How to tell if you are lactose intolerant

Ever find yourself bloated, full of gas and abdominal pain a few hours after ingesting dairy products such as milk, cheese or yoghurt? These symptoms are typical in cases of lactose intolerance but may also occur as a result of other conditions such as irritable bowel syndrome (IBS). Therefore, it is important to see a specialist for a correct diagnosis and management plan to help relieve and manage your symptoms.

Here, expert consultant gastroenterologist Dr Ian Johnston thoroughly explains everything you need to know about testing for lactose intolerance.
 

What is lactose and why some people intolerant to it?

Lactulose is a type of sugar called a disaccharide. It occurs in all mammal’s milk as well as many food products. Foods which are particularly high in lactose are milk, yoghurt, fromage frais, icecream, custard and milk puddings. Of note, cow's, goat’s and sheep’s milk all contain lactose.

There are a number of other lower lactose food products and these include lactose-free yoghurt, soya yoghurt and soya puddings. Lactulose free normal cow's milk has recently been developed and this has revolutionised things for patients with lactose intolerance. There are cheeses which are naturally low in lactulose such as hard cheeses including cedar, parmesan and Emmental.

Lactase is the enzyme within the small bowel, which is responsible for breaking down lactose. If this is deficient either because of a genetic cause or due to damage to the fine brush border of the small bowel due to disease (for example, coeliac disease) then the ingested lactose is undigested and passes through into the large bowel.

In the large bowel, normal healthy bacteria break down the lactose sugar creating gas. This can lead to symptoms of bloating, flatulence, cramping and diarrhoea.

Lactulose intolerance is much more common in some races than others. European populations tend to have infrequent lactose intolerance but it is very common in Asian populations.
 

When would my doctor suggest a lactose intolerance test?

I would suggest a lactose intolerance test in anyone who has symptoms suggestive of lactose intolerance such as those listed above. I would certainly consider a test in anyone who has been told that there may have been irritable bowel syndrome (IBS) or who suspects they may have irritable bowel syndrome; the symptoms can overlap considerably.

Some people are able to self diagnose lactose intolerance. They may have noticed that the develop symptoms of bloating, cramping, flatulence and diarrhoea after ingesting significant quantities of milk or other lactose products.
 

What are the different types of test and what do they entail?

Patients can do a simple test at home. They should avoid eating any lactose-containing foods for a few days and then at the weekend drink two glasses of milk and no other food or drink. They should then wait and see if they develop any of the symptoms of lactose tolerance identified above. This will not lead to a formal diagnosis but it can be highly suggestive of the diagnosis of lactose intolerance. Doctors can perform other tests for lactose intolerance.

The first test involves drinking a test amount of lactose solution. This is then followed by regular blood tests at intervals measuring blood sugar levels. This is not a very sensitive test and it does have the disadvantaged of requiring blood tests. A more common test involves drinking lactose solution followed by breath tests at intervals. The breath test procedure provides accurate results and is completely non-invasive with no need for blood testing.
 

Do you think self-testing kits that can be done at home are just as reliable?

Home testing kits using hair samples can be purchased online however these are non-scientific and do not test for lactose intolerance. They are not reliable and should not be trusted.
 

How long does it take to receive test results following a breath test?

The lactose hydrogen breath test procedure provides accurate results immediately. No samples need to be sent off to the laboratory for analysis so there are no delays.
 

If results show that I am lactose intolerant what is the next step?

I would normally refer patients to a dietitian to discuss a lactose-free or low lactose diet. Some people may be happy to follow a diet sheet and do this self-directed, however, I believe that the involvement of a professional who is an expert in this area does lead to better results and better symptom control.



If you are worried that you are living with symptoms of lactose intolerance, you can book an appointment with Mr Johnston via his Top Doctor’s profile here. Can’t make it in person? He is also available for a video call using our e-Consultation, which can be found on his profile too.