They’re already known to aid in digestion and are believed to be helpful in treating and preventing a host of common illnesses, from urinary tract infections to eczema. Now researchers say probiotics may aid in weight loss.

A new study out of the Stanford University School of Medicine finds gastric bypass surgery patients who received a probiotic supplement everyday for three months following their procedure had a significantly higher weight loss, an average of 47.6 percent, than those who got a placebo pill, an average of 38.5 percent.

In addition, the group that was given the probiotics was able to avoid a vitamin B12 deficiency, which is a common side effect of gastric bypass surgery.

Almost two-thirds, or 66 percent, of adult Americans are overweight. Gastric bypass is the most
common weight loss surgery because it is associated with fewer complications than other weight loss procedures.

Vitamin B12 is a critical vitamin important for metabolism, the formation of red blood cells, and maintenance of the central nervous system.

Probiotics are available in supplement form. They can also be found in foods like yogurt and other cultured milk products, miso, tempeh, and some juices and soy beverages.