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Think You Might Have a Food Intolerance? Here's How to Figure It Out

An issue dietitians hear all too often is: 'Why do I still feel horrible even though I’m eating really healthily?' Often, the culprit is a food intolerance. Yep, you can be eating all the ‘right things’ and still have uncomfortable and debilitating symptoms.

Here, we explain exactly what a food intolerance is, the signs you might have one and what to do about it.

What is a food intolerance?

Food intolerance is a broad term used to describe a variety of adverse reactions to eating certain foods.

What is the difference between a food intolerance and an allergy?

It can be difficult to differentiate between food intolerance and food allergy because some symptoms and the compounds within foods that trigger a reaction can be similar. The key difference is that food allergies cause an immune reaction in the body, leading to the development of antibodies which cause an almost immediate reaction such as hives, swelling of the mouth, lips and tongue, vomiting, diarrhoea, breathing difficulties and potentially life-threatening anaphylaxis.

On the other hand, a food intolerance does not involve the immune system and symptoms generally appear hours or even several days later in a dose response manner, meaning symptoms may not appear until the body has exceeded its ‘dose threshold’, which varies between individuals. Whilst the symptoms of food intolerance are generally not life threatening, they can certainly be troublesome and negatively impact one’s quality of life.

What are the symptoms of a food intolerance?

Symptoms will differ depending on the person and trigger food involved.

Often food intolerance symptoms occur in the digestive symptoms and the following symptoms can occur:

  • Gas
  • Nausea
  • Cramps
  • Bloating
  • Diarrhoea
  • Constipation

Certain chemicals in food can also cause the following symptoms:

  • Hives
  • Headaches
  • A rapid pulse
  • Coughing
  • Sinus or breathing problems

What causes a food intolerance?

Some food intolerances are triggered by enzyme deficiencies and carbohydrate malabsorption, leading to lactose, fructose or gluten intolerance in some individuals.

Other triggers relate to certain chemical compounds present within food, such as preservatives, salicylates, amines, colourants, flavour enhancers, sweeteners, sodium glutamate (MSG) and sulphites.

Moreover, many individuals are intolerant to certain sugars found in FODMAP foods, which includes a wide range of fruit, vegetables, breads, cereals, nuts, legumes and confectionary (see below for more details).

What are the most common FODMAP triggers?

Common trigger foods are termed ‘FODMAP’ foods because they contain certain sugars that can be difficult to digest. These include fructans, GOS (galacto-oligsaccharides), disaccharides (lactose) and fructose.

The list of foods containing these sugars is long and includes:

  • FODMAP fruit: fruit containing excess sorbitol and/or fructose – apples, pears, mangoes, cherries, figs, watermelon, dried fruit, blackberries, peaches, plums.
  • FODMAP vegetables: vegetables rich in fructans and/or mannitol – artichoke, garlic, leek, onion, spring onion, mushrooms, cauliflower, snow peas.
  • FODMAP grains and cereals rich in fructans and GOS: wheat and rye-based products.
  • FODMAP legumes and pulses: rich in GOS – red kidney beans, split peas, falafels, baked beans.
  • FODMAP dairy: dairy foods high in lactose – soft cheese, milk, yoghurt
  • FODMAP proteins: processed and marinated meats.
  • FODMAP nuts and seeds: rich in GOS and/or fructans include cashews, pistachios.
  • FODMAP honey and sugarL sweetened foods rich in fructose and sweeteners – sorbitol, xylitol, erythrytol.

What to do if you think you have a food intolerance

Navigating a suspected food intolerance and identifying your trigger food can be tricky. The important first step is to see an accredited practicing dietitian for professional advice.

A food diary is generally undertaken at the outset.

Then a temporary elimination diet (such as a gluten free diet or low FODMAP diet) is often implemented (under strict medical supervision), followed by individual food challenges (gradual re-introduction of foods) to attempt to pinpoint the offending chemical or trigger food.

Unlike a food allergy where the trigger foods need to be completely avoided, foods that cause a food intolerance can still be eaten in small amounts. This is particularly important when treating children who require a balanced diet, including representation of all the five food groups.

If necessary, dietitians will recommend replacement foods to counteract any elimination requirements to help maintain adequate nutrition to support growth and development.

Explore more content like this in our series, Ask a Dietitian.

Health & Performance Collective is the brainchild of Sydney Dietitians Jessica Spendlove and Chloe McLeod. They use their 20 years of combined knowledge and skills as dietitians to work with motivated people to live and perform at their best.

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