Environmental medicine
Allergy and intolerance
Food allergy is a very clear and unpleasant reaction to foods. For instance,
if somebody is allergic to shrimps or peanuts they will, within a fairly
short time of ingesting them (usually minutes), experience an immediate
allergic reaction which may give rise to unpleasant swellings in the
face or throat and sometimes acute asthma. Usually such reactions pass
within 20 or 30 minutes and can be treated with anti-allergic drugs such
as antihistamines. Sometimes they can be potentially life-threatening
as they progress to anaphylatic shock. Anaphylaxis is a very acute and
life-threatening allergic reaction in which the throat and breathing
tube become so swollen that they close up for a short period of time.
Anaphylaxis is completely reversible with an injection of adrenalin.
If you have a true food allergy then you must seek the advice of a conventional
allergist and carry with you at all times an adrenalin injection in case
you inadvertently eat the food to which you are allergic. Food allergy
is usually quite straightforward to diagnose on a basis of blood and
skin tests and requires complete and lifelong avoidance of the food to
which you are allergic.
Food intolerance works through different physiological mechanisms to
allergy, these mechanisms have not yet been clearly defined. However,
clinically, a variety of diseases will improve with long-term food avoidance.
These illnesses include migraine, arthritis, inappropriate or hyperactive
behaviour among children, childhood eczema, irritable bowel syndrome
and inflammatory bowel disease such as colitis and Crohn's. All of these
conditions have been shown to have a dietary link. There is no particular
food for any specific condition, but there is an individual diet that
a sufferer may need to follow in order to improve their condition.
While the mechanism of food intolerance is unclear, it is clear that
people with these conditions may actually be addicted to a particular
food that they have in different forms at regular intervals during the
day. For instance, a child with eczema may be eating largely milk, yoghurt
and cheese. Food "addiction" often runs side by side with food
intolerance.
Furthermore, the intolerance is masked; until the susceptible individual
has avoided the food, often for 3 or 4 weeks, no clinical improvement
may occur. While this phenomena of food intolerance is well documented,
and there are a number of studies which demonstrate benefit, there is
no completely reliable method for diagnosing food intolerance.
Placing people on diets that are unlikely to contain allergens is the
simplest but also the most time-consuming diagnostic process. For instance,
a "stone age" diet of fruit, meat and a few vegetables will
often clear symptoms over a 3 or 4 week period, but then foods need to
be reintroduced very slowly and the individual's acute reaction to those
foods carefully monitored over a month or two in order to define the
foods to which they are intolerant.
A variety of unconventional tests have been used to work out "safe"
and "unsafe" foods on an individual basis. Some of these involve
muscle testing or applied kinesiology, while others involve unconventional
blood tests in which food extracts are placed in a small tube along with
red and white blood cells, and the reaction of the blood cells is monitored
microscopically. Testing acupuncture points in a "circuit" and
seeing how various foods may influence skin resistance is also used to
diagnose food intolerance. The mechanism of this process (Vegatesting)
is unclear. None of these tests is completely reliable and none of them
have been satisfactorily scientifically validated. However, both practitioners
and patients do find some of these tests valuable in a clinical context.
Do diets produce benefits?
Modifying our modern diet removing "junk food" would certainly
have a benefit on both our own and our children's health. There is also
clear evidence that in some instances specific food avoidance diets are
of benefit in certain conditions. The use of dietary intervention in
childhood behavioural problems has been discussed in the medical literature
for the last 45 years and while diets are not the only mechanism of managing
this condition, the evidence that they may be effective in a significant
proportion of children is overwhelming. Relapse rates in bowel inflammation
(inflammatory bowel disease includes Crohn's disease and ulcerative colitis)
are clearly reduced if people avoid the specific foods that upset them.
While we know that food intolerance does have an effect on some illness
processes, there is much confusion about its use in clinical practice,
partially because we have no clear mechanisms for how it might be working
and partially because of the very unconventional and unreliable nature
of the tests that are employed to ‘unmask’ food intolerance.
