A food intolerance is a repeated adverse reaction to a specific food. Every time the food to which there is an intolerance is eaten, the same reaction occurs. Lactose intolerance is not a food allergy, but is an intolerance to. lactose - the sugar in milk - due to lack of a ferment (enzyme) in the lining of the intestine. (Allergy to the protein in milk does occur and such people cannot take milk).
Milk is a very nourishing food, rich in protein, calcium and vitamin D which .are important for the development of strong bones and teeth. Milk also contains a naturally occurring sugar called lactose. Like all sugars, lactose is a good source of energy. The body cannot absorb lactose until it is broken down into two component sugars which can then pass from the gut into the blood stream.
The body uses a ferment (enzyme) called lactose in the lining of the small bowel to break down the lactose to the two sugars of which it is composed. Some people get upsets from milk and the most common reason for an upset is lactose intolerance.
What is hypolactasia?
Hypolactasia is the medical term for having less lactase than normal. If there is little or no
lactase in the
lining of the gut:
- lactose is either not digested or only partially digested;
- lactose remains in the gut and can cause diarrhoea, bloating or stomach cramps, the symptoms of lactose intolerance.
How common is hypoiactasia?
A small number of people have congenital alactasia. This means they don't have any lactase at all, even from birth. These babies therefore cannot digest lactose which is present in breast milk and standard infant milks.
Most adults had normal amounts of lactase as a child but lactase production gradually declines as they get older, though hypolactasia can occur at any age. Lactase tends to decline more rapidly and completely in some people originating from Eastern Europe, Africa, Asia or the Mediterranean area.
Lactose intolerance can occur after a bout of gastro-enteritis. This is because gastro-enteritis damages the lining of the gut where lactose is produced. This is often referred to as secondary lactose intolerance and is usually temporary. It may also be associated with untreated coeiiac disease (gluten sensitivity).
How is hypolactasla/lactose intolerance diagnosed?
Often it is obvious by the description of the problem. The doctor can confirm the diagnosis as follows:
A test dose of milk
If the usual symptoms occur after drinking a glass of milk, lactose intolerance is likely.
Hydrogen breath test
Following a drink containing lactose, breath samples are taken for 2 or 3 hours. If the level of hydrogen rises it means lactose is being digested by the bacteria in the large bowel instead of by the enzyme lactase in the small bowel.
Small intestinal biopsy
A small sample of the lining of the gut is taken via endoscopy (narrow flexible telescope) and the amount of lactase measured.
How do symptoms occur?
If lactose is not digested, it passes through the gut and acts as a laxative. When it reaches the large bowel, it is digested by bacteria. Bacteria digest lactose differently and the gas hydrogen is produced. Hydrogen causes bloating. (The amount of hydrogen is never dangerous). Cramps "(or spasms) occur because the gut responds to the bloating by contracting.
How is hypolactasia/lactose intolerance treated?
There is no cure, lactase cannot be replaced. However in some cases of lactose intolerance the problem may only be temporary.
Children with congenital lactase deficiency need a milk free diet and should be advised by a dietician to avoid deficiency of essential nutrients.
For affected adults, taking lactose in milk causes no harm, the worst that can happen is the development of wind or mild diarrhoea. For most adults, it is a matter of finding how much milk can be taken without causing symptoms. This is done by noting when you take milk or a milk product and whether or not it causes any symptoms. Most people will find, for example, that they can take milk in tea or coffee, though a glass of milk or a milk pudding causes them a mild upset.
Some people can take yoghurt without trouble because the lactose in the milk has been fermented by the bacteria used to make it. Hard cheese is naturally low in lactose and is usually well tolerated. There are lactose reduced milks, which are available in supermarkets. These can be used with cereals or in puddings.
It is important to try to include cheese, yoghurt and low lactose milk in the diet if normal milk is being avoided. Dairy products are an excellent source of vitamins and calcium.