July 17 (HealthDay News) -- Taking a probiotics supplement after gastric bypass surgery helps patients lose weight faster and avoid vitamin B deficiency, a new study finds.

Probiotics are the "good" bacteria found in yogurt and in dietary supplements that aid digestion.

The Stanford University School of Medicine study included 44 patients who had Roux-en-Y gastric bypass surgery and were randomly assigned to either a probiotics group or a control group. Both groups received the same bariatric medical care and nutritional counseling and both were allowed to consume yogurt, a natural source of probiotics. Patients in the probiotics group also took one pill per day of a probiotics supplement.

After three months, the probiotics group had a 47.6 percent weight loss, compared with 38.5 percent in the control group. Patients in the probiotics group also had higher levels of vitamin B-12 three months after surgery than those in the control group -- 1,214 picograms per milliliter as opposed to 811 picograms per milliliter, a significant difference since B-12 deficiency is common after gastric bypass surgery.

The study appears in the July issue of the Journal of Gastrointestinal Surgery.

SOURCE: Stanford University, news release, July 13, 2009