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Last Updated
3rd o November, 2011
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Lactose is the main carbohydrate found in milk and dairy products and is digested by the enzyme lactase into its absorbable components - glucose and galactose - which are then used as fuel by the body. Lactose maldigestion occurs when insufficient amounts of the enzyme lactase are available in the gut to digest lactose. This results in undigested lactose passing into the large intestine where it can be fermented by the bacteria in the colon and may cause unpleasant gastrointestinal symptoms in some individuals, such as flatulence, diarrhoea and abdominal pain.
Lactose intolerance is the occurrence of these symptoms, in people with clinically diagnosed lactose maldigestion, after consumption of lactose (as it is important to note that not everyone with lactose maldigestion will experience intolerance symptoms).
Lactose intolerance is a genetically determined condition, and several different types exist:
Congenital lactase deficiency - most people produce sufficient amounts of lactase at birth and during childhood to digest normal amounts of dietary lactose. Occasionally infants are born without the ability to produce any lactase at all. This is known as congenital lactase deficiency and becomes apparent after the first exposure to breast milk. This type of lactose intolerance is extremely rare with only 40 cases ever reported, but it can only be treated by complete exclusion of lactose from the diet for life.
Primary lactase deficiency - In some people, lactase production will begin to decline at some point after weaning, usually at about 2-3 years of age. In these individuals, production of lactose usually stops during childhood or occasionally may continue into adolescence before stopping completely. This is known as primary lactase deficiency and is usually treated by careful control of lactose intake in the diet.
Secondary or acquired lactase deficiency - This occurs in people who normally produce sufficient levels of lactose, but have suffered damage to the lining of the intestine, from which lactose is usually produced. Common causes of damage include food poisoning or conditions such as coeliac disease (caused by allergy to gluten). This type of lactase deficiency is usually reversible after the individual has recovered from the original cause.
Familial lactase deficiency - This is a genetically inherited condition where newborn babies are born with the ability to produce a substantial amount of lactase, but the enzyme does not work and cannot break down the lactose. Complete avoidance of lactose in essential from birth.
Symptoms
The symptoms of lactose intolerance may include flatulence (production of excess gas in the gut), abdominal bloating, diarrhoea and stomach cramps. In extreme cases nausea and vomiting may also occur.
The symptoms can occur anytime from 15 minutes to 2 hours after consumption of lactose-containing food or drink and will vary depending upon the amount of lactose consumed and the ability of the specific individual to tolerate lactose.
As mentioned earlier, not everyone who has difficulty digesting lactose will suffer the symptoms of lactose intolerance.
Diagnosis
Lactose intolerance can be diagnosed using several techniques:
The lactose intolerance test - This test involves consumption of approximately 50g of lactose followed by blood glucose tests after a period of 30 minutes.
The blood tests measure glucose concentration in the blood and will indicate whether sufficient lactase is present to digest the lactose into its absorbable components -glucose and galactose. If blood glucose levels are raised this indicates that sufficient lactase is being produced to tolerate lactose. If they are not raised it suggests that lactose is not being digested and that insufficient amounts of lactase are being produced.
Hydrogen breath test - This test also involves consumption of approximately 50g of lactose, followed by measurement of hydrogen levels in breath over the following 3-6 hours. Hydrogen is produced as a by-product from the bacterial fermentation of lactose that has escaped digestion and has subsequently passed into the large intestine. Elevated breath hydrogen levels will indicate that levels of lactose reaching the large intestine are also elevated which suggests that the individual is not digesting lactose and is therefore intolerant.
This test is thought to be the cheapest, most economical, non-invasive and reliable test to measure lactose intolerance.
Intestinal biopsies - In certain cases, patients will undergo a minor operation to remove a small sample of the intestine in order to study the cells which produce lactase. This technique is usually avoided as other less invasive and more reliable tests are now available.
Source: http://www.milk.co.uk/
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