taking and observation of food-related
reactions may indicate the source of
The food history should include:
- Identification of suspect food,
drink, sweets / candy, or chewing gum.
- What is the time lag between eating
and development of symptoms?
- What types of symptoms ensue?
- What amount of food is required to
- Does the reaction occur with every
ingestion of the food?
- Does the reaction only occur under
certain circumstances, e.g. exercise or
- When did the last reaction occur?
- Do allergies exist, e.g. hay fever,
- Do other family members have food
reactions, if so, which?
Breath tests are the most useful and
non-invasive tests for determining the
various sugar (e.g. fructose, lactose,
sucrose) and sugar alcohol (e.g.
sorbitol, xylitol) intolerances. They
are well validated, widely used, but
some discussion still exists about the
ideal test conditions. These tests
should not be used in infants and
reduced doses of test compound are used
in children. The tests procedures are
identical for all the intolerances (View the videoclip)
Purchase breath tests by clicking here
. Following are important details regarding the test procedure.
- Dietary restrictions, no smoking or
excessive exercise from the day before
testing and no antibiotics or
colonoscopy in the last week pre-test.
- Ingestion of a specific amount of
the sugar or sugar alcohol to be tested
- Regular breath samples taken for a
standardized period (at clinic or at
- Diary of symptoms during the next
day for calculation of the symptom
- Measurement of specific gases, e.g.
hydrogen and methane, in the breath
An intolerance is diagnosed based on the
symptoms following the test and the gas
concentrations in the breath samples.
The diagnosis is confirmed by a
significant decrease in symptoms whilst
on a diet low in the poorly tolerated
sugar or sugar alcohol. Expert dietary
advice is very helpful for the
identification of food and drink
containing the difficult-to-spot
offending ingredient. (Inquire about online dietary advice by clicking here). Examples of such
ingredients are so-called hidden lactose or fructans in vegetables or whole-meal
Direct enzyme quantification in tissue
Direct enzyme levels can be determined in biopsies of the small intestine. Only a few laboratories can perform these complex analyses, including our own (click here for link to clinic). Sucrase-isomaltase deficiency, a quite rare genetic disorder, is preferentially diagnosed using this method.
Genetic testing is available for some of
the sugar intolerances. (Possible in our clinic).
intolerance: the severest genetic
form of intolerance (CC13910 / GG22018
i.e. homozygotes) can be very reliably
diagnosed using a simple genetic test
with cells taken, for example, from the
inside of the cheek. The breath test is
abnormal in all these individuals. Those
with an intermediate genetic form of
intolerance (CT13910 / GA22018 i.e.
heterozygotes), which are the majority
of individuals, have a wide range of
intolerance severity to lactose. This is
most usefully assessed using the breath
test measuring the actual effect of
lactose ingestion. Even a sizeable
percentage of individuals without the
genetic signature of intolerance
(TT13910 / AA22018) have lactose
intolerance. In summary, breath testing
is overall the most useful form of
testing. Genetic testing reliably
identifies a proportion of severely
affected individuals and is also useful
in screening larger numbers of
individuals or relatives of patients
Order Tests online).
intolerance due to malabsorption (common
no specific genetic test is currently
available. Testing is by breath test
Order Tests online).
Hereditary fructose intolerance (HFI): about 70% of genetic aberrations (polymorphisms) associated with HFI can currently be identified and these should be determined in case of clinical suspicion, due to the lifelong and possibly severe consequences of not excluding fructose meticulously from the diet (These tests can be performed at our clinic . Click here for a link to the clinic).
Sucrase-isomaltase deficiency (sucrose - starch intolerance): genetic
analysis from duodenal biopsies is not widely available, but has demonstrated
several genetic polymorphisms, i.e. abnormalities.
xylitol intolerance: no specific
genetic tests are currently available.
Testing is by breath test (See
Order Tests online).
Other tests: stool, blood
Various stool tests, including pH tests, have
been used, but they should no longer be
advocated except for testing in infants.
Measurement of blood glucose following
ingestion of lactose (lactose tolerance
test) is less specific than breath
testing and is susceptible to more
interference. Use of this test is
diminishing and should be discouraged.
Wilder-Smith CH et al. Fructose and lactose intolerance and malabsorption testing:
the relationship with symptoms in functional gastrointestinal
disorders. Aliment Pharmacol Ther 2013