Lactose Intolerance (cont.)
How are lactase deficiency and lactose intolerance diagnosed?
Although there are several good ways to diagnose lactose intolerance, most
people who consider themselves lactose intolerant have never been formally
tested for intolerance. This is unfortunate because at least 20% of people who
think they are lactose intolerant are not, and 20% of people who think they are
not intolerant, in fact, are intolerant.
Why should so many people believe that they are lactose intolerant when they are
not? This erroneous belief may be common for several reasons. People with unexplained
(undiagnosed) gastrointestinal symptoms are looking for an explanation
for their symptoms. Since lactose intolerance is a well-known condition,
it provides these people with a ready (and welcome) explanation for their
symptoms. Confirmation that lactose intolerance is present often is made subjectively
and without careful correlation between ingestion of milk or milk
products and symptoms.
Formal testing for lactose intolerance is valuable. Not only can testing
confirm lactose intolerance and prompt the institution of a reduced or
lactose-free diet, but it also can exclude lactose intolerance and direct
attention to diagnosing other conditions and diseases that are responsible for
the symptoms.
Elimination diet
Probably the most common way that people self-diagnose lactose intolerance is
by an elimination diet, a diet that eliminates obvious milk and milk products.
There are several problems with this type of "testing."
- Milk products are so common in prepared foods from the supermarket or restaurant
that it is likely that an elimination diet that is not rigorous (i.e.,
does not eliminate all milk-containing products) will still include substantial amounts of
milk. Thus, persons with severe lactase deficiency attempting an elimination
diet may be ingesting enough lactose to have symptoms and erroneously conclude
that lactose intolerance is not responsible for the symptoms.
- People often make the assumption that they are lactose intolerant based on
a short trial of elimination. A short trial may be adequate if symptoms are
severe and occurring daily, but not if the symptoms are subtle and/or variable.
In the latter case, an elimination diet may need to be continued for weeks.
- Because symptoms of lactose intolerance are subjective and variable, there
always is the possibility of a "placebo effect" in
which people think they feel better eliminating milk when, in fact, they are
no better. With subjective symptoms such as those of lactose intolerance, a
placebo effect can be expected
to occur 20%-40% of the time.
If an elimination diet is to be used for diagnosing lactose intolerance, it
should be a rigorous diet. A rigorous diet requires counseling by a dietician or
reading a guide to a lactose-elimination diet. The diet also needs to be
continued long enough to clearly evaluate whether or not symptoms are better. If
there is doubt about improvement on the diet, particularly if symptoms normally
fluctuate in intensity over weeks or months, repeated periods of lactose
elimination should be tried until a firm conclusion can be drawn. Elimination of
all milk products should eliminate symptoms completely if lactose intolerance
alone is the cause of the symptoms.
Next: Milk challenge »
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