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Lactose intolerance is a common problem. It is more frequent amongst people of Mediterranean and Asian background. It becomes more common as one gets older. It is due to an inability to break iactose down into its component parts which are glucose and galactose. This is done by an enzyme called lactase. This enzyme is found in the lining of the small bowel. When lactose is not broken down it ferments and causes bloating, abdominal discomfort and diarrhoea. Many people believe that it is also responsible for a number of other symptoms which can include headaches and nasal stuffiness. Almost 100 years ago there was a study published which suggested that in people with this problem some lactose was absorbed across the small bowel lining and it was this that caused such symptoms.

There has been considerable discussion as to the amount of lactose that can cause symptoms. It is usually suggested that the amount of lactose found in a glass of milk is needed. However, there have been a few studies which suggest that even the small amounts of lactose found in some tablets is sufficient to cause symptoms. Lactose is commonly used as a whitening and sweetening agent by both the pharmaceutical and food industries. It is often found in unusual situations and it is for this reason that almost 50% of the lactose we eat each day is described as hidden. It can be quite difficult to identify whether lactose is present in many foods. It is not always clearly labelled and care should be taken when it is written that the product contains milk solids or other derivatives of a milk origin.

Although some people believe that the source of milk is important this is only the case where there is sensitivity to milk protein. Milk protein sensitivity and lactose intolerance are very different. For such people with milk protein sensitivity there can be an advantage to using either goat’s or sheep’s milk. In addition, there is a growing fashion for using buffalo milk or camel milk. In all four of these milks the protein is different. However, lactose is the same whatever its source. Reactions to cow’s milk protein are quite distinct from reaction to lactose. Although reactions to cow’s milk
protein were considered to mainly occur in children it is now recognised that they also occur in adults.
How can I check whether I have lactose intolerance?

There are various ways that you can formally check lactose intolerance. These include blood, breath and biopsy tests. However, you can carry out a simple test at home. Simply stop drinking and eating all sources of lactose for three days and then drink a glass of normal milk. If this causes symptoms it is likely that you have lactose intolerance.

What can I do if I have lactose intolerance?

You need to stop eating and drinking lactose. This is much easier said than done. Lactose is very common in many foods. You will need to look at labels of food that you buy to see if there is lactose present. You can now buy lactose-free dairy products. There are also substitutes such as soya, rice or oat-based milks. Unfortunately some people who are intolerant of lactose also experience problems with soya.

It is possible to purchase lactase tablets. These can be taken with favourite foods such as ice cream and so allow you to still enjoy them. In addition, some people find live yoghurt helpful. This is because such yoghurt contains lactobacillus or other bacteria which can digest lactose. However, if there is lactose present in the yoghurt this can sometimes cause symptoms before you experience the benefits of the bacteria. As well as live yoghurts some people use kefir which they grow at home.

One potential advantage of kefir is that it is possible to develop a product which is water-based. However, kefir is not generally available commercially in the UK at present.

If you are following a lactose free diet you will need to ensure that you have an adequate intake of calcium. Dairy products provide a good source of calcium and if you are not eating them regularly it puts you at possible risk of bone thinning conditions such as osteoporosis. In this situation you need to consider taking calcium supplements.

Further Reading:

Harrington LK & Mayberry JF (2008)

A re-appraisal of lactose intolerance

International Journal of Clinical Practice 62: 1541 - 1546