Skip to content
Winnowleaf home

Supplements for Lactose Intolerance: Lactase, Probiotics, and What to Skip

For lactose intolerance, lactase enzyme taken right before dairy has the best support: small placebo-controlled trials found less gas, bloating and breath hydrogen (grade B), though it fails for some people. Probiotic capsules have weak, strain-by-strain evidence (grade C). Most adults can handle about 12 g of lactose, roughly one cup of milk, with no pill at all. If you cut dairy, replace its calcium, and see a doctor about weight loss or blood in your stool.

Published How we grade evidenceEditorial policy

The short version

  • Lactase enzyme with dairy: less gas, bloating and breath hydrogen in small placebo-controlled trials. Grade B (Baijal 2021; Montalto 2005).
  • A modest serving of lactose, no pill: in blinded trials, a meal-sized dose caused little more trouble than a dummy sugar. Grade A (Savaiano 2006).
  • Yogurt and kefir with live cultures: their lactose is digested better than milk's. Grade B (Hertzler 2003; Savaiano 2014).
  • A purified GOS prebiotic for about a month: fewer symptoms in two trials with 462 people. Grade B (Oliveira 2022).
  • Probiotic capsules: results depend on the strain, and confidence is low. Grade C (Ahn 2023; Oliveira 2022).

Lactose intolerance means gas, bloating, belly pain or diarrhea after eating lactose, the sugar in milk, because the small intestine makes too little lactase, the enzyme that splits it (Misselwitz 2019). Many people who blame milk digest lactose normally (NIH consensus, Suchy 2010).

How much lactose can you handle without a pill?

Grade A. A meta-analysis pooled 21 blinded trials in which poor lactose digesters drank 7 to 25 g of lactose, the amount in a typical meal, or a look-alike placebo. Bloating, pain and gas were not clearly different; only loose stools were slightly more common (Savaiano 2006). A 2010 review of 36 randomized trials agreed that most adults handle 12 to 15 g, about one cup of milk, at one sitting (Shaukat 2010).

Spreading it out helps: symptoms grew clearer above 12 g and hit most people at 50 g, yet 24 g split across the day was generally tolerated (Wilt 2010). In a double-blind trial, 31 women with lactose maldigestion added 2 cups of milk plus cheese and yogurt for a week (34 g of lactose a day). Compared with lactose-free versions, they passed more gas, but bloating, pain and diarrhea did not differ (Suarez 1998).

Gut bacteria may adapt too. Grade C. After 20 adults took slowly rising doses of lactose daily for 10 days, gas after a lactose test fell 50% compared with 10 days of a different sugar (Hertzler 1996). The 2010 review judged this evidence insufficient (Shaukat 2010).

Does lactase work, and how should you take it?

Grade B. In a double-blind crossover trial, 47 adults with a positive breath test took chewable lactase tablets or a placebo before lactose; on lactase, symptom scores fell and total breath hydrogen over 180 minutes was 55% lower (Baijal 2021). Two smaller crossover trials that added the enzyme to 400 ml of milk found the same pattern (Corazza 1992; Montalto 2005).

It doesn't work for everyone. Among 96 people given a standard dose, the breath test became normal in about a fifth (21.88%) and barely moved in three-fifths (60.41%) (Ibba 2014). Our database page grades lactase A for bloating. We grade it B because the trials were small, each tested one serving in a lab, and the 2010 federal evidence report found the evidence insufficient for every agent it checked, enzymes included (Wilt 2010).

How to use it:

  • Timing. Take tablets right before your first bite or sip of dairy, or add drops to milk before drinking (NIDDK). Milk treated with drops 10 hours ahead gave a lower symptom score than milk treated 5 minutes before (Montalto 2005).
  • Units. Lactase strength is measured in FCC units, a lab measure. With a 12.5 g lactose drink, 3,300 and 9,000 units of acid lactase cut peak breath hydrogen by 29% and 33%, and only the higher dose was reported to ease gas. One unit splits about 5 mg of lactose in a lab solution; what a dose digests in your body can't be pinned down (de Vrese 2015). Our protocol page lists its amounts.
  • Daily use. In 128 adults who took a lactase tablet three times a day for 42 days, two products worked about equally, with no serious side effects; there was no placebo group (Francesconi 2016).

Is yogurt or kefir easier on the gut than milk?

Grade B. Yogurt brings its own lactase: its bacteria survive the stomach inside their cells and keep splitting lactose in the small intestine, and ordinary commercial yogurts differ little (Savaiano 2014). In 15 adults given 20 g of lactose, breath hydrogen scored 224 after milk, 76 after plain yogurt and 87 after plain kefir, and gas was rated 54% to 71% less severe with the fermented foods (Hertzler 2003).

European rules let yogurt and fermented milk say live cultures improve lactose digestion only when they hold at least 100 million (10^8) live starter bacteria per gram (EU Regulation 432/2012, based on an EFSA opinion). Check that the label lists live cultures.

Do probiotic supplements help?

Grade C. A 2023 meta-analysis of 12 studies found less pain, diarrhea and gas with probiotics, but also signs of publication bias for most results (Ahn 2023). A 2022 systematic review of placebo-controlled adult trials found some risk of bias in every probiotic trial and rated its confidence low (Oliveira 2022). Our condition page's summary calls the Lactobacillus evidence moderate; with one small trial per strain, we grade it C.

Lactobacillus reuteri

Grade D. In a 60-person trial, 20 people took L. reuteri twice a day for 10 days, 20 took one lactase dose a quarter of an hour before a lactose test, and 20 took a placebo. Both beat placebo, but the single lactase dose beat 10 days of the probiotic (Ojetti 2010). The 2022 review names the strain as DSM 17938 (Oliveira 2022).

Lactobacillus acidophilus

Grade D. In a crossover trial, adults took the DDS-1 strain of L. acidophilus or a maltodextrin placebo daily for 4 weeks; during a 6-hour lactose challenge, diarrhea, cramping and overall scores were lower on the probiotic (Pakdaman 2016). One author worked for the strain's supplier.

Bifidobacteria

Grade D. In 50 adults, one serving of ice cream with B. bifidum strain 900791 eased symptoms, but a month of daily probiotic ice cream did no better than plain ice cream (Aguilera 2021). In 21 adults, B. adolescentis iVS-1 for 2 weeks cut daily symptoms and diarrhea against placebo, in a trial funded by a company tied to the strain (Ramakrishnan 2025).

Can a prebiotic retrain your gut bacteria?

Grade B. GOS (galacto-oligosaccharides) are short sugar chains made from lactose that feed gut bacteria (Ramakrishnan 2025). Two trials tested a highly purified (over 95%) GOS being developed as a medicine (Azcarate-Peril 2017; Chey 2020). In the larger, 377 adults took one of two doses or a placebo for 30 days; 40% on GOS reached the main symptom goal against 26% on placebo, and they went on to consume more dairy (Chey 2020). In the 85-person trial, results only trended better, though half of those with belly pain at the start had none 30 days after treatment (Savaiano 2013).

Caveats: the company developing the product funded the trials, with authors who worked for or advised it (Chey 2020), and no trial we found tested the GOS powders sold as supplements.

Calcium and vitamin D when you cut back on dairy

Grade C. Across 13 observational studies of adults, people with lactose intolerance usually ate less calcium than others; their blood calcium looked normal, and bone findings were inconsistent (Almalki 2026). Poor lactose digestion doesn't seem to block calcium absorption; the bone risk comes from eating less dairy (Hodges 2019).

No trial we found tested calcium or vitamin D pills in lactose intolerance. Adults need 1,000 mg of calcium a day, rising to 1,200 mg for women from 51 and everyone over 70. Lactose-free dairy has the same calcium as regular dairy, and canned fish with bones, kale, broccoli and fortified foods add more (NIH ODS; ODS professional sheet). Adults need 600 IU of vitamin D a day, or 800 IU over 70 (NIH ODS).

What we'd skip

  • Probiotic blends sold "for lactose" with no published trial of their strains.
  • "Digestive enzyme" blends that don't state lactase in FCC units. We found no trial of mixed blends for this.
  • Supplement GOS powders as a stand-in for the trial product.
  • Cutting out all dairy with no plan for calcium.

Safety and interactions

  • Lactase: no side effects in one crossover trial (Montalto 2005), none serious over 42 days (Francesconi 2016). A case report describes eye swelling, shortness of breath and throat tightness after one lactase tablet, confirmed as an allergy to the enzyme (Voisin 2016). No interaction studies were found for lactase.
  • Probiotics: generally safe, but case reports describe systemic infections in susceptible people (Doron 2015). If your immune system is weakened, ask your doctor first.
  • GOS: safe and well tolerated in the 377-person trial (Chey 2020).
  • Calcium: the upper limit from food and supplements is 2,500 mg a day for adults 19 to 50 and 2,000 mg from 51. Take 500 mg or less at a time; supplements can cause gas, bloating or constipation (NIH ODS), and high supplemental intakes might raise kidney stone risk (NIH ODS).
  • Calcium interactions: levothyroxine (thyroid hormone) is poorly absorbed within 4 hours of calcium carbonate, and quinolone antibiotics such as ciprofloxacin within 2 hours of calcium (NIH ODS).
  • Vitamin D: the adult upper limit is 4,000 IU a day (NIH ODS).

When to see a doctor

  • Get tested before cutting dairy for good. In a hydrogen breath test you drink a set dose of lactose (25 g in the North American consensus); a rise of 20 parts per million or more over your starting level counts as positive (Rezaie 2017).
  • Rule out celiac disease. Of 54 adults with a positive lactose breath test, 24% had celiac antibodies, against 2% of blood donors, so the authors suggest a celiac blood test before a milk-free diet (Ojetti 2005).
  • Symptoms that start later in life. The inherited type usually starts by early adulthood; later onset can mean small-intestine damage from infection, celiac disease, Crohn's disease or radiation (NIDDK; Szilagyi 2016).
  • Red flags: losing weight without trying, blood in or on your stool, black stools, waking at night with diarrhea, fever, repeated vomiting, or symptoms that persist when you avoid lactose fully.
  • Signs of a milk allergy instead. An allergy is an immune reaction whose gut symptoms can look alike (Di Costanzo 2018). Hives, a hoarse voice, wheezing, or swelling of the lips, face or tongue, usually within 2 hours of eating, need urgent care (MedlinePlus). Lactase does nothing for an allergy.
  • IBS and anxiety make symptoms after lactose more likely (Misselwitz 2019); see our irritable bowel syndrome stack.

If symptoms began after a new medicine, don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant, breastfeeding or under 18, ask a clinician.

FAQ

What is the best supplement for lactose intolerance? Lactase enzyme taken right before dairy has the most support (grade B). It doesn't help everyone, so try it with a normal serving first.

Can probiotics fix lactose intolerance for good? No trial shows that. A few strains eased symptoms in single small trials (grade D each). A purified GOS prebiotic helped in two larger trials (grade B), but store GOS powders are untested.

How much milk can I drink if I'm lactose intolerant? Most adults handle about 12 g of lactose at once, roughly a cup of milk, and more when spread through the day. Yogurt and kefir are usually easier than milk.

Is lactose intolerance the same as a milk allergy? No. Lactose intolerance is trouble digesting milk sugar. A milk allergy is an immune reaction that can cause hives, wheezing or swelling and can be dangerous; lactase pills don't help it.

Sources

  1. Baijal R, et al. Effect of lactase on symptoms and hydrogen breath levels in lactose intolerance: A crossover placebo-controlled study. JGH Open. 2021. PubMed 33490624 · doi:10.1002/jgh3.12463
  2. Montalto M, et al. Effect of exogenous beta-galactosidase in patients with lactose malabsorption and intolerance: a crossover double-blind placebo-controlled study. Eur J Clin Nutr. 2005. PubMed 15674309 · doi:10.1038/sj.ejcn.1602098
  3. Corazza GR, et al. beta-Galactosidase from Aspergillus niger in adult lactose malabsorption: a double-blind crossover study. Aliment Pharmacol Ther. 1992. PubMed 1543816 · doi:10.1111/j.1365-2036.1992.tb00545.x
  4. Ojetti V, et al. The effect of oral supplementation with Lactobacillus reuteri or tilactase in lactose intolerant patients: randomized trial. Eur Rev Med Pharmacol Sci. 2010. PubMed 20391953
  5. Ibba I, et al. Effects of exogenous lactase administration on hydrogen breath excretion and intestinal symptoms in patients presenting lactose malabsorption and intolerance. Biomed Res Int. 2014. PubMed 24967391 · doi:10.1155/2014/680196
  6. de Vrese M, et al. 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 trial. Clin Nutr. 2015. PubMed 25042846 · doi:10.1016/j.clnu.2014.06.012
  7. Francesconi CF, et al. ORAL ADMINISTRATION OF EXOGENOUS LACTASE IN TABLETS FOR PATIENTS DIAGNOSED WITH LACTOSE INTOLERANCE DUE TO PRIMARY HYPOLACTASIA. Arq Gastroenterol. 2016. PubMed 27706451 · doi:10.1590/S0004-28032016000400004
  8. Shaukat A, et al. Systematic review: effective management strategies for lactose intolerance. Ann Intern Med. 2010. PubMed 20404262 · doi:10.7326/0003-4819-152-12-201006150-00241
  9. Wilt TJ, et al. Lactose intolerance and health. Evid Rep Technol Assess (Full Rep). 2010. PubMed 20629478
  10. Savaiano DA, et al. Lactose intolerance symptoms assessed by meta-analysis: a grain of truth that leads to exaggeration. J Nutr. 2006. PubMed 16549489 · doi:10.1093/jn/136.4.1107
  11. Suchy FJ, et al. NIH consensus development conference statement: Lactose intolerance and health. NIH Consens State Sci Statements. 2010. PubMed 20186234
  12. Suarez FL, et al. Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products. Am J Clin Nutr. 1998. PubMed 9808231 · doi:10.1093/ajcn/68.5.1118
  13. Hertzler SR, et al. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr. 1996. PubMed 8694025 · doi:10.1093/ajcn/64.2.232
  14. Savaiano DA. Lactose digestion from yogurt: mechanism and relevance. Am J Clin Nutr. 2014. PubMed 24695892 · doi:10.3945/ajcn.113.073023
  15. Hertzler SR, et al. Kefir improves lactose digestion and tolerance in adults with lactose maldigestion. J Am Diet Assoc. 2003. PubMed 12728216 · doi:10.1053/jada.2003.50111
  16. Oliveira LS, et al. The use of probiotics and prebiotics can enable the ingestion of dairy products by lactose intolerant individuals. Clin Nutr. 2022. PubMed 36308983 · doi:10.1016/j.clnu.2022.10.003
  17. Ahn SI, et al. Effects of probiotics administration on lactose intolerance in adulthood: A meta-analysis. J Dairy Sci. 2023. PubMed 37225575 · doi:10.3168/jds.2022-22762
  18. Pakdaman MN, et al. The effects of the DDS-1 strain of lactobacillus on symptomatic relief for lactose intolerance - a randomized, double-blind, placebo-controlled, crossover clinical trial. Nutr J. 2016. PubMed 27207411 · doi:10.1186/s12937-016-0172-y
  19. Aguilera G, et al. Improvement in Lactose Tolerance in Hypolactasic Subjects Consuming Ice Creams with High or Low Concentrations of Bifidobacterium bifidum 900791. Foods. 2021. PubMed 34681517 · doi:10.3390/foods10102468
  20. Ramakrishnan M, et al. Two-week supplementation of Bifidobacterium adolescentis iVS-1 reduces symptoms associated with lactose intolerance in lactose maldigesters. Gut Microbes Rep. 2025. PubMed 41909904 · doi:10.1080/29933935.2025.2508199
  21. Savaiano DA, et al. Improving lactose digestion and symptoms of lactose intolerance with a novel galacto-oligosaccharide (product code omitted): a randomized, double-blind clinical trial. Nutr J. 2013. PubMed 24330605 · doi:10.1186/1475-2891-12-160
  22. Chey W, et al. Galacto-Oligosaccharide (product code omitted) Improves Multiple Clinical Outcomes in Lactose-Intolerant Patients. Nutrients. 2020. PubMed 32290344 · doi:10.3390/nu12041058
  23. Azcarate-Peril MA, et al. Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals. Proc Natl Acad Sci U S A. 2017. PubMed 28049818 · doi:10.1073/pnas.1606722113
  24. Almalki AH, et al. Calcium, Vitamin D, and Phosphorus Levels and Bone Health in Adults with Lactose Intolerance: A Systematic Review. Nutr Rev. 2026. PubMed 42770947 · doi:10.1093/nutrit/nuag131
  25. Hodges JK, et al. Lactose Intolerance and Bone Health: The Challenge of Ensuring Adequate Calcium Intake. Nutrients. 2019. PubMed 30925689 · doi:10.3390/nu11040718
  26. Voisin MR, et al. Anaphylaxis to supplemental oral lactase enzyme. Allergy Asthma Clin Immunol. 2016. PubMed 27999602 · doi:10.1186/s13223-016-0171-8
  27. Doron S, et al. Risk and safety of probiotics. Clin Infect Dis. 2015. PubMed 25922398 · doi:10.1093/cid/civ085
  28. Rezaie A, et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017. PubMed 28323273 · doi:10.1038/ajg.2017.46
  29. Ojetti V, et al. High prevalence of celiac disease in patients with lactose intolerance. Digestion. 2005. PubMed 15775678 · doi:10.1159/000084526
  30. Misselwitz B, et al. Update on lactose malabsorption and intolerance: pathogenesis, diagnosis and clinical management. Gut. 2019. PubMed 31427404 · doi:10.1136/gutjnl-2019-318404
  31. Szilagyi A, et al. Systematic review and meta-analysis of lactose digestion, its impact on intolerance and nutritional effects of dairy food restriction in inflammatory bowel diseases. Nutr J. 2016. PubMed 27411934 · doi:10.1186/s12937-016-0183-8
  32. Di Costanzo M, et al. Lactose Intolerance: Common Misunderstandings. Ann Nutr Metab. 2018. PubMed 30783042 · doi:10.1159/000493669