The use of Bifidobacteria to support or treat lactose intolerance is primarily justified by scientific evidence, though the evidence is moderate rather than strong. Bifidobacteria are a genus of probiotic bacteria naturally found in the human gut, especially in infants, and are known for their ability to ferment various carbohydrates, including lactose. Several clinical studies have shown that supplementation with certain strains of Bifidobacteria can improve lactose digestion and reduce symptoms of lactose intolerance such as bloating, abdominal pain, and diarrhea. The proposed mechanism is that Bifidobacteria possess β-galactosidase (lactase) activity, which helps break down lactose in the gut, thereby reducing the amount of undigested lactose that reaches the colon and is fermented by gas-producing bacteria.

However, the strength of evidence varies by strain and study design. Not all Bifidobacteria strains have the same efficacy, and some studies show only modest benefit. Meta-analyses and systematic reviews (such as those published in journals like Alimentary Pharmacology & Therapeutics and Journal of Dairy Science) generally conclude that probiotics containing Bifidobacteria can be helpful for some individuals with lactose intolerance, but the overall effect size is moderate, and not all patients respond. More research is needed to identify the most effective strains and optimal dosing.