Physicochemical properties of oat β-glucan influence its ability to reduce serum LDL cholesterol in humans: a randomized clinical trial.
BACKGROUND
Consumption of 3 g oat β-glucan/d is considered sufficient to lower serum LDL cholesterol, but some studies have shown no effect. LDL cholesterol lowering by oat β-glucan may depend on viscosity, which is controlled by the molecular weight (MW) and amount of oat β-glucan solubilized in the intestine (C).


OBJECTIVE
Our 2 primary objectives were to determine whether consumption of 3 g high-MW oat β-glucan/d would reduce LDL cholesterol and whether LDL cholesterol lowering was related to the log(MW × C) of oat β-glucan.


METHODS
In a double-blind, parallel-design, multicenter clinical trial, subjects with LDL cholesterol ≥3.0 and ≤5.0 mmol/L (n = 786 screened, n = 400 ineligible, n = 19 refused, n = 367 enrolled, and n = 345 completed) were randomly assigned to receive cereal containing wheat fiber (n = 87) or 3 g high-MW (2,210,000 g/mol, n = 86), 4 g medium-MW (850,000 g/mol, n = 67), 3 g medium-MW (530,000 g/mol, n = 64), or 4 g low-MW (210,000 g/mol, n = 63) oat β-glucan/d (divided doses, twice daily) for 4 wk.


RESULTS
LDL cholesterol was significantly less with 3 g high-MW, 4 g medium-MW, and 3 g medium-MW oat β-glucan cereals than with the wheat-fiber cereal by 0.21 (5.5%; 95% CI: -0.11, -0.30; P = 0.002), 0.26 (6.5%; 95% CI: -0.14, -0.37; P = 0.0007), and 0.19 (4.7%; 95% CI: -0.08, -0.30; P = 0.01) mmol/L, respectively. However, the effect of 4 g low-MW oat β-glucan/d (0.10 mmol/L) was not significant (2.3%; 95% CI: 0.02, -0.20). By analysis of covariance, log(MW × C) was a significant determinant of LDL cholesterol (P = 0.003). Treatment effects were not significantly influenced by age, sex, study center, or baseline LDL cholesterol.


CONCLUSIONS
The physicochemical properties of oat β-glucan should be considered when assessing the cholesterol-lowering ability of oat-containing products; an extruded breakfast cereal containing 3 g oat β-glucan/d with a high-MW (2,210,000 g/mol) or a medium-MW (530,000 g/mol) lowered LDL cholesterol similarly by ≈0.2 mmol/L (5%), but efficacy was reduced by 50% when MW was reduced to 210,000 g/mol. This trial was registered at www.clinicaltrials.gov as NCT00981981.
Wolever
Thomas M S
TM
Glycemic Index Laboratories Inc, Toronto, Canada. thomas.wolever@utoronto.ca
Tosh
Susan M
SM
Gibbs
Alison L
AL
Brand-Miller
Jennie
J
Duncan
Alison M
AM
Hart
Valerie
V
Lamarche
Benoît
B
Thomson
Barbara A
BA
Duss
Ruedi
R
Wood
Peter J
PJ
D000328:Adult; D000368:Aged; D000924:Anticholesteremic Agents / Q000627:therapeutic use*; D018554:Avena; D002784:Cholesterol / Q000097:blood*; D002791:Cholesterol, Dietary; D008078:Cholesterol, LDL / Q000097:blood / Q000187:drug effects; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004043:Dietary Fiber; D004311:Double-Blind Method; D002523:Edible Grain; D002149:Energy Intake; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D014908:Triticum; D047071:beta-Glucans / Q000627:therapeutic use*
D000924:Anticholesteremic Agents; D002791:Cholesterol, Dietary; D008078:Cholesterol, LDL; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004043:Dietary Fiber; D047071:beta-Glucans; D002784:Cholesterol