A survey shows that up to one in five people believe they have a problem with gluten, a protein found in wheat, barley and rye.
An intolerance to gluten often causes unpleasant gut symptoms like stomach ache, bloating, gas, indigestion, constipation and diarrhoea.
The best way to overcome gluten intolerance is to ditch the ingredient from your life. However, this can have the unintended consequence of reducing other nutrients in your diet.
Gut health expert Dr Megan Rossi explained there is now a four-day test to find out if you're actually intolerant to gluten or something else.
What is the four-day gluten test?
Dr Megan Rossi explained that the first thing you need to do is exclude all sources of gluten from your diet for two weeks.
This includes not only obvious items like bread, pasta and cakes that contain wheat, but other things like soy sauce and barley squash drinks.
If your symptoms resolve after these two weeks, then you can move to the four-day gluten test to make sure that your intolerance is actually due to gluten.
The main idea is to reintroduce food with gluten into your diet without you being aware of it.
Get a friend or family member to include your test food - which can either be a slice of wheat bread or even a placebo - into your diet for up to four days.
Day 1: Start with one slice of the test food (you will not know which it is) with your meal
Day 2: See if you have any symptoms. If you experience any, wait a few days until they subside and then repeat with half a dose of the test food. If you don't have any symptoms, add two portions with your meal.
Day 3: Assess your symptoms again. If you have any symptoms wait for a while and when they subside switch to another test food and repeat the steps from Day 1. If you don't have symptoms, add three portions of the test food.
Day 4: Check in on your symptoms. If you have any, wait a few days until they subside and then repeat the steps from Day 1 using the other test food. If you don't have symptoms, switch to the second test food (wheat bread or placebo) for another four days.
Once you finish the test with both foods, ask whoever is helping you to reveal which food had gluten in it.
If you had no symptoms with the wheat bread, then you can be quite confident that your intolerance is not towards wheat/gluten.
If you had some symptoms while eating wheat bread, then trial it again with two tablespoons of onion or half a clove of garlic in a meal, to rule out whether your problem is with gluten or with another component in the bread called fructans.
What else could you have if not gluten intolerance?
If your symptoms don't resolve in the two weeks after you exclude gluten from your diet, then it's best to reintroduce your restricted diet and consult a GP or dietitian.
If your symptoms include chronic tiredness, anaemia, unexplained weight loss and mouth ulcers - or if you have Type 1 diabetes, thyroid disease or IBS - then it's best to get checked for coeliac disease first.
Coeliac disease is an autoimmune condition that damages the gut, and you can find out if you have the disease with a simple blood test.
While it's vital that you eat gluten for at least six weeks before the test, so that antibodies indicating coeliac can be detected, people with coeliac should avoid gluten at all costs, as even a small crumb can do considerable damage.
If you don't have coeliac disease, but still find that gluten doesn't agree with you, then it's best to see a dietitian.
Unlike with coeliac disease, there is no blood test for gluten intolerance, which is where the double-blind placebo-controlled food challenge suggested by Dr Megan Rossi comes into play.
