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Why do intolerances develop in adulthood?


Confused by why a food you could once eat is now making you feel sick? Worried that you have developed an intolerance?

Intolerances are different from allergies

Allergies involve an immune response that can cause rashes, hives, shortness of breath, or even be life-threatening. Intolerances are due to difficulties digesting or metabolising a food and can cause more gut-related symptoms including bloating, stomach pain and diarrhoea.

What causes intolerance?

Our body uses enzymes (chemicals that speed up reactions in the body) to break down foods; if something goes wrong with these enzymes digestion is disturbed and intolerance can occur. For example lactose (a sugar in milk and lots of our favourite dairy products) intolerance, which is pretty common, occurs with not enough lactase enzyme. Luckily there are great lactose-free products available these days!

Why does intolerance often appear later in life?

–  Intolerance can be triggered by metabolic and gastrointestinal disorders (e.g. IBS) and infections (e.g. food poisoning).
–  Digestion slows down with age and less of the enzymes needed for digestion are produced which can increase the risk of intolerance.
–  As you age you may become more sensitive to additives in food such as sulphites (in wine and dried fruit) and MSG (in processed foods and takeaways).


Beware of anyone offering intolerance testing! Unfortunately, most of these tests (bar those for lactose intolerance) are not validated – see our post on testing on the grid.

It’s important to note that lactose or other intolerances are sometimes temporary so permanent exclusion isn’t always the answer and can lead to deficiencies and negatively affect our gut microbiota in the long-term.

The only way to diagnose an intolerance is by using the 3R’s process: Record, Restrict, Reintroduce. We can help you with this in the clinic whilst also optimising the diet and gut health to help you feel your best

Head over to The Gut Health Clinic for more information on services and to get in touch for help.