By James Collier BSc (Hons) RNutr – Contributor in Nutrition
We frequently here people say that they’re ‘allergic’ to a particular food, and if you always took this to be the truth, almost everybody would be allergic to something or other! Obviously this is not the case and people incorrectly use the term ‘allergy’.
When used correctly, ‘food allergy’ refers to a hypersensitivity reaction to a particular food or constituent of a food mediated by substances in the blood called immunoglobulins. Antibodies are produced in response to the food being miss-recognised as a foreign, dangerous particle.
Allergies are basically the body’s own immune system gone wrong, and examples include nut allergy and atopic eczema cause by food. Symptoms can be initiated by even a minute amount of the offending food and can vary from a mild rash, swelling or an upset stomach, to severe anaphylactic shock which is life-threatening without medical treatment.
Often allergies are manifested in childhood while the immune system is still maturing, and in some cases sufferers can ‘grow out’ of the allergy. Less sensitive people may be able to tolerate small amounts of the food to which they are allergic. Other allergies may only appear in adulthood due to a later exposure. One in three people believe he/she has a food allergy, yet only about 1% of adults suffer from a true food allergy.
In adults, common allergic reactions are caused by fish and shellfish, peanuts and nuts such as walnuts or pecans, and eggs. In children, common food allergy culprits are milk, egg, peanuts, wheat, and soya.
Symptoms usually appear within a few seconds or minutes, although in some conditions, for example Coeliac disease, the nature of the reaction means that the sufferer may not be aware of the symptoms, until damage builds up over a period of time.
Unlike food allergies, a ‘food intolerance’ does not involve the immune system; rather it is a physical problem by an irritant or poor digestion of a food. The physical symptoms of a food intolerance, however, such as intestinal discomfort, can resemble those of a food allergy, therefore a food intolerance reaction may be easily confused with an allergic reaction. Examples of this are irritable bowel syndrome (IBS) and intolerance to lactose. Although food intolerances are far more common than allergies, people still blame too many of their ailments on food intolerance, when in reality food may not be involved.
Symptoms usually occur from between a few minutes up to a couple of days after eating an offending food. A person with an intolerance may be able to eat small quantities of the food without a problem, and only be intolerant to it at higher levels, for example in lactose intolerance, or alactasia, which is a genetic deficiency in the enzyme lactase which is involved in digesting the milk sugar lactose.
In lactose intolerance it is extremely rare to be able to synthesise any lactase at all, but it is not uncommon to have lower than normal levels of the enzyme. Such people can digest small amounts of dairy produce perfectly fine, but larger amounts cause abdominal discomfort, bloating and loose stools. Furthermore, if the individual has no milk products for a few weeks, and then has a small amount or milk, they’ll find they are less tolerant than previously, whereas if they continue to have a small amount daily, they can generally tolerate this amount with zero problems.
There are a vast number of clinics and health food shops which offer a multitude of ways to test for, diagnose and treat food allergies/intolerances. Such tests are frequently very expensive and procedures include skin, nails, hair and muscle tests concluding with a list of foods which the client is supposedly ‘intolerant’ too. There is no evidence validating these sort of tests, but they remain popular, as, due to the technical nature of the test, people feel they have had some good information. If they do have favourable results it may be that in effect, they are now following a healthy diet due to being more aware of what they are eating.
Some food intolerance testers inform clients that they may be intolerant to certain foods even if they have no symptoms, using the premise that they will ‘feel better generally’ if they exclude the offending food. Often, though, there is no dietary advice provided as to which foods the client can include in order to stay healthy. In particular watch out for allergy tests which say you are ‘slightly allergic’ to something. With genuine food allergies you either are or are not allergic to something, there’s no in between, and in genuine allergies you must eliminate the offending food from your diet entirely.
There are some tests which are more reputable, but these are generally expensive or hard work to follow. One such test is the RAST test where blood levels of immunoglobulins and white blood cells are measured in response to a potential allergen. This procedure is very expensive, complex and time consuming and has to be undertaken under specific clinical conditions at certified clinics for allergy testing. There are few in the UK and access via the National Health Service is limited.
Indeed few NHS trusts even employ an allergist, so access to a specialist is very difficult. Fortunately many Registered Dietitians across the world are au fait with treatment of food allergies and intolerances and can advise on the best cause of action in liaison with your doctor.
Other than direct food intolerance tests, your Registered Dietitian or Registered Nutritionist may be able to help you diagnose and/or treat food intolerance by other methods. One of these is the exclusion diet, which is one of the most effective ways of discovering a true food intolerance or allergy. This procedure involves excluding all foods most likely to cause food intolerance for at least two weeks. If symptoms have cleared, this is followed by a period of controlled reintroduction of foods, where reactions are assessed. This diet is very restrictive and hard work and may take months to complete. It has to be supervised by a professional and adhered to strictly. It is however a very effective way of identifying offending foods, or, indeed, if the intolerance is nutritional in origin at all.
If the client has an idea as to which foods are offensive, in liaison with a dietitian/nutritionist, they can discuss an elimination diet, where all foods and food products containing the suspected offender can be eliminated from the diet and symptoms monitored. There is a lot of trial and error with this way, but it is quite popular as it is no where near as restrictive as the exclusion diet.
Another dietary regimen is the moderate fibre, low irritant diet used to treat some cases of IBS with considerable success. This involves cutting down on all fatty products and fibrous foods which may irritate the bowel, while at the same time encouraging a good fluid intake and fibre from foods which are less likely to irritate the bowel. Examples of foods to cut down on include nuts, pulses, seeds and tough skins and stalks, and consuming large amounts of wholemeal products, leafy and root veg and peeled fruit instead. The low irritant regimen is successful in milder cases of IBS; more extreme cases may have a gut motility problem and need more in depth treatment.
Food choices and physical performance
Once a true food allergy/intolerance has been diagnosed, strict avoidance of the offending food(s) is the only treatment. Read food labels carefully as sometimes the food may be present in manufactured products. Legislation on food labelling is improving but still cannot be relied upon, so for additional information, contact the food company. When eating out, ask about ingredients and how the dish was prepared. Always heed the phrase: ‘If in doubt, leave it out’. Lists of free-from foods are an invaluable aid and are available from your dietitian/nutritionist, on the internet or from supermarkets and health food stores.
For optimal health and physical performance there is no single food you need to have, so if you do have an intolerance, do not worry, there are plenty of other foods you can consume to ensure good nutrition. For example, milk is one of the more common offenders, but there are loads of calcium-enriched alternatives available which are also high in protein and energy. The same applies for wheat allergy where alternatives include rye bread, rice cakes and rice pasta.
As milk and dairy products are a good source or protein and calcium, people who are genuinely lactose intolerant need to look out for other good sources. Meat, poultry and fish are obvious high protein sources, with sardines and pilchards being especially useful due to their high calcium content (as well as being rich in essential fatty acids). There are plenty of milk alternatives available, especially soya products, many fortified with calcium: soya milk, yogurts and desserts. Rice, oat and coconut milk can also be bought from health food stores. Eggs, quorn, pulses, nuts and tofu are other good sources of protein, especially for the lactose intolerant vegetarian.
Don’t self diagnose food allergies and intolerances, but if you suspect you have one seek the advice of a qualified professional who can also help you devise a suitable dietary regimen to ensure optimal physical performance.