Daily consumption of 3 g oat β-glucan is considered sufficient to lower serum LDL cholesterol (LDL-C), but not all studies show an effect. The ability of oat β-glucan to reduce LDL-C is thought to depend on viscosity which is controlled by the molecular weight (MW) and the amount of oat β-glucan solubilized in the intestinal lumen (C), but this has not been demonstrated in human subjects.
Therefore, our two primary objectives were to determine if consuming 3 g high-MW oat-β-glucan daily reduced LDL-C, and if LDL-C-lowering was related to log(MW×C) of oat-β-glucan. To address these objectives, we conducted a randomized, controlled, double-blind parallel design clinical trial in two contract–research–organisations and three university nutrition research centres in Canada, Australia and UK. A volunteer sample of healthy subjects with LDL-C ≥3.0 and ⩽5.0 mmol/l (n 786 screened, n 400 ineligible, n 19 refused, n 367 randomized, n 345 completed) were randomly assigned by the computer to receive one of five treatments. Subjects consumed cereal containing wheat fibre (n 87) or a total of 3 g high-MW (n 86), 4 g medium-MW (n 67), 3 g medium-MW (n 64) or 4 g low-MW (n 63) oat β-glucan daily (OatWell®, divided doses, twice-daily) for 4 weeks. Using an intent-to-treat analysis, serum-LDL-C concentration after 4 weeks was compared between treatments after adjusting for baseline LDL-C.
After 4 weeks, LDL-C on 3 g high-MW oat β-glucan cereal was less than on wheat-fibre cereal by 0.21 mmol/l (95% CI; −0.11, −0.30, P=0.0023). By analysis of covariance log(MW×C) was a significant determinant of week 4 LDL-C-cholesterol (P=0.003). The treatment effect was not significantly influenced by age, sex, study centre or baseline LDL-C.
It was concluded that consuming only 3 g high-MW oat β-glucan daily in a ready-to-eat cereal reduced LDL-C by 0.2 mmol/l; efficacy was reduced in cereals containing oat β-glucan with low MW. Thus, the physicochemical properties of oat β-glucan should be considered when assessing the cholesterol-lowering ability of oat-containing products.
The trial was registered at www.clinicaltrials.gov NCT00981981.
Funding was provide by the Swedish Governmental Agency for Innovations Systems and CreaNutrition.