What is lactose intolerance? This is a common disorder arising from an inability to digest lactose (milk sugar) because of...
What is a food intolerance?
Food intolerance is used to describe many different conditions where food causes unpleasant symptoms that happen each time that food is eaten, but are not a food allergy. A food intolerance is different to food allergy and intolerances are not caused by the immune system and do not have the risk of a severe and potentially life-threatening allergic reaction (anaphylaxis).
How common is food intolerance?
There are many different types of food intolerances which more commonly affect people than a food allergy. It is important to understand that not all reactions to food are because of a food allergy.
Most people at some point would have experienced an occasion where a food did not agree with them causing unwanted symptoms. This may be due to one of the following conditions:
- Food poisoning
- Over indulgence
- Food toxicity
- Irritable bowel syndrome
- Food additives
Symptoms of food intolerance
There are many possible symptoms that could be caused by having an intolerance to food. Depending on the type of food that is suspected depends on the possible range of symptoms. These symptoms may also be experienced in other conditions in the absence of food being a problem so should always be discussed with a health professional. Symptoms commonly effect the digestive, skin and respiratory systems.
Skin symptoms may include flushing of the skin, urticaria (raised red, itchy rash), eczema flares or angioedema (deep swelling of the tissue). Digestive symptoms can include abdominal pain, diarrhoea, bloating, stomach cramps, and constipation. The respiratory (breathing) system can also be affected rhinitis ,breathing difficulties and a wheeze. Other symptoms include headaches and palpitations.
It is important to understand the difference between a food allergy and food intolerance but also to be able understand which particular condition is causing your problems. With food intolerance the person may be able to tolerate a small amount of the food before they experience symptoms.
Those with an immediate food allergy will have to strictly avoid the food(s) especially those with immediate type (IgE mediated) types of food allergy are associated with the risk of a severe allergic reaction (anaphylaxis) which is a medical emergency.
Food allergies happen when the immune system mistakenly recognises a food as harmful and an allergic response and symptoms are seen. Food intolerances are caused by a substance within the food itself or by the body which has problems with digesting that food (such as lactose intolerance due to a lack of the lactase enzyme whose job it is to break down the lactose in foods).
Common types of food intolerances
Lactose intolerance happens when there are reduced levels of the enzyme lactase in the digestive system needed to break down the ‘sugar’ founds in cow’s milk or where there has been a gastrointestinal infection which results in a reduction of the lactase enzyme levels (secondary lactose intolerance). Lactose found in cow’s milk and other dairy produce including cheese and yoghurt.
Gluten intolerance gluten is a mixture of proteins found in foods like wheat, barley and rye. Gluten can be found in foods like bread, biscuits, crackers, pasta and cakes. Some people with a gluten intolerance may also need to avoid oats because of contamination issues.
Non Coeliac gluten sensitivity is a mild form of gluten intolerance the exact role of the immune system in non-coeliac gluten sensitivity is unclear and further research is needed.
Food additives and food chemicals It is possible to have reactions to naturally occurring substances or those added as a preservative in food including:
- Benzoates (Benzoic acid) are produced by many plants and have also been detected in animals, they are found in foods like berries and milk. Benzoates are added to foods like soft drinks, jams, pickles sweets and chocolates.
- Caffeine is a well-known stimulant, it occurs naturally in plants and is mainly used in drinks such as tea, coffee, and energy drinks and can also be found in chocolate.
- Alcohol (ethanol) is an organic substance and is mainly consumed in alcoholic drinks such as wine, beer or spirits.
- Monosodium Glutamate (MSG) commonly are naturally occurring in ripening fruits and cured meats. Also commonly added to savoury food.
- Salicylates are a group of naturally occurring chemicals that are produced by plants as a defence against things such as diseases, insects and bacteria. Foods containing salicylates include fruits, vegetables, herbs and spices. Manufactured (synthetic) salicylates are used in aspirin and other non-steroidal anti-inflammatory (NSAID’S) medication.
- Sulphur dioxide (sulphites) is often in cider, wine, beer and dried fruits. Sensitivity to sulphites mainly affects patients with asthma, especially those with severe steroid-dependant asthma.
- Vaso active amines (including Histamine) are produced by bacteria during fermentation, storage or decay. They are found in foods like cured meats, fruit, vegetables and fermented soy products, green tea, coffee, champagne, wine, beer, and fresh fruit juice.
Diagnosing a food intolerance
If you suspect a food may be the cause of the symptoms you or your child has experienced it is important to avoid that food and discuss further with a Health Professional they should take a detailed patient history and decide if a trial elimination and re-introduction is necessary. There are no tests e.g. a blood test used to diagnose a food intolerance. If a non IgE mediated food allergy is suspected then a trial elimination usually for 2-6 weeks is recommended.
Keeping a food and symptoms diary of the food eaten and symptoms experienced can be a useful way to build up patterns and highlight suspected food related reactions and reproducibility.
A dietitian (specialist in food and nutrition) is a useful resource for those who are concerned over a suspected food intolerance or need dietary advice on food avoidance and replacement. It is important not to unnecessarily exclude several foods as this can result in the diet being restricted and lacking important nutrients. If after taking a dietary history a food or food additive is identified, a dietitian will be able to guide on an elimination and reintroduction diet if this is deemed necessary. To access a dietitian through the NHS speak to your GP.
Elimination diets involve removing the suspected food from the diet for a set time to see if this helps improve any symptoms. Reading food labels is an important part of ensuring that the food is avoided as some foods are not always an obvious ingredient. More information can be found in the reading a food label fact sheet. During an elimination diet, usually 4 weeks is long enough to know whether removing the suspected food from the diet has helped or not. After this time re-introducing the food is recommended to confirm if the food triggers symptoms again and is how a diagnosis of a food intolerance is made.