Resistant starch may be beneficial to health because colonic fermentation by microflora produces short chain fatty acid (SCFA) that cause beneficial physiological changes. These include a decrease in gut pH that inhibits the growth of pathogens, increased electrolyte absorption, increases visceral blood blow and improved smooth muscular activity. Acetate, propionate and butyrate are the SCFA most commonly produced during fermentation of resistant starch, but butyrate may be of particular importance because it is the preferred energy source for colonocytes and may limit carcinogenesis within gut tissue. Because butyrate may be beneficial to health, researchers are interested in dietary practices which promote formation of butyrate in the colon. High resistant starch diets are one strategy that may be appropriate, but other methods such as the delivery of SCFA esterified to resistance starch molecules have shown promise at raising colonic butyrate concentrations.
Animal studies have shown that acylated, propionated and butyrated resistant starched can deliver SCFA to the colon because bacteria can hydrolyse the ester bonds and release the SCFA to the lumen of the gut. Early human studies using ileostomy patients showed that such esterified resistant starches allowed faecal recovery of roughly 75% of the ingested dose of butyrate. In order to determine if humans with intact ileums could benefit from butyrated resistant starch, researchers1 fed subjects diets containing 20 or 40g of cooked high amylose maize starch or 20 or 40g of butyrated high amylose maize starch in a cross over design. Butyrate faecal concentrations were raised following consumption of the butyrated resistant starch, when compared to baseline or the non-butyrated starch. The 40g dose of butyrated starch was more effective at raising faecal butyrate when compared to the 20g dose.
Butyrated starch therefore raises colonic concentrations of butyrate in healthy humans, as demonstrated previously in animals and ileostomy patients. Estimations suggested that roughly 57.2% of the ingested dose was released in the colon, with 27% of the total esterified butyrate being absorbed in the small intestine and 15.8% being recovered in the faeces. In addition, the authors conducted microbial analysis using PCR analysis and concluded that Parabacteroides distasonis was probably responsible for the hydrolysis of the butyrate. Estimates of butyrate absorption in subjects following a Western diet have been put at roughly 64mmol per day from the fermentation of resistant starch, whereas in this study total butyrate released into the colon was estimated to be 18.2 to 33.1mmol per dose. Therefore two doses of butyrated starch provided a normal daily does of butyrate and may therefore be an effective way to increase colonic butyrate concentrations.
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