Lactobacillus species, particularly Lactobacillus acidophilus and Lactobacillus bulgaricus, are commonly used probiotics that have been studied for their potential to alleviate symptoms of lactose intolerance. The scientific rationale is based on the fact that some Lactobacillus strains produce the enzyme β-galactosidase (lactase), which can help break down lactose in the gut. Clinical studies have shown that consumption of yogurt containing live Lactobacillus cultures is often better tolerated than milk by lactose-intolerant individuals, suggesting that these bacteria can aid in lactose digestion.

A number of randomized controlled trials and meta-analyses (e.g., Szilagyi et al., 2016, British Journal of Nutrition) have reported modest improvements in gastrointestinal symptoms (like bloating and diarrhea) among lactose-intolerant people consuming certain probiotic Lactobacillus strains, though not all studies are positive and the effect size is generally small to moderate. The evidence is strongest for yogurts with live cultures, while encapsulated probiotic supplements have shown more variable results. Overall, there is scientific support for the use of some Lactobacillus strains in managing lactose intolerance, but the benefit is not universal and depends on the specific strain and product used.