Condition

Lactose Intolerance

Lactose intolerance happens when the body makes too little lactase, the enzyme that digests lactose, so undigested milk sugar ferments in the gut and causes uncomfortable symptoms. The evidence is strongest for lactase enzyme supplements, and bloating improved in trials of people using them. That finding rests on a fairly small group of 66 people, while the evidence for Lactobacillus probiotics is moderate.

Supplements studied: 1
Graded outcomes: 2
Trials: 10
People studied: 298

Evidence by supplement

Strong
Moderate
Limited
Very limited

1 supplement

Lactase Enzyme

Lactase Enzyme: outcomes studied for Lactose Intolerance
Grade	Outcome	Effect	Size	Studies	People
	Bloating Moderate Improvement	Improves (the measure goes down)	Moderate effect		66 people
	Abdominal Pain Small Improvement	Improves (the measure goes down)	Small effect		85 people
	Breath Hydrogen	Improves (the measure goes up)		6 studies	283 people
Studies that measured breath hydrogen Effective reduction of lactose maldigestion in preschool children by direct addition of beta-galactosidases to milk at mealtimePediatrics · PMID 3106927 Effects of exogenous lactase administration on hydrogen breath excretion and intestinal symptoms in patients presenting lactose malabsorption and intoleranceBiomed Res Int · PMID 24967391 Dietary manipulation of postprandial colonic lactose fermentation: II. Addition of exogenous, microbial beta-galactosidases at mealtimeAm J Clin Nutr · PMID 3918430 and 3 more on the Lactase Enzyme page
	Flatulence	Changes; see studies		4 studies	96 people
Studies that measured flatulence A combination of acid lactase from Aspergillus oryzae and yogurt bacteria improves lactose digestion in lactose maldigesters synergistically: A randomized, controlled, double-blind cross-over trialClin Nutr · PMID 25042846 The effect of oral supplementation with Lactobacillus reuteri or tilactase in lactose intolerant patients: randomized trialEur Rev Med Pharmacol Sci · PMID 20391953 Enzyme replacement therapy for primary adult lactase deficiency. Effective reduction of lactose malabsorption and milk intolerance by direct addition of beta-galactosidase to milk at mealtimeGastroenterology · PMID 6434367 and 1 more on the Lactase Enzyme page
	Diarrhea Symptoms	Improves (the measure goes down)			66 people
	Headaches	Improves (the measure goes down)			26 people
	Heartburn Symptoms	Improves (the measure goes down)			15 people
	Lactose Intolerance Symptoms	Improves (the measure goes down)			101 people
	Nausea Symptoms	Improves (the measure goes down)			30 people
	Stool Consistency	Improves (the measure goes up)			30 people

Key findings

BloatingLactase EnzymeImproves (the measure goes down)
Abdominal PainLactase EnzymeImproves (the measure goes down)

The Lactose Intolerance Management protocol

2 primary supplements · 2 supporting supplements

Lactase Enzyme3,000–9,000 FCC units before dairy consumption
Probiotics (Lactobacillus strains)10–20 billion CFU daily (lactose-digesting strains)

See the full protocol

Shop the evidence-backed picks

Fullscript collectionGut and digestion: evidence-graded picksOpen on Fullscript

The collection holds the supplements we grade A or B for its theme, in third-party tested products where the catalog has them. It opens in our Fullscript store. You can look through it without signing in; Fullscript asks for a free account to order.

Or shop one supplement

The supplement graded A or B for Lactose Intolerance. Each opens third-party tested products for that supplement.

Grade A

We earn from purchases made in our Fullscript store, and links to Fullscript, iHerb or Thorne carry our referral, so we may earn a commission at no extra cost to you. Grades come from the research and never change based on what we earn. Full disclosure

Studies cited

11 studies from PubMed

A combination of acid lactase from Aspergillus oryzae and yogurt bacteria improves lactose digestion in lactose maldigesters synergistically: A randomized, controlled, double-blind cross-over trialClin Nutr · PMID 25042846
The effect of oral supplementation with Lactobacillus reuteri or tilactase in lactose intolerant patients: randomized trialEur Rev Med Pharmacol Sci · PMID 20391953
Enzyme replacement therapy for primary adult lactase deficiency. Effective reduction of lactose malabsorption and milk intolerance by direct addition of beta-galactosidase to milk at mealtimeGastroenterology · PMID 6434367
Long-term acceptance of low-lactose milkAm J Clin Nutr · PMID 114042
Effective reduction of lactose maldigestion in preschool children by direct addition of beta-galactosidases to milk at mealtimePediatrics · PMID 3106927
Effects of exogenous lactase administration on hydrogen breath excretion and intestinal symptoms in patients presenting lactose malabsorption and intoleranceBiomed Res Int · PMID 24967391
Dietary manipulation of postprandial colonic lactose fermentation: II. Addition of exogenous, microbial beta-galactosidases at mealtimeAm J Clin Nutr · PMID 3918430
Effect of exogenous beta-galactosidase in patients with lactose malabsorption and intolerance: a crossover double-blind placebo-controlled studyEur J Clin Nutr · PMID 15674309
beta-Galactosidase from Aspergillus niger in adult lactose malabsorption: a double-blind crossover studyAliment Pharmacol Ther · PMID 1543816
Beta-galactosidase tablets in the treatment of lactose intolerance in pediatricsAm J Dis Child · PMID 2122719
Treatment of lactase deficiency in children's obesity with genotype c/c 13910 of lactase geneWiad Lek · PMID 30796855