Before we even look at whether a food intolerance or food allergy is causing your constipation, it is really important that we distinguish the difference between these two conditions as they are very different.
A food allergy is when your body reacts to a certain food by triggering an immune response, and generally causes mild symptoms such as swelling of the tongue or face, an itchy throat, a red rash on the body and feeling faint or nausea. However, in some cases it can be severe and lead to anaphylaxis where the body reacts quite violently causing breathing problems, disorientation and possibly unconsciousness (call an ambulance immediately if anyone goes into anaphylactic shock!).
Common allergy foods include wheat, dairy, nuts, shellfish and strawberries, so if you are allergic to a certain food then you must avoid it altogether. For more information on food allergies you can look at the NHS Food Allergy health pages.
A food intolerance on the other hand is when certain foods cause a reaction within the digestive system, not the immune system, such as constipation, bloating, cramps and nausea. Common foods include dairy, wheat and gluten and are best avoided as much as possible within the diet in order to see any relief in the symptoms.
So how do I know if a certain food is causing my constipation?
You may already be aware or suspect that certain foods trigger your constipation but start keeping a food diary over the next two to four weeks, writing down everything you eat and drink and the digestive complaints that occur, and you should start to see a pattern whereby every time you’ve eaten a certain food there has been a reaction.
Let’s say that you suspect dairy is causing your constipation. The next step is then to cut dairy out of your diet completely for at least two weeks – this is sometimes referred to as an elimination diet. This may seem like a long time but it’s really important that your body has the chance to adjust and get used to not having that particular food. After two weeks, slowly re-introduce dairy, about once every two to three days, back into your diet and see if your symptoms (or in this case constipation) returns or worsens.
If there has been no effect then you are ok to eat dairy and it may be another food, such as wheat, causing the problem so you need to start the process again. Eliminate wheat from your diet for a minimum of two weeks and then slowly start to reintroduce it.
It can be a question of trial and error, and seem a hassle, but it is worth it! This will really allow you to start listening to your body and understanding how you personally react to certain foods - as no two people are the same.
Can I test for a food intolerance or allergy?
You can yes! They can be quite effective and there are several different ones to choose from, but they can also be quite expensive as well.
If you are looking for a good company to get a food test from though, then I would recommend the FoodScan Programme from York Test Laboratories which costs £250.
For other ideas on what may be causing your constipation, read 'Causes of Constipation'.