Most people familiar with the diabetes drug metformin know that it can have some unpleasant effects on the digestive tract including nausea and diarrhea. Long term use of the drug can also lead to a deficiency of vitamin B-12 due to decreased absorption of the vitamin.
Studies also suggest that metformin can alter the composition of the microbiome and enhance the growth of a bacterium called Akkermansia muciniphila and other bacteria that produce short-chain fatty acids (SCFAs). SCFAs like butyrate, propionate, and acetate have been associated with a decrease in obesity and insulin resistance, and can protect against colon cancer. An abundance of A. muciniphila has been associated with less abdominal fat, lower blood sugar levels and improved insulin sensitivity. This may in part explain how metformin can help with weight loss and blood sugar control.
While there are many probiotic products available, they do not typically contain Akkermansia. This is likely because the bacterium was only recently discovered, and the ideal amount needed in the microbiome is not yet clear.
For people not taking metformin who want to increase levels of beneficial A. muciniphila, consumption of navy beans has been shown to be effective. More here
SCFAs, especially butyrate can be found in supplements or in a healthy diet. Cow’s milk is a good source of butyrate, and high-fiber foods will increase butyrate during fermentation in the intestines by gut microbes. More here