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Drugs & Diseases > Gastroenterology Lactose Intolerance Updated: Dec 04, 2019 * Author: Praveen K Roy, MD, AGAF; Chief Editor: Burt Cagir, MD, FACS more... * Share * Email * Print * Feedback Close * Facebook * Twitter * LinkedIn * Google+ Sections Lactose Intolerance * Sections Lactose Intolerance * Overview + Background + Pathophysiology + Etiology + Epidemiology + Prognosis + Show All * Presentation * DDx * Workup + Laboratory Studies + Other Tests + Procedures + Show All * Treatment * Medication + Medication Summary + Digestive enzymes + Show All * Questions & Answers * References Overview Background Lactose intolerance is a common disorder and is due to the inability to digest lactose into its constituents, glucose and galactose, secondary to low levels of lactase enzyme in the brush border of the duodenum.^ [1] Lactase deficiency is the most common form of disaccharidase deficiency. Enzyme levels are the highest shortly after birth and decline with aging, despite continued intake of lactose. Within the animal world, nonhuman mammals usually lose the ability to digest lactose as they reach adulthood. Some populations of the human species, including those of Asian, South American, and African descent, have a propensity for developing lactase deficiency. By contrast, races descended from northern Europe or from the northwestern Indian subcontinent are likely to retain the ability to absorb lactose into adulthood.^ [2] Symptoms of lactose intolerance include loose stools, abdominal bloating and pain, flatulence, nausea, and borborygmi.^ [3, 4, 5] A diagnosis or even the suggestion of lactose intolerance leads many people to avoid milk and/or to consume specially prepared food with digestive aids, adding to health care costs. eMedicine Logo Next: Pathophysiology Lactose, a disaccharide, is present in milk and processed foods. Dietary lactose must be hydrolyzed to a monosaccharide in order to be absorbed by the small intestinal mucosa. A deficiency of intestinal lactase prevents hydrolysis of ingested lactose. The osmotic load of the unabsorbed lactose causes secretion of fluid and electrolytes until osmotic equilibrium is reached. Dilation of the intestine caused by the osmosis induces an acceleration of small intestinal transit, which increases the degree of maldigestion. Within the large intestine, free lactose is fermented by colonic bacteria to yield short-chain fatty acids and hydrogen gas.^ [6] The combined increase in fecal water, intestinal transit, and generated hydrogen gas accounts for the wide range of gastrointestinal symptoms. An association between certain single nucleotide polymorphisms (C>T-13910 and G>A-22018) with lactose tolerance in a northeaster Brazilian population has been reported.^ [7] In Indo-Europe, lactase deficiency is associated with rs4982235 SNP (or -13910C>T), which may predispose affected individuals to lactose intolerance.^ [8] eMedicine Logo Previous Next: Etiology Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.^ [9, 10] Primary lactose intolerance is due to low levels of lactase, which develop after childhood. Secondary, or acquired, lactase deficiency may develop in a person with a healthy small intestine during episodes of acute illness. This occurs because of mucosal damage or from medications. Some causes of secondary lactase deficiency are as follows: * Acute gastroenteritis * Giardiasis * Ascariasis * Crohn disease * Celiac sprue * Tropical sprue * Gastrinoma * Radiation enteritis * Diabetic gastropathy * Carcinoid syndrome * Whipple syndrome * HIV enteropathy * Kwashiorkor * Chemotherapy eMedicine Logo Previous Next: Epidemiology United States statistics The prevalence of primary lactose intolerance varies according to race. As many as 25% of the white population (prevalence in those from southern European roots) is estimated to have lactose intolerance, while among black, Native American, and Asian American populations, the prevalence of lactose intolerance is estimated at 75-90%.^ [2] International statistics An estimated 70-75% off the world's population is lactose-deficient.^ [8, 11] Lactose intolerance is very common among Asian, South American, and African persons. Lactose intolerance also appears to have a higher prevalence in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) than healthy individuals.^ [12] Race-, sex-, and age-related demographics Persons of all races are affected by lactose intolerance, with a higher prevalence among Asian, African, and South American persons. Males and females are equally affected by lactose intolerance. However, of adult women who are lactose intolerant, 44% regain the ability to digest lactose during pregnancy. This is probably due to slow intestinal transit and bacterial adaptation during pregnancy. Few data are available regarding the prevalence of lactose intolerance in children aged 1-5 years; however, primary lactose intolerance in this group is estimated to be 0-17.9%, whereas it is a reported 0-19% for secondary lactose intolerance.^ [13] Among adults, the age of presentation of lactose intolerance is 20-40 years.^ [9, 14] eMedicine Logo Previous Next: Prognosis The prognosis of patients with lactose intolerance is excellent with dietary restrictions. Morbidity/mortality include the following: * Lactose intolerance is not lethal. * Morbidity is low from lactose intolerance. * Osteopenia can be a complication of lactose intolerance.^ [15, 16, 17] Vitamin D deficiency appears to be associated with the LCT-13910C>T gene variant of lactose intolerance in white populations.^ [17] eMedicine Logo Previous Clinical Presentation References 1. Vesa TH, Marteau P, Korpela R. Lactose intolerance. J Am Coll Nutr. 2000 Apr. 19(2 Suppl):165S-175S. [Medline]. 2. Newcomer AD, McGill DB, Thomas PJ, et al. Tolerance to lactose among lactase-deficient American Indians. Gastroenterology. 1978 Jan. 74(1):44-6. [Medline]. 3. Di Stefano M, Miceli E, Mazzocchi S, et al. Visceral hypersensitivity and intolerance symptoms in lactose malabsorption. Neurogastroenterol Motil. 2007 Nov. 19(11):887-95. [Medline]. 4. Micic D, Rao VL, Rubin DT. Clinical approach to lactose intolerance. JAMA. 2019 Sep 26. [Medline]. 5. Malik TF, Panuganti KK. Lactose intolerance. Stat Pearls. 2019 Jan. [Medline]. [Full Text]. 6. Zhong Y, Priebe MG, Vonk RJ, et al. The role of colonic microbiota in lactose intolerance. Dig Dis Sci. 2004 Jan. 49(1):78-83. [Medline]. 7. Ponte PR, de Medeiros PH, Havt A, et al. Clinical evaluation, biochemistry and genetic polymorphism analysis for the diagnosis of lactose intolerance in a population from northeastern Brazil. Clinics (Sao Paulo). 2016 Feb. 71(2):82-9. [Medline]. [Full Text]. 8. Delacour H, Leduc A, Loucano-Perdriat A, Plantamura J, Ceppa F. Diagnosis of genetic predisposition for lactose intolerance by high resolution melting analysis. Ann Biol Clin (Paris). 2017 Feb 1. 75(1):67-74. [Medline]. 9. Auricchio S, Rubino A, Landolt M, Semenza G, Prader A. Isolated intestinal lactase deficiency in the adult. Lancet. 1963 Aug 17. 2(7303):324-6. [Medline]. 10. Upton J, Mackay R, George P. A simple gene test for lactose intolerance/adult hypolactasia. N Z Med J. 2007 Nov 9. 120(1265):U2817. [Medline]. 11. Corgneau M, Scher J, Ritie-Pertusa L, et al. Recent advances on lactose intolerance: tolerance thresholds and currently available answers. Crit Rev Food Sci Nutr. 2017 Oct 13. 57(15):3344-56. [Medline]. 12. Xiong L, Wang Y, Gong X, Chen M. Prevalence of lactose intolerance in patients with diarrhea-predominant irritable bowel syndrome: data from a tertiary center in southern China. J Health Popul Nutr. 2017 Nov 21. 36(1):38. [Medline]. [Full Text]. 13. Harvey L, Ludwig T, Hou AQ, et al. Prevalence, cause and diagnosis of lactose intolerance in children aged 1-5 years: a systematic review of 1995-2015 literature. Asia Pac J Clin Nutr. 2018. 27(1):29-46. [Medline]. [Full Text]. 14. Kern F Jr, Struthers JE Jr. Intestinal lactase deficiency and lactose intolerance in adults. JAMA. 1966 Mar 14. 195(11):927-30. [Medline]. 15. Kudlacek S, Freudenthaler O, Weissboeck H, et al. Lactose intolerance: a risk factor for reduced bone mineral density and vertebral fractures?. J Gastroenterol. 2002. 37(12):1014-9. [Medline]. 16. Di Stefano M, Veneto G, Malservisi S, et al. Lactose malabsorption and intolerance and peak bone mass. Gastroenterology. 2002 Jun. 122(7):1793-9. [Medline]. 17. Alharbi O, El-Sohemy A. Lactose intolerance (LCT-13910C>T) genotype is associated with plasma 25-hydroxyvitamin D concentrations in caucasians: a Mendelian randomization study. J Nutr. 2017 Jun. 147(6):1063-9. [Medline]. 18. Bayless TM, Rothfeld B, Massa C, et al. Lactose and milk intolerance: clinical implications. N Engl J Med. 1975 May 29. 292(22):1156-9. [Medline]. 19. Deng Y, Misselwitz B, Dai N, Fox M. Lactose intolerance in adults: biological mechanism and dietary management. Nutrients. 2015 Sep 18. 7(9):8020-35. [Medline]. [Full Text]. 20. Mishkin S. Dairy sensitivity, lactose malabsorption, and elimination diets in inflammatory bowel disease. Am J Clin Nutr. 1997 Feb. 65(2):564-7. [Medline]. 21. Portincasa P, Bonfrate L, de Bari O, Lembo A, Ballou S. Irritable bowel syndrome and diet. Gastroenterol Rep (Oxf). 2017 Feb. 5(1):11-9. [Medline]. [Full Text]. 22. Beyerlein L, Pohl D, Delco F, et al. Correlation between symptoms developed after the oral ingestion of 50 g lactose and results of hydrogen breath testing for lactose intolerance. Aliment Pharmacol Ther. 2008 Apr. 27(8):659-65. [Medline]. 23. Hermans MM, Brummer RJ, Ruijgers AM, et al. The relationship between lactose tolerance test results and symptoms of lactose intolerance. Am J Gastroenterol. 1997 Jun. 92(6):981-4. [Medline]. 24. Arola H. Diagnosis of hypolactasia and lactose malabsorption. Scand J Gastroenterol Suppl. 1994. 202:26-35. [Medline]. 25. Carroccio A, Montalto G, Cavera G, et al. Lactose intolerance and self-reported milk intolerance: relationship with lactose maldigestion and nutrient intake. Lactase Deficiency Study Group. J Am Coll Nutr. 1998 Dec. 17(6):631-6. [Medline]. 26. 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 Jul 6. 333(1):1-4. [Medline]. 27. Patel YT, Minocha A. Lactose intolerance: diagnosis and management. Compr Ther. 2000 Winter. 26(4):246-50. [Medline]. 28. Suarez FL, Savaiano DA, Levitt MD. Review article: the treatment of lactose intolerance. Aliment Pharmacol Ther. 1995 Dec. 9(6):589-97. [Medline]. 29. Sethi S, Tyagi SK, Anurag RK. Plant-based milk alternatives an emerging segment of functional beverages: a review. J Food Sci Technol. 2016 Sep. 53(9):3408-23. [Medline]. [Full Text]. 30. Paul AA, Kumar S, Kumar V, Sharma R. Milk analog: plant based alternatives to conventional milk, production, potential and health concerns. Crit Rev Food Sci Nutr. 2019 Oct 16. 1-19. [Medline]. 31. Pakdaman MN, Udani JK, Molina JP, Shahani M. 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 May 20. 15(1):56. [Medline]. [Full Text]. 32. Shi LH, Balakrishnan K, Thiagarajah K, Mohd Ismail NI, Yin OS. Beneficial properties of probiotics. Trop Life Sci Res. 2016 Aug. 27(2):73-90. [Medline]. [Full Text]. 33. Vonk RJ, Priebe MG, Koetse HA, et al. Lactose intolerance: analysis of underlying factors. Eur J Clin Invest. 2003 Jan. 33(1):70-5. [Medline]. 34. Suarez FL, Savaiano D, Arbisi P, et al. 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Media Gallery of 0 Tables Previous Next Back to List Contributor Information and Disclosures Author Praveen K Roy, MD, AGAF Clinical Assistant Professor of Medicine, University of New Mexico School of Medicine Praveen K Roy, MD, AGAF is a member of the following medical societies: American Gastroenterological Association, American Society for Gastrointestinal Endoscopy Disclosure: Nothing to disclose. Coauthor(s) Sarah D Komanapalli, MBBS Resident Physician in Internal Medicine, Marshfield Clinic Sarah D Komanapalli, MBBS is a member of the following medical societies: American College of Physicians Disclosure: Nothing to disclose. Homayoun Shojamanesh, MD Former Fellow, Digestive Diseases Branch, National Institutes of Health Homayoun Shojamanesh, MD is a member of the following medical societies: American College of Gastroenterology, American Gastroenterological Association, American Society for Gastrointestinal Endoscopy Disclosure: Nothing to disclose. Showkat Bashir, MD Assistant Professor, Department of Medicine, Division of Gastroenterology, George Washington University, Washington, DC Showkat Bashir, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Medical Association Disclosure: Nothing to disclose. Specialty Editor Board Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Received salary from Medscape for employment. for: Medscape. BS Anand, MD Professor, Department of Internal Medicine, Division of Gastroenterology, Baylor College of Medicine BS Anand, MD is a member of the following medical societies: American Association for the Study of Liver Diseases, American College of Gastroenterology, American Gastroenterological Association, American Society for Gastrointestinal Endoscopy Disclosure: Nothing to disclose. Chief Editor Burt Cagir, MD, FACS Clinical Professor of Surgery, The Commonwealth Medical College; Director, General Surgery Residency Program, Robert Packer Hospital; Attending Surgeon, Robert Packer Hospital and Corning Hospital Burt Cagir, MD, FACS is a member of the following medical societies: American College of Surgeons, American Medical Association, Society for Surgery of the Alimentary Tract Disclosure: Nothing to disclose. Additional Contributors Ronnie Fass, MD, FACP, FACG Chief of Gastroenterology, Head of Neuroenteric Clinical Research Group, Southern Arizona Veterans Affairs Health Care System; Professor of Medicine, Division of Gastroenterology, University of Arizona School of Medicine Ronnie Fass, MD, FACP, FACG is a member of the following medical societies: American College of Gastroenterology, American College of Physicians-American Society of Internal Medicine, American Gastroenterological Association, American Neurogastroenterology and Motility Society, American Society for Gastrointestinal Endoscopy, Israeli Medical Association Disclosure: Received grant/research funds from Takeda Pharmaceuticals for conducting research; Received consulting fee from Takeda Pharmaceuticals for consulting; Received honoraria from Takeda Pharmaceuticals for speaking and teaching; Received consulting fee from Vecta for consulting; Received consulting fee from XenoPort for consulting; Received honoraria from Eisai for speaking and teaching; Received grant/research funds from Wyeth Pharmaceuticals for conducting research; Received grant/research funds f. Douglas M Heuman, MD, FACP, FACG, AGAF Chief of Hepatology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center; Professor, Department of Internal Medicine, Division of Gastroenterology, Virginia Commonwealth University School of Medicine Douglas M Heuman, MD, FACP, FACG, AGAF is a member of the following medical societies: American Association for the Study of Liver Diseases, American College of Physicians, American Gastroenterological Association Disclosure: Received grant/research funds from Novartis for other; Received grant/research funds from Bayer for other; Received grant/research funds from Otsuka for none; Received grant/research funds from Bristol Myers Squibb for other; Received none from Scynexis for none; Received grant/research funds from Salix for other; Received grant/research funds from MannKind for other. Abhishek Choudhary, MD Resident Physician, Department of Internal Medicine, University Hospital of Missouri-Columbia Abhishek Choudhary, MD is a member of the following medical societies: American College of Physicians Disclosure: Nothing to disclose. Close What would you like to print? What would you like to print? * Print this section * Print the entire contents of * Print the entire contents of article * Sections Lactose Intolerance * Overview + Background + Pathophysiology + Etiology + Epidemiology + Prognosis + Show All * Presentation * DDx * Workup + Laboratory Studies + Other Tests + Procedures + Show All * Treatment * Medication + Medication Summary + Digestive enzymes + Show All * Questions & Answers * References Medscape Logo Find Us On About About Medscape Privacy Policy Editorial Policy Cookies Do Not Sell My Personal Information Terms of Use Advertising Policy Help Center Membership Become a Member Email Newsletters Manage My Account Apps Medscape CME & Education WebMD Network WebMD MedicineNet eMedicineHealth RxList WebMD Corporate Editions English Deutsch Español Français Português All material on this website is protected by copyright, Copyright © 1994-2020 by WebMD LLC. This website also contains material copyrighted by 3rd parties. 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