A biochanin-enriched isoflavone from red clover lowers LDL cholesterol in men.

OBJECTIVE

To determine whether the two major isoflavones in red clover differ in their effect on low-density lipoprotein cholesterol (LDL-C).

DESIGN

A randomised, placebo-controlled, double-blind trial; two parallel groups taking one of the two isoflavones within which treatment and placebo were administered in a crossover design.

SETTING

Free-living volunteers.

SUBJECTS

A total of 46 middle-aged men and 34 postmenopausal women.

INTERVENTION

Two mixtures of red clover isoflavones enriched in either biochanin (n=40) or formononetin (n=40) were compared. Placebo and active treatment (40 mg/day) were administered for 6 weeks each in a crossover design within the two parallel groups.

MAIN OUTCOME MEASURES

Plasma lipids were measured twice at the end of each period.

RESULTS

Baseline LDL-C concentrations did not differ significantly between men (n=46) and women (n=34), nor between those randomised to biochanin or formononetin. Interaction between time and treatments, biochanin, formononetin and corresponding placebos (two-way ANOVA) on LDL-C showed a significant effect of biochanin treatment alone. The biochanin effect was confined to men; median LDL-C was 3.61 (3.05-4.14) mmol/l with biochanin and 3.99 (3.16-4.29) mmol/l with the corresponding placebo (RM ANOVA with Dunnett's adjustment P<0.05). The difference between placebo and biochanin effects on LDL-C was 9.5%. No other lipid was affected and women failed to respond significantly to treatment.

CONCLUSION

Isolated isoflavones from red clover enriched in biochanin (genistein precursor) but not in formononetin (daidzein precursor), lowered LDL-C in men. This may partly explain the previous failure to demonstrate cholesterol-lowering effects with mixed isoflavones studied predominantly in women.

SPONSORSHIP

Novogen Ltd, North Ryde NSW, Australia, provided partial support including provision of tablets and outside monitoring.