Hypercholesterolaemia is the presence of high levels of cholesterol in the blood. In humans, hypercholesterolaemia is often due to high low-density-lipoprotein (LDL)-cholesterol levels, the so-called 'bad' cholesterol. People with hypercholesterolaemia have a higher risk of developing cardiovascular diseases such as heart attacks or strokes. Isoflavones, which are chemicals in plants similar to phyto-oestrogen, may be helpful in improving hypercholesterolaemia. Soy and red clover are rich sources of isoflavones. Asian people consume more isoflavones from their regular diet than Western people.

To assess the effects of isoflavones for the treatment of hypercholesterolaemia, we examined five randomized controlled trials of isoflavones or soy protein containing isoflavones. The trials lasted three to six months and involved 208 participants. There were no outcome data on death from any cause, cardiovascular events such as heart attack or stroke, morbidity, complications, health-related quality of life and costs. Two trials reported adverse effects, including gastrointestinal discomfort (bloating and constipation) and an increased number of hot flushes. They observed no serious adverse events. In our included studies, we found no cholesterol-lowering effect of isoflavones. However, the quality of the included trials had some considerable limitations and the number of the participants was low. Further higher-quality and rigorously performed studies on patient-important outcome measures such as cardiovascular diseases and health-related quality of life are required.