Gut microbiota, illustration. The human intestine microflora's primary benefit is the uptake of energy from the fermentation of undigested carbohydrates and the absorption of short chain fatty acids. Medical research has show that the relationship between intestinal flora and humans is not just commensal (a non-harmful coexistence), but rather a mutualistic relationship. The human body carries about 100 trillion microbes in the intestinal tract, a number 10 times greater than the total number of human cells in the body.