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Lactase (Beta-Galactosidase Enzyme)
A digestive enzyme taken with dairy to break down lactose. Small placebo-controlled challenge trials mostly show less breath hydrogen and, in most, fewer symptoms in people with lactose malabsorption, but responses vary widely between people and products and no pooled analysis in adults exists.
What the evidence says
Lactase doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from medium-quality meta-analyses and randomised trials published 1992–2024 with a typical study size of 47 participants.
Based on 15 studies · 1 meta-analysis · 10 RCTs · 962 total participants
Confidence
Moderate confidenceBy outcome
Moderate 5.5 reflects a mostly consistent effect in its one real use: across about ten small placebo-controlled or crossover trials, lactase taken with a lactose challenge lowered breath hydrogen and usually eased symptoms. It is held below Strong because nearly all trials are single-dose laboratory challenges in a few dozen people, no meta-analysis in adults exists and the one systematic review could not pool the data, responses vary widely between people and between products, a 50 g lactose load given in water overwhelmed 3,000 to 6,000 units in one trial, and in one of two 2022 trials that included a lactase arm it did not beat placebo.
Lactase is the enzyme that splits lactose, the sugar in milk, into glucose and galactose so it can be absorbed.
Most adults worldwide lose much of their own intestinal lactase after childhood, and in some of them undigested lactose reaches the colon, where bacteria ferment it and cause bloating, pain, gas and diarrhoea.
Supplemental lactase is a microbial beta-galactosidase, usually from the moulds Aspergillus oryzae or Aspergillus niger, or from the yeast Kluyveromyces lactis, taken as tablets, capsules or chewables with dairy, or added as drops to milk.
Around ten small randomised or crossover trials, most of them single lactose challenges measured over a few hours, find that it lowers breath hydrogen and usually eases symptoms compared with placebo. The limits are real.
The one systematic review of lactose intolerance management could not pool the trials and called for more research, a single-arm study found that most patients barely responded to a standard dose, products of similar labelled strength did not behave the same in a head-to-head trial, a 50 g lactose load given in water overwhelmed 3,000 to 6,000 units in one trial (9,900 units still helped in another, where the lactose was given in milk), and in one of two 2022 trials that included a lactase arm lactase did not beat placebo.
Most adults with presumed lactose intolerance tolerate about one cup of milk without any enzyme. Lactase does nothing for milk protein allergy or galactosaemia, and evidence for infant colic is inconclusive.
Lactase is a beta-galactosidase that cleaves lactose into glucose and galactose, which the small intestine can absorb. Taken with dairy, it stands in for the brush-border lactase that declines in adults with lactase non-persistence.
When less undigested lactose reaches the colon, gut bacteria have less to ferment into hydrogen and other gases. Exhaled hydrogen after a lactose dose is the main outcome the trials measure, and bloating, pain and flatulence follow the same fermentation.
Mould-derived lactase from Aspergillus oryzae is an acid lactase that is active in the stomach, so it is taken as a tablet with food. Yeast-derived lactase from Kluyveromyces lactis works at neutral pH and is usually added to milk before drinking.
Most adults with presumed lactose intolerance tolerate 12 to 15 g of lactose (about one cup of milk) without any enzyme. A breath test or a supervised dairy trial shows whether lactose is the cause.
Do not use lactase as a way to eat dairy. Galactose must still be avoided.
Evidence is inconclusive. Discuss with a paediatrician.
Not studied. Ask a clinician or pharmacist before use.
Tip: Stop and seek urgent care. Avoid all lactase-containing products after any allergic reaction.
Lactase has an evidence score of 5.5/10 — moderate evidence based on 15 indexed studies, including 1 meta-analysis. A digestive enzyme taken with dairy to break down lactose. Small placebo-controlled challenge trials mostly show less breath hydrogen and, in most, fewer symptoms in people with lactose malabsorption, but responses vary widely between people and products and no pooled analysis in adults exists. Representative study: PMID 38426798.
Dosing for Lactase: Taken per lactose-containing meal, not as a daily dose. Trials gave 3,000 to 11,250 units of lactase (mostly FCC units) immediately before or with a single dairy or lactose challenge. One 2022 trial used 4,662 FCC units and describes 4,500 FCC units as the amount in the EU-approved health claim. More lactose needs more enzyme: 50 g of lactose given in water overwhelmed about 6,000 units in one trial. Products differ, so dose by the enzyme units on the label rather than by tablet count. Individual needs vary, so check the right dose for you with a healthcare provider.
The best time to take Lactase is with meals. Take it with food. The enzyme only works on lactose it meets in the gut, so trials gave it immediately before or together with the dairy.
Lactase is generally well-tolerated and considered safe for most healthy adults when used as in the cited trials. Reported side effects are uncommon and include allergic reaction to the enzyme, including anaphylaxis. Use caution if any of these apply to you: Galactosaemia: lactase releases galactose from lactose rather than removing it, so it does not make dairy safe; Known allergy to lactase enzyme preparations (anaphylaxis has been reported).
Digestive Enzymes
Too few graded studiesEnzyme blend that helps break down proteins, fats and carbohydrates. Small trials suggest less discomfort in functional dyspepsia, but the evidence for everyday bloating is mixed.
Oral Proteolytic Enzymes
Too few graded studiesCombinations of protein-cleaving enzymes (trypsin, chymotrypsin, papain, bromelain), often with rutoside, taken between meals for joint pain and swelling. In osteoarthritis they were non-inferior to diclofenac in two 6-week trials designed to test that, and a pooled reanalysis reported fewer adverse events than diclofenac, but placebo-controlled evidence is mixed and a 721-person ankle sprain trial found no benefit.
AN-PEP
Mostly mechanism / observationalAn oral enzyme from the mould Aspergillus niger that breaks down gluten in the stomach. Small trials show it lowers the gluten reaching the small intestine after a meal, but it is not a treatment for coeliac disease and does not make gluten safe for people with coeliac disease to eat.
Diamine Oxidase (DAO)
Too few graded studiesAn oral enzyme, usually from pig kidney or pea sprouts, taken just before meals to break down histamine from food in the gut. Small trials in people with suspected histamine intolerance report fewer symptoms, but the trials in migraine, urticaria, fibromyalgia and insomnia mostly failed to show a clear difference from placebo.
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Reviewed by Dr. Baher Al Hakim · Last reviewed October 2026 · evidence from 15 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.