A 2012 research review published in the Journal of the American Medical Association (JAMA) found that probiotics reduced the risk of antibiotic-associated diarrhea by 42 percent—but many of the studies had flaws, so these findings should be interpreted with caution. A 2013 Cochrane review of 23 trials also concluded that probiotics may be effective for preventing antibiotic-related diarrhea. However, the largest and best-designed study to date, published in the Lancet in 2013, found that probiotics were no better than a placebo in preventing diarrhea in older people taking antibiotics.