Kefir is a fermented milk drink and it is lovely! If you like a sour mix between milk and yoghurt, kefir may be worth trying. Kefir has also been researched a lot for the health benefits it may provide to your gut community.
Some kefir can contain more than 50 different species of bacteria and yeast but this depends on where it was made, how fresh it is and who made it. All kefir is not equal. The current research has shown kefir to have multiple possible positive health benefits including antiobesity, anti-hepatic steatosis, antioxidative, antiallergenic, antitumor, anti-inflammatory, cholesterol-lowering, constipation-alleviating, and antimicrobial properties. But, this would depend on the individual, their current diet and health status. If you have a poor diet, just adding something like kefir will not change much.
The reason kefir is special is that it can resist digestion through the gastrointestinal tract and may have the ability to colonise the gut microbiota. Kefir has also been suggested to modulate, or alter, the gut microbiota and mycobiota (the fungi species of the gut community). These types of changes have only been seen in a small number of studies so far with very different factors involved but the evidence for kefir is looking good so far. Make your own if you like. It’s not hard and you can buy a kit easy enough. Just by adding in little things like kefir to your diet it can help make small changes over time if you are trying to improve your overall health. Small steps make big changes especially when it comes to gut health.
Bourrie, B. C. T., Willing, B. P., & Cotter, P. D. (2016). The Microbiota and Health Promoting Characteristics of the Fermented Beverage Kefir. Frontiers in Microbiology, 7, 647-647. doi:10.3389/fmicb.2016.00647
Kim, D.-H., Jeong, D., Kim, H., & Seo, K.-H. (2019). Modern perspectives on the health benefits of kefir in next generation sequencing era: Improvement of the host gut microbiota. Crit Rev Food Sci Nutr, 59(11), 1782-1793. doi:10.1080/10408398.2018.1428168