Benefits
Helps maintain healthy LDL cholesterol
About 3 g a day of oat beta-glucan, as part of a diet low in saturated fat and cholesterol, is the basis of an FDA-authorized health claim. A meta-analysis of 28 randomized trials found LDL 0.25 mmol/L lower than control; a second, of 58 trials, found 0.19 mmol/L, with large variation between trials. HDL and triglycerides did not change.
Smaller blood sugar rise after carbohydrate meals
In a meta-analysis of 103 single-meal comparisons in 538 people, adding oat beta-glucan (as concentrate or oat bran) to a carbohydrate meal cut the glucose response by 23% and the insulin response by 22%. Material below 300 kg/mol molecular weight did not work. This measures single meals; longer-term effects on blood sugar are less certain.
Bowel regularity in older adults
In a small trial in 30 frail residents of a geriatric hospital, adding 7 to 8 g of oat bran a day to meals for 12 weeks let 59% of the fiber group stop laxatives, while laxative use rose 8% in the control group. The trial was controlled but not described as randomized, and other trials of extracted oat beta-glucan found stool frequency unchanged.
Mechanism of action
Bile acid binding (the main cholesterol mechanism)
Beta-glucan's viscous gel binds bile acids in the small intestine and increases their loss in stool. The liver then uses cholesterol to make new bile acids and takes up more LDL from the blood.
Reduced cholesterol absorption
The gel may also trap dietary and biliary cholesterol and reduce its absorption. In the 28-trial meta-analysis, doses from 3.0 to 12.4 g a day did not give clearly larger effects than 3 g.
Slower stomach emptying and glucose absorption
Beta-glucan thickens stomach contents and slows emptying, and in the small intestine the gel slows glucose uptake. The result is a smaller rise in blood sugar after a carbohydrate meal, which depends on the fiber keeping its high molecular weight.
Fermentation in the colon
Beta-glucan that reaches the colon is fermented by gut bacteria into short-chain fatty acids such as acetate, propionate and butyrate, and butyrate is a fuel for colon cells. Effects of these products on health in people have not been established by the studies cited here.
Clinical trials
Meta-analysis of 28 randomized trials comparing at least 3 g a day of oat beta-glucan with a control, including in-house reports from CreaNutrition AG (Whitehead et al. 2014, Am J Clin Nutr)
Pooled trials using 3.0 to 12.4 g a day for 2 to 12 weeks.
LDL cholesterol was 0.25 mmol/L lower (95% CI 0.20 to 0.30) and total cholesterol 0.30 mmol/L lower than control, with some heterogeneity and no effect on HDL or triglycerides. Dose and duration did not change the result; lowering was greater with higher starting LDL.
Systematic review and meta-analysis of randomized trials of at least 3 weeks (Ho et al. 2016, Br J Nutr)
58 trials, 3,974 participants; median dose 3.5 g a day.
LDL cholesterol was 0.19 mmol/L lower, non-HDL cholesterol 0.20 mmol/L lower and apoB 0.03 g/L lower than control. Heterogeneity was considerable (I-squared 79% for LDL), so effects varied between trials.
Systematic review and meta-analysis of acute crossover feeding trials adding oat beta-glucan concentrate or oat bran to carbohydrate meals (Zurbau et al. 2021, Eur J Clin Nutr)
103 trial comparisons in 538 people with and without diabetes.
Glucose response fell by 23% and insulin response by 22%, with high certainty of evidence and a linear dose response. Material below 300 kg/mol molecular weight did not lower glucose. These are single-meal results.
Controlled intervention trial adding 7 to 8 g of oat bran a day to the ward diet for 12 weeks; not described as randomized (Sturtzel et al. 2009, J Nutr Health Aging)
30 frail long-term care residents aged 57 to 100 who were using laxatives; 15 per group.
Laxatives were discontinued by 59% of the oat bran group (P < 0.001), while use rose 8% in the control group. Body weight stayed stable with oat bran and fell in the control group. A small trial in a specific population.