Lactose intolerance (LI) is characterized by the presence of primarily 
gastrointestinal clinical signs resulting from colonic fermentation of lactose, 
the absorption of which is impaired due to a deficiency in the lactase enzyme. 
These clinical signs can be modified by several factors, including lactose dose, 
residual lactase expression, concurrent ingestion of other dietary components, 
gut-transit time, and enteric microbiome composition. In many of individuals 
with lactose malabsorption, clinical signs may be absent after consumption of 
normal amounts of milk or, in particular, dairy products (yogurt and cheese), 
which contain lactose partially digested by live bacteria. The intestinal 
microbiota can be modulated by biotic supplementation, which may alleviate the 
signs and symptoms of LI. This systematic review summarizes the available 
evidence on the influence of prebiotics and probiotics on lactase deficiency and 
LI. The literature search was conducted using the MEDLINE (via PUBMED) and 
SCOPUS databases following Preferred Reporting Items for Systematic Reviews and 
Meta-Analyses (PRISMA) guidelines, and included randomized controlled trials. 
For each study selected, the risk of bias was assessed following the Cochrane 
Collaboration methodology. Our findings showed varying degrees of efficacy but 
an overall positive relationship between probiotics and LI in relation to 
specific strains and concentrations. Limitations regarding the wide 
heterogeneity between the studies included in this review should be taken into 
account. Only one study examined the benefits of prebiotic supplementation and 
LI. So further clinical trials are needed in order to gather more evidence.