Potter, S.M., et al. "Soy Protein and Isoflavones: Their Effects on Blood Lipids and Bone Density in Postmenopausal Women," American Journal of Clinical Nutrition (1998) 68(6 Suppl):1375S.
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Use
Soybeans were grown in China as far back as 1000 B.C. and were used in both the human diet and as animal feed. Some time later, Koreans and Japanese began growing the plant. Contact with the West eventually spread its use to Europe.
Americans began growing soybeans in the early 19th century, almost exclusively as animal feed. Eventually, American growers began exporting soybeans to Asia. Today, the U.S. produces 49% of the world's soybean crop. Soybeans are a major American agricultural export.
Most American-grown soybeans are used for animal feed. But as Americans eat less meat and more soy foods (tofu, soy burgers, soy franks, other meat substitutes, and textured vegetable protein) a growing percentage of the soy crop is turning up on dining tables. [10]
Instructions
Incorporate soy foods or supplements into your diet.
For prevention and treatment of heart disease, soy researcher James Anderson, M.D., of the University of Kentucky, recommends eating 50 to 70 grams of soy protein per week for the general population (approximately 5 ounces of tofu); 110 to 140 grams for those at risk of heart disease; and 170 to 210 grams for those with diagnosed heart disease. [11]
There are no specific recommendations for the other conditions, but most authorities suggest 2 to 3 servings of soy foods or the supplement equivalent a week.
Some soy foods, notably soy franks, are high in fat. Look for low-fat soy foods.
Sources
10 Anon. "Soy," The Review of Natural Products 9-98, p.1.
11 Hudnall, M. "Soy as Superhero," Environmental Nutrition 2-99, p. 4.
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Watch for sensitivities
Food sensitivities to soy protein are possible. If you experience any unusual symptoms after eating soy, eliminate it, and see if the symptoms diminish. If they do, you are probably sensitive, and should limit or eliminate soy from your diet.
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Sources & Further Reading
1. Albertazzi, P., et al. "The Effect of Dietary Soy Supplementation on Hot Flashes," Obstetrics and Gynecology (1008) 91:6.
2. Anon. "Soy," The Review of Natural Products 9-98.
3. Arjmandi, B.H., et al. "Bone-Sparing Effect of Soy Protein in Ovarian Hormone-Deficient Rats is Related to its Isoflavone Content," American Journal of Clinical Nutrition (1998) 68(6 Suppl):1364S.
4. Helmuth, L. "Nutritionists Debate Soy's Health Benefits," Science News 4-24-99.
5. Hudnall, M. "Soy as Superhero," Environmental Nutrition 2-99.
6. Ingram, D., et al. "Case-Control Study of Phytoestrogens and Breast Cancer," The Lancet (1997) 350:990.
7. Jancin, B. "Soy Can Bring Down Cholesterol," Family Practice News 5-15-98.
8. Kaplan, D. "Phytoestrogens: Fact and Fiction," Patient Care 3-30-99.
9. Potter, S.M., et al. "Soy Protein and Isoflavones: Their Effects on Blood Lipids and Bone Density in Postmenopausal Women," American Journal of Clinical Nutrition (1998) 68(6 Suppl):1375S.
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