Nutrition team

Healthy eating is about balance. The general advice is that no food, taken in moderation, is bad. However, some people react badly to certain everyday foods that can be safely eaten by most other people. When this happens, even the tiniest amount of that specific food can cause a health risk. Symptoms can range from a mild skin rash to life-threatening anaphylactic shock.

The current estimate for the prevalence of food allergy in the UK is that it affects 1.4% (one to two people in 100) of the population. On the other hand 20% (1 in 5) of the adult population believe themselves to be allergic to a food, although tests fail to confirm that this is the case. The prevalence is at its highest in young children (because their immune systems are not yet fully developed) at 5-7%, although 80-90% of sufferers have outgrown their sensitivity by the age of three years.

FOOD ALLERGIES AND INTOLERANCES - WHAT ARE THEY?

Food Allergy: This occurs when the body perceives the food as a threat to its immune system.

Food Intolerance: Food intolerance is more to do with metabolism. Here the body cannot break down certain foods properly, usually because of a chemical deficiency.

Common allergies and intolerances

Wheat

While there has been plenty of press coverage of intolerance or sensitivity to proteins in wheat products recently, there is no evidence that the true prevalence of wheat intolerance is on the increase. Since wheat is such an important staple food in this country, self-diagnosis or a flawed diagnosis from an unqualified alternative therapist could pose a health threat, particularly if it results in poor nutrition.

For those who have true wheat allergies or intolerances, a wheat-free diet can be extremely restrictive, since wheat is often a hidden ingredient in foods such as soups and sauces, ready-meals and even beers. Coeliac disease is the main form of wheat intolerance although it is estimated to have an incidence of only one person in 300.

Eggs

One of the most common causes of food allergy in infants and young children is the egg. Most children, however, grow out of this condition by the age of five. The egg is made up of various proteins, many of which are highly allergenic. Most people with an egg allergy are allergic to the egg white proteins, but there are those who are allergic to the yolk. The egg yolk contains different allergenic proteins than the egg white.

The many foods which contain eggs or egg products include baked goods, baking mixes, batters, cake icing, breaded meats, breakfast cereals, some sweets, biscuits, creamy fillings, custards, some pasta and noodles, fondants, frozen desserts, some sauces, ice cream, marshmallow products, malted cocoa drinks, mayonnaise, meatloafs, meringues, noodle soups, pancakes, many processed meats, puddings, many salad dressings, sausages, some sherbet. Sometimes pretzels, bagels, buns, candy or other baked goods are brushed with egg white to give them a shiny appearance. Cosmetics, shampoos, laxatives and pharmaceuticals sometimes contain egg proteins, so be sure to read the labels carefully.

Seafood

In countries where large quantities of seafood are eaten or processed, seafood allergies tend to be more prevalent. For example, shrimp allergy is more common in the southern United States while fish allergy is more common in Spain and the Scandinavian countries. Factory workers in seafood-processing industries are also highly affected, as well as fishermen and restaurant workers.

Fish allergies are more common in children, whereas shellfish allergies seem be more prevalent in adults. Some breast-fed infants have been sensitized to cod via their mother's milk. These allergies do not usually go away or diminish with age as with some other food allergies. These allergies usually last a lifetime with the reactions becoming more severe with each subsequent exposure.

Peanuts

Although this type of allergy is much publicised, the prevalence of peanut allergy is not known. Some studies suggest that 0.5% (one person in 200) might be affected to a greater or lesser extent. Studies have suggested that infants can become sensitised to peanuts through breastfeeding, even through cuts and scraps on the skin, or via the lungs following exposure to peanut allergen (e.g. derived from some milk formulas and nipple creams) or via small amounts of allergen present in the air.

There is also some evidence that sensitisation can occur in the womb. Long-term management of peanut allergy consists of careful and complete avoidance of all sources of peanuts. Contrary to many other food allergies, it is rare to grow out of peanut allergy. The food manufacturing industry has become more aware of this allergy in recent years and warnings that products contain nuts or traces of nuts are now common.

Milk

Lactose intolerance is the most common adverse reaction to cows’ milk among adults and adolescents. Before it can be absorbed by the body, lactose (the sugar found in milk) needs to be broken down in the gut by the enzyme lactase before it can be absorbed into the body. When levels of this enzyme are low, large quantities of lactose remain undigested and this can sometimes cause flatulence, bloating, abdominal pain and diarrhoea.

The inability to breakdown lactose in the gut runs in families and is more prevalence among some racial groups than others. Lactase deficiency is present in about 5% of white British people and a larger proportion of those from some ethnic minorities. Having reduced levels of lactase does not necessarily imply that lactose cannot be digested. Some people are more sensitive than others and for some the more dairy products eaten the more severe the reaction, as lactose intolerance is dose-dependant.

Therefore many individuals who are lactase deficient can usually tolerate small amounts of dairy products. Patients with severe lactose intolerance can usually eat yogurt, hard cheeses and lactose-reduced milk and all are encouraged to eat these as a source of calcium and other nutrients.

Common symptoms

Symptoms of food allergies vary between individuals but can include the following:

- Stomach cramps, diarrhoea, vomiting

- Headaches

- Hives

- Swelling of the lips, mouth and throat

- Difficulty breathing

Diagnosis of food allergy and food intolerance

Although it’s sometimes easy to blame food when you don’t feel 100%, never try to diagnose your own food allergy. You could be risking an imbalance in your diet and maybe even a nutritional deficiency.

Allergic reactions to foods can be measured by blood tests and sometimes skin prick tests, although these are less reliable. A proper diagnosis should always be sought. Do not start removing foods from your diet without consulting a doctor or dietitian.