Lactose intolerance

Lactose intolerance is the inability of your body to completely break down lactose, a type of sugar found in milk. The problem is caused by a lack of lactase (a type of enzyme) normally produced in your small intestine. Lactase breaks down lactose into simpler forms of sugar (glucose and galactose) so that it can be absorbed into the blood stream.

Milk is the only dietary source of lactose.

When this lactose enzyme is missing or depleted the person is said to be lactose intolerant. If this happens, lactose can build up in your large intestine. The lactose ferments which causes the main symptoms: stomach cramps, wind and diarrhoea.

Lactose intolerance varies between different ethnic groups:

95% of Asian people
75% of Afro-Caribbean people
50% of Mediterranean people
10% of northern European people
Adults and children may learn to adjust their diets so that the amount of dietary lactose is not greater than they can tolerate.

Lactose intolerance usually develops slowly over time. As some children grow, their body begins to produce less lactase, but symptoms of lactose intolerance may not appear until adulthood. The exact cause is not known.

In other cases, injuries (e.g. post- infective diarrhoea) to the mucus membrane of the small intestine can cause a temporary problem in producing lactase. Also digestive diseases of the small intestine (e.g. ulcerative colitis and Crohn's disease) can cause lactose intolerance.

Very rarely a baby is born without the ability to produce lactase.

The symptoms of lactose intolerance vary widely, but generally include:

Wind (flatulence)
Nausea
Stomach cramps
Bloated stomach
Diarrhoea
How much lactose you can take into your body before getting these symptoms will depend on how much lactase your body produces. If your body only produces a small amount of lactase, it will soon become overwhelmed if you eat too much food containing lactose and the symptoms will appear.

Symptoms usually begin between half an hour to two hours after eating or drinking foods containing lactose.

Because the symptoms of lactose intolerance and irritable bowel syndrome (IBS) are very similar, misdiagnosis between the two conditions is common.

If you think you might have a problem with lactose intolerance, you should visit your G.P.

Your GP may suggest further tests to find out how much lactase your body is producing and what might be causing the deficiency.

Other tests include:

A drink of lactose solution followed by a breath test. Your body produces hydrogen if the lactose is fermenting rather than being broken down
A drink of lactose solution followed by a blood-sugar test. Your blood-sugar levels will only rise slowly if your body is having difficulty digesting the lactose
Testing your stool (faeces; bowel movement). The stool test is often used to check babies for lactose intolerance

The symptoms can be prevented by being careful with your diet. Generally, young children with lactose intolerance should not eat or drink foods containing lactose (i.e. dairy products). They should eat non-dairy butter and cream, and use soya-milk. It should be noted that most hard mature cheeses, ricotta, cottage and cream cheese contain only small amounts of lactose.

Older children and adults may be able to tolerate certain amounts. It is best to try this by gradually introducing into the diet.

Lactase enzyme in liquid form (usually as drops) can be taken before a meal or added to milk. This can be very effective in helping your digestive system to digest the lactose in the meal. You can also take lactase pills (lactase enzyme capsules) before a meal.

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