Isoflavones for Hypercholesterolaemia in Adults

Summary

A Cochrane review [Abstract] 1 included 5 studies with a total of 208 subjects. The participants in the included trials were postmenopausal women, and the interventions ranged from 3 to 6 months. Three studies used isoflavones interventions and placebo controls, and 2 studies used soy protein-containing isoflavones and compared this with soy isolated protein plus less than 4 mg isoflavones/day. Isoflavones are plant-based chemicals related to phyto-oestrogen, which are found in soy and red clover. Asian people consume more isoflavones from their regular diet than Western people. Four studies reported results in non-Asian populations published in English and one study reported results in Chinese people published in Chinese. The Chinese study was excluded from meta-analysis due to substantial differences in clinical characteristics of participants. There were no outcome data on death from any cause, morbidity, complications, health-related quality of life and costs.

Compared with placebo, there was a statistically significant effect of isoflavones alone on triglycerides (MD -0.46 mmol/L, 95% CI -0.84 to -0.09; 2 studies, n=52) and no statistically significant effect on total cholesterol, LDL-cholesterol or HDL-cholesterol. There was no statistically significant effect of soy protein containing isoflavones on hypercholesterolaemia. Combined results for isoflavones versus placebo or soy protein + isoflavones versus soy protein are shown in table T1.

Two studies reported adverse effects, including gastrointestinal discomfort (bloating and constipation) and an increased number of hot flushes. None of the trials found serious adverse events.