Butyrate, a fatty acid, comes from two dietary sources. First, it is one of the metabolic end products of unabsorbed dietary carbohydrate that has been bacterially fermented in the gut. Butyrate is the single biggest metabolite of fiber. Second, the only direct source in the diet is from butter, which contains 3% butyrate. Adequate amounts of butyrate are necessary for the health of the large intestine cells.
It has a particularly important role in the colon, where it is the preferred substrate for energy generation by colonic cells. Whether by supplement or by enema, a few pilot studies suggest it is useful in reducing symptoms and restoring indicators of colon health in ulcerative colitis, but one study showed no benefit over placebo. Several doctors claim that many people are helped with butyrate enemas. Butyrate levels are commonly measured in comprehensive stool analyses and act as a marker for levels of beneficial bacteria.
Butyrate has been shown to significantly inhibit the growth of cancerous colon cells. Scientists have found a human gene that stops the growth of cancer cells when activated by fiber processing in the colon. Although scientists have long linked butyrate to overall reductions in the incidence of colon cancer, the molecular basis of that benefit has remained largely unknown. Butyrate effects a chemical “unloosening” of molecules that otherwise bind and constrict the activity of the p21 gene. This gene is responsible for the manufacture of p21 protein, a compound that slows the growth of cancer cells. A separate study has indicated a possible benefit in breast cancer prevention.