Short‐Chain Fatty Acids: Ready for Prime Time?

Abstract

The concept of colonic health has become a major target for the development of functional foods such as probiotics, prebiotics, and synbiotics. These bioactive agents have a profound effect on the composition of the microflora, as well as on the physiology of the colon, and display distinct health benefits. Dietary carbohydrates escaping digestion/absorption in the small bowel and prebiotics undergo fermentation in the colon and give rise to short-chain fatty acids (SCFA). As the main anions of the colon and the major source of energy for colonocytes, SCFA are rapidly absorbed by nonionic diffusion mostly but also by active transport mediated by a sodium-coupled transporter, thereby fostering the absorption of sodium and water. SCFA in general and butyrate in particular enhance the growth of lactobacilli and bifidobacteria and play a central role on the physiology and metabolism of the colon. The effect of prebiotics on cell proliferation, differentiation, apoptosis, mucin production, immune function, mineral absorption, lipid metabolism, and gastrointestinal (GI) peptides has been well documented experimentally. These effects seem to be largely mediated by SCFA, but evidence from human studies remains inconsistent. The food industry is making a leap of faith in their efforts to commercialize prebiotics and exploit potential health benefits. The future lies with the design of studies to further explore basic mechanisms, and gene expression in particular, but emphasis should be placed on human intervention trials.

Lactaturia and Loss of Sodium-dependent Lactate Uptake in the Colon of SLC5A8-deficient Mice

“…This coincides with the fact that most of the monocarboxylates produced by bacterial fermentation, such as butyrate and propionate, occur in the large intestine. Furthermore, it is reported that butyrate forms the main nutrition for the colon epithelium and is necessary for differentiation of colonocytes (42,43). Interestingly, we found that SLC5A8 has a strong prevalence to transport lactate but does not contribute significantly to the butyrate or propionate uptake of the colon at physiological conditions.…”

Quantification by computerized morphometry of tissue levels of sulfomucins and sialomucins in diversion colitis in rats

“…SCFAs, which are produced from fermentation of dietary fibers caused by anaerobic bacteria in the intestinal lumen, represent 90% of all the energy supplies used by the epithelial cells of the colon mucosa 23 . SCFAs modulate both cell proliferation and local immunity and they have an important role in relation to the integrity of the colon epithelium 24,25 . Reductions in the supply of SCFAs, as occurs during intestinal diversion operations, are accompanied by morphological and functional changes, thereby causing reductions in protein synthesis capacity 26 .…”

Butyric acid in gastrointestinal tract

“…Kwas masłowy w jelicie grubym powstaje głównie w wyniku rozkładu pentoz [3], a kwas glukonowy może być prebiotykiem wybiórczo stymulującym powstawanie maślanu. Najbogatszymi źródłami kwasu masłowego w jelicie grubym są: oporna skrobia, owies i otręby pszenne [3].…”

“…Najbogatszymi źródłami kwasu masłowego w jelicie grubym są: oporna skrobia, owies i otręby pszenne [3]. Oporna skrobia znajduje się w takich pokarmach, jak: częściowo zmielone ziarna zbóż i nasiona, surowe ziemniaki, zielone banany, warzywa oraz skrobia z dużą zawartością amylozy.…”

“…Według Roy i wsp. [3] dobowa produkcja SCFA w jelicie grubym u zdrowego czło-wieka wynosi 300-400 mmol. U ludzi wraz z wiekiem obserwuje się zmniejszenie całkowitej produkcji SCFA oraz proporcjonalny wzrost SCFA o rozgałęzionym łańcuchu.…”