Three papers on oat β-glucan’s effects in humans, starting with a 2023 study that compared different doses:
“Two randomized, double-blind, controlled studies were conducted with asymptomatic subjects between 20 and 40 years of age, male or female, normal weight or overweight.
In the first study – a crossover trial comprising two days of testing (β-glucan and control) separated by at least one week – 14 subjects ingested a breakfast with or without β-glucan from oats (5.2 g). Results indicate that acute intake of 5 g β-glucan slows transit time and decreases hunger sensation and postprandial glycaemia without affecting bile-acid synthesis. These changes were associated with decreased plasma insulin, C-peptide, and ghrelin, and increased plasma gastric inhibitory polypeptide and pancreatic polypeptide.
In the second study, 32 subjects were distributed into 2 groups to ingest daily foods with (3 g/day) or without β-glucan for 3 weeks. Results indicate a regular daily intake of 3 g β-glucan is not sufficient to have an effect on fecal microbiota composition, suggesting that health-promoting effects at 3 g/d are probably due more to their physiological effect in the proximal part of the gastrointestinal tract than to their prebiotic effect in the colon.”
https://www.mdpi.com/2304-8158/12/4/700 “Modulation of Postprandial Plasma Concentrations of Digestive Hormones and Gut Microbiota by Foods Containing Oat ß-Glucans in Healthy Volunteers”
I’ll use a 2021 study Rapid Determination of β-Glucan Content of Hulled and Naked Oats Using near Infrared Spectroscopy Combined with Chemometrics to estimate my daily β-glucan intake. Those researchers tested 100 varieties of Avena nuda that varied between 3.12% and 5.22% β-glucan. My intake from 82 g (dry weight) of hulless oats (cinnamon sprinkled for taste) is probably between (82 g x .0312) = 3 g and (82 g x .0522) = 4 g.
They also tested 79 varieties of hulled Avena sativa that varied between 3.1% and 5.5% β-glucan. Oat sprouts analysis tested a Avena sativa variety where the β-glucan content decreased from 3.48% to 2.10% over four days of sprouting, a 40% reduction.
My daily β-glucan intake from 40 g (dry weight) of three-day-old hulled oat sprouts is probably 1 g [(40 g x .031) x .6 = 1 g and (40 g x .055) x .6 = 1 g]. That’s okay, because oat sprouts have other benefits per Oat sprouts analysis and Advantages of 3-day-old oat sprouts over oat grains.
My daily oat β-glucan intake is 4 – 5 grams. I’ve maintained that for two years, and don’t see any reason to stop.
A second 2023 paper from a clinical trial investigated effects of combining oat bran along with orange juice:
“Orange juice (OJ) is a rich dietary source of bioactive flavanones, and consuming OJ has been associated with beneficial effects including decreased inflammation and improved lipid profiles. However, dietary recommendations are to limit OJ consumption to one serving per day due to high sugar and low fiber content. Metabolic concerns are increased postprandial insulin response to a high sugar load which in individuals at risk may promote insulin resistance.
Consumption of 22 g oat bran containing 6 g of β-glucan together with 500 mL of OJ by healthy subjects impacts on OJ flavanone bioavailability with the 0-24 post-intake excretion of phase II metabolites, such as hesperetin-7-glucuronide, being reduced ~3-fold. This was not a consequence of bran affecting the rate of gastric transport, and underlying mechanisms behind reduced excretion of OJ flavanone metabolites remain a matter of conjecture.
The pool of bound phenolics in bran linked to polysaccharides appears not to be converted to free phenolics. It was rather principally a consequence of a bran-mediated increase in quantities of flavanones passing from the upper to the lower bowel where they were subjected to microbiota-mediated catabolism.”
https://www.sciencedirect.com/science/article/abs/pii/S0891584923000515 “Bioavailability of orange juice (poly)phenols: β-glucan-rich oat bran decreases urinary excretion of flavanone phase II metabolites and enhances excretion of microbiota-derived phenolic catabolites” (not freely available) Thanks to Dr. José Manuel Moreno-Rojas for providing a copy.
This paper referenced a preliminary study by many of the same coauthors that found oat bran with 3 g of β-glucan didn’t have similar effects.
A 2022 meta-analysis investigated differences between whole oats and purified β-glucan:
“This systematic review and meta-analysis evaluated the impact of oats or β-glucan supplements on the lipid profile. Our findings show that both oat and isolated β-glucan interventions can improve lipid profiles, specifically total cholesterol and low density lipoprotein cholesterol (LDL) concentrations, and should be incorporated into one’s regular eating habits.
Interventions ranged from 14 to 84 days in length. Quantity of β-glucan ingested (oats and isolated β-glucan) ranged from 1.2 g/day to 11.2 g/day.
Limitations and additional considerations include:
- We did not have enough studies that matched total fiber intake between intervention and control groups, and so could not evaluate if results were exclusively influenced by oat/isolated β-glucan supplementation, or if other types of dietary fiber would have a similar impact on lipidemia.
- Mechanisms of changes in concentrations of triglycerides (TG) are linked to carbohydrates. An increase in availability of glucose in serum, resulting from absorption of carbohydrates, stimulates secretion of insulin and, as a result, synthesis of fatty acids in the liver is increased. Mixed results found in this and other meta-analyses regarding TG may be related to the fact that oats and isolated β-glucan were frequently administered through day-to-day processed foods which have sugar and other types of refined flour in their recipes.
- Different oat cooking procedures, processing methods, and molecular weights modify viscosity and impact in cholesterol concentrations differently. Less processed oats appear to be more effective than processed oat products in improving lipidemia. Higher molecular weight is associated with increased viscosity, and greater reduction in LDL. Also, the process used to treat oats affects its molecular weight, and the highest viscosities were observed as a consequence of dry processes in comparison to ones that exhibit enzymatic activity.
- Reducing saturated fat intake may be, in combination with increased viscous fiber intake from oats or isolated β-glucan, the most effective way to improve dyslipidemia. In future studies, amount and type of fat in diet should be evaluated and considered accordingly.”
http://dx.doi.org/10.1016/j.clnesp.2022.12.019 “The separate effects of whole oats and isolated beta-glucan on lipid profile: A systematic review and meta-analysis of randomized controlled trials” (not freely available)