Dietary Fiber increases beneficial bacteria in the gut.

gutThe University of Illinois has published a new study revealing that fiber increases the amount of beneficial bacteria in the gut impacting on weight loss.

The researchers analyzed the genome information of bacteria in the gut after a diet had been supplemented with polydextrose and soluble corn fiber. The samples used in this study originate from a study conducted in 2012. In that study, 20 healthy men with an average fiber intake of 14 grams a day were given snack bars to supplement their diet. The control group received bars that contained no fiber; a second group ate bars that contained 21 grams of polydextrose, which is a common fiber food additive; and a third group received bars with 21 grams of soluble corn fiber.

“In the gut, bacteria have the capacity to do a lot of different things, such as fermenting proteins, carbohydrates, or other substrates,” Kelly Swanson, the lead professor of the study, said. “We have already been able to identify what bacteria are there and the changes that occur with diet, and now we are asking if we can change the machinery or the capacity of what functions the bacteria have. Knowing what bacteria are there may matter, but it may not matter as much as identifying their function.”

The study revealed a shift in the bacterial ratio from Bacteroidetes:Firmicutes to more Bacteroidetes, something the researchers had not seen previously.

“This was of particular interest to us because other research has shown that having more Bacteroidetes may be beneficial because the higher that proportion is, the individual tends to be leaner. With higher Firmicutes, that individual tends to be more obese,” Holscher, another study author, said. “We don’t know if there is any causality for weight loss, but studies have shown that having a higher fiber diet is protective against obesity. It’s an exciting shift and helps to drive researchers to study these fibers as part of a weight loss diet.”

“We saw that there was a decrease in genes associated with protein metabolism, which correlated with the reduced protein fermentation that occurred in the study participants’ guts when they consumed the fibers,” she said “The information from this study, in combination with the results from the previous study, has allowed us to put together a more complete picture of what the bacteria in our gut are doing.”

The researchers stress that if people want to have a healthy lifestyle, that the changes need to be done on daily basis as the bacteria revert back to the original gut composition when fiber supplementation was stopped.


H. D. Holscher, J. G. Caporaso, S. Hooda, J. M. Brulc, G. C. Fahey, K. S. Swanson. Fiber supplementation influences phylogenetic structure and functional capacity of the human intestinal microbiome: follow-up of a randomized controlled trial. American Journal of Clinical Nutrition, 2014; DOI: 10.3945/%u200Bajcn.114.092064

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