Materiały źródłowe

• #1 Lactose intolerance – Symptoms & causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232

  People with lactose intolerance are unable to fully digest the sugar (lactose) in milk. […] Too little of an enzyme produced in your small intestine (lactase) is usually responsible for lactose intolerance. […] Lactose intolerance occurs when your small intestine doesn’t produce enough of an enzyme (lactase) to digest milk sugar (lactose). […] Normally, lactase turns milk sugar into two simple sugars glucose and galactose which are absorbed into the bloodstream through the intestinal lining. […] If you’re lactase deficient, lactose in your food moves into the colon instead of being processed and absorbed. In the colon, normal bacteria interact with undigested lactose, causing the signs and symptoms of lactose intolerance. […] There are three types of lactose intolerance. Different factors cause the lactase deficiency underlying each type.

• #2 Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/187249-overview

  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. […] Lactase deficiency is the most common form of disaccharidase deficiency. […] 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. […] Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.

• #3 Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

  Lactose intolerance occurs in people who lack the enzyme they need to break down lactose, the sugar in milk. It causes digestive distress when you eat dairy products. […] Lactose malabsorption is the inability to break down and absorb lactose molecules in your digestive system. Its common in fact, about 65% of adults worldwide can’t break down and absorb lactose. […] Two factors contribute to lactose intolerance: lactose malabsorption and gut sensitivity. Lactose malabsorption is the most important factor. Its the inability to break down and absorb lactose in your small intestine that leads to lactose later entering your large intestine and triggering symptoms. […] Your small intestine needs a specific enzyme, called lactase, to break down lactose into smaller molecules that it can absorb. Most people naturally produce lactase in their small intestines during infancy to help digest breast milk. Most people begin to make less of it as they grow up.

• #4 What Causes Lactose Intolerance? Types and Prevention

  https://www.webmd.com/digestive-disorders/causes-lactose-intolerance

  Lactose intolerance means that your body cant digest lactose, a sugar found in milk and dairy products. This happens when your small intestine doesnt make enough lactase, the enzyme that breaks down lactose. […] There are four types of lactose intolerance, and they all have different causes. […] Primary lactose intolerance is the most common form. Our bodies typically stop making lactase by about age 5 (as early as age 2 for African-Americans). As lactase levels decrease, dairy products become harder to digest. People with primary lactose intolerance make a lot less lactase. That makes dairy products hard to digest by adulthood. Its caused by genes and is common among people of an African, Asian, Hispanic, Mediterranean and southern European background. Its less common if your heritage is from northern or western Europe.

• #5 Lactose intolerance – Wikipedia

  https://en.wikipedia.org/wiki/Lactose_intolerance

  Lactose intolerance is caused by a lessened ability or a complete inability to digest lactose, a sugar found in dairy products. […] Lactose intolerance is due to the lack of the enzyme lactase in the small intestines to break lactose down into glucose and galactose. […] Primary lactose intolerance occurs as the amount of lactase declines as people grow up. […] Secondary lactose intolerance is due to injury to the small intestine. Such injury could be the result of infection, celiac disease, inflammatory bowel disease, or other diseases. […] Lactose intolerance is a consequence of lactase deficiency, which may be genetic (primary hypolactasia and primary congenital alactasia) or environmentally induced (secondary or acquired hypolactasia). […] Lactose intolerance in infants (congenital lactase deficiency) is caused by mutations in the LCT gene.

• #6 Lactose intolerance – Symptoms & causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232

  People who develop primary lactose intolerance the most common type start life producing enough lactase. […] As children replace milk with other foods, the amount of lactase they produce normally drops, but usually remains high enough to digest the amount of dairy in a typical adult diet. In primary lactose intolerance, lactase production falls off sharply by adulthood, making milk products difficult to digest. […] This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, injury or surgery involving your small intestine. […] It’s possible, but rare, for babies to be born with lactose intolerance caused by a lack of lactase.

• #7 Lactose Intolerance – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK532285/

  Lactase enzyme deficiency can occur in individuals with lower levels of this enzyme, resulting in failure to hydrolyze lactose into absorbable glucose and galactose components. There are four leading causes of lactase deficiency. […] It is the most common cause of lactase deficiency, also known as lactase non-persistence. There is a gradual decline in lactase enzyme activity with increasing age. Enzyme activity begins to decline in infancy, and symptoms manifest in adolescence or early adulthood. More recently, it has been observed that lactase non-persistence is of the ancestral form (normal Mendelian inheritance), and lactase persistence is secondary to mutation. […] Due to several infectious, inflammatory, or other diseases, injury to intestinal mucosa can cause secondary lactase deficiency.

• #8 Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

  The four types, and their causes, are: Primary (caused by diminishing lactase production in your small intestine). Secondary (caused by injury or disease that damages your small intestine). Congenital (caused by lactase deficiency present at birth). Developmental (caused by premature birth, when the small intestine is underdeveloped). […] Genes determine how likely you are to continue to produce lactase, the enzyme that helps you digest lactose. […] Most people develop lactose intolerance as they grow from childhood into adulthood. The most common type of lactose intolerance, primary lactose intolerance, happens because you gradually stop producing lactase, the enzyme that digests lactose. […] You can develop secondary lactose intolerance suddenly as a result of damage to your small intestine. Injury, surgery, infections or chronic diseases may damage the cells that produce lactase. This can cause sudden lactose malabsorption and intolerance, even if you could previously digest lactose.

• #9 What Causes Lactose Intolerance? Types and Prevention

  https://www.webmd.com/digestive-disorders/causes-lactose-intolerance

  Lactose intolerance means that your body cant digest lactose, a sugar found in milk and dairy products. This happens when your small intestine doesnt make enough lactase, the enzyme that breaks down lactose. […] There are four types of lactose intolerance, and they all have different causes. […] Primary lactose intolerance is the most common form. Our bodies typically stop making lactase by about age 5 (as early as age 2 for African-Americans). As lactase levels decrease, dairy products become harder to digest. People with primary lactose intolerance make a lot less lactase. That makes dairy products hard to digest by adulthood. Its caused by genes and is common among people of an African, Asian, Hispanic, Mediterranean and southern European background. Its less common if your heritage is from northern or western Europe.

• #10 Lactose Intolerance | ACG

  https://gi.org/topics/lactose-intolerance-in-children/

  Lactose intolerance occurs more frequently in certain families. […] One of the most important factors affecting the rate of developing lactose intolerance is an individual’s ethnic background. […] Approximately 15% of adult Caucasians, and 85% of adult African Americans in the United States are lactose intolerant. […] The rate of lactose intolerance is also very high in individuals of Asian descent, Hispanic descent, Native Americans and Jewish individuals. […] Primary Lactase Deficiency: This condition is very rare and occurs when babies are born with a deficiency or absence of the enzyme lactase. […] Secondary Lactase Deficiency: The most common cause of temporary lactose intolerance in infants and young children is by an infection that affects the gastrointestinal tract and can damage the lining of the small intestine.

• #11 Lactose Intolerance – Cause, Symptoms, Diagnosis, Treatment

  https://www.webmd.com/digestive-disorders/digestive-diseases-lactose-intolerance

  Millions of Americans cant digest a certain sugar in milk and milk products called lactose. If youre one of them, you have lactose intolerance. […] The main cause of lactose intolerance is that you produce too little lactase, the enzyme in your small intestine that breaks down lactose. […] Most people become less tolerant of lactose as they get older, because our bodies produce less lactase as we age. […] Lactose intolerance is common. The risk of it is linked to your ethnicity. Lactose intolerance affects about 85% of Black adults in the U.S. and about 15% of White adults. It’s also more likely to affect you if you have Hispanic, Asian, Native American, or Jewish ancestry. […] Risk factors for developing lactose intolerance include: Age. You produce less lactase as you grow older. Ethnicity. If your heritage is African, Asian, Hispanic, or Native American, your risk is higher.

• #12 Lactose intolerance: MedlinePlus GeneticsLock

  https://medlineplus.gov/genetics/condition/lactose-intolerance/

  Lactose intolerance is a condition that makes it difficult to digest lactose, a sugar found in milk and several other dairy products. Lack or loss of lactase has both genetic and non-genetic causes. […] Congenital lactase deficiency is caused by variants (also called mutations) in the LCT gene. The LCT gene provides instructions for making the lactase enzyme. Variants in the LCT gene that cause congenital lactase deficiency are believed to interfere with the processing and function of lactase, causing affected infants to have a severely impaired ability to digest the lactose in breast milk or formula. […] Lactase nonpersistence in adulthood is caused by the gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans. LCT gene expression is controlled by a DNA sequence called a regulatory element, which is located within a nearby gene called MCM6. Some individuals have inherited changes in this element that lead to sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactase nonpersistence.

• #13 Genes and lactose intolerance — Science Learning Hub

  https://www.sciencelearn.org.nz/resources/2016-genes-and-lactose-intolerance

  The ability to digest milk or milk products is inherited from our parents. […] After about 5 years of age, most people (about 75% of the worlds population) stop producing the lactase enzyme. Without lactase, they can no longer digest milk, and they become lactose intolerant. […] Individuals who have a cytosine (C) on both alleles close to the lactase gene do not produce lactase in adulthood and are lactose intolerant. […] A single point mutation in the near to the lactase gene changes the cytosine (C) to a thymine (T). Individuals who have the thymine (T) nucleotide are lactose tolerant and can digest milk products in adulthood. […] Most people in the world are lactose intolerant, but a genetic mutation where a cytosine (C) nucleotide in a persons DNA is replaced with a thymine (T) nucleotide allows them to digest milk.

• #14 Lactose intolerance – Symptoms & causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232

  People who develop primary lactose intolerance the most common type start life producing enough lactase. […] As children replace milk with other foods, the amount of lactase they produce normally drops, but usually remains high enough to digest the amount of dairy in a typical adult diet. In primary lactose intolerance, lactase production falls off sharply by adulthood, making milk products difficult to digest. […] This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, injury or surgery involving your small intestine. […] It’s possible, but rare, for babies to be born with lactose intolerance caused by a lack of lactase.

• #15 Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/187249-overview

  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. […] Lactase deficiency is the most common form of disaccharidase deficiency. […] 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. […] Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.

• #16 Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

  The four types, and their causes, are: Primary (caused by diminishing lactase production in your small intestine). Secondary (caused by injury or disease that damages your small intestine). Congenital (caused by lactase deficiency present at birth). Developmental (caused by premature birth, when the small intestine is underdeveloped). […] Genes determine how likely you are to continue to produce lactase, the enzyme that helps you digest lactose. […] Most people develop lactose intolerance as they grow from childhood into adulthood. The most common type of lactose intolerance, primary lactose intolerance, happens because you gradually stop producing lactase, the enzyme that digests lactose. […] You can develop secondary lactose intolerance suddenly as a result of damage to your small intestine. Injury, surgery, infections or chronic diseases may damage the cells that produce lactase. This can cause sudden lactose malabsorption and intolerance, even if you could previously digest lactose.

• #17 Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/187249-overview

  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. […] Lactase deficiency is the most common form of disaccharidase deficiency. […] 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. […] Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.

• #18 Lactose intolerance | NHS inform

  https://www.nhsinform.scot/illnesses-and-conditions/nutritional/lactose-intolerance/

  The main types of lactase deficiency are outlined below. […] Primary lactase deficiency is the most common cause of lactose intolerance worldwide. This type of lactase deficiency is caused by an inherited genetic fault that runs in families. […] Secondary lactase deficiency is a shortage of lactase caused by a problem in your small intestine. It can occur at any age, and may be the result of another condition, surgery to your small intestine, or taking certain medication. […] Possible causes of secondary lactase deficiency include: gastroenteritis an infection of the stomach and intestines, coeliac disease a bowel condition caused by an adverse reaction to a protein called gluten, Crohn’s disease a long-term condition that causes inflammation of the lining of the digestive system, ulcerative colitis a long-term condition that affects the large intestine, chemotherapy a cancer treatment, long courses of antibiotics.

• #19 What Is Lactose Intolerance? Symptoms, Causes, Diagnosis, Treatment, and Prevention

  https://www.everydayhealth.com/lactose-intolerance/guide/

  Risk factors for lactose intolerance include: Age (it tends to appear after adolescence or young adulthood), A person’s race or ethnicity, Premature birth. […] Several gastrointestinal disorders and other conditions can also cause lactose intolerance. They include: Gastroenteritis (inflammation of the intestinal lining caused by a virus, bacteria, or parasite), Celiac disease, Crohn’s disease, Ulcerative colitis (ulcers in the intestinal lining), Irritable bowel syndrome (IBS), Any injury to the small bowel, Chemotherapy or radiation treatment for cancer. […] A condition called small intestine bacterial overgrowth (SIBO) may also cause sensitivity to lactose and, in some cases, the tell-tale gastrointestinal symptoms.

• #20 Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

  Secondary lactose intolerance may not be permanent. If your small intestine recovers its usual function, you may regain the ability to digest lactose. […] Lactase supplements can give your body the lactase it needs to break down lactose. […] Secondary lactose intolerance caused by damage to your small intestine might be reversible after your small intestine recovers. This will depend on how permanent the damage is. […] If you have primary or congenital lactose intolerance, you wont ever start naturally producing more lactase. But its possible your symptoms could change if your intestinal health or microbiome changes. […] Lactose intolerance will affect your diet, which means youll have to pay attention to the nutrients youre getting. If you avoid all dairy products, you could end up low in calcium and vitamin D. […] Lactose intolerance is a reaction in your digestive system to lactose, the sugar in milk. It causes uncomfortable symptoms after you eat dairy products.

• #21 Lactose intolerance | NHS inform

  https://www.nhsinform.scot/illnesses-and-conditions/nutritional/lactose-intolerance/

  Lactose intolerance is usually the result of your body not producing enough lactase. […] Lactase is an enzyme (a protein that causes a chemical reaction to occur) normally produced in your small intestine that’s used to digest lactose. […] If you have a lactase deficiency, it means your body doesn’t produce enough lactase. […] People with lactose intolerance don’t produce enough lactase, so lactose stays in the digestive system where it’s fermented by bacteria. This leads to the production of various gases, which cause the symptoms associated with lactose intolerance. […] Depending on the underlying reason why the body isn’t producing enough lactase, lactose intolerance may be temporary or permanent. Most cases that develop in adults are inherited and tend to be lifelong, but cases in young children are often caused by an infection in the digestive system and may only last for a few weeks.

• #22 Lactose Intolerance – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK532285/

  There is a decrease or absence of lactase enzyme activity since birth due to autosomal recessive inheritance. It manifests in the newborn after ingestion of milk. It is a rare cause of the deficiency, and its genetics are not very well known. […] It is seen in premature infants born at 28 to 37 weeks of gestation. The infant’s intestine is underdeveloped, resulting in an inability to hydrolyze lactose. This condition improves with increasing age due to the maturation of the intestine, which results in adequate lactase activity.

• #23 Lactose intolerance: MedlinePlus GeneticsLock

  https://medlineplus.gov/genetics/condition/lactose-intolerance/

  Lactose intolerance is a condition that makes it difficult to digest lactose, a sugar found in milk and several other dairy products. Lack or loss of lactase has both genetic and non-genetic causes. […] Congenital lactase deficiency is caused by variants (also called mutations) in the LCT gene. The LCT gene provides instructions for making the lactase enzyme. Variants in the LCT gene that cause congenital lactase deficiency are believed to interfere with the processing and function of lactase, causing affected infants to have a severely impaired ability to digest the lactose in breast milk or formula. […] Lactase nonpersistence in adulthood is caused by the gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans. LCT gene expression is controlled by a DNA sequence called a regulatory element, which is located within a nearby gene called MCM6. Some individuals have inherited changes in this element that lead to sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactase nonpersistence.

• #24 What Causes Lactose Intolerance? Types and Prevention

  https://www.webmd.com/digestive-disorders/causes-lactose-intolerance

  Secondary lactose intolerance happens because of an injury, illness or possibly a surgery. Any of these can affect your small intestine and cause you to make less lactase. Celiac disease and Crohns disease are two of the most common intestinal diseases linked to low lactase. […] Developmental lactose intolerance happens in babies who are born prematurely. It usually goes away on its own, lasting for only a short time after birth. […] Congenital lactose intolerance is very rare and happens when no lactase (or a very small amount of it) is produced by the small intestine from birth. Its a genetic disorder, and both parents have to pass the gene on to their child.

• #25 Lactose intolerance | NHS inform

  https://www.nhsinform.scot/illnesses-and-conditions/nutritional/lactose-intolerance/

  Congenital lactase deficiency is a rare condition that runs in families and is found in newborn babies. […] It’s caused by an inherited genetic fault that means affected babies produce very little or no lactase. […] Some babies born prematurely (before the 37th week of pregnancy) have a temporary lactose intolerance because their small intestine wasn’t fully developed by the time they were born.

• #26 Lactose Intolerance – Cause, Symptoms, Diagnosis, Treatment

  https://www.webmd.com/digestive-disorders/digestive-diseases-lactose-intolerance

  This happens when an illness or injury causes your body to slow or stop making lactase. It could happen because of a condition like Crohn’s disease, a bacterial infection of your intestines, or celiac disease. […] It’s rare, but you might be born not being able to produce enough lactase. This is caused by a gene you inherit from both parents. […] Premature babies sometimes have lactose intolerance because their small intestines weren’t fully developed at birth.

• #27 Lactose Intolerance – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK532285/

  There is a decrease or absence of lactase enzyme activity since birth due to autosomal recessive inheritance. It manifests in the newborn after ingestion of milk. It is a rare cause of the deficiency, and its genetics are not very well known. […] It is seen in premature infants born at 28 to 37 weeks of gestation. The infant’s intestine is underdeveloped, resulting in an inability to hydrolyze lactose. This condition improves with increasing age due to the maturation of the intestine, which results in adequate lactase activity.

• #28 What Causes Lactose Intolerance? Types and Prevention

  https://www.webmd.com/digestive-disorders/causes-lactose-intolerance

  Secondary lactose intolerance happens because of an injury, illness or possibly a surgery. Any of these can affect your small intestine and cause you to make less lactase. Celiac disease and Crohns disease are two of the most common intestinal diseases linked to low lactase. […] Developmental lactose intolerance happens in babies who are born prematurely. It usually goes away on its own, lasting for only a short time after birth. […] Congenital lactose intolerance is very rare and happens when no lactase (or a very small amount of it) is produced by the small intestine from birth. Its a genetic disorder, and both parents have to pass the gene on to their child.

• #29 Lactose Intolerance: Symptoms, Causes, Tests, and More

  https://www.healthline.com/nutrition/lactose-intolerance-101

  Developmental lactose intolerance occurs in infants, too. It’s typically only seen in premature babies, who are born before their digestive system is fully developed, and it causes symptoms like digestive distress. […] Lactose intolerance is typically categorized as primary, which is caused by declining lactase levels as you age, or secondary, which is caused by another condition that affects your small intestine. In rare instances, this condition can also affect babies.

• #30 Lactose Intolerance – Cause, Symptoms, Diagnosis, Treatment

  https://www.webmd.com/digestive-disorders/digestive-diseases-lactose-intolerance

  This happens when an illness or injury causes your body to slow or stop making lactase. It could happen because of a condition like Crohn’s disease, a bacterial infection of your intestines, or celiac disease. […] It’s rare, but you might be born not being able to produce enough lactase. This is caused by a gene you inherit from both parents. […] Premature babies sometimes have lactose intolerance because their small intestines weren’t fully developed at birth.

• #31 Lactose intolerance

  https://www.nhs.uk/conditions/lactose-intolerance/

  Lactose intolerance is when the body does not make enough of an enzyme called lactase, which helps you digest lactose. […] Lactose intolerance can start at any age and can also be caused by conditions such as inflammatory bowel disease and Coeliac disease. […] Other causes include bowel infections, bowel surgery, and an injury to the bowel. […] Some premature babies are unable to digest lactose because their bowel has not developed enough, but this usually gets better as your baby gets older. […] Some people do not make any lactase at all, but this is very rare.

• #32 Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

  https://www.mdpi.com/2072-6643/7/9/5380

  Lactose intolerance related to primary or secondary lactase deficiency is characterized by abdominal pain and distension, borborygmi, flatus, and diarrhea induced by lactose in dairy products. […] Lactose intolerance depends not only on the expression of lactase but also on the dose of lactose, intestinal flora, gastrointestinal motility, small intestinal bacterial overgrowth and sensitivity of the gastrointestinal tract to the generation of gas and other fermentation products of lactose digestion. […] About two thirds of the World’s population undergoes a genetically programmed decrease in lactase synthesis after weaning (primary lactase deficiency). […] Additionally, in individuals with lactase persistence the occurrence of gastrointestinal infection, inflammatory bowel disease, abdominal surgery and other health issues can also cause a decrease in lactase activity (secondary lactase deficiency).

• #33 Lactose Intolerance | ACG

  https://gi.org/topics/lactose-intolerance-in-children/

  Lactose intolerance occurs more frequently in certain families. […] One of the most important factors affecting the rate of developing lactose intolerance is an individual’s ethnic background. […] Approximately 15% of adult Caucasians, and 85% of adult African Americans in the United States are lactose intolerant. […] The rate of lactose intolerance is also very high in individuals of Asian descent, Hispanic descent, Native Americans and Jewish individuals. […] Primary Lactase Deficiency: This condition is very rare and occurs when babies are born with a deficiency or absence of the enzyme lactase. […] Secondary Lactase Deficiency: The most common cause of temporary lactose intolerance in infants and young children is by an infection that affects the gastrointestinal tract and can damage the lining of the small intestine.

• #34 Lactose Intolerance Causes, Dairy Foods, Symptoms & Tests

  https://www.medicinenet.com/lactose_intolerance/article.htm

  The most common cause of lactase deficiency is a decrease in the amount of lactase that occurs after childhood and persists into adulthood, referred to as adult-type hypolactasia. […] Lactase deficiency (and lactose intolerance) is most common among Asians, affecting more than 90% of adults in some communities. […] People with ancestry from Northern Europe, on the other hand, have a 5% rate of lactase deficiency.

• #35 Lactose intolerance – cause and symptoms | Arla

  https://www.arla.com/articles/lactose-intolerance-cause-and-symptoms-info/

  People who suffer from lactose intolerance have low levels of lactase in their digestive system. […] A person who suffers from lactose intolerance, also known as lactose maldigestion or dairy intolerance, has low levels of lactase. […] In the absence of sufficient lactase, more of the lactose will pass unsplit into the large intestine, where gut bacteria will start to break it down. […] While the majority of children of European descent maintain their ability to digest lactose in their teens and throughout adulthood, children of many other ethnicities often produce less and less lactase as they grow older and many eventually become lactose intolerant. […] It is estimated that around 65% of the worlds population is lactose intolerant to some degree. […] In some communities in Asia, however, up to 90% of the population are lactose intolerant.

• #36 Lactose Intolerance | ACG

  https://gi.org/topics/lactose-intolerance-in-children/

  Lactose intolerance occurs more frequently in certain families. […] One of the most important factors affecting the rate of developing lactose intolerance is an individual’s ethnic background. […] Approximately 15% of adult Caucasians, and 85% of adult African Americans in the United States are lactose intolerant. […] The rate of lactose intolerance is also very high in individuals of Asian descent, Hispanic descent, Native Americans and Jewish individuals. […] Primary Lactase Deficiency: This condition is very rare and occurs when babies are born with a deficiency or absence of the enzyme lactase. […] Secondary Lactase Deficiency: The most common cause of temporary lactose intolerance in infants and young children is by an infection that affects the gastrointestinal tract and can damage the lining of the small intestine.

• #37 Lactose intolerance: MedlinePlus Medical EncyclopediaLock

  https://medlineplus.gov/ency/article/000276.htm

  Lactose intolerance develops when the small intestine does not make enough of this enzyme. […] Babies born too early (premature) sometimes have lactose intolerance. […] Lactose intolerance is very common in adults. It is rarely dangerous. About 30 million American adults have some degree of lactose intolerance by age 20. […] In white people, lactose intolerance often develops in children older than age 5. This is the age when our bodies may stop making lactase. […] In African Americans, the problem can occur as early as age 2. […] The condition is very common among adults with Asian, African, or Native American heritage. […] An illness that involves or injures your small intestine may cause less of the lactase enzyme to be made. […] Babies may be born with a genetic variant, which may make them unable to make any of the lactase enzyme.

• #38 The Science Behind Lactose Intolerance – Carolina Knowledge Center

  https://knowledge.carolina.com/discipline/life-science/ap-biology/the-science-behind-lactose-intolerance/

  Lactose intolerance is marked by the production of excessive gas, bloating, and abdominal pain. […] People can also become lactose intolerant because they have a condition that damages the lactase-producing cells in their intestines. […] Lactose intolerance should not be confused with lactase deficiency, which is relatively rare. […] It is estimated that approximately 75% of the adult world population is not able to digest lactose, the main carbohydrate in milk. […] The ability to make lactase as an adult varies between populations. […] Current evidence suggests that the ability of humans to express the lactase enzyme into adulthood did not arise until after dairying practices had begun.

• #39 Lactose Intolerance | AAFP

  https://www.aafp.org/pubs/afp/issues/2002/0501/p1845.html

  The wide variation in prevalence has caused speculation that lactase deficiency is the normal or natural state, and the persistence of significant lactase activity into adult life in northern European populations is an abnormal mutation that provides a selective advantage to groups using dairy products.

• #40 Lactose Intolerance: Bacteria That Causes It and How to Treat It

  https://flore.com/blogs/learn/lactose-intolerance-bacteria-that-causes-it-and-how-to-treat-it?srsltid=AfmBOopihlqP6pX9NY6sU9xu34khtvoHzAstlmgJ3KEFlEHlvSfhDCgD

  Lactose intolerance occurs when a person undergoes lactose malabsorption. […] The basis for lactose intolerance can be genetic. People with lactose non persistence (where lactase production slows after childhood) and congenital lactase deficiency (where lactase production is slow or nonexistent from birth) have small intestines that do not make enough lactase for proper lactose digestion. […] However, lactose intolerance can also be mediated by one’s gut microbiome. […] Certain bacteria in the colonic microbiome digest the lactose that passes through the gastrointestinal system. […] These microbes are called lactic acid bacteria. […] Two main types of bacteria are responsible. […] Lactobacillus […] These bacteria metabolize lactose. […] Bifidobacterium […] This genus includes several bacterial species that, like Lactobacillus, can digest lactose. […] Lactose intolerance is also linked to a few diseases, like colon cancer.

• #41 Lactose Intolerance: Bacteria That Causes It and How to Treat It

  https://flore.com/blogs/learn/lactose-intolerance-bacteria-that-causes-it-and-how-to-treat-it?srsltid=AfmBOopihlqP6pX9NY6sU9xu34khtvoHzAstlmgJ3KEFlEHlvSfhDCgD

  Lactose intolerance occurs when a person undergoes lactose malabsorption. […] The basis for lactose intolerance can be genetic. People with lactose non persistence (where lactase production slows after childhood) and congenital lactase deficiency (where lactase production is slow or nonexistent from birth) have small intestines that do not make enough lactase for proper lactose digestion. […] However, lactose intolerance can also be mediated by one’s gut microbiome. […] Certain bacteria in the colonic microbiome digest the lactose that passes through the gastrointestinal system. […] These microbes are called lactic acid bacteria. […] Two main types of bacteria are responsible. […] Lactobacillus […] These bacteria metabolize lactose. […] Bifidobacterium […] This genus includes several bacterial species that, like Lactobacillus, can digest lactose. […] Lactose intolerance is also linked to a few diseases, like colon cancer.

• #42 What is Lactose Intolerance? Symptoms and Treatment – Canadian Digestive Health Foundation

  https://cdhf.ca/en/what-is-lactose-intolerance-symptoms-and-treatment/

  In people with lactose intolerance, the colon microflora become very good at fermenting lactose into acids and gases. […] Taking a lactase enzyme before you eat foods that contain dairy, may prevent the symptoms of lactose intolerance. […] The simplest, and probably most reliable way of diagnosing whether an individual is lactose intolerant or not is to remove all lactose products from the diet for 1 to 2 weeks and see if the symptoms resolve.

• #43 Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

  https://www.mdpi.com/2072-6643/7/9/5380

  Whatever the cause, lactose malabsorption causes symptoms by several mechanisms: unabsorbed lactose leads to osmotic diarrhea; products of its bacterial digestion lead to secretory diarrhea and gas can distend the colon. […] Recent studies have provided important new insight into the complex relationship between lactase deficiency, lactose malabsorption and symptom generation.

• #44 Top four lactose intolerance symptoms

  https://www.henleynutrition.co.uk/single-post/top-four-lactose-intolerance-symptoms

  Secondary lactose intolerance is caused by small intestinal disease or injury affecting the previous normal supply of lactase enzymes. […] The typical causes of secondary lactose intolerance are: IBS, Coeliac disease, Inflammatory bowel disease, Gastroenteritis and other gut infections from bacteria and virus, Dysbiosis an overgrowth of certain gut bacteria such as SIBO Small Intestinal Bacterial Overgrowth. […] The risk of symptoms and the severity of lactose intolerance symptoms have been shown to be significantly increased in IBS patients, especially at low to moderate levels of lactose found in the average diet. […] Patients with a new diagnosis of coeliac disease often have lactose intolerance. However, a study found that many recover the ability to digest lactose after 12 months on a gluten-free diet.

• #45 Top four lactose intolerance symptoms

  https://www.henleynutrition.co.uk/single-post/top-four-lactose-intolerance-symptoms

  It is believed that damage to the small intestine can lead to reduced production of lactase enzymes. […] Many cases of gastrointestinal infections from bacteria and viruses have been shown to cause lactose intolerance, often termed Post-infectious lactose intolerance. […] A recent Hungarian study showed that 60% of their lactose intolerant group also had diagnosed SIBO, which after treatment, resolved the lactose malabsorption.

• #46 Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/187249-overview

  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. […] Lactase deficiency is the most common form of disaccharidase deficiency. […] 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. […] Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.

• #47 Pediatric Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/930971-overview

  Lactose intolerance is caused by a low or absent activity of the enzyme lactase. […] This deficiency results from an unusual mechanism that involves a developmentally regulated change of the lactase gene product, resulting in a reduced synthesis of the precursor protein. Differences in the rate of gene transcription account for much of the differences in lactose intolerance observed among racial groups. […] Low lactase activity in the small intestine allows undigested lactose to pass into the colon. In the colon, bacteria ferment the sugar to hydrogen gas and organic acids. The gas produces distention of the bowel, creating the sensation of bloating, cramping, and abdominal pain. Organic acids can be absorbed, but the quantity produced is rarely large enough to cause systemic symptoms or metabolic acidosis.

• #48 Pediatric Lactose Intolerance: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/930971-overview

  Lactose intolerance is caused by a low or absent activity of the enzyme lactase. […] This deficiency results from an unusual mechanism that involves a developmentally regulated change of the lactase gene product, resulting in a reduced synthesis of the precursor protein. Differences in the rate of gene transcription account for much of the differences in lactose intolerance observed among racial groups. […] Low lactase activity in the small intestine allows undigested lactose to pass into the colon. In the colon, bacteria ferment the sugar to hydrogen gas and organic acids. The gas produces distention of the bowel, creating the sensation of bloating, cramping, and abdominal pain. Organic acids can be absorbed, but the quantity produced is rarely large enough to cause systemic symptoms or metabolic acidosis.

• #49 Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

  https://www.mdpi.com/2072-6643/7/9/5380

  Whatever the cause, lactase deficiency results in unabsorbed lactose being present in the intestinal tract, which has effects that can lead to symptoms of lactose intolerance in susceptible individuals. […] Symptoms of lactose intolerance generally do not occur until there is less than 50% of lactase activity. […] Regular lactose intake may also have an effect. […] Lactase enzyme replacement is another important approach in patients with “isolated” lactose intolerance that wish to enjoy dairy products. […] A related strategy involves probiotics that alter the intestinal flora and may have beneficial effects in IBS patients. […] Although restricting dietary lactose or FODMAPs may improve gastrointestinal complaints, long-term effects of a diet free of dairy or FODMAPs products may be of concern.

• #50 Causes and diagnosis of lactose intolerance | informedhealth.org

  https://www.informedhealth.org/causes-and-diagnosis-of-lactose-intolerance.html

  If bigger amounts of lactose do enter the colon, they are broken down and converted by bacteria. This fermentation process increases the production of gases like carbon dioxide (CO2), methane and hydrogen, as well as other byproducts like liquids and fatty acids. This is what causes flatulence (bloating and wind) and diarrhea. […] The severity of the symptoms depends on both the amount of available lactase and other factors: Some people may produce hardly any lactase, but have a large intestine that works quickly. They can handle fairly large amounts of lactose quite well because the lactose doesnt stay in their colon for very long. […] Another factor is the type of food a person eats and what they drink, because that determines how long lactose stays in the stomach or small intestine. Food that has a lot of fat in it can slow down your digestion. This gives the small intestine more time to produce enough lactase to break down the lactose, often resulting in less severe symptoms.

• #51 Causes and diagnosis of lactose intolerance | informedhealth.org

  https://www.informedhealth.org/causes-and-diagnosis-of-lactose-intolerance.html

  If bigger amounts of lactose do enter the colon, they are broken down and converted by bacteria. This fermentation process increases the production of gases like carbon dioxide (CO2), methane and hydrogen, as well as other byproducts like liquids and fatty acids. This is what causes flatulence (bloating and wind) and diarrhea. […] The severity of the symptoms depends on both the amount of available lactase and other factors: Some people may produce hardly any lactase, but have a large intestine that works quickly. They can handle fairly large amounts of lactose quite well because the lactose doesnt stay in their colon for very long. […] Another factor is the type of food a person eats and what they drink, because that determines how long lactose stays in the stomach or small intestine. Food that has a lot of fat in it can slow down your digestion. This gives the small intestine more time to produce enough lactase to break down the lactose, often resulting in less severe symptoms.

• #52 Lactose Intolerance – Cause, Symptoms, Diagnosis, Treatment

  https://www.webmd.com/digestive-disorders/digestive-diseases-lactose-intolerance

  Millions of Americans cant digest a certain sugar in milk and milk products called lactose. If youre one of them, you have lactose intolerance. […] The main cause of lactose intolerance is that you produce too little lactase, the enzyme in your small intestine that breaks down lactose. […] Most people become less tolerant of lactose as they get older, because our bodies produce less lactase as we age. […] Lactose intolerance is common. The risk of it is linked to your ethnicity. Lactose intolerance affects about 85% of Black adults in the U.S. and about 15% of White adults. It’s also more likely to affect you if you have Hispanic, Asian, Native American, or Jewish ancestry. […] Risk factors for developing lactose intolerance include: Age. You produce less lactase as you grow older. Ethnicity. If your heritage is African, Asian, Hispanic, or Native American, your risk is higher.

• #53 What Is Lactose Intolerance? Symptoms, Causes, Diagnosis, Treatment, and Prevention

  https://www.everydayhealth.com/lactose-intolerance/guide/

  Risk factors for lactose intolerance include: Age (it tends to appear after adolescence or young adulthood), A person’s race or ethnicity, Premature birth. […] Several gastrointestinal disorders and other conditions can also cause lactose intolerance. They include: Gastroenteritis (inflammation of the intestinal lining caused by a virus, bacteria, or parasite), Celiac disease, Crohn’s disease, Ulcerative colitis (ulcers in the intestinal lining), Irritable bowel syndrome (IBS), Any injury to the small bowel, Chemotherapy or radiation treatment for cancer. […] A condition called small intestine bacterial overgrowth (SIBO) may also cause sensitivity to lactose and, in some cases, the tell-tale gastrointestinal symptoms.

• #54 Lactose Intolerance: Types, Symptoms, Causes, Diagnosis, Treatment and More

  https://www.health.com/lactose-intolerance-overview-7152514

  Lactose intolerance is caused by lactose malabsorption, which occurs when your small intestine makes low levels of the enzyme lactase and can’t digest all the lactose you eat or drink. […] When you have a lactase deficiency, your body doesn’t produce enough lactase in order to digest the lactose in your foods and drinks. […] Some people are born with lactose intolerance while others develop the condition as they age. […] There are four types of lactase deficiency that could potentially lead to lactose intolerance: Lactase non-persistence, Secondary lactase deficiency, Developmental lactase deficiency, and Congenital lactase deficiency. […] While some people inherit the condition, you also can be at risk as you age as well as if you have certain medical conditions. […] Having a parent with lactose intolerance, getting older, having gastroenteritis, developing a bowel disease like Crohn’s disease or ulcerative colitis, receiving chemotherapy, taking antibiotics, and being born prematurely are some of the more common risk factors for lactose intolerance.

• #55 Lactose Tolerance Test – ADH – Windsor Center for Digestive Health

  https://windsordigestivehealth.com/procedures/lactose-tolerance-test/

  The main risk factor of lactose intolerance is age. Babies are rarely born without enough lactase, but as we age, levels can decrease. This means that an onset of lactose intolerance can occur at any time. Other risk factors include: Ethnicity. Lactose intolerance is more common in those of Asian, African, American Indian, or Hispanic descent. Small intestine diseases. If you already have a digestive disorder of the small intestine, such as Crohn’s disease or celiac disease, this puts you at higher risk. Prematurity. If you were born prematurely, you may have had a lower amount of lactase at birth, leading to lactose intolerance later in life. Cancer treatments. Radiation and chemotherapy can change how your body digests lactose.

• #56 What Is Lactose Intolerance? Symptoms, Causes, Diagnosis, Treatment, and Prevention

  https://www.everydayhealth.com/lactose-intolerance/guide/

  Risk factors for lactose intolerance include: Age (it tends to appear after adolescence or young adulthood), A person’s race or ethnicity, Premature birth. […] Several gastrointestinal disorders and other conditions can also cause lactose intolerance. They include: Gastroenteritis (inflammation of the intestinal lining caused by a virus, bacteria, or parasite), Celiac disease, Crohn’s disease, Ulcerative colitis (ulcers in the intestinal lining), Irritable bowel syndrome (IBS), Any injury to the small bowel, Chemotherapy or radiation treatment for cancer. […] A condition called small intestine bacterial overgrowth (SIBO) may also cause sensitivity to lactose and, in some cases, the tell-tale gastrointestinal symptoms.

• #57 Lactose Intolerance: Symptoms, Diagnostic Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance

  Secondary lactose intolerance may not be permanent. If your small intestine recovers its usual function, you may regain the ability to digest lactose. […] Lactase supplements can give your body the lactase it needs to break down lactose. […] Secondary lactose intolerance caused by damage to your small intestine might be reversible after your small intestine recovers. This will depend on how permanent the damage is. […] If you have primary or congenital lactose intolerance, you wont ever start naturally producing more lactase. But its possible your symptoms could change if your intestinal health or microbiome changes. […] Lactose intolerance will affect your diet, which means youll have to pay attention to the nutrients youre getting. If you avoid all dairy products, you could end up low in calcium and vitamin D. […] Lactose intolerance is a reaction in your digestive system to lactose, the sugar in milk. It causes uncomfortable symptoms after you eat dairy products.

• #58 Lactose Intolerance: Types, Causes, and Treatment

  https://www.healthline.com/health/lactose-intolerance

  Congenital or developmental lactose intolerance (being born with the condition) […] In very rare cases, lactose intolerance is inherited. […] This is referred to as congenital lactose intolerance. […] Developmental lactose intolerance occurs when a baby is born prematurely. […] Lactose intolerance cannot be prevented. […] The symptoms of lactose intolerance can be prevented by eating less dairy.

• #59 Lactose Intolerance: Types, Causes, and Treatment

  https://www.healthline.com/health/lactose-intolerance

  Congenital or developmental lactose intolerance (being born with the condition) […] In very rare cases, lactose intolerance is inherited. […] This is referred to as congenital lactose intolerance. […] Developmental lactose intolerance occurs when a baby is born prematurely. […] Lactose intolerance cannot be prevented. […] The symptoms of lactose intolerance can be prevented by eating less dairy.

• #60 Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

  https://www.mdpi.com/2072-6643/7/9/5380

  Whatever the cause, lactase deficiency results in unabsorbed lactose being present in the intestinal tract, which has effects that can lead to symptoms of lactose intolerance in susceptible individuals. […] Symptoms of lactose intolerance generally do not occur until there is less than 50% of lactase activity. […] Regular lactose intake may also have an effect. […] Lactase enzyme replacement is another important approach in patients with “isolated” lactose intolerance that wish to enjoy dairy products. […] A related strategy involves probiotics that alter the intestinal flora and may have beneficial effects in IBS patients. […] Although restricting dietary lactose or FODMAPs may improve gastrointestinal complaints, long-term effects of a diet free of dairy or FODMAPs products may be of concern.

• #61 What Causes Lactose Intolerance? – Gastroenterology Medical Associates

  https://gastrospecialistsnj.com/what-causes-lactose-intolerance/

  Congenital lactase deficiency – a rare form that presents itself at birth due to genetic factors, where the body produces little to no lactase from infancy. […] Understanding the underlying causes of lactose intolerance can help individuals manage their symptoms through dietary adjustments and appropriate treatment options.

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