Lactose intolerance is a condition in which people have symptoms because of the decreased ability to digest lactose, the sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pain, bloating, diarrhea, gas, and nausea. These symptoms usually begin 30 minutes to two hours after milk-based foods or drinks. The severity usually depends on the number of people who eat or drink. Lactose intolerance does not cause damage to the gastrointestinal tract.
Lactose intolerance is due to a lack of lactase enzymes in the small intestine to break down lactose into glucose and galactose. There are four types: primary, secondary, developmental, and congenital. Primary lactose intolerance occurs when the amount of lactase decreases with age. Secondary lactose intolerance is due to injury to the small intestine such as from infection, celiac disease, inflammatory bowel disease, or other diseases. Lactose intolerance progression can occur in premature infants and usually improves over a short period of time. Congenital lactose intolerance is a very rare genetic disorder in which little or no lactase is made from birth.
Diagnosis can be confirmed if symptoms disappear after removal of lactose from the diet. Other supporting tests include hydrogen breath test and stool acidity test. Other conditions that may produce similar symptoms include irritable bowel syndrome, celiac disease, and inflammatory bowel disease. Lactose intolerance is different from milk allergy. Management is usually by reducing the amount of lactose in the diet, taking lactase supplements, or treating underlying diseases. People can usually drink at least one cup of milk per sitting without developing significant symptoms, with larger amounts tolerated if taken with meals or throughout the day.
The exact number of adults with lactose intolerance is unknown. One estimate puts an average of 65% of the global population. Lactose intolerance rates vary across regions, from less than 10% in Northern Europe to as high as 95% in parts of Asia and Africa. Onset usually occurs in older children or early adulthood. The ability to digest lactose into adulthood evolved in some human populations independently, perhaps as an adaptation to dairy domestication 10,000 years ago.
Video Lactose intolerance
Terminology
Lactose intolerance refers primarily to a syndrome that has one or more symptoms on the consumption of a lactose-containing dietary substance. Individuals may be lactose intolerant with varying degrees, depending on the severity of these symptoms. "Lactose malabsorption" refers to physiology as lactase deficiency (ie, the body does not have sufficient lactase capacity to digest the amount of digestible lactose). Hypolactasia (lactase deficiency) is distinguished from alactasia (total lactase deficiency), rare congenital defects.
Lactose intolerance is not an allergy, because it is not an immune response, but a sensitivity to milk caused by lactase deficiency. Milk allergy, occurring in only 4% of the population, is a separate condition, with different symptoms occurring when the presence of milk proteins triggers an immune response.
Maps Lactose intolerance
Signs and symptoms
The main symptoms of lactose intolerance are adverse reactions to products containing lactose (especially milk), including flatulence and cramps, flatulence, diarrhea, nausea, borborygmi, and vomiting (especially in adolescents). This appears one and a half to two hours after consumption. The severity of the symptoms usually increases with the amount of lactose consumed; most people who are lactose intolerant can tolerate a certain level of lactose in their diet without adverse effects.
Cause
Lactose intolerance is a consequence of lactase deficiency, which may be genetic (primary hypolactasia and primary congenital alaktasia) or induced environment (secondary or acquired hypoalactasia). In both cases, the symptoms are caused by insufficient levels of lactase in the duodenal lining. Lactose, a disaccharide molecule found in milk and milk products, can not be directly absorbed through the small intestinal wall into the bloodstream, so, in the absence of lactase, it passes intact to the large intestine. The bacteria in the colon can metabolize lactose, and the resulting fermentation produces a large amount of gas (a mixture of hydrogen, carbon dioxide, and methane) that causes various stomach symptoms. Unabsorbed sugars and fermentation products also increase osmotic pressure of the colon, leading to increased flow of water into the intestine (diarrhea). Gene LCT gives instructions for making lactase. Specific DNA sequences in the MCM6 genes help control whether the LCT genes are turned on or off. At least a few thousand years ago, some humans developed mutations in the MCM6 gene that made the LCT gene turn on even after breastfeeding was stopped. People who are lactose intolerant do not have this mutation. The LCT and MCM6 genes are both located on the long arm (q) of chromosome 2 in region 21. This place can be expressed as 2q21. Lactase deficiency can also be associated with certain inheritance. About 75 percent of African Americans, Native Americans, and American Jews are lactose intolerant, as are 90 percent of Asian Americans and 53 percent of Mexican Americans. DNA analysis of 94 ancient skeletons in Europe and Russia concluded that mutations for lactose tolerance emerged about 4,300 years ago and spread throughout the European population.
Some human populations have developed persistence of lactase, in which lactase production continues to mature as possible in response to the benefits of being able to digest milk from farm animals. Some argue that this associates intolerance with natural selection favoring lactose individuals, but is also consistent with physiological responses to reduce lactase production when not needed in cultures where dairy products are not a source of food available. Although populations in Europe, India, Arabia and Africa were first suspected to have high lactase persistence rates due to single mutations, lactase persistence has been traced to a number of mutations occurring independently.
Different alleles for lactase persistence have grown at least three times in the East African population, with persistence extending from 26% in Tanzania to 88% in Beja's pastoralist population in Sudan.
Lactose intolerance is classified according to the cause as:
Primary hyperlactasia
Primary hyperlactasia, or primary lactase deficiency, is genetic, affects only adults, and is caused by the absence of persistent lactase alleles. In individuals without persistent lactase alleles, less lactase is produced by the body over time, leading to hypolactasia in adulthood. The frequency of persistence of lactase, which allows lactose tolerance, varies widely throughout the world, with the highest prevalence in Northwest Europe, declining across southern and middle eastern Europe and low in Asia and most of Africa, although it is common in African shepherd populations.
Secondary hyperlactasia
Secondary hyperlactasia or secondary lactase deficiency, also called acquired hypolactasia or acquired lactase deficiency, is caused by an injury to the small intestine. This form of lactose intolerance can occur in infants and adults persistent lactase and is generally reversible. It may be caused by acute gastroenteritis, celiac disease, Crohn's disease, ulcerative colitis, chemotherapy, intestinal parasites (such as giardia), or other environmental causes.
Primary congenital alaktasia
Primary congenital congenital, also called congenital lactase deficiency, is an extremely rare autosomal recessive enzyme defect that prevents lactase expression at birth. People with congenital lactase deficiency can not digest lactose from birth, so can not digest milk. This genetic defect is characterized by a lack of lactase (alactasia). About 40 cases have been reported worldwide, especially in Finland. Before the 20th century, infants born with congenital lactase deficiency often did not survive, but mortality rates declined with soy formulas and produced lactose-free dairy products.
Diagnosis
To assess lactose intolerance, bowel function is challenged by digesting more dairy products than can be digested. Clinical symptoms usually appear within 30 minutes, but can take up to two hours, depending on food and other activities. Substantial variability in response (symptoms of nausea, cramps, bloating, diarrhea, and flatulence) is to be expected, because the degree and severity of lactose intolerance vary among individuals.
The next step is to determine whether it is caused by primary lactase deficiency or an underlying disease that causes secondary lactase deficiency. Doctors should investigate the presence of undiagnosed celiac disease, Crohn's disease, or other enteropathies when secondary lactase deficiency is suspected and infectious gastroenteritis has been ruled out.
Lactose intolerance is different from milk allergy, immune response to cow's milk protein. They can be distinguished in diagnosis by providing lactose-free milk, producing no symptoms in cases of lactose intolerance, but the same reaction with normal milk in the presence of milk allergies. A person can have both conditions. If positive confirmation is required, four tests are available.
Hydrogen breath test
In a hydrogen breath test, the most accurate lactose intolerance test, after an overnight fast, 25 grams of lactose (in aqueous solution) is ingested. If lactose can not be digested, enteric bacteria metabolize and produce hydrogen, which, together with methane, if produced, can be detected on a patient's breath by clinical gas chromatography or a compact solid-state detector. This test takes about 2.5 hours to complete. If the hydrogen levels in the patient's breathing are high, they may have lactose intolerance. This test is usually not done on infants and very young children, as it can cause severe diarrhea.
Blood test
In association, measuring blood glucose levels every 10 to 15 minutes after consumption will show a "flat curve" in individuals with lactose malabsorption, while persistent lactase will have a significant "peak", with typical elevations of 50% to 100%, in one to two hour. However, due to the need for frequent blood sampling, this approach has been largely replaced by a breath test.
After an overnight fast, blood is taken and then 50 grams of lactose (in a dilute solution) is swallowed. The blood is then drawn again at the 30 minute mark, 1 hour, 2 hours, and 3 hours. If lactose can not be digested, blood glucose levels will rise less than 20 mg/dl.
Test the acidity of the stool
This test can be used to diagnose lactose intolerance in infants, for whom other forms of testing are risky or impractical. Babies are given lactose to drink. If the individual is tolerant, lactose is digested and absorbed in the small intestine; if not, it is not digested and absorbed, and reaches the colon. Bacteria in the colon, mixed with lactose, causes acidity in the stool. Stools passing after ingestion of lactose are tested for acidity levels. If the stool is acidic, the infant is intolerant of lactose. The PH of the stool in lactose intolerance is less than 5.5.
Bowel biopsy
Intestinal biopsy may confirm lactase deficiency after the discovery of high hydrogen in a hydrogen breath test. Modern techniques have enabled bedside testing, identifying the presence of lactase enzymes in upper gastrointestinal endoscopy instruments. However, for research applications such as mRNA measurements, a specialist laboratory is required.
Sugar chocolate chromatography
Chromatography can be used to separate and identify the undigested sugars present in the feces. Although lactose can be detected in faeces of people with lactose intolerance, this test is not considered reliable enough to reliably diagnose or exclude lactose intolerance.
Genetic Diagnosis
Genetic testing may be useful in assessing whether a person has primary lactose intolerance. Persistence of lactase activity in adults is associated with two polymorphisms: C/T 13910 and G/A 22018 located in the MCM6 gene. These polymorphisms can be detected by molecular biology techniques in DNA taken from blood or saliva samples; Special genetic kits for this diagnosis are available. This procedure consists of extracting and strengthening the DNA of the sample, along with the hybridation protocol in a strip. Colored ribbons are obtained as a final result, and depending on different combinations, it will be possible to determine whether the patient is lactose intolerant. This test allows a definitive diagnosis of noninvasive.
Management
When lactose intolerance is due to secondary lactase deficiency, treatment of underlying diseases allows lactase activity to return to normal levels. In people with celiac disease, lactose intolerance usually returns or improves a few months after starting a gluten-free diet, but dietary restriction while lactose may be necessary.
People with primary lactase deficiency can not change their body's ability to produce lactase. In a society where lactose intolerance is the norm, it is not considered a condition that requires treatment. However, if dairy products are a larger component of a normal diet, a number of efforts may be useful. There are four general principles in dealing with lactose intolerance: avoid lactose diets, substitutions to maintain nutritional intake, regulation of calcium intake, and use of enzyme replacements. Regular consumption of dairy foods by lactase-deficient individuals may also reduce the symptoms of intolerance by promoting adaptation of intestinal bacteria.
Avoid diet
The main way to manage lactose intolerance symptoms is to limit the intake of lactose to a tolerable level. Individuals with lactase deficiency vary in tolerable amounts of lactose, and some report that their tolerance varies over time, depending on their health status and pregnancy. However, as a rule of thumb, people with primary lactase deficiency and no small bowel injuries can usually consume at least 12 grams of lactose per asymptomatic sit, or with only mild symptoms, with larger amounts tolerated if consumed by eating or All day.
Lactose is found mainly in dairy products, which vary in the amount of lactose it contains:
- Milk - unprocessed cow's milk is about 4.7% lactose; goat's milk 4.7%; sheep's milk 4.7%; buffalo milk 4,86%; and yak milk 4.93%.
- sour cream and buttermilk - if made in the traditional way, this may be tolerable, but most modern brands add milk solids.
- Butter - butter-making processes largely eliminate lactose, but still present in small amounts; clarified butter contains a negligible amount of lactose.
- Yogurt - lactobacilli used in the production of yogurt removes lactose in varying degrees, depending on the type of yogurt. The bacteria found in yogurt produce their own enzyme, lactase, which facilitates intestinal digestion in lactose intolerant individuals.
- Cheese - fermentation also reduces the lactose content of cheese and reduces further aging; Traditionally made cheese may contain 10% lactose found in equal milk volume. However, cheese produced can be produced using a process that does not have the same lactose-reducing properties.
There is no standard method for measuring food lactose content. The content of dairy products mentioned also varies according to the process of making and labeling practices, and commercial terminology varies between languages ​​and regions. As a result, absolute numbers for the amount of lactose consumed (by weight) may not be reliable. Halal products labeled pareve or fleishig are free from milk. However, if "D" (for "dairy") is present next to "K", "U", or else circled hechsher, the food product may contain milk solids, although it may also indicate only the product generated on the equipment together with other products containing milk derivatives.
Lactose is also a commercial food additive used for texture, taste, and adhesive quality. It is found in additives that are labeled as casein, casein, whey, lactoserum, milk solids, modified milk ingredients, etc. Like lactose found in foods such as processed meat (sausages/hot dogs, sliced ​​meats, pÃÆ'¼Å © s), broth powder, margarine, sliced ​​bread, breakfast cereals, potato chips, processed foods, medicines, ready meals foodstuffs (powders and bars), protein supplements (powders and bars), and even beer in the style of milk. Some barbecue sauce and liquid cheese used in fast food restaurants may also contain lactose. Lactose is often used as a main filler (the main ingredient) in most prescription and non prescription pill prescription drugs, although product labeling rarely mentions the presence of 'lactose' or 'milk', and does not monograms the products given to pharmacists, and most pharmacists are unaware of the large but common use of lactose in these drugs until they contact the supplier or manufacturer for verification.
Milk substitute
â € Å"Milksâ € based on crops and derivatives such as soy milk, rice milk, almond milk, coconut milk, hazelnut milk, wheat milk, hemp milk, and nut milk are essentially lactose-free. Lactose-low and lactose-free versions of food are often available to replace milk-based foods for those with lactose intolerance.
Lactase Supplement
When lactose avoidance is not possible, or at times when a person chooses to consume these items, enzymatic lactase supplements may be used.
Lactase enzymes similar to those produced in the human small intestine are produced industrially by the fungi of the genus Aspergillus . The enzyme, -galaktosidase, is available in tablets in various doses, in many countries without a prescription. It works well only in high acid environments, such as those found in human intestines due to the addition of stomach fluid from the stomach. Unfortunately, too much acid can change its properties, so it should not be taken on an empty stomach. Also, the enzyme is ineffective if it does not reach the small intestine at the time the food is in trouble. Individuals that are sensitive to lactose can experiment with time and dose settings to meet their specific needs.
While essentially the same process as normal bowel lactose digestion, the direct treatment of milk uses various types of industrial-produced lactase. This enzyme, produced by the yeast of the genus Kluyveromyces, takes longer to act, must be thoroughly mixed throughout the product, and destroyed by a rather acidic environment. Its main use is in producing lactose-free or lactose-less dairy products sold in supermarkets.
Rehabituation to dairy products
Regular consumption of lactose-containing dairy foods promotes adaptation of intestinal bacteria, promotes a favorable microbioma, which allows people with primary lactase deficiency to reduce their intolerance and consume more dairy foods. The way to induce tolerance is based on progressive exposure, consume smaller amounts frequently, distributed throughout the day. Lactose intolerance can also be managed by ingesting live yoghurt cultures containing lactobacilli that are capable of digesting lactose in other dairy products. This may explain why many South Asians, although genetically lactose intolerant, can consume large amounts of milk without much symptoms of lactose intolerance, since consuming a living yoghurt culture is very common among South Asians.
Epidemiology
Overall, about 65% of people experience some form of lactose intolerance because of their age through infancy, but there is a significant difference between population and region, with rates as low as 5% among Northern Europeans and as high as over 90% of adults in some communities in Asia.
Some populations, from an evolutionary perspective, have better genetic makeup to tolerate lactose than others. In Northern European countries, vitamin D deficiency from the sun is balanced by consuming more milk and therefore more calcium. These countries have built tolerance to lactose. In contrast, regions in the south, such as Africa, rarely have vitamin D deficiency and therefore tolerance of milk consumption does not develop in the same way as in Northern European countries. Lactose intolerance is common among Jewish people, as well as from West Africa, Arab countries, Greece, and Italy. Different populations will present the construction of certain genes depending on the pre-arrangement of evolution and culture of the geographic region.
History
Lactase persistence is a phenotype associated with a variety of autosomal dominant alleles that extend lactase activity outside the infant; conversely, lactase nonpersistence is a phenotype associated with primary lactase deficiency. Among mammals, persistence of lactase is unique to humans - it develops relatively recently (in the last 10,000 years) among some populations, and the majority of people around the world keep lactase un persistent. For this reason, the persistence of lactase is some interest in the field of anthropology, human genetics, and archeology, which usually uses the term derived persistence/non-persistence genetic.
The emergence of dairy products and dairy products derived from cow's milk alone varies in different regions of the world, in addition to genetic predisposition. The process of turning milk into cheese dates back earlier than 6500 BC
Genetic analysis shows the persistence of lactase has evolved several times in different places independently in the example of convergent evolution.
History of research
It is only recently that western medicine recognizes the prevalence of worldwide lactose intolerance and its genetic causes. The symptoms are described as early as Hippocrates (460-370 BC), but until the 1960s the prevailing assumption was that tolerance was the norm. Intolerance is described as the result of milk allergies, intestinal pathogens, or as psychosomatic - it is recognized that some cultures do not practice dairying work, and people from those cultures often react badly to consuming milk. Two reasons have been given for this misunderstanding. One is that most of the population of European descent has a low lactose intolerance incidence and a broad cultural history of dairying work. Therefore, tolerance is actually the norm in most societies investigated by early medical researchers. Another reason is that lactose intolerance tends to be less reported: Individual lactose intolerance can tolerate at least some lactose before they show symptoms, and their symptoms differ in severity. Most people can digest a small amount of milk, such as tea or coffee, without suffering side effects. Fermented milk products, such as cheese, also contain less lactose than regular milk. Therefore, in a society where tolerance is the norm, many lactose intolerant people who consume only a small amount of milk, or have only mild symptoms, may not realize they can not digest lactose.
Finally, in the 1960s, it was recognized that lactose intolerance correlated with race in the United States. Subsequent research revealed that lactose intolerance is more common globally than tolerance, and that variation is due to genetic differences, not adaptation to cultural practices.
Other animals
Most mammals usually stop producing lactase and become lactose intolerant, after weaning.
See also
References
External links
- Lactose intolerance in Curlie (based on DMOZ)
- Human Culture, The Power of Evolution
Source of the article : Wikipedia
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