Food Intolerance

Food Intolerance

Food intolerance is a non-IgE-mediated (non-allergic) food hypersensitivity, characterised by difficulty in digesting certain foods. It is different from a food allergy: a food allergy triggers the immune system, whereas food intolerance does not. The symptoms of food intolerance also generally take longer to appear than those of an allergy. In food intolerance, some people develop digestive problems after eating particular foods.

The foods most commonly associated with food intolerance include dairy products, grains that contain gluten, and gas-forming foods such as beans and cabbage. Gluten in wheat is one of the most common causes. Some people are intolerant to several groups of foods, which makes it harder to tell whether the problem is a chronic illness or an intolerance, and identifying the responsible foods can take a long time. The symptoms are varied and can include stomach-ache, bloating, nausea, irritable bowel, hives, migraine, mild fever and cough.

Types of Food Intolerance

• Absence of an enzyme. Enzymes are needed to digest food fully. If a particular enzyme is missing or insufficient, proper digestion is affected. The classic example is lactose intolerance, caused by a deficiency of the enzyme lactase. Without enough lactase, a person cannot break down lactose (milk sugar) into smaller molecules for absorption, so they become intolerant to milk and milk products. Undigested lactose left in the digestive tract causes stomach-ache, spasms, bloating, gas and diarrhoea.
• Chemical causes. Certain natural chemicals in foods and drinks can cause intolerance - for example, amines in some cheeses and caffeine in coffee, tea and chocolate. Some people are far more susceptible to these chemicals than others.
• Toxins due to food poisoning. Some foods contain naturally occurring chemicals that are toxic to humans, causing diarrhoea, nausea and vomiting. Peanuts and undercooked beans, for instance, can carry aflatoxins that produce very unpleasant digestive problems.
• Salicylates. Salicylates are derivatives of salicylic acid, which occurs naturally in plants as a defence against bacteria, fungi, insects and disease. They are present in most plant foods - the majority of fruits and vegetables, spices, herbs, tea and flavour additives - with especially high levels in mint flavouring, tomato sauce, berries and citrus fruits. Most people tolerate them without any problem, but salicylate-sensitive individuals develop symptoms after eating large amounts and should avoid high-salicylate foods (processed foods with flavour additives are usually high in them too).
• Gluten intolerance. Gluten is a protein found mainly in wheat, barley and rye. In a gluten-intolerant person it can cause digestive problems such as gas, abdominal pain or diarrhoea. Gluten intolerance is sometimes confused with coeliac disease or thought of as a food allergy. Anyone who suspects it should see a doctor before giving up gluten, because cereals are an important source of several nutrients.
• Food additives and intolerance. Additives are used to enhance flavour, improve appearance and lengthen shelf life. Additive intolerance has grown steadily as more and more foods contain them. Nitrates (high in processed meats) are known to cause itching and skin rashes; MSG (monosodium glutamate), a flavour enhancer, is known to trigger headaches; and some colourings, especially carmine (red) and annatto (yellow), can also cause intolerance.

Diagnosis and Treatment

It is very difficult to tell an intolerance from an allergy because their signs and symptoms often overlap. Patients are therefore advised to keep a food diary, noting which foods were eaten, what the symptoms were and when they appeared; a dietician or doctor can use this record to identify the culprit foods and decide what to do next. …