Lactose intolerance

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Mahda Alihashemi M.D. [2] [3] [4] [5] [6]

Lactose intolerance is the term used to describe a decline in the level of lactase, an enzyme needed for proper metabolization of lactose (a sugar that is a constituent of milk and other dairy products), in human beings.

Lactose intolerance first discovered by Hippocrate, ancient Greek physician 2500 years ago. In 1906, Pimmer discovered lactase enzyme in the intestine of infant dogs, pigs, and rats. The association between ethnic and lactose intolerance was discovered in 1966 by Bayless and Rosensweig. In1978, breath hydrogen test was used by Levitt, to diagnose lactose intolerance.

There is no established system for the classification of lactose intolerance. Lactose intolerance may be classified according to its causes into 2 groups: primary lactose malabsorption and secondary lactose malabsorption. Primary lactose malabsorption may be classified into 3 subtypes: acquired primary lactase deficiency, congenital lactase deficiency and developmental lactase deficiency. Secondary lactose malabsorption occurs as a result of the underlying intestinal diseases such as small intestinal bacterial overgrowth, small intestinal infection such as giardiasis and small intestinalinflammation.

It is thought that lactose intolerance is the result of lactose malabsorption that it is caused by low level of small intestinal lactase. Lactose is metabolized by intestinal lactase to galactose and glucose in villous enterocytes. In colon, unabsorbed lactose is converted to hydrogen gas and short chain fatty acids such as acetate, butyrate and propionate by intestinal bacteria and creates symtoms of lactose intolerance. Lactose intolerance is transmitted in an autosomal recessive pattern. Acquired primary lactase deficiency is associated with a CC genotype at -13.9 kb upstream of the lactase gene. On gross and microscopic pathology, there are no characteristic findings of lactose intolerance.

The most common cause of lactose intolerance is acquired primary lactase deficiency. Less common causes of lactose intolerance include Small intestinal bacterial overgrowth, Infections such as giardiasis, Drug induced enteritis, Celiac sprue, Tropical sprue, Whipple’s disease.

The differential diagnosis must distinguish lactose intolerance from milk allergy, which is an abnormal immune response (usually) to milk proteins.

The prevalence of lactose intolerance is approximately 75000 per 100,000 individuals worldwide. The prevalence of lactose intolerance is low in children younger than six years. Europeans and European Americans individuals are less likely to develop lactose intolerance. Lactose intolerance affects men and women equally. The majority of lactose intolerance cases are reported in the Far East

The most potent risk factor in the development of lactose intolerance is ethnicity. Other risk factors include increasing age, infection and drug.

There is insufficient evidence to recommend routine screening for lactose intolerance.

If left untreated, patients with lactose intoelrance may progress to develop malnutrition, osteomalacia , and osteopenia. Common complications of lactose intoelrance include if they do not intake calcium include osteoprosis, osteopenia, osteomalacia and malnutrition. Prognosis is generally excellent.

Small bowel biopsy such as jejunal or duodenal biopsy is the gold standard test for the diagnosis of lactose intolerance. Low lactase activity in small bowel biopsy is confirmatory of lactose intolerance.The diagnostic study of choice for lactose intolerance is lactose breath hydrogen test. Lactose intolerance is diagnosed based on a rise in hydrogen concentration of 20 ppm ( parts per million) and presentation of symptoms such as bloating, diarrhea and abdominal pain.

A positive history of abdominal pain and bloating after ingestion of milk-containing products is suggestive of lactose intolerance. Common symptoms of lactose intolerance include abdominal pain, bloating and flatulence. Less common symptoms of lactose intolerance include nausea, vomiting, and watery diarrhea.

Physical examination findings are usually normal. Borborygmi may be audible.

Laboratory tests include hydrogen breath test, stool acidity test, and intestinal biopsy. Since lactose intolerance is the normal state for most adults on a worldwide scale, and not considered a disease condition, diagnosis is not necessarily required.

There are no ECG findings associated with lactose intolerance.

There are no x-ray findings associated with lactose intolerance.

There are no CT scan findings associated with lactose intolerance.

There are no MRI findings associated with lactose intolerance.

There are no echocardiography/ ultrasound findings associated with lactose intolerance.

There are no other imaging findings associated with lactose intolerance.

Lactose intolerance test may be helpful in the diagnosis of lactose intolerance. Findings suggestive of lactose intolerance include bloating, diarrhea and abdominal pain and rising of blood glucose by less than 20 mg/dL after ingestion of lactose. Genetic test can also be used for diagnosis of primary lactase deficiency that is associated with CC genotype at -13.9 kb upstream of the lactase gene.

The mainstay of treatment for lactose intolerance is lifestyle modification that includes reducing dairy products from the diet and taking lactose-free or reduced lactose dairy products. Pharmacologic medical therapies for lactose intolerance include lactase enzyme preparations such as lactaid, lactogest, dairyease.

Surgical intervention is not recommended for the management of lactose intolerance.

There are no established measures for the primary prevention of lactose intolerance.

Effective measures for the secondary prevention of lactose intolerance include reducing dairy products from the diet, taking lactose-free or reduced lactose dairy products and ingestion of lactaseenzyme tablets before eating the dairy product.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

Lactose intolerance was first discovered by Hippocrate, the ancient Greek physician 2500 years ago. In 1906, Pimmer discovered lactase enzyme in the intestine of infant dogs, pigs, and rats. The association between the ethnicity and lactose intolerance was discovered in 1966 by Bayless and Rosensweig. In 1978, breath hydrogen test was used by Levitt to diagnose lactose intolerance.

• Lactose intolerance was first discovered by Hippocrate, the ancient Greek physician 2500 years ago.^[1]
• In 1906, Pimmer was the first scientist to discover lactase enzyme in the intestine of infant dogs, pigs, and rats. He also found that this enzyme decreased in the adult intestine of these animals.^[1]
• In 1959, Durand and Holzei et al decribed congenital lactase deficiency^[1]

• The association between the ethnicity and lactose intolerance was discovered in 1966 by Bayless and Rosensweig and in 1968 by Neale.

• In the early 1970s, lactase-phlorizin hydrolase (LPH) gene mutations were first implicated in the pathogenesis of lactose intolerance.^[2]
• In 1978, breath hydrogen test was used by Levitt to diagnose lactose intolerance^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

There is no established system for the classification of lactose intolerance. Lactose intolerance may be classified according to its causes into 2 groups: primary lactose malabsorption and secondary lactose malabsorption. Primary lactose malabsorption may be classified into 3 subtypes: acquired primary lactase deficiency, congenital lactase deficiency and developmental lactase deficiency. Secondary lactose malabsorption occurs as a result of the underlying intestinal diseases such as small intestinal bacterial overgrowth, small intestinal infection such as giardiasis and small intestinal inflammation.

lactose intolerance

Primary lactose malabsorption

Secondary lactose malabsorption

Acquired primary lactase deficiency

Congenital lactase deficiency

Developmental lactase deficiency

Small intestinal bacterial overgrowth

Small intestinal infection

Small intestinal inflammation

• There is no established system for the classification of lactose intolerance.

• Lactose intolerance can be classified according to its causes into 2 groups:
  • Primary lactose malabsorption 
  • Secondary lactose malabsorption

• Primary lactose malabsorption can be classified into 3 subtypes:
  • Acquired primary lactase deficiency 
  • Congenital lactase deficiency
  • Developmental lactase deficiency

• The most common cause of primary lactase malabsorbtion.
• In this type of disease, environmental and genetic factors collaborate with each other to develop lactose intolerance.
• Autosomal recessive trait.^[1]

• Intestinal lactase levels are decreased at preschool age in many populations especially in Asia and Africa.
• Elevated lactase activity is maintained in Caucasians such as Northern European.
• Convergent evolution of lactase persistence is seen in some populations in Africa that domesticate cows and consume milk product into adulthood. ^[2]
• Persistence of intestinal lactase until adulthood is inherited in an autosomal dominant manner.^[3]

Congenital lactase deficiency

• Rare autosomal recessive disorder.^[4]
• Absence of lactase activity since birth
• Characteristic findings:^[5]
  • Watery diarrhea 
  • Medullary nephrocalcinosis
  • Hypercalcemia that will be ceased after one week lactose free diet.
• More in Finnish population

• Low lactase levels in premature infants that were born at 28 to 32 weeks of gestation^[6] 
• Clinical lactose intolerance is uncommon because colonic flora ferment lactose to hydrogen and short chain fatty acids and then fatty acids are absorbed by the colon.

Secondary lactose malabsorption occurs as a result of the underlying intestinal diseases such as:^[7]

• Small intestinal bacterial overgrowth: 
  • Fermentation of lactose in the small bowel may be increased and this leads to symptoms of lactose intolerance
  • Breath hydrogen levels peak very early in lactose challenge test
• Small intestinal infection such as giardiasis 
• Small intestinal inflammation:^{[8][9][10][11]}
  • It causes malabsorption through flattening of the villi of the intestinal epithelium.
  • Lactase enzyme is affected first because it is located at the distal part of the villi.
  • Following are some disease that cause small intestinal inflammation:
    • Whipple’s disease (intestinal lipodystrophy)
    • Celiac sprue
    • Tropical sprue
    • Inflammatory bowel disease (more in pateints with crohn’s disease)
    • Drug induced enteritis
    • Radiation induced enteritis
    • Severe gastroenteritis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

It is thought that lactose intolerance is the result of lactose malabsorption caused by low levels of small intestinal lactase. Lactose is metabolized by the intestinal lactase to galactose and glucose in villous enterocytes. In the colon, unabsorbed lactose is converted to hydrogen and short chain fatty acids such as acetate, butyrate and propionate by intestinal bacteria and creates symtoms of lactose intolerance. Lactose intolerance is inherited in an autosomal recessive pattern. Acquired primary lactase deficiency is associated with a CC genotype at -13.9 kb upstream of the lactase gene. On gross and microscopic pathology, there are no characteristic findings of lactose intolerance.

• Lactose is a disaccharide of glucose and galactose in ruminant and human milk.
  • Human milk contains ~7% lactose
  • Ruminant’s milk contains ~5% lactose

• It is thought that lactose intolerance is the result of lactose malabsorption caused by low levels of small intestinal lactase ( lactase-phlorizin hydrolase, or LPH)^[1]
• The most important causes of low level of small intestinal lactase are:
  • Mucosal injury
  • Reduced genetic expression of the enzyme lactase-phlorizin hydrolase
• Lactose is metabolized by intestinal lactase to galactose and glucose in the villous enterocytes and then uptaken by Na+/glucose cotransporter (SGLT1). ^[2][3]
• In the colon, unabsorbed lactose is converted to hydrogen and short chain fatty acids such as acetate, butyrate and propionate by intestinal bacteria and creates symptoms of lactose intolerance.
• Milk drinkers have greater lactase activity compared to non-drinkers. ^[4]

• Lactose intolerance is transmitted in an autosomal recessive pattern.^[5]
• Persistence of intestinal lactase until adulthood is inherited as an autosomal dominant manner.^[6]
• Genes involved in the pathogenesis of lactose intolerance include polymorphism of the MCM6 ( minichromosome maintenance complex component 6), gene located upstream from the gene lactase-phlorizin hydrolase (LPH) on the long arm (q) of chromosome 2 in region 21 (2q21). Lactase persistence is strongly related with the presence of the T allele of the single nucleotide polymorphisms (SNP ) located at -13.9 kb upstream of the lactase gene. This allele regulates lactase mRNA.^[7][8]
• Acquired primary lactase deficiency is associated with a CC genotype at -13.9 kb and lactase persistence is related to TT genotype.^[9]

• On gross pathology, there are no characteristic findings for lactose intolerance.

• On microscopic histopathological analysis, there are no characteristic findings for lactose intolerance.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

The most common cause of lactose intolerance is acquired primary lactase deficiency. Less common causes of lactose intolerance include Small intestinal bacterial overgrowth, Infections such as giardiasis, Drug induced enteritis, Celiac sprue, Tropical sprue, and Whipple’s disease.

• Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. There are no life-threatening causes of lactose intolerance.

The most common cause of lactose intolerance is

• Acquired primary lactase deficiency (lactase nonpersistence, adult-type hypolactasia)^[1][2]

Less common causes of lactose intolerance include:

• Secondary lactose malabsorption^[3][4][5][6]
  • Small intestinal bacterial overgrowth
  • Infections such as giardiasis 
  • Drug induced enteritis
  • Radiation induced enteritis
  • HIV enteropathy
  • Celiac sprue
  • Tropical sprue
  • Whipple’s disease (intestinal lipodystrophy)
  • Severe gastroenteritis
  • Carcinoid syndrome
  • Cystic fibrosis
  • Diabetic gastropathy
  • Kwashiorkor
  • Zollinger-Ellison syndrome
  • Iatrogenic causes such as chemotherapy 
• Congenital lactase deficiency^[7]
• Developmental lactase deficiency^[8]

• Lactose intolerance is caused by a mutation in the lactase-phlorizin hydrolase (LPH) gene.^[9][10][11]

Cardiovascular	No underlying causes
Chemical/Poisoning	No underlying causes
Dental	No underlying causes
Dermatologic	Celiac sprue,
Drug Side Effect	Drug induced enteritis,
Ear Nose Throat	No underlying causes
Endocrine	Carcinoid syndrome, Diabetic gastropathy, Kwashiorkor, Zollinger-Ellison syndrome
Environmental	No underlying causes
Gastroenterologic	Acquired primary lactase deficiency, Small intestinal bacterial overgrowth, Drug induced enteritis, Radiation induced enteritis, HIV enteropathy, Tropical sprue, Celiac sprue, Whipple’s disease, Gastroenteritis, Carcinoid syndrome, Cystic fibrosis, Diabetic gastropathy, Kwashiorkor, Zollinger-Ellison syndrome
Genetic	Celiac sprue, lactase-phlorizin hydrolase (LPH) gene mutation
Hematologic	No underlying causes
Iatrogenic	Radiation induced enteritis, Chemotherapy
Infectious Disease	Infections such as giardiasis, HIV enteropathy, Tropical sprue, Whipple’s disease,
Musculoskeletal/Orthopedic	No underlying causes
Neurologic	No underlying causes
Nutritional/Metabolic	Celiac sprue, Cystic fibrosis,
Obstetric/Gynecologic	No underlying causes
Oncologic	Carcinoid syndrome, Zollinger-Ellison syndrome,
Ophthalmologic	No underlying causes
Overdose/Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	Cystic fibrosis,
Renal/Electrolyte	No underlying causes
Rheumatology/Immunology/Allergy	Celiac sprue
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Miscellaneous	No underlying causes

List the causes of the disease in alphabetical order.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

Lactose intolerance must be differentiated from other diseases that cause diarrhea such as pancreatic insufficiency, irritable bowel syndrome, small intestinal bacterial overgrowth, celiac disease, and inflammatory bowel disease^[1][2][3]

• Lactose intolerance must be differentiated from other diseases that cause diarrhea such as pancreatic insufficiency, irritable bowel syndrome, small intestinal bacterial overgrowth, celiac disease, and inflammatory bowel disease^[1][2][3]
• Lactose intolerance must be differentiated from other causes that produce bloating and flatulence such as beans that contain stachyose and raffinose, two indigestible sugars.^[4]

Template:WH Template:WS The table below summarizes the findings that differentiate watery causes of chronic diarrhea^[1][2][3][4]

Cause			Osmotic gap		History	Physical exam	Gold standard	Treatment
			< 50 mOsm per kg	> 50 mOsm per kg*
Watery	Secretory	Crohns	+	–	Abdominal pain followed by diarrhea	Abdominal tenderness when palpated in severe disease Blood seen on rectal exam Fever Tachycardia Hypotension	Colonoscopy with biopsy	Topical mucosamine and corticosteroids are preferred Mesalamine and sulfasalazine are used for remission
		Hyperthyroidism	+	–	Excessive sweating Heat intolerance Increased bowel movements	Lump in the neck Proptosis Tremors Increased DTR	TSH with T3 and T4	Carbimazole and methimazole Beta blockers like propylthiouracil Iodine-131
		VIPoma	+	–	Watery diarrhea Dehydration (thirst, dry skin, dry mouth, tiredness, headaches, and dizziness) Lethargy, muscle weakness Nausea, vomiting Crampy abdominal pain Weight loss Flushing	Tachycardia Rash Facial flushing Abdominal distention Abdominal tenderness in the right upper abdominal quadrant	Elevated VIP levels Followed by imaging	Sandostatin or chemotherapy for malignant tumors Surgical removal of the tumor
	Osmotic	Lactose intolerance	–	+	Abdominal pain Bloating Diarrhea Flatulence	Abdominal tenderness	Intestinal biopsy	Avoidance of dietary lactose Substitution to maintain nutrient intake Regulation of calcium intake Use of enzyme lactase
		Celiac disease	–	+	May be asymptomatic Vague abdominal pain Diarrhea Weight loss Malabsorption / steatorrhea Bloatedness	Abdominal pain and cramping Abdominal distention Tetany Mouth ulcers Dermatitis herpetiformis Signs of the fat-soluble vitamins A, D, E, and K deficiency	IgA tissue transglutaminase Ab	Gluten-free diet
	Functional	Irritable bowel syndrome	–	–	Abdominal pain or discomfort recurring at least 3 days per month in the past 3 months and associated with 2 or more of the following: Improves with defecation Onset associated with change in frequency of stool Onset associated with change in appearance of stool 25% of bowel movements are loose stools History of straining is also common	Abdominal tenderness Hard stool in the rectal vault	Clinical diagnosis ROME III criteria Pharmacologic studies based criteria	High dietary fiber Osmotic laxatives such as polyethylene glycol, sorbitol, and lactulose Antispasmodic drugs (e.g. anticholinergics such as hyoscyamine or dicyclomine)

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The table below summarizes the findings that differentiate fatty causes of chronic diarrhea^[5][6][7]

Cause	Osmotic gap		History	Physical exam	Gold standard	Treatment
	< 50 mOsm per kg	> 50 mOsm per kg*
lactose intolerance	–	+	Bloating, Flatulence Abdominal pain, and/or chronic diarrhea after ingestion of lactose	Abdominal tenderness when palpated in severe disease Fever Hypotension Tachycardia Nausea and vomiting	Lactose breath hydrogen test	Restriction of lactose and maintain calcium and vitamin D intake.
Celiac sprue	–	+	Diarrhea with bulky, foul-smelling stools Growth failure in children, Weight loss, Anemia, Neurologic disorders Osteopenia	Neuropsychiatric disease Dermatitis herpetiformis Arthritis Iron deficiency Metabolic bone disease Hyposplenism Kidney disease Idiopathic pulmonary hemosiderosis	Immunoglobulin A (IgA) anti-tissue transglutaminase (TTG) antibody followed by upper endoscopy with biopsy.	Dietary counseling, elimination of gluten in the diet.
Whipple disease	–	+	Arthralgias Weight loss Diarrhea Abdominal pain	Leukocytopenia Thrombocytopenia Skin hyperpigmentation	Upper endoscopy with biopsies of the small intestine for T. whipplei testing (histology with PAS staining, polymerase chain reaction [[[PCR]]] testing, and immunohistochemistry)	Doxycycline and hydroxychloroquine are bactericidal

Lactose intolerance must be differentiated from diseases that cause abdominal pain and chronic diarrhea. The table below summarizes the findings that differentiate watery causes of chronic diarrhea:^{[8][1][2][3][4]}

Cause	Osmotic gap		History	Physical exam	Gold standard for diagnosis
	< 50 mOsm per kg	> 50 mOsm per kg*
Zollinger-Ellison syndrome	+	–	Abdominal pain and diarrhea Dyspepsia Upper or Lower gastrointestinal bleeding	Abdominal tenderness Hematochezia Hematemesis Tachycardia Hypotension	Gastrin levels
Crohn’s disease	+	–	Abdominal pain followed by diarrhea	Abdominal tenderness when palpated in severe disease Blood seen on rectal exam Fever Tachycardia Hypotension	Colonoscopy with biopsy
Hyperthyroidism	+	–	Excessive sweating Heat intolerance Increased bowel movements	Lump in the neck Proptosis Tremors Increased DTR	TSH with T3 and T4
VIPoma	+	–	Watery diarrhea Dehydration (thirst, dry skin, dry mouth, tiredness, headaches, and dizziness) Lethargy, muscle weakness Nausea, vomiting Cramping abdominal pain Weight loss Flushing	Tachycardia Rash Facial flushing Abdominal distention Abdominal tenderness in the right upper abdominal quadrant	Elevated VIP levels Followed by imaging
Lactose intolerance	–	+	Abdominal pain Bloating Diarrhea Flatulence	Abdominal tenderness	Intestinal biopsy
Celiac disease	–	+	May be asymptomatic Vague abdominal pain Diarrhea Weight loss Malabsorption/steatorrhea Bloatedness	Abdominal pain and cramping Abdominal distention Tetany Mouth ulcers Dermatitis herpetiformis Signs of the fat-soluble vitamins A, D, E, and K deficiency	IgA tissue transglutaminase Ab
Irritable bowel syndrome	–	–	Abdominal pain or discomfort recurring at least 3 days per month in the past 3 months and associated with 2 or more of the following: Improves with defecation Onset associated with change in frequency of stool Onset associated with change in appearance of stool 25% of bowel movements are loose stools History of straining is also common.	Abdominal tenderness Hard stool in the rectal vault	Clinical diagnosis ROME III criteria Pharmacologic studies based criteria

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

The prevalence of lactose intolerance is approximately 75,000 per 100,000 individuals worldwide. The prevalence of lactose intolerance is low in children younger than six years. Europeans and European Americans individuals are less likely to develop lactose intolerance. Lactose intolerance affects men and women equally. The majority of lactose intolerance cases are reported in the Far East.

• The prevalence of lactose intolerance is up to 75000 per 100,000 individuals worldwide.^[1][2]
• In North America, the prevalence of lactose intolerance:
  • Native America: 79000 per 100,000 individuals
  • Black: 75000 per 100,000 individuals
  • Hispanics: 51000 per 100,000 individuals
  • Caucasians: 21000 per 100,000 individuals
• The prevalence of lactose intolerance in Latin America, Africa, and Asia is 15000-100000 per 100,000 individuals.

• The prevalence of lactose intoleance is low in children younger than six years. ^[3][4]
• The prevalence of lactose intoleance incereses with age.

• Lactose intolerance usually affects the following populations:^[2][5]
  • African Americans
  • Hispanics
  • Asians
  • Asian Americans
  • Native Americans

• Europeans and European Americans are less likely to develop lactose intolerance.

• Lactose intolerance affects men and women equally.

• The majority of lactose intolerance cases are reported in the Far East.^[6]
• Northwestern Europe has the lowest prevalence of lactose intolerance.
• The following countries have the highest rates of lactose intolerance in Africa:^[7]
  • Nigeria
  • Malawi
  • Sudan
  • Ethiopia
  • Uganda

• The following countries have the lowest rates of lactose intolerance in Africa:
  • Cameroon 
  • Mali 
  • South Africa
  • Morocco

• Congenital lactase deficiency is a rare disease that tends to affect Finnish population.^[8]

• Secondary lactase deficiency is more common in children, particularly in the the developing countries due to high prevalence of infections. ^[9]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

The most potent risk factor in the development of lactose intolerance is ethnicity. Other risk factors include increasing age, infection and drug.

The most potent risk factor in the development of lactose intolerance is ethnicity. Other risk factors include increasing age, infection and drug.

• Common risk factors in the development of lactose intolerance include:^[1][2]
  • Increasing age: The prevalence of lactose intoleance is low in children younger than six years
  • Ethnicity: Lactose intolerance is more common in African Americans, Hispanics, Asians, Asian Americans, Native Americans

• Less common risk factors in the development of lactose intolerance include:^[3][4][5]
  • Premature birth
  • Infections such as giardia
  • Drug induced enteritis
  • HIV
  • Sprue
  • Whipple’s disease
  • Carcinoid syndrome
  • Diabetes mellitus
  • Zollinger-Ellison syndrome

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

There is insufficient evidence to recommend routine screening for lactose intolerance.

 There is insufficient evidence to recommend routine screening for lactose intolerance.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahda Alihashemi M.D. [2]

If left untreated, patients with lactose intoelrance may progress to develop malnutrition, osteomalacia, and osteopenia. Common complications of lactose intoelrance include include osteoprosis, osteopenia, osteomalacia (especially in the absence of calcium supplements) and malnutrition. Prognosis is generally excellent.

• The symptoms of lactose intoelrance usually develop after age of 6 and start with:^[1][2][3]
  • Abdominal pain
  • Flatulence
  • Bloating
  • Watery, frothy and bulky diarrhea
• If left untreated, patients with lactose intolerance may develop:
  • Malnutrition
  • Osteomalacia
  • Osteopenia

• Common complications of lactose intolerance i(especially in the absence of calcium supplements) include: ^[4][5][6]
  • Osteopenia
  • Osteoporosis
  • Malnutrition
  • Rickets
  • Osteomalacia

• Prognosis is generally excellent.

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