12 January - 20 June 2016

A high fibre diet found to be beneficial for type 2 diabetes

Research led by a Rutgers University-New Brunwisk and published in the journal Science has reported that a high fibre diet, diverse in fibre can lead to better glucose control, greater weight loss and better lipid levels in people with type-2 diabetes. A shortage of short chain fatty acids have been found in previous studies to be associated with type 2 diabetes and other diseases. Short chain fatty acids are produced from carbohydrate fermentation.

Research led by a Rutgers University-New Brunwisk and published in the journal Science has reported that a high fibre diet, diverse in fibre can lead to better glucose control, greater weight loss and better lipid levels in people with type-2 diabetes.  A shortage of short chain fatty acids have been found in previous studies to be associated with type 2 diabetes and other diseases. Short chain fatty acids are produced from carbohydrate fermentation.

In this randomised controlled study, Zhao et al. compared the effect of two different diets in participants with type 2 diabetes.  During the intervention, which lasted for 12 weeks, 16 people followed a low-fat, low carbohydrate diet (control diet), whilst 27 people consumed a high fibre diet containing whole-grains, traditional Chinese medicinal foods high in dietary fibres, and prebiotics. At baseline blood samples were taken and faecal and urine samples collected.

During intervention, both groups (participants aged 35 – 70 years) took the drug acarbose to help control blood glucose. Acarbose also makes people digest starch more slowly than usual, allowing it to reach the large intestine and microbes. Apart from the fibre, both groups consumed the same amount of energy and micro nutrients. For each meal the high fibre group were instructed to consume approx. 360g of Formula 1 comprising of diverse structure of fibre (β-glucan, arabinoxylan, cellulose, hemicellulose, resistant starch, gums and oligosacchairdes), 10g of formula 2 (a powder preparation infusion of bitter melon and oligosaccharides) and 15g of a powder preparation for infusion (containing kudzu starch, inulin and resistant dextrin), plus fruit, nuts and vegetables. Every 28 days anthropometric measurements, biological samples and metabolic testing was carried out. 

Zhao et al. report that over the 12 weeks, compared to baseline, hemogloblin A1C (indicates average level of blood sugar), decreased significantly in a time dependent manner, with the high fibre group having the largest reduction after 28 days.  The number of participants who also had adequate glycaemic control of <7% was significantly higher in the high fibre diet group, compared to the control (89% vs 50%).  Compared to the control group, the dietary fibre group were also found to have a greater reduction in body weight and better blood lipid profile. 

When Zhao et al transplanted faecals samples into germ free mice they found that that the mice that received the samples from those on the high fibre diet had the lowest fasting and postprandial blood glucose levels which they report mirrored the better metabolic outcome in the high fibre groups.

Zhao et al. also analysed 172 faecal samples collected at four time points during the intervention. Using next generation sequencing the team identified 141 bacterial strains as SCFA producers, of which 15 were promoted by dietary fibre. An increase in these strains, both in diversity and abundance, was found to improved haemoglobin A1c levels “partly via increased glucagon-like peptide 1 production.” Positive responder strains were found to also reduce the quantity of two harmful metabolites, namely hydrogen sulphide (linked with the development of Crohn’s disease, ulcerative colitis and colorectal cancer) and indole (linked with defective tryptophan metabolism and impaired serotonin synthesis). 

In conclusion Zhao et al state “Our study suggests that chronic diseases such as type 2 diabetes may be a consequence of the loss of deficiency in a beneficial function(s) such as SCFA production from carbohydrate fermentation in the gut ecosystem.” They continue by stating “restoring or enhancing the lost or deficient function by re-establishing  the functionally active ecological populations as ecosystems service providers is the key to a healthier microbiota which can help alleviate disease phenotypes.”

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