How to test for lactose intolerance

Lactose intolerance is caused by a deficiency of the enzyme lactase, which breaks down lactose in the small intestine. Lactose that is not digested passes through to the large intestine, where it is fermented by bacteria leading to a build-up of gas in your gut.  

The symptoms of lactose intolerance include bloating, flatulence, diarrhoea, stomach cramps and pain, stomach rumbling and nausea.  

If you think that having milk or other products containing lactose such as cheese, yoghurt, ice cream, shakes and smoothies may be causing you to experience some of these symptoms, it is a good idea to observe what you eat and what happens to your body for a few weeks. Keeping a note of your diet and symptoms in a diary will help you to spot any patterns, and can help a health care professional  to narrow down what may be causing your symptoms.  

If you think you may be lactose intolerant, you should discuss this with your doctor. Your doctor or a specialist may recommend avoiding lactose for a few weeks, drinking lactose-free milk and avoiding dairy products, and noting whether your symptoms continue or disappear. Bear in mind that lactose is not only in milk, but is also used as an ingredient in a host of processed foods. 

Whether you are confident or simply suspect that you have a lactose intolerance from your own observations, the only way to know for sure is by having a medical test. You should consult with your doctor and discuss your symptoms.  

Lactose intolerance symptoms can be similar to those of other quite different conditions, including irritable bowel syndrome (IBS), and coeliac disease, so testing and getting a solid diagnosis is very important.  

Lactose breath test 

A breath test is a common tool for diagnosing lactose intolerance. First, you must observe the dietary restrictions prior to the test, which may involve avoiding dairy and certain other foods for 24 hours and fasting for 12 hours before the appointment. When you arrive, you will be asked to blow up a balloon-like bag. This gives a sample of breath that will be tested to find out how much hydrogen is present, measured in parts per million (ppm).  

Then you will be given a lactose solution to drink and your breath will be tested periodically over the next few hours to see if the hydrogen level changes. If the hydrogen in your breath rises more than 20ppm above your baseline level at the start of the test, it is likely that you are lactose intolerant.   

Lactose tolerance test 

In a lactose tolerance test, you will be given a drink of lactose solution or a large glass of milk and a blood sample is taken. The blood is tested to see how much blood sugar (glucose) it contains. If you are lactose intolerant, your blood sugar levels will either rise very slowly or not at all, showing that your body is unable to break down lactose into glucose.  

Lactose intolerance genetic test 

Simple genetic tests, which involve a blood sample or a cheek swab, can be done to check whether a person has a genetic predisposition to lactose intolerance. 

Once you have been diagnosed with lactose intolerance, the treatment is to switch to a lactose-free diet. Sometimes lactose intolerance is a temporary result of an infection or another problem in the gut, in which case you could try reintroducing some lactose into your diet at a later point. And under supervision of your health care professional.  

If you are avoiding dairy products altogether, it is important to ensure that your diet has plenty of sources of calcium and vitamin D, vital nutrients for good bone health. Green leafy vegetables, soya beans, tofu, nuts and fish with edible bones, such as sardines, carbonated mineral water, are all good sources of natural calcium. Oily fish, red meat, liver and egg yolks contain lots of vitamin D. 

During the long Christmas holidays I returned to my native Puglia region in southeastern Italy. As always, I wanted to eat a lot of the local mozzarella, but given that I had been diagnosed lactose intolerant a few months earlier, regretfully I had to say no. I had suspected that I was lactose intolerant for some time, but had attributed my discomfort to different types of problems. The symptoms of lactose intolerance are easily confused with those of coeliac disease, for example. In my case, I convinced myself that the problem was something else, focusing on stress, flu, fatigue, and so on - until I took the test. Honestly, I had no idea what the test would be like, so I thought it might be interesting to explain what it consists of by telling you about my experience! My doctor gave me a slip, and I booked it with the hospital closest to me, and a few days later I received an email with all the instructions. The good news is that it’s not at all invasive and very simple to do. 

The breath test (as the name suggests) is based on the respiratory function. It lasts about three hours but also requires a simple preparation. The email I received asked me not to take antibiotics in the two weeks prior to the test and to avoid laxatives in the week beforehand. In the 24 hours prior to the test, I was told not to eat foods with a high fibre content such as fruit, vegetables, legumes, whole foods, potatoes, tomatoes or bran, and also to avoid milk and derivatives (cheese, ice cream or packaged foods containing milk).  

What was left for me to eat that day? I'll tell you what I had: for breakfast, tea and Schär Rusks; grilled steak for lunch; in the afternoon tea with lactose-free Schär Shortbread Cookies, and white rice for dinner. Not bad after all!  

On the morning of the test, I had to fast - only water is allowed. I was greeted by a nurse who, after a series of questions about symptoms and my state of health, made me blow into a special bag. Then he gave me a sachet of lactose powder to dissolve in half a glass of water. After this ‘drink’, you will have to repeat the breath test every 30 minutes. All of this takes about three hours, after which the results ​​obtained will show the doctor whether or not you are lactose intolerant.  

In my case, there was no doubt! I was one of the many people who have a deficiency of the enzyme lactase, which enables the digestion of lactose. In short, I am lactose intolerant, and must give up my binge eating of mozzarella and milk chocolate. But all is not lost; luckily, Schär’s Choco Chip Cookies biscuits are lactose free!