To boost the immune system, B. Lactis is a promising choice. One study had participants taking either a probiotic or a placebo for 6 weeks. At the end of the period, researchers measured antibody levels and found greater increases in antibodies of the B. Lactis group than in placebo participants, concluding that this probiotic may help improve immune function [1]. In addition, a 2009 study found that supplementation of the strain B. Lactis DN-173 led to self-reported improvements in digestive comfort [2].
Even if some of the bacteria in a probiotic managed to survive and propagate in the intestine, there would likely be far too few of them to dramatically alter the overall composition of one's internal ecosystem. Whereas the human gut contains tens of trillions of bacteria, there are only between 100 million and a few hundred billion bacteria in a typical serving of yogurt or a microbe-filled pill. Last year a team of scientists at the University of Copenhagen published a review of seven randomized, placebo-controlled trials (the most scientifically rigorous types of studies researchers know how to conduct) investigating whether probiotic supplements—including biscuits, milk-based drinks and capsules—change the diversity of bacteria in fecal samples. Only one study—of 34 healthy volunteers—found a statistically significant change, and there was no indication that it provided a clinical benefit. “A probiotic is still just a drop in a bucket,” says Shira Doron, an infectious disease expert at Tufts Medical Center. “The gut always has orders of magnitude more microbes.”
If you go with a supplement, know that the FDA regulates these products but treats them like foods and not medications. Unlike drug manufacturers, supplement makers don’t have to show their products are safe or effective to sell them. That means that these firms are in charge of checking the safety and labeling of their products before they sell them to make sure they meet FDA rules.

Probiotics are “friendly” bacteria that inhabit your body. Sound strange? These microscopic roommates can be your best buds if you show them a little love. One surefire way to do that is with probiotic supplements. Probiotics support the right ratio of good to bad bacteria in your gut. For bonus points, call on digestive enzymes. These unique blends offer specific nutritional support to assist digestion and nutrient absorption. Your healthy body will quickly appreciate these lifelong friends.