Funded by the National Heart, Lung, and Blood Institute, the study involved 216 Caucasian and African-American postmenopausal women, who had borderline LDL-C (low-density lipoprotein cholesterol elevation) but were otherwise healthy. The women were randomized to receive either 20g isolated soy protein containing isoflavones or a placebo of 20g of protein from casein each day, for six weeks.
At the end of the trial, the researchers found that the LDL-C and low-density lipoprotein particle number (LDL-P) were decreased in the women taking the soy protein, regardless of age, race, other lipoproteins, dietary saturated fat intake and weight. The decreases were significantly greater in those taking soy than in those taking casein.
Although there has been evidence that it may benefit heart health in post menopausal women, until now there has been a lack of research involving sufficient numbers of African-American women, said principal investigator Jerilyn Allen, associate dean for research at the Johns Hopkins University School of Nursing.
"Our findings could have significant public health implications for postmenopausal women and will add substantially to the limited body of knowledge of the effects of soy," said Allen.
In 1999 the FDA approved an unqualified health claim linking consumption of soy foods to a reduced risk of coronary heart disease. According to a 2000 report in FDA Consumer, consumption of soy foods increased 20 percent per year since 1995 and the approval of this claim led to surging interest.
The new findings, presented a the meeting of the American Heart Association in Dallas, Texas, yesterday come on the back of an examination of 68 studies into soy and cholesterol levels by the Health & Human Services' Agency for Healthcare Research and Quality (AHRQ).
AHRQ reported in September that consumption of soy products resulted in a 5mg/dL (about 3 percent) reduction in LDL and an 8mg/dL (about 6 percent) decrease in triglyceride levels across the studies.
The average dose of soy protein in the studies was equivalent to about one pound of tofu or three soy shakes daily, but among these studies a large variety of soy products, doses of soy protein, and doses of soy isoflavones were tested.
Soy isoflavones (phytoestrogens or weak forms of the hormone estrogen) have also been used to alleviate menopausal symptoms, such as hot flashes.
According to the American Heart Association, 34 percent of non-Hispanic white women and 34 pecent of men have some form of cardiovascular disease.
For non-Hispanic black women, the figure is 44.7 percent, and for non-Hispanic black men 41 percent.