Researchers from HHS' Agency for Healthcare Research and Quality had reported that the benefits of soybean on health may have been overrated, as the reported health benefits from this product are too less.
Daily consumption of soy protein found in tofu and other soybean products may result in a small reduction in low-density lipoprotein (LDL, known as bad cholesterol) and triglyceride levels. In addition, isoflavones found in soy may reduce the frequency of hot flashes in post-menopausal women.
Overall, across the 68 studies that examined the impact of soy on cholesterol levels, consumption of soy products resulted in a 5 mg/dL (about 3 percent) reduction in LDL and an 8 mg/dL (about 6 percent) decrease in triglyceride levels in the populations studied. Among these studies, a large variety of soy products, doses of soy protein, and doses of soy isoflavones were tested. The average dose of soy protein in the studies was equivalent to about one pound of tofu or three soy-shakes daily.
There was some indication that soy consumption may be more effective at lowering LDL among people with higher LDL levels. Also, larger amounts of soy protein, but not soy isoflavones, are more effective in people with abnormally elevated LDL levels. Similarly, soy consumption may be more effective at lowering triglycerides among people with higher triglyceride levels; however, there was no evidence of how much soy protein or isoflavones would be needed to affect triglycerides.
Reviews on the relationship between soy consumption and high-density lipoprotein (HDL, known as good cholesterol) levels and between soy consumption and blood pressure did not find significant effects. The evidence review completed by AHRQ's Tufts-New England Medical Center Evidence-based Practice Center also found insufficient data among the 200 human studies examined as part of this analysis to suggest that soy had an effect on bone health, cancer, kidney disease, endocrine function, reproductive health, neuro-cognitive function, or glucose metabolism.
This report shows that there is a lot we don't know about soy, and that more research is needed to determine if soy has any impact on a number of health conditions, said the researchers.