Dietitian Services

Food Intolerances


For most of us, food is more than a daily necessity. We get personal pleasure from it. We nurture our children with it. And sharing it around the table is at the heart of our family and social life. For some people, though, foods can cause distressing, even dangerous, reactions, or chronic ill health.

Foods can upset people for many reasons. Having a food problem may restrict your food choices somewhat, but it doesn’t mean you can’t enjoy eating and sharing with family and friends.

Understanding the difference between intolerance and other types of food reaction is an important starting point because the approach to dealing with them is quite different. Unlike allergies and coeliac disease, which are immune reactions to food proteins, intolerances don’t involve the immune system at all. They are triggered by food chemicals which cause reactions by irritating nerve endings in different parts of the body, rather in the way that certain drugs can cause side-effects in sensitive people.

The chemicals involved in food intolerances are found in many different foods, so the approach involves identifying them and reducing your intake of groups of foods, all of which contain the same offending substances. By contrast, protein allergens are unique to each food (for example, egg, milk and peanut), and dealing with a food allergy involves identifying and avoiding all traces of that particular food. Similarly, gluten, the protein involved in coeliac disease, is only found in certain grains (wheat, barley, rye) and their elimination is the basis of a gluten-free diet.

Dealing with food intolerances

foodintolerancePeople vary in their degree of sensitivity to food chemicals, and whether or not they get symptoms depends on the dose ingested. If you’re not too sensitive (with a high dose threshold) you may only react after a particularly rich meal or after bingeing on highly preserved/flavoured/coloured foods. Avoiding these may be all you need to do to stay well.

However, if you’re at the other end of the spectrum (with a low dose threshold) you may develop symptoms over several days or weeks from the cumulative effects of small amounts of natural chemicals. Because these are present in many otherwise ‘healthy’ foods in a normal diet, you’ll have to be much more careful with what you eat on a daily basis.

Food intolerances can be distressing, but they don’t cause permanent damage to the body. If you have persistent symptoms it’s a good idea to first make sure some serious disease hasn’t been overlooked.

If you’re having trouble working out which foods are upsetting you, professional help may be needed to investigate the problem more systematically. This first step is to follow a strict elimination diet for 3 or 4 weeks to see if symptoms disappear. You may get a withdrawal effect in the first week or so (with a temporary flare-up of symptoms for a few days) so don't give up too soon. Once your symptoms have settled and you're feeling better for at least 7 days in a row, your're ready to start doing challenges to find out which chemicals in your diet cause reactions.

Challenges can either be done double-blind (with purified food chemicals taken in capsules), or with carefully selected foods each containing only one problem substance. Once your problem substances have been identified, a dietitian with experience in the field can advise you how to manage your diet.

Don’t be discouraged — food intolerances needn’t be permanent. You may well be able to build up your tolerance level by gradually increasing the amount and variety of ‘low’ and ‘moderate’ foods over several weeks or months, and eventually return to a more normal diet. Even if this is not possible, you’ll learn ways of avoiding severe reactions by looking out for the foods that upset you most. Our article on living with food intolerance can help.

Food intolerance reactions

Symptoms triggered by food chemical intolerances vary from person to person. The commonest ones are recurrent hives and swellings, headaches, sinus trouble, mouth ulcers, nausea, stomach pains and bowel irritation. Some people feel vaguely unwell, with flu-like aches and pains, or get unusually tired, run-down or moody, often for no apparent reason. Children can become irritable and restless, and behavioural problems can be aggravated in those with nervous system disorders such as ADHD (attention deficit hyperactivity disorder). Even breast-fed babies can have food intolerance reactions due to chemicals from the mother’s diet getting into the breast milk, causing colicky irritable behaviour, loose stools, eczema and nappy (diaper) rashes.

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