Here we present the recent research that supports the contention that replacement of rapidly digested carbohydrates (High Glycemic Carbohydrates) with resistant carbohydrates (fiber) may counteract obesity and prevent many non-communicable diseases.
Grazing animals eat little other than fiber and they obtain nutrition from fiber fermentation by symbiotic intestinal microorganisms that produce large amounts of short chain fatty acids (SCFA’s ) which are their main energy source. We share 99% of our DNA and have similar colon anatomy with the great apes and they derive greater than 50% of their energy from SCFA's from fibre fermentation. SCFA’s serve as energy substrates in man as well as other mammals and are essential substrates for colonic epithelial cells but also have important cell signalling effects by activating SCFA receptors on many cells throughout the body. Besides SCFA’s, bacterial fermentation may be a source of other important nutrients such as folate, biotin, other water soluble B vitamins and vitamin K as colonic transporters for biotin, thiamine, riboflavin, pyridoxine and folate have recently been discovered.
Most fruits and vegetables are high in fiber. Here is a comprehensive list of foods high in fiber:
Numerous epidemiological studies and controlled trials on fiber consumption have prompted the European and American authorities to approve several health claims associated with increased fiber consumption.
Positive associations between fibre intake and health become more convincing as the molecular mechanisms behind numerous beneficial effects of fiber are being resolved by basic science researchers. Acetate, propionate and butyrate are the most common SCFA’s produced by bacterial fermentation of fiber which takes place mainly in the terminal ileum and large intestine. The SCFA’s, particularly butyrate, are important energy substrates for intestinal epithelial cells and excess SCFA passes through to the liver and systemic circulation performing dual roles as an energy substrate and activators of important cell signaling pathways. Two G-protein coupled receptors for SCFA have been identified FFAR2 and FFAR3 which preferentially bind acetate/propionate and butyrate respectively. There is a direct link between fiber consumption producing SCFA and increased Glucagon Like Peptide (GLP1) secretion from intestinal L cells which is triggered via the SCFA receptors FFAR2 and FFAR3. In addition SCFA’s can have direct effects on gene expression by inhibition of Histone Deacetylases HDAC which have anti-proliferative and anti-inflammatory effects in vitro, and in in vivo models of intestinal inflammation and either of these mechanisms are thought to be responsible for widespread beneficial effects of short chain fatty acids as listed below:
The figure below is from a combined analysis of multiple studies showing an increasing protection against cardiovascular disease with increasing consumption of dietary fibre, the studies suggest much larger amounts (60-70 g/day) would be more protective than current nutritional guidelines (25-35 g/day).
Consumption of fiber helps prevent cardiovascular disease
Otherwise known as the "Leaky Gut Concept," the barrier between the gut contents and blood stream prevents toxins and sensitizing proteins from entering the circulation and failure of tight junctions between intestinal cells may be the triggering event in inflammatory conditions and autoimmune diseases such as IBD, celiac disease, arthritis and type 1 diabetes. Fiber has been found critical to maintaining integrity of the intestinal barrier.
Short chain fatty acids have been found to reduce inflammation and regulate adipokine secretion in adipose tissue increasing leptin and decreasing the pro-inflammatory resistin.They also reduce inflammation occurring in colitis, arthritis and asthma
Short chain fatty acids produced from intestinal fermentation of fiber activate specific receptors (called FFAR2 & FFAR3) that are widely expressed throughout body tissue importantly on immune cells and adipose tissue and suppress inflammation while the FFAR2 receptors in intestinal cells produce additional signaling molecules GLP1 and PYY which suppress appetite, stimulate hepatic HDL production and contribute to further anti-inflammatory and metabolic regulatory functions. They also trigger Glucagon Like Peptide release (GLP1) from intestinal L cells. GLP1 slows gastric emptying, lowers glucose levels, and reduces food consumption and suppresses appetite.