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Lactose is a type of sugar which is found in milk and milk products. It can also be found in a variety of other foods such as cheeses and yoghourts and ice creams and in medicines and pills. Lactose is too big a molecule to be absorbed by the intestine and so it is digested and split into two more simple sugars glucose and galactose which can then be absorbed by the body and used as nourishment. In order to do this the lining of the small intestine produces an enzyme lactase. When this is absent or in short supply, lactose digestion is impaired and symptoms can occur. The symptoms of lactose intolerance are therefore dose related and are not an actual allergy. In infants, milk is the main part of the diet, whereas adults do not eat so much milk. This is particularly the case with animals who may also have lactose intolerance problems in adulthood - don't feed your adult dogs milk!). Hence it is natural and normal for lactase production to gradually decrease as the individual grows older and the diet becomes more varied. This tends to occur in childhood and adolescence in African Americans, Native American Indians, Mediterranean races, Arabs, Jews, and Asians. Northern European white races seem to keep lactase production the longest. When lactase is absent, lactose passes through the intestine to the colon (large bowel), carrying extra fluid with it. Normally lactose would not reach the colon because it would be digested before it reached that level. In the colon, bacteria break down lactose into lactic acid and certain gases. Lactic acid is an irritant and laxative. It can cause symptoms such as bloating, diarrhoea, abdominal cramps, and gas or flatus. Lactase activity is reduced in people with certain intestinal conditions such as Crohn's disease, ulcerative colitis, and celiac disease (gluten enteropathy). Patients taking certain drugs and alcoholic patients may also be lactose intolerant. Finally, patients with surgical removal of part of the stomach or a large portion of the small intestine may need to reduce lactose in the diet because there will be less active cells to produce the enzyme lactase - again a dosage effect. It is important to remember that while lactose intolerance can cause quite uncomfortable symptoms, it does not cause damage to the intestine. The purpose of this diet is to eliminate lactose or reduce it to tolerable levels. One way of alleviating symptoms is to add a dose of lactase to the diet - a supplement of lactase is taken before a lactose meal.
Nutrition Facts
What is lactose intolerance?
1. congenital which means it is present from birth, which is a rare form particularly since babies eat milk. This should not be confused with milk intolerance which can occur in infants and which is due to a reaction to cows milk proteins in babies fed on cows milk or given supplements. 2. secondary or developmental. This type of deficiency is caused by conditions which may have destroyed the intestinal lining and lactase - for example chronic severe diarrhoea from infections or coeliac disease. 3. Developmental - in most species of mammals the infant is capable of digesting milk and has adequate lactase for this task, whereas lactase is gradually lost with age as milk is no longer a part of the individuals diet. This is the most common cause of lactase deficiency and is seen in many races to varying degrees. some eastern and Mediterranean populations may loose significant amounts of lactase relatively early on in life whereas white races from northern Europe keep lactase levels high until much later in life. (Prevalence of adult-type hypolactasia among different ethnic groups - Asian populations almost 100%, American Indians 80%, Negroid races 70%; Caucasians 20%. Age of onset Asian populations age 5, Blacks and Mexican-Americans age 10.)
Lactase deficiency does not equate exactly with lactose intolerance since milder deficiencies of lactase may cause no symptoms even persons with moderate deficiencies of lactase may not have symptoms. A diagnosis of lactase deficiency is made when the amount of lactase in the intestine is reduced, but a diagnosis of lactose intolerance is made only when the reduced amount of lactase causes symptoms.
What are the symptoms of lactose intolerance? The common symptoms of lactose intolerance are gastrointestinal, primarily, abdominal pain, diarrhoea, flatulence (passing gas), and, less commonly, abdominal bloating, abdominal distension, and nausea. Unfortunately, these symptoms can be caused by other gastrointestinal conditions or diseases, so the presence of these symptoms are not very good at predicting whether a person has lactase deficiency or lactose intolerance. Symptoms occur because the unabsorbed lactose passes through the small intestine and into the colon. In the colon, one type of normal bacterium contains lactase and is able to split the lactose and use the resulting glucose and galactose for its own purposes. Unfortunately, when they split the lactose into glucose and galactose, these bacteria also release hydrogen gas. Some of the gas is absorbed from the colon and into the body and is then excreted by the lungs in the breath. Most of the hydrogen, however, is used up in the colon by other types of bacteria. A small proportion of the hydrogen gas is expelled and is responsible for the increased flatus (passing gas). Some people have an additional type of bacterium in their colons that changes the hydrogen gas into methane gas, and these people will excrete only methane or both hydrogen and methane gas in their breath and flatus. Not all of the lactose that reaches the colon is split and used by colonic bacteria. The unsplit lactose in the colon draws water into the colon (by osmosis). This leads to loose, diarrhoeal stools. The severity of the symptoms of lactose intolerance vary greatly from person to person. One reason for this variability is that people have different amounts of lactose in their diet; the more lactose in the diet, the more likely and severe the symptoms. Another reason for the variability is that people have differing severities of lactase deficiency, that is, they may have mildly, moderately, or severely reduced amounts of lactase in their intestines. Thus, small amounts of lactose will cause major symptoms in severely lactase deficient people but only mild or no symptoms in mildly lactase deficient people. Finally, people may have different responses to the same amount of lactose reaching the colon. Whereas some may have mild or no symptoms, others may have moderate symptoms. The reason for this is not clear but may relate to differences in their intestinal bacteria.
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