Eight RCTs were included in the review (n=391): five parallel design (n=342); two crossover design with a four-week washout period (n=28); and one crossover design with insufficient crossover period that was treated as a parallel group (n=21). Sample sizes ranged from 10 to 155. Two studies were double-blinded. Three studies were industry funded.
Barley consumption significantly reduced total cholesterol (WMD -13.38mg/dL, 95% CI -18.46 to -8.31; eight studies), low density lipid cholesterol (WMD -10.02mg/dL, 95% CI -14.03 to -6.00; seven studies) and triglycerides (WMD -11.83mg/dL, 95% CI -20.12 to -3.55; six studies) compared to control. High density lipid cholesterol was not significantly reduced by barley consumption compared to control. There was no evidence of significant statistical heterogeneity. The results were not significantly altered when a fixed-effects model was used. There was no evidence of publication bias except for the outcome of total cholesterol (Egger's test p=0.02). When crossover studies and studies that were not double-blinded were excluded, barley no longer significantly reduced triglycerides. Other outcomes were unaffected by sensitivity analyses.
In hypercholesterolaemic patients, barley significantly reduced total cholesterol (WMD -12.56, 95% CI -17.89 to -7.24) and low density lipid cholesterol (WMD -9.38, 95% CI -14.13 to -4.63), but not high density lipid cholesterol or triglycerides, compared to control. The effect of barley on total cholesterol and low density lipid cholesterol was more robust when combined with dietary modification.