Atherosclerosis (hardening of the arteries is a common problem in postmenopausal women that can lead to cardiovascular problems such as heart attacks and strokes. In addition, some premenopausal women have a significant degree of atherosclerosis. A study was conducted to determine whether a soy supplement would reduce the development of atherosclerosis. The findings were published online on July 28 in the journal Menopause.
The objective of the study was to determine how life stage and preexisting atherosclerosis influence the effectiveness of high-isoflavone soy diet in slowing the progression of atherosclerosis. For the study, the researchers used monkeys that had been bred to develop atherosclerosis.
For 34 months, the monkeys were fed an atherogenic diet, with protein derived primarily from either animal sources (casein-lactalbumin (CL); 37 animals) or high-isoflavone soy beans (soy; 34 animals). The researchers noted that the monkeys on the soy diet simulated the diet of Asian women who resided in Asia. The monkeys then had their ovaries removed to place them in a postmenopausal status. The animals were randomly assigned to groups fed the same diet (CL-CL (20 monkeys); Soy-Soy (17 monkeys) or an alternate diet (CL-Soy (17 monkeys); Soy-CL (17 monkeys) for an additional 34 months. During the ovary removal, the monkeys had a lower abdominal artery evaluated for the degree of premenopausal atherosclerosis. At the conclusion of the study, a lower abdominal artery and the coronary arteries were examined for the degree of atherosclerosis. The animals fed the CL-CL diet served as control subjects.
The investigators found that the monkeys fed soy protein both premenopausally and postmenopausally, modeling Asian women who remained in Asia, had a significantly reduced degree of coronary artery atherosclerosis. The animals that modeled Asian women who migrate to a Western country (consuming soy premenopausally and CL postmenopausally) had increased progression of postmenopausal iliac artery atherosclerosis and were not protected from the development of coronary artery atherosclerosis. Similar to the administration of soy diets to postmenopausal Western women, monkeys fed CL premenopausally and switched to soy postmenopausally were found to have atheroprotective benefits only if they began the postmenopausal treatment period with relatively small (below average) plaques. This group (with small plaques at ovary removal had reduced progression of iliac artery atherosclerosis and smaller coronary artery plaques that were less complicated (P = 0.05) relative to controls.
The authors concluded that the findings suggest that significant atheroprotective benefits of dietary soy are derived from treatment that begins premenopausally and continues postmenopausally or from treatment that is started during early postmenopause (when plaques are still small).