Two studies on the impact of fibre supplements on diabetes were published this month (March 2018).
Neither study involved a low carb approach but both studies found significant benefits from fiber supplementation. However, there were much more powerful effects from multiple fibers than a single source. The benefits of fiber supplements work through entirely different mechanisms to carbohydrate restriction and will likely greatly improve the metabolic improvements seen with low carb diets.
The German study by Honsek et al involved a single supplement of oat fibre (Vitacel OF 560-30; Rettenmaier & Söhne) as well as advice to follow a high fibre diet to subjects with insulin resistance.
The Chinese study involved providing a high fibre diet with multiple different fibre types from whole plant foods and pre-biotics. Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes. Zhao et al., Science 359, 1151–1156 (2018) 9 March 2018.
The authors of the German study point out "large epidemiological studies have identified dietary fibre as one of the most effective nutrient components for diabetes prevention [3]. Fibre intake is currently far below the recommended levels in most countries that consume Western-style foods [4].
The goal of the study was to provide dietary advice to increase fibre intake as part of a healthy diet in both study groups. A sub-group was given a supplement to take twice a day adding a total of 15g insoluble oat fibre in addition to the dietary counseling both groups received. The significant outcome reported was a greater decrease in HgbA1c with fibre supplement.
"All participants were given detailed advice about how to achieve the goals of the lifestyle intervention: an increase in fibre intake to at least 15 g per 4200 kJ; a reduction in weight of 5% or more (if baseline BMI >25 kg/m2); a reduction in total intake of fat to less than 30% of energy consumed and of saturated fat to less than 10% of energy consumed; and moderate exercise for at least 30 min per day. Frequent ingestion of whole-grain products, legumes, vegetables, fruits, in particular berries, low-fat milk and meat products, soft margarines, and vegetable oils rich in unsaturated fatty acids was recommended."
dietary advice alone fails to increase fibre intake without supplements
Behavior change through intensive counseling involving 12 separate 2 hour sessions failed to increase fiber from food sources in both groups apart from fiber supplements in the sub-group . Only 14% of the control group achieved the recommended intake of fiber and that increased to 67% in the fiber supplemented group. Even though the incidence of diabetes was 43% lower with fiber supplementation that outcome did not reach statistical significance. Using intention to treat statistical analysis where 35% drop out and 33% who failed to achieve target fiber intake are included in the different outcomes it is little wonder why there was no statistically significance. An analysis dividing all study patients into quintiles of fiber intake to compare against outcomes might appear quite different.
The Chinese study was remarkably different
for its mechanistic detail and highly important findings. Both groups had standard treatment for diabetes: dietary advice and Acarbose, a drug blocks small intestinal carbohydrate digestion. In addition, the study group received functional food supplements with a variety of fibers and prebiotics, a total fiber intake of 38g/day compared to 12g/day. To quickly summarize their extensive list of findings: there was a change in the gut microbiota but also a change in the enzymes produced by the microbiota. Some microbiota common to both groups responded by increasing enzymes producing short chain fatty acids when stimulated with increased fiber.
There was a dose response of more SCFAs with increased fiber along with increased production of gut hormones GLP1 and PYY:
these two hormones suppress appetite, improve pancreatic function, and can be considered antidotes to diabetes.
The pharmaceutical industry is engaged in a modern day gold rush to produce best GLP1 mimicking drugs.
In a much more natural and likely beneficial way Zhao et al. have shown us that GLP1 can be increased and diabetes alleviated with a diverse spectrum of fibers and pre-biotics.