lactose intolerance
by Dr Stephanie B Matthews Professor Anthony K Campbell
Welston Court Science Centre Department of Medical
Milton Biochemistry and Immunology
Cardiff University
Advances in the diagnosis of lactose intolerance - experiences from
Dr Stephanie Matthew’s Clinic, Cardiff
Summary
A new definition for Lactose Intolerance and Lactose
We have made discoveries about the symptoms of
Sensitivity
people who are sensitive to lactose, the sugar in milk, and
We prefer to use the term lactose sensitivity rather
their cause. Dietitians now need to revise their approach to
than lactose intolerance as everybody has their own
the management of people with lactose sensitivity and food
threshold and can tolerate some lactose. In some
intolerance.
people the threshold is the amount in a cup of tea and
Our food intolerance clinic was started in 2001. One
in others it can be equivalent to over a litre of milk.
of the early patient groups were people we had seen in
The first breakthrough was that the syndrome of lac-
the lipid clinic with dyslipideamia who were suffering from
tose sensitivity described in the textbooks and taught to
muscle pain and were being recommended to stop their
medical students, dietitians and other health profession-
statin therapy. This became unnecessary as the cause of the
als, was incorrect. The conventional wisdom in 2000 was
pain was shown to be a food intolerance. The clinic ran for
that lactose sensitivity caused osmotic diarrhoea after
six years during which time the audit process led to our rec-
ingestion of too much lactose and was accompanied
ommended diagnostic and treatment protocol (Fig 1 and
by bloating, flatus, abdominal pain and borborygmi. The
ref 1). Unfortunately the clinic was closed by the NHS in 2007
cause was low lactase enzyme in the small intestine (hy-
because of funding difficulties, having seen more than 1,000
polactasia) and could be controlled by reducing dairy
people and with many hundreds still on the waiting list.
products in the diet. It was treated as a mild, if irritating
condition only really of note when found transiently in
What is lactose? children following gut infections.
Lactose is two simple sugars linked together to form We now know that this is only partially correct. Lactose
the disaccharide, galactose β 1,4 glucose. It is the sensitivity does cause gut symptoms, but in 30 percent of
sugar in the milk of all mammals, apart from the Pin- cases the main complaint is of constipation, not the diar-
nepedia (sea-lions and walruses). rhoea (2,3,4). The constipation can be severe and there
is often a history of problems since childhood. It can also
lead to severe nausea and vomiting. The diarrhoea can-
Recommended management in patients investigated
not be osmotic and is more likely to be due to a signal-
for lactose sensitivity
ling mechanism analogous to the cholera toxin (5).
• Buccal sample for polymorphism C/T-13910 analysis. Importantly, lactose can also cause a wide range of
• If CC immediate removal of all lactose from diet. If symptoms
systemic symptoms shown in fig 2. The most prevalent
improve after one month diagnosis of lactose sensitivity confirmed.
are the fatigue, headache, loss of concentration and
difficulty with short-term memory, and joint and muscle
• If CT or TT carry out lactose tolerance test.
pain. These symptoms can be very severe and persis-
• New lactose tolerance test:
tent. They have been missed for many reasons. First is
a. 50g (1g/kg for children) oral lactose.
because of the spasmodic nature of the symptoms, dif-
b. Record breath hydrogen every 30 min for 3h, then
hourly up to 6h.
ferent symptoms occurring in different people and also
c. Record all symptoms for 48h.
within the individual over time. Mainly though, the prob-
lem stems from the overspecialisation within medicine
• If the breath test is positive, advice to change to a lactose free
and lactose sensitivity not being recognised as a whole
diet is given.
body problem. This has led to non-diagnosis, misdiagno-
• Every patient should be followed up in 12 weeks for a definitive
sis, over prescribing and invasive investigations. Many in
diagnosis. If the referred symptoms have significantly improved
the medical professions have been dismissive, and those
the diagnosis of lactose intolerance made.
striving to help were hindered by lack of information.
• If the breath test is negative, but there is a significant increase
The patient often becomes depressed, socially restricted
in symptoms after the lactose load, the patient should undergo
(knowing the location of every public toilet), and chil-
a supervised trial to determine their lactose threshold.
dren underachieve.
• Family studies to determine other affected individuals.
• Hypolactasia caused by infections such as Giardia or rotavirus
The genetics of lactose sensitivity
should be investigated if there is no evidence of family history. Lactose is hydrolysed by the enzyme lactase (6,7),
• Give advice on lactose free meals, and danger of hidden
found only in the small intestine. All mammals, apart
lactose.
from white Northern Europeans (Caucasians) and a few
other ethnic groups such as the Bedouins and African
• Follow up in 1 year.
dairying tribes such as Fulani, are hypolactasic, i.e. they
• Calcium and vitamin D status should be monitored, and advise
have a low lactase. This is because they lose some 80-
given on the use of probiotics.
90% of the enzyme within a few years of weaning. The
Fig 1
precise molecular mechanism causing this loss of lactase
NHDmag.com Aug/Sep ‘08 - issue 37 17
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