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LONDON: Consumption of probiotic yoghurt may help us to digest carbohydrates more efficiently, but does not alter the gut's bacterial makeup, according to new research.
These results go some way to supporting the many health giving claims made about probiotics, although the researchers say that more work is needed to test how the change in carbohydrate metabolism seen in their study affects digestion.
"Now, we can directly test the influence of existing or candidate probiotics on the ability of our gut microbial community to digest various components of our diets," said study author Jeffrey Gordon from Washington University School of Medicine in the U.S. of the paper published in the current issue of Science Translational Medicine.
"Our group's goal is to help develop new ways to improve the nutritional value of the foods we consume, in part by optimising the features contained in the gut microbial communities of people at various stages of life and from different cultural traditions," he said.
Of mice and men
The researchers first fed yoghurt containing five strains of probiotic bacteria to mice reared in a sterile environment. Prior to this experiment the mice were implanted with 15 genetically sequenced strains of common human gut bacteria.
This enabled Gordon and colleagues to see whether the bacteria in the yoghurt had become resident in the gut of the mice or changed the existing stomach bacteria in any way.
The team found that consumption of the yoghurt did not appear to change the proportional representation of the human gut bacteria species present in the stomach of the mice, nor the gene content of the bacteria.
Carbohydrate breakdown
However, when the investigators looked more closely at the gene expression of each mouse's gut bacteria and at the chemical content of their urine, they found that exposure to the microbes in the yoghurt led to changes in several metabolic processes, specifically those involved with carbohydrate breakdown.
"Carbohydrates are an important part of our diet, and the way they are broken down by gut microbes is an important part of digestive health," Gordon said. "A number of carbohydrates are quite complex and can only be digested by enzymes made by gut microbes. We found that when the mice were given the bacterial strains found in the yoghurt, at doses comparable to those consumed by humans, they could more efficiently break down certain classes of carbohydrates."
Twin confirmation
To test the effects of the same probiotic yoghurt on human gut bacteria, the researchers recruited seven young and healthy adult women and their identical twins. By testing identical twins, the effects of genetic variation can be minimised or accounted for, as they have the same genetic make-up.
The women consumed the yoghurt twice a day for seven weeks. Faecal sampling was used to measure changes in the proportions or gene expression of the women's gut bacteria before, during, and after the test period.
