Food allergies and intolerance
Most of us know someone who has a food allergy or intolerance. It might be a child who is allergic to peanuts, a workmate told they are wheat intolerant or your mother advised to stay away from dairy foods. But what is the difference between an allergy and an intolerance, and how can you be sure it’s real?
A true food allergy is the body’s response to a food protein, such as nuts or fish. The body mistakenly believes the offending protein, known as an allergen, is harmful and creates antibodies to attack it. Reactions can occur within minutes or up to a few hours after eating the food and include:
- difficulty in breathing or swelling in the throat
- swollen or itching lips or tongue
- hives, skin rashes or eczema
- stomach cramps, vomiting or diarrhoea
- faintness or collapse.
About 1% of adults and less than 10% of children are ‘at risk’ of allergic reactions to foods. A small number of foods are responsible for around 90% of food allergies - including shellfish, fish, milk, eggs, peanuts, tree nuts, wheat and soybeans. The most common allergies in adults are to peanuts, tree nuts, fish and shellfish. Children are commonly allergic to dairy milk and eggs, with the majority growing out of this allergy between the ages of 3 and 5.
Allergy New Zealand can offer advice and support to allergy sufferers.
In food intolerance, the body’s immune system does not create antibodies, as in an allergic reaction. But as in an allergic reaction, symptoms can be seen both immediately and up to 20 hours after a food is eaten, so it can be hard to distinguish between the two.
Food intolerance can be a result of a sensitivity to naturally occurring chemicals in food, such as salicylates, amines and glutamate. Another common food intolerance is to lactose, the sugar found in milk products. This is caused by a shortage of the enzyme needed to help the body digest milk. An allergic reaction to milk is also possible when the body reacts to milk protein, although the symptoms will differ.
In contrast to some food allergies, food intolerances aren’t life threatening –but they can impact on health and quality of life. Unfortunately, they can be problematic to diagnose as many of the symptoms - such as bloating, wind, diarrhoea and stomach pain - are unspecific and difficult to attribute to a particular food.
The smallest traces of a food can trigger an allergic reaction, whereas small amounts of a food can usually be eaten before symptoms appear in most food intolerances. The amount tolerated, however, depends on the individual.
Food allergies and intolerances should be diagnosed by a doctor or registered dietitian before any foods are excluded from the diet. Various methods are used to determine allergies and intolerances, including skin prick tests, blood tests, diet histories, food diaries and elimination diets. Self-diagnosis can lead to the unnecessary avoidance of foods, putting yourself at risk nutritionally. The doctor or dietitian will advise you if any foods are to be avoided. The manufactured foods database (www.mfd.co.nz) provides lists of foods appropriate for people with allergies such as egg, milk, soya, legumes (such as chickpeas, kidney beans, lentils), peanut and wheat, and for those with lactose intolerance.
There is no proven way to prevent allergies. Breastfeeding babies exclusively until they are six months old, may help reduce the risk. It is not recommended that women avoid common food allergens during pregnancy or breastfeeding, as this is more likely to put mother and baby at risk nutritionally than to prevent allergies.
About one in 300 New Zealanders is affected by coeliac disease, a condition in which the body’s immune system reacts to gluten, found in the grains wheat, rye, barley and possibly oats. This disease causes inflammation of the bowel, which affects the body’s ability to absorb nutrients from food, leading to poor nutrition, bloating, weight loss, diarrhoea and fatigue if not treated.
Coeliac disease is treated by following a gluten-free diet, advised by your doctor or registered dietitian. The manufactured foods database (www.mfd.co.nz) provides a list of gluten-free foods available in New Zealand. There are an increasing number of gluten-free products available, including gluten-free bread, cereals and bakery products. Further information is also available from the Coeliac Society of New Zealand.
Food manufacturers in New Zealand are required to list the most common allergenic foods on their food labels. This includes milk, egg, soy, peanut, tree nut, sesame, fish, shellfish and gluten-containing grains, including wheat.
If there is significant risk of cross-contamination, manufacturers also have to include precautionary statements, such as ‘may contain traces of peanuts’. This may occur, for example, if biscuits containing peanuts are produced on the same production line as another biscuit.
Allergy New Zealand: www.allergy.org.nz
Coeliac Society of New Zealand: www.colourcards.com/coeliac
Food Standards Australia New Zealand: www.foodstandards.govt.nz
Manufactured Food Database: www.mfd.co.nz