Lactobacillus bulgaricus is a transient bacterium from yogurt that does not colonize the gut but delivers benefits as it moves through. People have used it in fermented dairy for ages, and it shows up in many multi-strain probiotic blends.
It aids lactose breakdown and supports immune function. When paired with other probiotics, it helps keep the gut environment balanced.
Take it with a meal to shield the bacteria from stomach acid. Forms include capsules and freeze-dried powders. Doses differ from product to product.
Most people handle it well, but it can trigger mild bloating at first. Anyone with a severely weakened immune system or dairy allergy should speak with a doctor before use.