Dietary carbohydrate digestion and fermentation: relevance for prevention of type 2 diabetes

PhD ceremony: Mr. H. Wang, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: Dietary carbohydrate digestion and fermentation: relevance for prevention of type 2 diabetes

Promotor(s): prof. R.J. Vonk

Faculty: Medical Sciences

Consumption of carbohydrates is associated with the prevention of type 2 diabetes. Two important physiological processes thereby play a role: 1. slow digestion in the small intestine which leads to a low blood glucose response after a meal and 2. the fermentation of non-digestible carbohydrates in the large intestine. It is supposed that the fermentation process plays a role by means of the production of short chain fatty acids (SCFA).

Firstly, we have developed a mathematical model to examine non-invasively the contribution of digestion as well as fermentation after intake of carbohydrate-rich meals in humans. The fermentation of non-digestible carbohydrates, inclusive dietary fiber, is not investigated in detail until now. This is why we also developed an analytical method to be able to measure the SCFA profile in blood and in urine. The test meals were labeled with stable isotopes which enabled us to relate the SCFA profile to the investigated test meals. We found that SCFA profiles in plasma and urine could be changed by different non-digestible carbohydrates.

Furthermore, we found that healthy men had a lower glucose response and lower inflammation markers in blood after breakfast when they had eatennon-digestible carbohydrates in the evening. The higher hydrogen excretion in breath and the higher bloodSCFA concentrations in the morning strongly suggest that fermentation in the large intestine is responsible for these beneficial effects with SCFAs as the intermediary factor.

Manipulation of fermentation of carbohydrates in the large intestine seem to be a promising approach for the prevention of type 2 diabetes.