Food intolerance is a reaction to natural chemicals in our food that causes inflammation and a variety of unpleasant symptoms, affecting up to 20% of the population. It is different to an allergy, which is a full-blown IgE-mediated immune reaction, usually to the protein in a specific food and affects around 4% of people. Intolerance is either a delayed immune response involving IgG antibodies, or a nervous system reaction, and both can present with very similar symptoms to allergy*.
Food chemicals are in every food in varying amounts and certain groups of foods contain similar chemicals. For example, salicylates are found in many brightly coloured fruits and vegetables, herbs and spices and honey. Amines are in processed meats and fish, cheeses, most nuts and seeds and sauces. Glutamates are both natural and artificial (MSG), and have that rich, umami taste. See our top food swaps to know what to avoid and what’s ok. Histamine-containing foods (wine, cheese, chocolate), sulphites (in wine and dried fruits) and other additives can also cause adverse reactions. IgG immune reactions are more commonly to foods such as wheat, gluten, dairy and soy, but can be to any food, not just high chemical foods.
Quantity is the key with intolerance. Eating a little of the foods you’re intolerant to might not cause a reaction, however once a person’s threshold for that chemical has been reached, symptoms will appear. This makes it hard to identify which foods are causing the problem, as the reaction is often delayed or built up over time.
Reactions to these natural food chemicals can be just as bad as reactions to artificial colours, flavours and preservatives – and similar in nature. Symptoms can include:
- gut issues – pain, diarrhoea, bloating;
- behavioural issues – irritable, moody, restless, defiant;
- skin problems – eczema, hives;
- headaches and migraines; and
- feeling run-down.
Everyone’s threshold is different, and it’s important to work out the amount of your problem foods you can eat before you react, so you can keep your diet as broad and nutritious as possible and most importantly, enjoy your food! For example, I’m intolerant to citric acid, which is in many fruits and vegies, but I’ve worked out I can eat tomatoes in moderation but not citrus fruits. For my kids, no dairy is best to keep their eczema under control.
Intolerance may also be associated with chronic inflammatory disease, such as Chron’s, IBS and coeliac, so it’s worth getting tested if you’re concerned something else is going on.
* Skypala, I 2011, ‘Adverse Food Reactions—An Emerging Issue for Adults’, Journal of the American Dietetic Association, vol. 111, no. 12, pp.1877-91.