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Lactose intolerance: Clinical manifestations, diagnosis, and management

Heinz F Hammer, MD
Christoph Högenauer, MD
Section Editor
Lawrence S Friedman, MD
Deputy Editor
Shilpa Grover, MD, MPH, AGAF


Intolerance to lactose-containing foods is common [1]. Clinical symptoms of lactose intolerance include abdominal pain, flatulence, and diarrhea after ingestion of milk or milk-containing products. These symptoms have been attributed to lactose malabsorption, which results from low levels of small intestinal lactase, which may be due to mucosal injury or, much more commonly, reduced genetic expression of the enzyme lactase-phlorizin hydrolase. This topic will review the clinical manifestations, diagnosis, and management of lactose intolerance. Other causes of malabsorption are discussed in detail, separately. (See "Mechanisms of nutrient absorption and malabsorption" and "Clinical features and diagnosis of malabsorption" and "Overview of the treatment of malabsorption".)


Lactase deficiency – Lactase deficiency is characterized by an intestinal brush border lactase enzyme activity that is lower than that of normal individuals.

Lactose malabsorption – Lactose malabsorption is characterized by a failure of the small bowel to absorb a sizable fraction of ingested lactose.

Lactose intolerance – Lactose intolerance is a clinical syndrome in which lactose ingestion causes symptoms (eg, abdominal pain, bloating, flatulence, diarrhea) due to lactose malabsorption.


The prevalence of lactase deficiency has been described in most regions of the world and in people with diverse ethnic backgrounds. However, the prevalence of lactose malabsorption and lactose intolerance is unclear due to methodological limitations of existing studies that have used varying definitions of lactose malabsorption and intolerance. Evaluation of epidemiological trends suggests that the prevalence of lactose intolerance varies across racial and ethnic groups, with the lowest prevalence in Europeans and European Americans and higher prevalence in African Americans, Hispanics, Asians, Asian Americans, and Native Americans. In Africa, some ethnic groups have high rates of lactase intolerance (South Nigerian, Hausa, Bantu), while others have low rates (Hima, Tutsi, nomadic Fulani). The prevalence of lactose malabsorption and intolerance are low in children younger than six years and increases with age [2,3].

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Literature review current through: Nov 2017. | This topic last updated: Nov 28, 2017.
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  1. Suchy FJ, Brannon PM, Carpenter TO, et al. National Institutes of Health Consensus Development Conference: lactose intolerance and health. Ann Intern Med 2010; 152:792.
  2. Rao DR, Bello H, Warren AP, Brown GE. Prevalence of lactose maldigestion. Influence and interaction of age, race, and sex. Dig Dis Sci 1994; 39:1519.
  3. Di Stefano M, Veneto G, Malservisi S, et al. Lactose malabsorption and intolerance in the elderly. Scand J Gastroenterol 2001; 36:1274.
  4. Maiuri L, Raia V, Potter J, et al. Mosaic pattern of lactase expression by villous enterocytes in human adult-type hypolactasia. Gastroenterology 1991; 100:359.
  5. Martín MG, Turk E, Lostao MP, et al. Defects in Na+/glucose cotransporter (SGLT1) trafficking and function cause glucose-galactose malabsorption. Nat Genet 1996; 12:216.
  6. Shaw AD, Davies GJ. Lactose intolerance: problems in diagnosis and treatment. J Clin Gastroenterol 1999; 28:208.
  7. Hammer HF, Santa Ana CA, Schiller LR, Fordtran JS. Studies of osmotic diarrhea induced in normal subjects by ingestion of polyethylene glycol and lactulose. J Clin Invest 1989; 84:1056.
  8. Hertzler SR, Savaiano DA. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr 1996; 64:232.
  9. Briet F, Pochart P, Marteau P, et al. Improved clinical tolerance to chronic lactose ingestion in subjects with lactose intolerance: a placebo effect? Gut 1997; 41:632.
  10. Tishkoff SA, Reed FA, Ranciaro A, et al. Convergent adaptation of human lactase persistence in Africa and Europe. Nat Genet 2007; 39:31.
  11. Scrimshaw NS, Murray EB. The acceptability of milk and milk products in populations with a high prevalence of lactose intolerance. Am J Clin Nutr 1988; 48:1079.
  12. Sahi T, Isokoski M, Jussila J, et al. Recessive inheritance of adult-type lactose malabsorption. Lancet 1973; 2:823.
  13. Harvey CB, Hollox EJ, Poulter M, et al. Lactase haplotype frequencies in Caucasians: association with the lactase persistence/non-persistence polymorphism. Ann Hum Genet 1998; 62:215.
  14. Enattah NS, Sahi T, Savilahti E, et al. Identification of a variant associated with adult-type hypolactasia. Nat Genet 2002; 30:233.
  15. Kuokkanen M, Enattah NS, Oksanen A, et al. Transcriptional regulation of the lactase-phlorizin hydrolase gene by polymorphisms associated with adult-type hypolactasia. Gut 2003; 52:647.
  16. Olds LC, Sibley E. Lactase persistence DNA variant enhances lactase promoter activity in vitro: functional role as a cis regulatory element. Hum Mol Genet 2003; 12:2333.
  17. Troelsen JT, Olsen J, Møller J, Sjöström H. An upstream polymorphism associated with lactase persistence has increased enhancer activity. Gastroenterology 2003; 125:1686.
  18. Lewinsky RH, Jensen TG, Møller J, et al. T-13910 DNA variant associated with lactase persistence interacts with Oct-1 and stimulates lactase promoter activity in vitro. Hum Mol Genet 2005; 14:3945.
  19. Rasinperä H, Savilahti E, Enattah NS, et al. A genetic test which can be used to diagnose adult-type hypolactasia in children. Gut 2004; 53:1571.
  20. Kuchay RA, Thapa BR, Mahmood A, Mahmood S. Effect of C/T -13910 cis-acting regulatory variant on expression and activity of lactase in Indian children and its implication for early genetic screening of adult-type hypolactasia. Clin Chim Acta 2011; 412:1924.
  21. Högenauer C, Hammer HF, Mellitzer K, et al. Evaluation of a new DNA test compared with the lactose hydrogen breath test for the diagnosis of lactase non-persistence. Eur J Gastroenterol Hepatol 2005; 17:371.
  22. Marton A, Xue X, Szilagyi A. Meta-analysis: the diagnostic accuracy of lactose breath hydrogen or lactose tolerance tests for predicting the North European lactase polymorphism C/T-13910. Aliment Pharmacol Ther 2012; 35:429.
  23. Baffour-Awuah NY, Fleet S, Montgomery RK, et al. Functional significance of single nucleotide polymorphisms in the lactase gene in diverse US patients and evidence for a novel lactase persistence allele at -13909 in those of European ancestry. J Pediatr Gastroenterol Nutr 2015; 60:182.
  24. Raz M, Sharon Y, Yerushalmi B, Birk R. Frequency of LCT-13910C/T and LCT-22018G/A single nucleotide polymorphisms associated with adult-type hypolactasia/lactase persistence among Israelis of different ethnic groups. Gene 2013; 519:67.
  25. Mulcare CA, Weale ME, Jones AL, et al. The T allele of a single-nucleotide polymorphism 13.9 kb upstream of the lactase gene (LCT) (C-13.9kbT) does not predict or cause the lactase-persistence phenotype in Africans. Am J Hum Genet 2004; 74:1102.
  26. Enattah NS, Jensen TG, Nielsen M, et al. Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture. Am J Hum Genet 2008; 82:57.
  27. Troelsen JT, Mehlum A, Olsen J, et al. 1 kb of the lactase-phlorizin hydrolase promoter directs post-weaning decline and small intestinal-specific expression in transgenic mice. FEBS Lett 1994; 342:291.
  28. Krasinski SD, Upchurch BH, Irons SJ, et al. Rat lactase-phlorizin hydrolase/human growth hormone transgene is expressed on small intestinal villi in transgenic mice. Gastroenterology 1997; 113:844.
  29. Fang L, Ahn JK, Wodziak D, Sibley E. The human lactase persistence-associated SNP -13910*T enables in vivo functional persistence of lactase promoter-reporter transgene expression. Hum Genet 2012; 131:1153.
  30. Fang R, Santiago NA, Olds LC, Sibley E. The homeodomain protein Cdx2 regulates lactase gene promoter activity during enterocyte differentiation. Gastroenterology 2000; 118:115.
  31. Krasinski SD, Van Wering HM, Tannemaat MR, Grand RJ. Differential activation of intestinal gene promoters: functional interactions between GATA-5 and HNF-1 alpha. Am J Physiol Gastrointest Liver Physiol 2001; 281:G69.
  32. San Roman AK, Aronson BE, Krasinski SD, et al. Transcription factors GATA4 and HNF4A control distinct aspects of intestinal homeostasis in conjunction with transcription factor CDX2. J Biol Chem 2015; 290:1850.
  33. Troelsen JT. Adult-type hypolactasia and regulation of lactase expression. Biochim Biophys Acta 2005; 1723:19.
  34. Escher JC, de Koning ND, van Engen CG, et al. Molecular basis of lactase levels in adult humans. J Clin Invest 1992; 89:480.
  35. Fajardo O, Naim HY, Lacey SW. The polymorphic expression of lactase in adults is regulated at the messenger RNA level. Gastroenterology 1994; 106:1233.
  36. Rossi M, Maiuri L, Fusco MI, et al. Lactase persistence versus decline in human adults: multifactorial events are involved in down-regulation after weaning. Gastroenterology 1997; 112:1506.
  37. Lorenzsonn V, Lloyd M, Olsen WA. Immunocytochemical heterogeneity of lactase-phlorizin hydrolase in adult lactase deficiency. Gastroenterology 1993; 105:51.
  38. Saarela T, Similä S, Koivisto M. Hypercalcemia and nephrocalcinosis in patients with congenital lactase deficiency. J Pediatr 1995; 127:920.
  39. Kuokkanen M, Kokkonen J, Enattah NS, et al. Mutations in the translated region of the lactase gene (LCT) underlie congenital lactase deficiency. Am J Hum Genet 2006; 78:339.
  40. Mobassaleh M, Montgomery RK, Biller JA, Grand RJ. Development of carbohydrate absorption in the fetus and neonate. Pediatrics 1985; 75:160.
  41. Mishkin B, Yalovsky M, Mishkin S. Increased prevalence of lactose malabsorption in Crohn's disease patients at low risk for lactose malabsorption based on ethnic origin. Am J Gastroenterol 1997; 92:1148.
  42. Kirschner BS, DeFavaro MV, Jensen W. Lactose malabsorption in children and adolescents with inflammatory bowel disease. Gastroenterology 1981; 81:829.
  43. Buller HA, Grand RJ. Lactose intolerance. In: Annual Review of Medicine: Selected Topics in the Clinical Sciences, Creger WP, Coggins CH, Hancock EW (Eds), Annual Reviews Inc, Palo Alto 1990. p.141.
  44. Montgomery R, Buller HA, Rings EH, et al. Lactose intolerance and regulation of small intestine lactase activity. In: Nutrition and Gene Expression, Berdanier CD, Hargrove JL (Eds), CRC Press, Boca Raton 1992. p.23.
  45. Suarez FL, Savaiano DA, Levitt MD. A comparison of symptoms after the consumption of milk or lactose-hydrolyzed milk by people with self-reported severe lactose intolerance. N Engl J Med 1995; 333:1.
  46. Serra J, Azpiroz F, Malagelada JR. Intestinal gas dynamics and tolerance in humans. Gastroenterology 1998; 115:542.
  47. Hammer HF, Petritsch W, Pristautz H, Krejs GJ. Evaluation of the pathogenesis of flatulence and abdominal cramps in patients with lactose malabsorption. Wien Klin Wochenschr 1996; 108:175.
  48. Hammer HF, Fine KD, Santa Ana CA, et al. Carbohydrate malabsorption. Its measurement and its contribution to diarrhea. J Clin Invest 1990; 86:1936.
  49. Hammer HF, Hammer J. Diarrhea caused by carbohydrate malabsorption. Gastroenterol Clin North Am 2012; 41:611.
  50. Johnson AO, Semenya JG, Buchowski MS, et al. Correlation of lactose maldigestion, lactose intolerance, and milk intolerance. Am J Clin Nutr 1993; 57:399.
  51. Newcomer AD, McGill DB, Thomas PJ, Hofmann AF. Prospective comparison of indirect methods for detecting lactase deficiency. N Engl J Med 1975; 293:1232.
  52. Joseph F, Rosenberg AJ. Identifying lactose malabsorbers through breath hydrogen measurements. Lab Med 1986; 17:85.
  53. Gasbarrini A, Corazza GR, Gasbarrini G, et al. Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference. Aliment Pharmacol Ther 2009; 29 Suppl 1:1.
  54. Hammer HF, Petritsch W, Pristautz H, Krejs GJ. Assessment of the influence of hydrogen nonexcretion on the usefulness of the hydrogen breath test and lactose tolerance test. Wien Klin Wochenschr 1996; 108:137.
  55. Yang J, Deng Y, Chu H, et al. Prevalence and presentation of lactose intolerance and effects on dairy product intake in healthy subjects and patients with irritable bowel syndrome. Clin Gastroenterol Hepatol 2013; 11:262.
  56. Suarez FL, Savaiano D, Arbisi P, Levitt MD. Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance. Am J Clin Nutr 1997; 65:1502.
  57. Suarez FL, Adshead J, Furne JK, Levitt MD. Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products. Am J Clin Nutr 1998; 68:1118.
  58. Pribila BA, Hertzler SR, Martin BR, et al. Improved lactose digestion and intolerance among African-American adolescent girls fed a dairy-rich diet. J Am Diet Assoc 2000; 100:524.
  59. Montalto M, Gallo A, Santoro L, et al. Low-dose lactose in drugs neither increases breath hydrogen excretion nor causes gastrointestinal symptoms. Aliment Pharmacol Ther 2008; 28:1003.
  60. Rosado JL, Solomons NW, Lisker R, Bourges H. 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 mealtime. Gastroenterology 1984; 87:1072.
  61. Ramirez FC, Lee K, Graham DY. All lactase preparations are not the same: results of a prospective, randomized, placebo-controlled trial. Am J Gastroenterol 1994; 89:566.
  62. Harvey JA, Zobitz MM, Pak CY. Dose dependency of calcium absorption: a comparison of calcium carbonate and calcium citrate. J Bone Miner Res 1988; 3:253.