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Eating probiotic yogurt might change the way the bacteria in your gut break down the carbs you eat, a new study suggests.
Researchers found that eating yogurt daily did not alter the species of microbes in the intestines of people, or mice transplanted with human gut microbes.
However, when the researchers looked at the activity of bacterial enzymes in the mice's guts, they discovered significant changes in some of the enzymes — particularly those involved in metabolizing carbohydrates.
Essentially, the live bacteria in the yogurt allowed the mice to break down certain classes of carbohydrates more efficiently, the study showed, and many of these changes also occurred in the study's 14 human participants.
"It's interesting that just by virtue of introducing species, you can get quite dramatic changes in the expression of genes in the gut microbes," said Susan Lynch, an associate professor of medicine at the University of California, San Francisco, who was not involved in the research.
But she says that larger studies are needed to really understand how the probiotics, or "good bacteria," affect the bacterial communities in people's intestines.
The effects of probiotics
Our guts are home to swarms of bacteria, known collectively as the microbiome. These communities help us in a variety of ways, such as harvesting energy from the food we eat, preventing the growth of harmful bacteria and producing nutrients such as vitamins K and H.
Studies have shown that probiotics, such as those found in yogurt, can help with certain intestinal issues, such as irritable bowel syndrome. Recent research suggests that ingesting probiotics may even affect our behavior and could someday treat depression.
But despite the purported health benefits of probiotics, it's unclear how exactly they affect our gut microbiomes, and influence our overall health.
In the new study, researchers recruited seven pairs of identical female twins and gave them two servings of yogurt a day for seven weeks. The yogurt had five strains of live bacteria.
"The idea of using twins is a nice one," Lynch said. "To some extent, it can standardize genetic and environmental factors that could have an affect on the results."
The researchers analyzed stool samples from the women throughout the study, and found yogurt didn't change the species or genes of the bacterial communities in the women's intestines.
In other words, the bacteria in the yogurt did not appear to colonize the participants' guts. In fact, two weeks after the women stopped eating yogurt, the researchers could not detect any live yogurt bacteria in the stool samples of the majority of the participants.
But the researchers then carried out a similar experiment with mice, and found significant changes in the way the mice metabolized carbohydrates.
A new model
Jun Sun, an assistant professor of medicine at the University of Rochester in New York, said the researcher's method of using mice with humanized microbiomes could be useful for future studies, particularly those that test the health benefits of yogurts and other fermented milk products.
The research provides a nice model to test how the introduction of different probiotics affects our gut microbial communities, Sun said. [Are Probiotics Safe?]
Lynch said studies like this "are fundamental to understanding the possible benefits of microbial supplementation approaches."
The study was published today (Oct. 26) in the journal Science Translational Medicine.
Pass it on: Some types of yogurt may alter the way you break down carbs, but more research is needed to really understand the effects of probiotics.