- Soy protein, lipids and bone density in postmenopausal women
Full source: American Journal of Clinical Nutrition, 1998, Vol 68, Iss 6, Suppl. S, pp 1375S-1379S
The effects of soy protein (40 g/day) on blood fat profiles, mononuclear cell LDL receptor messenger RNA, and bone mineral density (BMD) and content were investigated in 66, postmenopausal women with high cholesterol during a 6 month period. They followed a low-fat, low-cholesterol diet. Group I diet: 40 g protein/day obtained from casein (milk protein) and nonfat dry milk; Group II diet: 40 g protein/day from isolated soy protein containing 1.39 mg isoflavones/g protein, and Group III diet: 40 g protein/day from isolated soy protein containing 2.25 mg isoflavones/g protein. The results showed that LDL cholesterol for both Groups II and III was reduced compared with Group I. HDL cholesterol increased in both Groups II and III. Significant increases occurred in both bone mineral content and density in the lumbar spine only for Group III compared with the control group (Group I). Thus, the intake of soy protein at both isoflavone concentrations for 6 months may decrease the risk factors associated with cardiovascular disease in postmenopausal women. Only the higher isoflavone-containing product protected against spinal bone loss.
Editors note: This study required that 40 grams of concentrated soy protein powder be ingested to obtain 90 mg of the active isoflavones. Just two tiny capsules of MegaSoy extract provide 110 mg of the soy isoflavones genistein, diadzein and glycitein. Most people prefer taking small capsules of soy protein instead of consuming tablespoons of powder.
- Cholesterol-lowering effect of soy protein
Full source: American Journal of Clinical Nutrition, 1998, Vol 68, Iss 6, Suppl. S, pp 1380S-1384S
Cardiovascular heart disease is a major health problem in the United States. Elevated blood cholesterol has been shown to significantly increase the risk of cardiovascular heart disease. Soy protein has been shown to lower cholesterol, particularly in those with high cholesterol. It has been shown that dietary soy protein, compared with casein (principal protein of milk), reduces blood LDL cholesterol and increases HDL cholesterol concentrations in healthy women and men. Soy protein has been shown to lower cholesterol, particularly in those with high cholesterol. Thirteen men aged 20-50 with normal cholesterol and 13 with high cholesterol men were fed either a soy-protein diet or the animal protein diet for 5 weeks. After 1 month of consuming each diet, HDL cholesterol concentrations were increased by the soy-protein diet. In 5 individuals, soy protein reduced mean LDL cholesterol concentrations by 26%, whereas HDL cholesterol increased by 11%. In 3 other individuals, soy protein increased mean HDL cholesterol by 17%, but did not lower LDL. The cholesterol lowering effect of soy protein was found to be independent of age, body weight, pretreatment blood fat concentrations, and sequence of dietary treatment. The researchers identified 3 types of responses from excess lipids in the blood to that of dietary soy protein, which all involved a reduction in atherogenic LDL and increase in antiatherogenic HDL. The results indicated that soy protein enhances the cholesterol lowering effect in men with both normal and high cholesterol.
- Effects of soy isoflavones on atherosclerosis
Full source: American Journal of Clinical Nutrition, 1998, Vol 68, Iss 6, Suppl. S, pp 1390S-1393S
It has long been recognized that coronary heart disease rates are lower in Japan, where soy consumption is common, than in Western countries. Studies have demonstrated the reduction in atherosclerosis in animals fed diets containing soy protein compared with animal protein. This study evaluated the effect of the soy protein versus soy protein with the isoflavones extracted, on cardiovascular disease and its risk factors. Monkeys were fed diets that contained either 1) casein (milk protein) as the source of protein, 2) soy protein isolate from which the isoflavones were extracted, or 3) isoflavone-intact soy protein. Group 3 had significant improvements in LDL cholesterol and HDL cholesterol. HDL cholesterol was significantly improved in group 2 compared with the casein group. The casein group had the most atherosclerosis, group 3 had the least, and group 2 was intermediate but did not differ significantly from the casein group. Potential mechanisms by which soy isoflavones might prevent atherosclerosis include a beneficial effect on blood lipid concentrations, antioxidant effects, antiproliferative and antimigratory effects on smooth muscle cells, effects on thrombus formation (a solid mass formed in blood vessels), and maintenance of normal vascular reactivity.
- Soy prevents precancerous colonic lesions
Full source: American Journal of Clinical Nutrition, 1998, Vol 68, Iss 6, Suppl. S, pp 1394S-1399S
This study tried to determine whether diets containing soy products would inhibit the early stages of colon cancer. Additional objectives were to determine whether feeding starch instead of sucrose, feeding additional calcium (0.5% compared with 0.1%), or feeding a low-fiber powdered formula would influence early colon cancer. Colon cancer was initiated artificially and a 12-week dietary treatment period was started. Results showed precancerous colon lesions were 133 using soy concentrate (low concentration of phytochemicals), 111 (starch substituted for sucrose), 98 [full-fat soy flakes (whole soybeans)], 87 (defatted soy flour), 77 (0.015% genistein), and 70 (0.5% Ca). The soy flour and full-fat soy flake diets contained 0.049% genistein derivatives (primarily glycosides), but were less effective in inhibiting the formation of precancerous colon lesions than the diet containing 0.015% genistein. Thus, the use of supplemental genistein from soybeans may reduce the early stages of colon cancer more effectively than other soy preparations.
- Genistein: potential for breast cancer prevention
Full source: American Journal of Clinical Nutrition, 1998, Vol 68, Iss 6, Suppl. S, pp 1400S-1405S
Asian women and men who consume a traditional diet high in soy products have low incidences of breast and prostate cancers, respectively. Yet, Asians who immigrate to the United States and adopt a Western diet lose this protection. Researchers investigated the potential of genistein, a component of soy, to protect against breast cancer and to cause reproductive and developmental toxicity. The study showed that injections of genistein in rats during the prepubertal period resulted in a 50% reduction of chemically induced mammary tumor growth. Genistein exposure resulted in fewer terminal end buds and more lobules type LI in mammary glands. Cell proliferation with genistein was less than that in control animals. Reproductive and developmental toxicity studies did not find significant alterations to any of the following: fertility, number of male and female offspring, body weight, anogenital distance, vaginal opening, testes descent, estrus cycle, or follicular development. The conclusion was that pharmacologic doses of genistein given to immature rats enhance mammary gland differentiation (progressive diversification of embryonic cells), resulting in a significantly less proliferative gland that is not as susceptible to mammary cancer. Speculation was that breast cancer protection in Asian women consuming traditional soy-containing diets is, in part, derived from early exposure to genistein-containing soy. Therefore, early programming events are essential for cancer protection benefits.
- Prediction of progression in prostate cancer
Full source: American Journal of Surgical Pathology, 1998, Vol 22, Iss 12, pp 1491-1500
Clinical outcome is variable in prostate cancer patients with regional lymph node metastasis. This study looked at 269 patients who had regional lymph node metastasis at the time of radical prostatectomy (prostate removal) and pelvic lymphadenectomy (removal of lymph nodes) at the Mayo Clinic between January 1987 and December 1992. Two hundred fifty-three (94%) patients received androgen (male hormone) deprivation therapy within 90 days of radical prostatectomy. Patients ranged in age from 47 to 79 years. Median follow-up was 6.1 years. Systemic "progression" of the disease was defined as the "presence of distant metastasis" documented by biopsies or radiographic examinations. Five-year progression-free survival was 90%. Resulting analysis showed a correlation between cancer node volume, the number of positive nodes, the collective length of metastases, and the diameter of the largest cancer node. (The correlation figures were 0.37, 0.63, 0.96, and 0.95, respectively). The data indicates that volume of the cancer nodes was the most significant determinant of nodal progression to distant metastasis in lymph node-positive prostate cancer patients. The authors recommend that the diameter of the largest metastasis be evaluated in patients with metastases, because this is a more powerful predictor of patient outcome than current methods, which recommend mere counting of the number of positive nodes.