Dietary Intolerance
 Adverse
reactions to ingredients in the diet may well be one of the
commonest yet least recognised causes of ill-health in pets
and humans.
In
theory, any dietary ingredient can cause an intolerance. In
practice, protein (e.g. beef, milk) or carbohydrate (e.g.
wheat, lactose) sources are the most likely causes although
it is possible that chemical additives such as food colourings
and preservatives could cause a reaction.
Understanding
and recognising dietary intolerance is not helped by pet food
legislation which allows pet food manufacturers to declare
ingredients such as “animal derivatives and cereals”
rather than naming the actual ingredients. This means that
one cannot know precisely what one is feeding and the ingredients
can be changed at will.
In
general, adverse reactions to food can be divided into those
which act through the immune system (allergy) and those which
do not (intolerance). Although the mechanisms of the two are
different, the symptoms are indistinguishable.
Signs
of intolerance (symptoms) vary widely and are not well understood
or documented.
A reaction can be instantaneous or delayed, even for several
days. It can be mild and ill-defined causing non-specific
signs of ill-health such as lethargy, loss of appetite, abdominal
pain, stiffness, unthriftiness, unpleasant body odours, bad
breath, discharge from orifices and so on.
At
the other extreme an adverse reaction can be severe and unmistakeable.
An anaphylactic reaction can cause shock and death. Some people
with an allergy to nuts are affected in this way.
In
theory, any organ or system can be affected and this can give
rise to a wide range of symptoms.
In
dogs dietary intolerance most commonly affects the skin or
digestive system causing disease/disorders related to these
organs. This might be eczema, itchy skin, dermatitis, otitis
(ear inflammation), vomiting, diarrhoea, colitis, gastroenteritis,
pancreatitis, hepatitis, abdominal discomfort etc.
Other
organ systems can also be affected e.g. immune system, musculoskeletal
system, nervous system, endocrine (hormonal) system. Any symptom
or disease affecting any of these organ systems could be caused
by a dietary intolerance. This would include arthritis, convulsions
(epilepsy), abnormal behaviour, allergic (pollen, house dust
mite) and inflammatory reactions (pancreatitis, hepatitis),
susceptibility to infection, Cushing’s, Addison’s,
under- and over-active thyroid etc.
Long-term
unrecognised dietary intolerance may be the underlying cause
of degenerative diseases such as heart or kidney failure and
cancer.
 It
is probably true that dietary intolerance is much more prevalent
than pet owners and veterinary surgeons realise. There are
diagnostic tests but these are only possible for the minority
which involve the immune system. In any case they are inaccurate
and even misleading in that they produce both false-positive
and false-negative results.
Any symptom of ill-health which persists despite treatment
or which recurs after treatment should arouse suspicion of
food intolerance.
A feeding (elimination)
trial is the only reliable method of diagnosis. This involves
eliminating the existing food from the diet and replacing
it with a food which is new to the animal. Home-made food
allows more control over ingredients but a commercial food
which is low fat, low protein and easily digestible may be
more suitable for long-term use. If symptoms improve when
the suspect food is eliminated then it can be presumed that
a dietary intolerance was responsible. Confirmation would
require the re-introduction of the suspect food to see if
the symptoms recur but, of course most pet-owners will be
understandably reluctant to take that step.
Disorders
of the digestive system which are due to dietary intolerance
often disappear within a few days of eliminating the food
which is responsible but most disorders will take 3-4 weeks
to respond to removal of the offending food.
Most
cases of dietary intolerance (those where the immune system
is not involved) are dose-sensitive. This means that the amount
of food can determine whether or not signs of intolerance
will disappear. This is why it is important that whatever
food is given, it should be fed sparingly.
It
is likely that many people suffer from undiagnosed dietary
intolerance with similar consequences except that the respiratory
system is more commonly affected than the skin.
|
