lactose intolerance

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Lactose Intolerance



Lactose intolerance refers to the inability of the body to digest lactose.


Lactose is the form of sugar present in milk. The enzyme lactase, which is normally produced by cells lining the small intestine, breaks down lactose into substances that can be absorbed into the bloodstream. When dairy products are ingested, the lactose reaches the digestive system and is broken down by lactase into the simpler sugars glucose and galactose. The liver changes the galactose into glucose, which then enters the bloodstream and raises the blood glucose level. Lactose intolerance occurs when, due to a deficiency of lactase, lactose is not completely broken down and the glucose level does not rise. While not usually dangerous, lactose intolerance can cause severe discomfort.
From 30 to 50 million Americans suffer from the symptoms of lactose intolerance, but not everyone who is deficient in lactase experiences symptoms. Experts believe that 75% of the adult population worldwide does not produce enough lactase and is at risk for some or all of the symptoms of lactose intolerance.

Causes and symptoms

Lactose intolerance can be caused by some diseases of the digestive system and by injuries to the small intestine that result in a decreased production of lactase. While rare, some children are also born unable to produce the enzyme. For many, however, lactase deficiency develops naturally because, after about two years of age, the body produces less lactase.
Symptoms include nausea, cramps, diarrhea, bloating and gas. The symptoms usually occur between 30 minutes to two hours after eating or drinking lactose-containing foods.


Usually, health care professionals measure the absorption of lactose in the digestive system by using the lactose tolerance test, hydrogen breath test or stool acidity test. Each of these can be performed outpatient, through a hospital, clinic or doctor's office.
People taking the lactose tolerance test must fast before being tested. They then drink a lactose-containing liquid for the test and medical personnel take blood samples during the next two hours to measure the patient's blood glucose level. The blood glucose level, or blood sugar level, indicates how well the body is digesting the lactose. A diagnosis of lactose intolerance is confirmed when blood glucose level does not rise. This test is not administered to infants and very young children because they are more prone to dehydration, which can result from diarrhea from the liquid.
Health care professionals measure the amount of hydrogen in the breath using the hydrogen breath test. Hydrogen is usually detected only in small amounts in the breath. However when undigested lactose found in the colon is fermented by bacteria, hydrogen in the breath is produced in greater quantities. The hydrogen is exhaled after being absorbed from the intestines and carried through the bloodstream to the lungs. The hydrogen breath test involves having the patient drink a lactose-containing beverage. Health care professionals monitor the breath at regular intervals to see if the hydrogen levels rise, which indicates improper lactose digestion. People taking the test who have had certain foods, medications or cigarettes before the test may get inaccurate results. While the test is available to children and adults, newborns and young children should not have it because of the risk of dehydration from drinking the beverage that can cause diarrhea in those who are lactose intolerant.
A stool acidity test measures the amount of acid in the stool. This is a safe test for newborns and young children. The test detects lactic acid and other short-chain fatty acids from undigested lactose fermented by bacteria in the colon. Glucose might also be in the stool sample, resulting form unabsorbed lactose in the colon.


Pediatricians might recommend that parents of newborns and very young children who are suspected of having lactose intolerance simply change from cow's milk to a soya formula. Since there is no treatment that can improve the body's ability to produce lactase, lactose deficiency treatments instead, are focused on controlling the diet.
Most people affected by lactose intolerance do well if they limit their intake of lactose foods and drinks. People differ in the amounts they can handle before experiencing symptoms. Some have to stop lactose completely. People who are sensitive after ingesting small amounts of lactose can take lactase enzymes, which are available without a prescription. Using the liquid form, people can add a few drops in their milk, put the milk in the refrigerator and drink it after 24 hours, when the lactase enzymes have worked to reduce the lactose content by 70%. If the milk is heated first and double the amount of lactase liquid is added, the milk will be 90 percent lactose free. Recently, researchers have developed a chewable lactase enzyme tablet. By taking three to six tablets just before eating, the tablets help people digest lactose-containing solid foods. Supermarkets also carry lactose-reduced mild and other products, which contain the needed nutrients found in the regular products but without the lactose.
Foods that contain lactose are milk, low-fat milk, skim milk, chocolate milk, buttermilk, sweetened condensed milk, dried whole milk, instant nonfat dry milk, low-fat yogurts, frozen yogurts ice cream, ice milk, sherbet, cheese, cottage cheese, low-fat cottage cheese, cream and butter. Other foods that may contain hidden lactose are: nondairy creamers, powdered artificial sweeteners, foods containing milk power or nonfat milk solids, bread, cake, margarine, creamed soups, pancakes, waffles, processed breakfast cereals, salad dressings, lunch meats, puddings, custards, confections and some meat products.


Lactose intolerance is easy to manage. People of all ages however, especially children, have to replace the calcium lost by cutting back on milk products by taking supplements and eating calcium-rich foods, such as broccoli, kale, canned salmon with bones, calcium-fortified foods and tofu. Many people who suffer with lactose intolerance will be able to continue eating some milk products. The condition is not considered dangerous.


Often, lactose intolerance is a natural occurrence that cannot be avoided. However, people can prevent symptoms by managing the condition with diet and lactase supplements.

Key terms

Galactose — Simple sugar derived from milk sugar.
Glucose — A simple sugar and the chief energy source in the body.
Lactase enzyme — The enzyme produced by cells that line the small intestine which allows the body to break down lactose.
Lactose — The primary sugar in milk.



American Dietetic Association. (800) 366-1655. 〈〉.


"Lactose Intolerance." 〈〉.


inability to withstand or consume; inability to absorb or metabolize nutrients.
activity intolerance a nursing diagnosis accepted by the North American Nursing Diagnosis Association, defined as a state in which a person has insufficient physiological or psychological energy to endure or complete necessary or desired daily activities. Causes include generalized weakness, sedentary lifestyle, imbalance between oxygen supply and demand, and bed rest or immobility. Defining characteristics include verbal report of fatigue or weakness, abnormal heart rate or blood pressure response to activity, exertional discomfort, and dyspnea.
carbohydrate intolerance inability to properly metabolize one or more carbohydrate(s), such as glucose, fructose, or one of the disaccharides.
disaccharide intolerance inability to properly metabolize one or more disaccharide(s), usually due to deficiency of the corresponding disaccharidase(s), although it may have other causes such as impaired absorption. After ingestion of the disaccharide there may be abdominal symptoms such as diarrhea, flatulence, borborygmus, distention, and pain. One common type is lactose intolerance.
drug intolerance the state of reacting to the normal pharmacologic doses of a drug with the symptoms of overdosage.
exercise intolerance limitation of ability to perform work or exercise at normally accepted levels, as measured in exercise testing.
glucose intolerance inability to properly metabolize glucose, a type of carbohydrate intolerance; see diabetes mellitus.
lactose intolerance a disaccharide intolerance specific for lactose, usually due to an inherited deficiency of lactase activity in the intestinal mucosa.
risk for activity intolerance a nursing diagnosis accepted by the North American Nursing Diagnosis Association, defined as the state in which an individual is at risk of having insufficient physiological or psychological energy to endure or complete required daily activities. See also activity intolerance.
Patient Care. Nursing activities and interventions are aimed at identifying those factors that contribute to activity intolerance, providing evidence of the patient's progress to the higher level of activity possible for the patient, and reducing signs of physiologic intolerance to increased activity (blood pressure and respiratory and pulse rates). Once the contributing factors are identified, plans are made to avoid or minimize them. For example, if inadequate sleep or rest periods are a factor, the nurse plans with the patient scheduled periods of uninterrupted rest during the day. Inadequate sleep at night should be assessed and appropriate interventions planned and implemented. Making an objective record of the patient's progress toward increased activity tolerance can help alleviate depression or lack of incentive, both of which can be contributing factors. Such assessment data could include measurements of blood pressure, pulse, and respiratory rates before and after an activity, gradual increase in the distance walked, and gradual resumption of responsibility for activities of daily living.

lac·tose in·tol·er·ance

a disorder characterized by abdominal cramps and diarrhea after consumption of food that contains lactose (for example, milk, ice cream); believed to reflect a deficiency of intestinal lactase; may appear first in young adults who had tolerated milk well as infants.

lactose intolerance

a sensitivity disorder resulting in the inability to digest lactose from milk products because of an inadequate production of or defect in the enzyme lactase. Symptoms of the disorder are bloating, flatus, nausea, diarrhea, and abdominal cramps. The diet is adjusted according to the tolerance level; the milk-derived foods (milk, cheese, butter, and margarine), and any products containing milk, such as cakes, ice cream, cream soups, and sauces, are restricted. Also called milk intolerance. See also lactase deficiency.

lactose intolerance

A term that encompasses an array of adverse responses to consumption of non-human milk, in particular the inability to digest lactose, a sugar in milk and many dairy products. Up to 75% of adults have a decrease in lactase with age, which presents clinically as abdominal bloating, cramps, flatulence, diarrhea, nausea and/or vomiting, and borborygmi (a rumbling noise of the intestines).

lactose intolerance

β-d-galactosidase deficiency, lactase deficiency Internal medicine An acquired, or AR condition characterized by an inability to digest lactose–often due to lactase deficiency, which may ↑ with age; LI is more common in African Americans, Native Americans, Mediterraneans, Asians, due to deficiency of lactase on intestinal brush borders Etiology GI disease–celiac sprue, viral or bacterial gastroenteritis, post-gastroduodenal surgery Clinical Abdominal bloating, nausea, cramps, flatulence, inability to metabolize disaccharides, resulting in osmotic diuresis, diarrhea, acidic stools Management Lactose restriction in diet unless pretreated with lactase; cultured milk products–eg, yogurt, buttermilk may be well tolerated. See Lactose, Lactose tolerance test.

a·dult lac·tase de·fi·cien·cy

(ă-dŭlt' lak'tās dĕ-fish'ĕn-sē)
A disorder involving onset of difficulties of ingesting lactase, with resulting milk intolerance and malabsorption, in adulthood. Inherited forms may not be manifested until adulthood; any process that damages the intestinal lining cells can cause lactase deficiency in adults.
Synonym(s): lactose intolerance.

lactose intolerance

The result of an insufficiency of the lactose-splitting enzyme lactase (beta-galacosidase) in the lining of the small intestine. Lactose in milk is acted on by gas-forming intestinal bacteria, causing abdominal discomfort, colicky pain and diarrhoea. Asian and African people who have undergone a change of diet to one with a higher lactose content are often affected in this way.

lac·tose in·tol·er·ance

(lak'tōs in-tol'ĕr-ăns)
Disorder characterized by abdominal cramps and diarrhea after consumption of food that contains lactose (e.g., milk, ice cream).


a sugar derived from milk, which on hydrolysis yields glucose and galactose.

lactose digestion test
oral test of foal's ability to digest milk sugar.
lactose intolerance
inability to digest lactose in the diet because of the lack of the enzyme lactase in the small intestine. Clinical consequences are intestinal discomfort and diarrhea.
lactose tolerance test
a monitor of intestinal epithelial damage, similar to the starch digestion test. The test measures the rise in blood glucose at timed intervals after oral administration of lactose; essentially a test of disaccharidase efficiency of the gut.

Patient discussion about lactose intolerance

Q. can you be lactose intolerant just in the morning? if i drink milk or eat a dairy product in the morning i get nausous, vomit and have diarehha. but i eat dairy products in the evening and im fine. is it possible to be lactose intolerant just in the morning?

A. Not that I'm aware of.. You are either lactose intolerant or you're not. However, it depends on how much dairy products you eat, and perhaps you consume more dairy products in the morning, on an empty stomach, where it all absorbs, where as in the evening you might eat less and combine it with other food. I would suggest you dicrease the total amount of dairy you eat, in order to get rid of these symptms.

Q. lactose intolerant If you are lactose intolerant and you consume a dairy related product can it cause a fever?

A. No
Lactose Intolerance means you lack the enzyme to digest milk.
You get diarrhea NOT fever

Q. I am lactose intolerant. Can I have any other dairy food?

A. If you are lactose intolerant then you must avoid all lactose containing foods like milk, yoghurt & cheese. You can consume these dairy products If your intolerance is less or else you can have cultured yoghurt and lactobacillus milk as a better dairy option.

More discussions about lactose intolerance
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