Whole-grain and blood lipid changes in apparently healthy adults: a systematic review and meta-analysis of randomized controlled studies.

Systematic review and meta-analysis of 24 randomized controlled studies reporting 52 treatment arms in apparently healthy adults not taking statins. Participants were adults aged 18 to 75 years from Europe, North America, and Asia, including both sexes and a range of body weights.

Active interventions were whole-grain foods or whole-grain diets compared with non-whole-grain control diets. Doses ranged from 13 to 66 g/day of whole grain, with intervention durations from 2 to 16 weeks; studied grains included oat, rye, barley, wheat, rice, and mixed whole-grain products. Several trials used test foods provided to both groups, and some were conducted on calorie-restricted background diets.

Whole-grain diets lowered total cholesterol and LDL cholesterol compared with non-whole-grain control diets, while HDL cholesterol and triglycerides were not significantly affected overall. The strongest cholesterol-lowering effect was seen with whole-grain oat products. Calorie-restricted background diets appeared to augment the cholesterol-lowering effect, and very high whole-grain doses did not provide extra benefit. Overall heterogeneity was generally low, but effects varied by grain type and data were limited for rye, barley, and rice.

Arm-specific sample sizes were not consistently reported in the provided text, limiting precision about per-group power. The evidence was heterogeneous by grain type, dose, background diet, and study duration, and several grain categories had limited data. Many trials were short, and some results may be less generalizable beyond apparently healthy adults not using statins.