What to eat?
We choose the food we eat based on a variety of reasons: taste, availability, cost, quality, dietary reasons. However, for a minority of people within society, eating particular foods can be particularly dangerous or even fatal. From dairy causing gastrointestinal upsets, to seafood causing anaphylaxis, food intolerance is a serious health concern.
What is Food Intolerance?
There are various causes of food intolerance, which causes a reproducible adverse response to a particular food. It can occur regardless of whether a person knows that they have eaten the food. In general, food intolerance includes immune system responses (eg. peanut allergy, coeliac disease etc.), enzyme deficiencies causing adverse reactions (eg. lactose intolerance), pharmacological reactions (eg. caffeine sensitivity), and other undefined responses. It is important to make the distinction between food intolerance and food poisoning. Food poisoning involves the ingestion of known poisons such as bacteria, viruses, chemicals, and toxins.
How Frequent is it?
Food intolerance affects approximately 5-8% of children, with the incidence rising. Fortunately, most children grow out of the intolerance with less than 1-2% adults with the problem. Interestingly, a much larger percentage of adults believe they are food intolerant when in fact they are not. Diagnosing food intolerance involves taking an accurate clinical history, and possibly allergy insensitivity testing. Some cases of food intolerance can be extremely limiting, associated with multiple food intolerances and allergies.
The most common food intolerance is usually in the form of an allergy that usually involves an adverse immune response following food consumption. Symptoms are often associated with the gastrointestinal system. These include nausea, vomiting, spitting up of food, colic pain, diarrhoea, and in children, a failure to thrive. However, in severe cases, an allergic response may manifest into anaphylaxis, with a rapid fall in blood pressure, shock, and acute respiratory problems. Most food allergies are recognised during childhood, the more common ones being milk, eggs, soya, peanuts, and wheat. In adults, the more common reactions are to shellfish, fish, peanuts and tree nuts.
Common food allergens
Cows’ milk, hens’ eggs, peanuts, tree nuts, soya beans and soya products, fish, shellfish, and gluten containing cereals—for example wheat (which causes a delayed response known as coeliac disease)
The Immune Response
Most cases of food allergy and intolerance are due to IgE-mediated immune responses. IgE is an antibody naturally produced by the body to act as a mediator of the immune system against infection. Unfortunately, higher than normal levels of IgE can cause inappropriate immune responses to non-infectious material, such as foods. In an allergic response, IgE binds to the allergen and causes a cascade of reactions to occur resulting in the stimulation of mast cells that release large quantities of histamine. This is usually associated with immediate reactions, however other more complex mechanisms involving T-cells are responsible for delayed reactions.
A Possible Explanation for the Increase in Food Intolerance
Many people are aware that the rate of food intolerance in children is increasing, and often the question is “why?” A current theory to explain this phenomenon recognises the early developmental role of T-helper cells, which regulate immune responses. In an allergic response, the increase in IgE is due to an imbalance in the ratio of T-helper cells (T-helper type 2 over T-helper type 1). Initially, Th2 is produced by the growing foetus to protect against immunological foetal rejection by the mothers immune system. After birth, Th2 acts to stimulate the generation of IgE against parasite infections. However, this process is regulated by Th1 to limit the overproduction of IgE. It has been proposed that the persistence of the Th2 response causing IgE excess is possibly related to improved or altered nutrition. Furthermore, the absence of early childhood infections (down regulating the effect of Th1) may also account for the increased rate of food allergies. It seems that our efforts to improve sanitation from infection, may in fact be a catch-22 in terms of allergic disorders.
Therapy for food intolerance consists of avoidance of the specific food, with antihistamines and steroids being required in severe forms of the disorder especially when the food is essentially unavoidable. Complementary and alternative medical approaches involve naturopathy, acupuncture and homeopathy. Immunotherapy has also become available where the patient is exposed to small doses of the irritant, in order to induce tolerance, however this should be conducted with the appropriate resuscitation equipment and expertise on hand. In emergency situations involving anaphylaxis, adrenaline delivered via an intramuscular pen device is required. People with this severe form of the condition are usually advised to carry an up-to-date adrenaline pen.
Food manufacturers are increasingly more likely to display potential allergens on produce, so it is important to watch what you eat. Food intolerance is a potential health danger in early childhood, therefore being aware of the symptoms of intolerance is important in early recognition of the condition. If you suspect you have a food intolerance or allergy, a health practitioner may help you to monitor and deal with the condition, and may potentially help you to avoid further complications. Although there is a lack of effective treatments for food intolerance, a better understanding of the condition may result in more successful alternatives.
- Buttriss, J, (2001). Food allergy and intolerance: what are the facts? Student BMJ, 9:pp367-9.