Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
The aims of this evidence report are to summarize the current evidence on the health effects of soy and its isoflavones on the following: menopausal symptoms, bone health, cancers, cardiovascular diseases, kidney diseases and cognitive function, as well as safety issues and drug interactions. In addition, this report also summarizes the formulations of soy products and/or soy food used in clinical trials. This report is requested and funded by the National Center for Complementary and Alternative Medicine (NCCAM) and the Office of Dietary Supplements at the National Institutes of Health (NIH), through the Evidence-based Practice Center (EPC) program at the Agency for Healthcare Research and Quality (AHRQ).
There is increasing interest in soy and health since the U.S. Food and Drug Administration (FDA) approved a health claim in October 1999 for use on food labels stating that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease. This claim was based on the beneficial results in reducing plasma low-density lipoprotein (LDL) levels from dozens of human controlled clinical trials.1 The health claim, however, covers only soy protein, since research results surrounding soy isoflavones were controversial.2
The aims of this report are to summarize the formulations of soy products and/or soy food used in clinical trials, and to reflect the current evidence on the health effects of soy and its isoflavones on the following:
• Cardiovascular disease.
• Menopausal symptoms.
• Endocrine function.
• Cancer.
• Bone health.
• Reproductive health.
• Kidney disease.
• Cognitive function.
• Glucose metabolism.
In addition, safety issues and drug interactions of using soy and its isoflavones as reported in the literature are summarized.