Probiotics are live microorganisms which provide health benefits when consumed, generally by improving or restoring the gut flora. The majority of probiotics are bacteria with the species of lactobacillus and bifidobacterium being the most common type of bacteria used.

Under natural conditions, a healthy gut microflora develops and there is no need for probiotic supplementation. However, a busy lifestyle and poor diet of processed food plus the overuse of antibiotics would alter the composition of gut microbiota. Probiotic replenish good bacteria in the gut, contributing a good microflora.