(When you react to
food...an allergy or an intolerance continued)
by Tish Richardson PhD.Food intolerance
While the
incidence of food allergy remains relatively very low, albeit with
recent notable increases in the incidence of allergies to foods such
as peanuts and sesame seeds, the incidence of the second form of
food sensitivity, namely food intolerance, is far more widespread
and, unlike food allergies, is prevalent amongst adults.
Unfortunately, the term ‘food intolerance’ is often confused and
interchanged with the term ‘food allergy’—but as mentioned above,
the pathways of these two reactions are, however, very different.
Their differentiation is important to ensure the correct diagnosis,
in understanding what and how the food is affecting you and,
importantly the ongoing management to optimise your health and
well-being in both the short and long term. Since, in many cases of
food intolerance there is no immune system involvement, no simple
test such as the blood or skin prick test used in diagnosing a food
allergy, is available to simplify diagnosis of a specific food
intolerance.
Given that the symptoms of food intolerance are usually more
vague than those resulting from a food allergy, they are often
confused with other medical problems. For example, symptoms commonly
associated with food intolerances can range from a recurrent feeling
of ‘just being off it’ or continual tiredness, to headaches, sleep
and concentration disturbances, stomach ache or distension,
diarrhoea or irritable bowel syndrome, eczema, asthma, joint pain,
depression or behavioural problems to name but a few. In most cases
food intolerance is initially suspected but diagnosis
usually starts with investigations to rule out any medical condition
that could be the cause of the presenting symptoms. Obviously, the
test results will be negative—and for those people with a food
intolerance in whom the reaction mirrors that of an allergic
reaction, the return of a negative allergy test is all the more
confusing.
Once a medical cause has been eliminated, a food intolerance
might just then be suspected and diagnosis at this stage might seem
quite simple—just eliminate any suspect food from the diet. But in
reality this can be quite complex—in the absence of simple tests,
where to start? Often there is no clear pattern to the symptoms to
enable pinpointing a food, more than one food may be problematic
with different foods causing different reactions. The onset of the
reaction may be delayed by up to 20 hours or more, and may not even
be triggered if only small amounts of the food are eaten or unless
it is eaten on consecutive days. Identification of the offending
food suddenly becomes all the more complex.
So which foods most commonly result in a food intolerance and
what in the food is responsible for the reaction? The cause can be
either a substance that occurs naturally in a food or one of the
myriad of artificial additives. For example, there are foods that
naturally contain a high level of certain chemicals, such as
salicylates or glutamates, monosodium glutamate including (MSG). The latter, for example, is
found in significant levels in foods such as tomatoes, corn,
mushrooms and parmesan cheese. Or, alternatively, the chemical may
be added by a food manufacturer to enhance some aspect of the food,
be it its colour (artificial colours), shelf life (preservatives),
flavour (flavour enhancers—such as MSG, additive 621), etc.
In addition to these chemically-evoked food intolerances, other
naturally occurring components of foods can elicit food
intolerances, perhaps two of the best known of which are gluten
intolerance and lactose intolerance. These again have very different
physiological bases.
It is now estimated that as many of 1 in 250 Australians cannot
tolerate gluten, one of the proteins found in wheat
and other grains (such as rye, barley and spelt). In many gluten intolerant
individuals, ingestion of this protein leads to marked changes in
the structure of the lining of the gut wall (coeliac disease), which
in turn leads to malabsorption of nutrients, the loss of some
digestive enzymes and a raft of other symptoms. Another well-recognised
effect is the development of in an itchy skin condition called
dermatitis herpetiformis.
Lactose is the naturally occurring sugar that is found in dairy products.
Lactose intolerance results from a deficiency of the enzyme
lactase in the intestine; lactase is responsible for the digestion
of the milk sugar prior to absorption. The lack of ability to digest
the milk sugar typically results bloating, gas, diarrhoea, stomach
discomfort and pain.
These intolerances will be discussed in more detail in sections
on ‘The Gluten-free Diet’ and ‘Dairy and Lactose Sensitivities’.
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