LACTOSE
INTOLERANCE
GIJ Stear, BSc Diet
K Horsburgh, BSc Diet
2
HA Steinman, MB Chb, DCh, Dip AvMed, IMM
–
A REVIEW
1
2
Registered Dietitian, Cape Town, South Africa
Food and Allergy Consulting and Testing Services
(FACTS), Cape Town, South Africa
1
2
lactose tolerance only when intolerance is clinically
proven. With the help of a qualified dietitian, individual lactose tolerance threshold levels can be determined to adjust the amount of lactose that can be
consumed comfortably at any one time. Strategies
are discussed to ensure this inclusion of milk and
other dairy products without implementing strict
elimination diets.
ABSTRACT
Cow’s milk allergy and cow’s milk intolerance are
often used interchangeably, resulting in confusion in
clinical practice and public understanding. Cow’s milk
intolerance refers to non-allergic, non-immunological
reactions to cow’s milk such as disorders of digestion, absorption or metabolism of certain cow’s milk
components. It is generally a benign condition with
mild, nonspecific and highly individual symptoms limited to the gastrointestinal tract (diarrhoea, bloating
and distension, flatulence and abdominal pain). The
severity of symptoms varies with the amount of lactose; conditions under which lactose is consumed;
and the ability to tolerate the lactose load.
Congenital lactase deficiency in infants is a rare condition. A primary lactase deficiency is the most common cause of cow’s milk intolerance, affecting all
age groups and may be life-long. Clinical manifestations usually only become evident at puberty or late
adolescence. In contrast, a secondary lactase deficiency is a transient condition which develops secondary to bacterial or viral infection.
Diagnosis of lactase deficiency is made on the basis
of a history of gastrointestinal symptoms, occurring
after and aggravated by milk ingestion; response to
an empiric trial of dietary lactose reduction or avoidance; a breath test demonstrating abnormal hydrogen levels; an abnormal lactose tolerance test; stool
sample for reducing substances or acidic pH; and/ or
small intestinal biopsy to assess direct lactase
enzyme activity
Symptoms are alleviated by complete elimination or
reduced consumption of lactose-containing foods.
Most lactose intolerant adults, however, can consume some lactose without major symptoms,
thereby reducing the need for strict elimination of
dairy (excellent source of calcium, phosphorous,
magnesium, vitamin A, riboflavin and protein). The
literature is explored on how much is needed to
cause actual clinical symptoms.
Controversial associations regarding the role of lactose intolerance in irritable bowel syndrome, infant
colic and inflammatory bowel disease are discussed
as well as the possible beneficial role in reducing the
incidence of ‘developed society’ large bowel diseases in the black African population.
Public awareness and misunderstanding of lactose
intolerance are at an all time high. Health professionals need to alleviate patients’ fears about lactose
intolerance, discuss the importance of calcium-richfoods and recommend dietary strategies to improve
Correspondence: Dr H Steinman, PO Box 565, Milnerton 7435. Tel/fax
021-551-2993, email: [email protected]
114
CASE REPORT
This case report was embellished to illustrate various
aspects of lactose intolerance.
A 20-year-old student presented to his general practitioner (GP) with a 3-day history of vomiting and severe
diarrhoea. Based on a stool culture, a bacterial infection
was diagnosed and the student was treated with the
correct antibiotic. Eating yoghurt or drinking milk
seemed to worsen his diarrhoea and the doctor advised
milk avoidance until it had settled. The diarrhoea started improving 3-4 days later, and once his 7-day course
of antibiotics was complete, his stools had normalised
and his appetite returned.
On his return to campus, he had lunch (tuna mayonnaise sandwich, yoghurt and a cup of coffee with milk)
at the cafeteria. That afternoon, he experienced
abdominal cramping but attributed it to hunger pangs.
To alleviate this, he ate a slab of chocolate and drank
250 ml flavoured milk. Approximately 1-2 hours later,
the cramps worsened and he developed diarrhoea. He
went back to the doctor, concerned that he had another ‘stomach bug’.
Fig. 1. Dairy products that contain lactose.
Current Allergy & Clinical Immunology, August 2005 Vol 18, No.3
Table I. Summary of differences between cow’s milk allergy
and lactose intolerance1,2
Cow’s milk allergy
Lactose intolerance
Prevalence
Low
High – possibly
overestimated
Racial variation
Low
High
Common age
Infancy
Adulthood
Offender
Bovine milk proteins
Mammalian milk sugar
Mechanism
Immunological
Enzyme deficiency
Symptoms
Gastrointestinal, skin,
respiratory, anaphylaxis
Gastrointestinal only
Morbidity
Can be high
Low
Diagnosis
Total IgE level Usually elevated
Normal
Screening
Stool appearance
pH & reducing
substances
Skin testing
In vitro tests
Confirmation Food challenge tests
Breath hydrogen
Lactose tolerance test
Jejunal biopsy
Treatment
Symptomatic medication
Avoid bovine milk completely
Selected substitutes
Reduce milk intake
Selected substitutes
Lactase replacement
Prognosis
Mostly self-limited
Mostly permanent
Prophylaxis
Breastfeeding
Special formulas
Delayed complementary
foods
Enzyme replacement
The following possible causes were considered:
• A possible second infection or incomplete treatment
for the first infection
• Food poisoning
• An allergic reaction to something which he had
ingested
• An intolerance of some kind.
Stool cultures were negative. He had no history of previous food or environmental allergies and after discussing his intake that day, the doctor attributed the
manifestation to possible lactose intolerance secondary
to his previous diarrhoea and antibiotic therapy. He was
advised to eliminate all milk and dairy products for
approximately 5-7 days. To make the transition easier, a
lactose-free milk substitute (soya, rice, oat milk) was
suggested as an alternative. He was told to gradually
reintroduce dairy-containing foods, starting with lower
lactose options, e.g. cheese and yoghurt, after a week.
After a bout of severe diarrhoea, the intestinal mucosa
and the villi are damaged. The degree of damage varies
depending on the severity and duration of the diarrhoea. Lactase is situated in the villi. The damaged villi
and mucosa need to repair before lactase can be sufficiently replenished. Presumably the student’s villi had
not repaired adequately and not enough lactase had
been produced since his infection for him to tolerate
the milky coffee, yoghurt, milk drink and chocolate.
The student followed instructions and the diarrhoea
and cramps resolved. He managed to reintroduce dairy
foods and was able to follow his usual routine again.
Two weeks later, he revisited the GP, again with diarrhoea, severe cramping and bloating.
After ruling out food poisoning and infection, the student’s diet and lifestyle were evaluated. He had started
drinking a flavoured milk drink almost daily. A primary
lactase deficiency was suspected. However, the stu-
dent was not convinced and enquired as
to why he had previously been able to tolerate milk in his coffee, as well as chocolate and yoghurt on various occasions.
Being of black African descent, he had
always had an underlying primary lactose
intolerance with a particular threshold. The
diarrhoea had resulted in damage to the
villi and therefore affected lactase production, precipitating intolerance at a lower
threshold level. Once the lactase had been
adequately replenished, he could once
again tolerate amounts of lactose lower
than his normal threshold, but when he
increased the intake of lactose by drinking
milk frequently, symptoms developed
again.
The doctor and dietitian suggested he
should determine his individual threshold
for lactose tolerance so that he could still
ingest calcium-rich dairy products without
inducing clinical reactions.
BACKGROUND INFORMATION
Adverse reactions to cow’s milk can be
divided into the following:
• Immune reactions:
° IgE-mediated
° Non-IgE-mediated.
• Non-immune reactions – intolerance:
° Enzyme deficiency (congenital,
primary andsecondary)
° Maldigestion
° Metabolic abnormalities
° Psychological aversion.
DISTINGUISHING BETWEEN COW’S MILK
ALLERGY AND LACTOSE INTOLERANCE
Although cow’s milk allergy and cow’s milk intolerance
are different conditions, the terms are often used interchangeably, resulting in confusion in clinical practice.
Cow’s milk allergy is an immunologically mediated
reaction to cow’s milk proteins that may involve the
gastrointestinal tract, skin, respiratory tract or multiple
systems, i.e. systemic anaphylaxis. Cow’s milk intolerance refers to non-allergic, non-immunological reactions to cow’s milk such as disorders of digestion,
absorption or metabolism of certain cow’s milk components. It is generally a benign condition with symptoms
limited to the gastrointestinal tract. The most common
cause of cow’s milk intolerance is lactase deficiency
and it may be life-long.1 Table I summarises the difference between the two conditions.
LACTOSE INTOLERANCE
What is lactose and where is it found?
Lactose is the sugar found in milk and dairy products
(Fig. 1). The lactose molecule is a disaccharide and
requires the digestive enzyme lactase to split it into the
monosaccharides glucose and galactose in order for
absorption to occur.2-5
Lactose content in dairy foods varies and may be influenced by the manufacturing process (heating,
hydrolysing, fermentation)5-7 (see Table II).
Epidemiology and pathogenesis
Lactose intolerance literally means an inability to digest
lactose because of a deficiency of the enzyme lactase,
Current Allergy & Clinical Immunology, August 2005 Vol 18, No. 3
115
Table II. Lactose content in dairy foods
Milk (whole, low fat,
skim milk)
4-5 g lactose/100 ml; 11-13 g
lactose/ 250 ml
Yoghurt (plain)
5 g lactose/250 ml
adaptation occurs to some sugars that remain undigested from the small intestine (non-digestible
oligosaccharides, lactulose). Lactulose ingestion
decreases the colonic pH, thus increasing hydrogen
excretion. This higher fermentative capacity may lead
to a reduction in lactose intolerance symptoms.7,13
Buttermilk
10 g lactose/250 ml
Cream
3 g lactose/125 ml
Clinical manifestations and symptoms
Gruyere cheese
2.9 g lactose/100 g
Ice cream
2.6-3.1 g lactose/100 g
Camembert cheese
Trace amounts/100 g
Butter
0.4 g lactose/100 g
The undigested lactose molecules and products of bacterial digestion result in predominantly gastrointestinal
symptoms including diarrhoea, bloating and distension,
flatulence and abdominal pain. The symptoms are generally mild, non-specific and highly individual.
Persistent, severe gastrointestinal symptoms may indicate another disorder. Psychological and physiological
factors may however also mimic the condition.2,4,5,8,11
The severity of symptoms varies with the amount of
lactose, conditions under which lactose is consumed,
and the ability to tolerate the lactose load. Symptoms
occur between 30 minutes and several hours after consuming lactose-containing food or drink. A person with
low lactase levels won’t necessarily develop intolerance or symptoms after lactose intake.2,4,5,8,11
located in the villus enterocytes of the small intestine.2-10
There are three main types of lactase deficiency:2,5,10
• Congenital
• Primary
• Secondary.
Lactase deficiency in infants (congenital) is uncommon
because lactose is the principle sugar in human milk
and the baby usually has enough lactase to digest the
lactose sufficiently. Most adults lose some degree of
lactase activity after puberty.2-10
Primary intolerance is the most common carbohydrate
intolerance and tends to affect all age groups. Typically,
lactase activity declines with the initiation of complementary feeding and in early childhood to about 10% of
the neonatal level. Clinical manifestations usually only
become evident at puberty or late adolescence.
Partially or undigested lactose remains in the gut and
acts osmotically to draw water into the intestines.
Colonic bacteria ferment the undigested lactose, generating short-chain fatty acids, carbon dioxide, hydrogen and methane gas.2-10
Approximately 75% of the world’s population are
affected by the primary lactase deficiency. Within various ethnic groups, it is present in up to 15% of people
of northern European descent, 80% of blacks and
Latinos and up to 100% of Asians and American
Indians. The age of onset also varies between population groups but symptoms tend to appear during adolescence. Although 75-85% of white adults of northern
European descent and some ethnic groups in India,
Africa and Mongolia retain high levels of lactase, it
remains half that of the other saccharidases.2,3,5,6,8,9,11
Maintenance of the lactase enzyme into adulthood is
attributed to inheritance of an autosomal-dominant
mutation that prevents the maturational decline of lactase expression. This genetic mutation is thought to be
evolutionary, having developed 10 000 years ago when
dairy farming was first introduced and spreading
throughout the world with population migration. The
highest incidence of lactose tolerance is in Sweden and
Denmark (97%). Lactose favours calcium uptake and
thus a lactose tolerance in these areas would have provided a selective advantage for greater health, reproduction and survival.3,8,9,12
Secondary lactase deficiency is a transient condition
which develops secondary to bacterial or viral infection
causing destruction of the gut mucosal epithelial where
lactase is normally active. It is most commonly caused
by gastroenteritis and severe diarrhoea, AIDS or giardiasis, which typically damage the intestinal villi, thus
reducing lactase activity. This condition may require
dietary manipulation or gut rest in severe cases.
Antibiotics and other drugs may also damage the
epithelial cells. Regular lactase activity will resume
once the cells have been able to repair.3
Colonic flora are also important in the condition. Colonic
116
Diagnosis and laboratory tests
Diagnosis of lactase deficiency is made on the basis of
one or more of following:2,3,5,8,11,12
• History of gastrointestinal symptoms, occurring after
and aggravated by milk ingestion
• Response to an empirical trial of dietary lactose
reduction or avoidance
• Breath test demonstrating abnormal hydrogen levels
• Abnormal lactose tolerance test
• Stool sample for reducing substances or acidic pH
• Small intestinal biopsy to assess direct lactase
enzyme activity.
Hydrogen breath test
This is considered the gold standard for diagnosing lactose intolerance. It is simple, safe and non-invasive.
The standard dose varies from the physiological dose
of 12.5 g lactose (1 cup milk) to the tolerance test dose
of 50 g lactose (1 litre milk) and should attempt to
closely approximate the person’s usual lactose consumption. Intolerant individuals will demonstrate high
fasting intestinal hydrogen production and 60 minutes
after lactose ingestion, a secondary rise. An increase of
>10-20 ppm above the baseline value is selected as the
cut-off point. The test is however not lactose-specific
as any undigested sugar in the intestine will be fermented by bacteria and produce hydrogen.2,3,6,14,15
Lactose tolerance test
In lactose intolerance, an oral dose of less than 50g lactose will cause an increase in blood glucose less than
25 µg/100 ml above the fasting level, and gastrointestinal manifestations. Little or no increase in blood glucose indicates that lactose has not been broken
down.3,6
Faecal reducing sugars
This test is considered very reliable. After ingestion of
a lactose-containing drink, a stool sample is collected
and Fehling’s solution is added. The presence of lactose will cause a change in colour from blue to red. A
simple kit is available to perform this test.6
Faecal pH test
Collected stools after ingestion of a lactose-containing
Current Allergy & Clinical Immunology, August 2005 Vol 18, No.3
drink will be acidic (< pH 6) in cases of intolerance. This
indicates fermentation of undigested sugars by the
colonic bacteria.6
For absolute confirmation, a double-blind placebo-controlled food challenge should be done. This helps identify individuals who may be convinced of intolerance
despite normal lactase levels and no symptoms after
ingestion of reasonable lactose intakes.2
Treatment and management
Symptoms are alleviated by complete elimination or
reduced consumption of lactose-containing foods.
Most lactose-intolerant adults can consume some lactose without major symptoms, thereby reducing the
need for strict elimination of dairy products. Regular
milk consumption in some lactose-intolerant individuals
has been found to increase the threshold tolerance
level at which diarrhoea occurs as a result of colonic
adaptation. Tolerance also seems improved when lactose-foods are eaten as part of a meal.2,3,7,10,16
Some health professionals consider soy-based infant
formulas to be the milk substitute of choice in lactoseintolerant infants. There are also lactose-free cow’s
milk-based formulas available.
Better tolerated dairy products include more solid and
semi-solid forms such as cheeses (which cause
delayed and slower gastric emptying) and yoghurt or
cultured dairy products. Yoghurt and fermented milk
products improve lactose digestion and eliminate
symptoms of lactose intolerance. Yoghurt with lacticacid-producing bacteria (including Lactobacillus and
Streptococcus spp.) has showed health benefits for lactose intolerance in some studies. These beneficial
effects are due to microbial beta-galactosidases present in the fermented milk products, delayed gastrointestinal transit, positive effects on intestinal functions
and colonic microflora, reduced sensitivity to symptoms and enhancement of gastrointestinal innate and
adaptive immune responses. Fermentation of dairy
products also breaks down much of the lactose into its
monosaccharides. Frozen yoghurt is however not well
accepted as freezing destroys the microbial
enzyme.2,3,7,12,15-19
Inconsistent results regarding the benefit of yoghurt
may be due to differences in bacteria strains used,
routes of administration, or investigational procedures;
further robust studies will clarify these factors.19
Lactose-containing medication, vitamin supplements
and certain sweeteners/ additives may pose a problem
for severely intolerant individuals.20
Commercial forms of the lactase enzyme exist in both
liquid and tablet forms (Liquid Lactase, Lactaid) and various milk products have been treated with lactase
(Parmalat Zymil) to facilitate better digestion and a less
restrictive diet. There appears to be no need for these
preparations however when the dosage of milk is limited to 1 cup.2,3,6,16,21
Dairy products with added probiotics (Lactobacillus and
Bifidobacterium spp.) may modulate gut microbial composition, leading to improved gut health and lactose
intolerance symptoms. However, more research is
needed regarding the therapeutic application of probiotics in this condition.3,12,22
When dairy products (and therefore excellent sources
of calcium (75% of dietary calcium consumed), phosphorous, magnesium, vitamin A, riboflavin and protein)
are eliminated, adequate nutrition must be provided in
both growing children and adults to ensure appropriate
bone growth, development and mineralisation, and to
avoid rickets and osteoporosis.2,3,20,23,24
Dietary management strategies to increase calcium
consumption in lactose-intolerant groups should
include:
• Dairy foods consumed with meals
• Yoghurt and other fermented dairy products
• Calcium-fortified foods
• Using digestive aids
• Dairy foods daily in the diet to enhance colonic
metabolism of lactose.
Good non-dairy sources of calcium, phosphorous, magnesium and protein include soya milk, soya yoghurt,
tofu, canned fish (including the bones), seeds and nuts,
beans and other legumes, dark green leafy vegetables,
oranges and some calcium-fortified breakfast cereals
and fruit juices. Additional calcium supplementation is
suggested to achieve the dietary reference intake for
calcium (1 000-1 300 mg/day for adults). Individuals
also need to obtain adequate vitamin D from moderate
sunlight (approximately 30-60 minutes a day depending
on age) and vitamin-D-enriched foods, e.g. margarine.2,3,5,6,10,20,23,24
Public awareness and misunderstanding of lactose
intolerance are at an all time high. Scientific findings
indicate that the prevalence of actual intolerance is
grossly overestimated and many people erroneously
believe they have developed intolerance symptoms
and eliminate dairy products unnecessarily from their
diet.2
A recent study suggests an increase in individually, selfdescribed ‘lactose intolerance’ with subsequent restriction of dairy and calcium intake that is a cause of
serious concern. These individuals demonstrated
reduced peak bone mass, increased incidence of
osteopenia and greater risk of osteoporosis and bone
fractures. Food challenges may be helpful in these
cases, as seen in a study where individuals with selfreported lactose intolerance did not differ in response
to milk chocolate samples containing different amounts
of lactose. In two other reports, a third and a half of the
lactose-intolerant subjects in the respective studies
experienced symptoms to both a lactose-containing
and lactose-hydrolysed milk under double-blind conditions, further highlighting the influence of social and
cultural beliefs and attitudes towards milk tolerance.2,12,25,26,27,28
Health professionals should alleviate patients’ fears
about lactose intolerance, discuss the importance of
calcium-rich foods, and recommend dietary strategies
to improve lactose tolerance only when intolerance is
clinically proven.2,12,25,26
How much lactose can be tolerated?
Lactose intolerance is dose related; however, the
degree of lactose malabsorption differs greatly among
individuals, and a positive diagnosis does not mean all
lactose-containing foods need to be eliminated. Most
lactose-intolerant adults can consume some lactose
without major symptoms, but the literature expresses
differing views on how much is needed to cause actual clinical symptoms.2,3,6
Age and the size (weight) of the individual will affect
the actual amount of lactose that can be tolerated
before symptoms develop; e.g., a 6-year-old child of 12
kg is unlikely to tolerate the same amount of milk that
can be safely consumed by a 60 kg adult with the same
degree of intolerance severity.
Symptoms of lactose intolerance seem rarely to cause
distress until more than 4-12 g lactose (100-240 ml
milk) is ingested. Ingestion of low levels of lactose
(below 7 g) shows no difference in non-specific intoler-
Current Allergy & Clinical Immunology, August 2005 Vol 18, No. 3
117
ance. A large psychological element was reported as
no differences in symptoms were found between subjects who consumed 7 g of lactose and subjects who
consumed no lactose. Consumption of quantities
greater than 12 g (equivalent of 240 ml milk) usually
leads to bloating, flatulence, abdominal cramps and
diarrhoea. Another source suggests safe ingestion of
200-400 ml of milk daily. Adults with more moderate
intolerance may be able to adapt, developing tolerance
to more than 12 g lactose if amounts are increased
gradually over 6-12 weeks.3,7,12,16
Symptoms tend to occur after large quantities of lactose (>50 g) are taken in a single dose. Cheese without
lactose (hard and semi-hard cheese) or low in lactose
(soft cheese contains only 10% lactose) can usually be
consumed. Yoghurt with approximately one-third less
lactose than milk is often well tolerated as previously
mentioned.4,11,29,30
People with laboratory-confirmed low levels of lactase
enzyme can safely consume 1 serving of milk (1 cup =
12 g lactose) with a meal or 2 servings of milk (2 cups)
per day in divided doses with breakfast and dinner.
Symptoms tend to occur as the lactose load is
increased, with the majority of individuals having symptoms when the equivalent of 1 litre of milk is ingested
in a single dose. People who describe themselves as
severely ‘lactose intolerant’ may mistakenly attribute a
variety of abdominal symptoms to lactose intolerance.
In the majority of patients a lactose intake limited to
approximately 1 cup of milk (240 ml) leads to negligible
symptoms, and use of lactose digestive aids are unnecessary.2,21,31
To further demonstrate whether a usual lactose intake
(2 cups milk daily with meals) could be consumed by
lactose maldigesters, a double-blind, randomised
crossover study was conducted in two groups with
confirmed positive hydrogen breath tests – those who
believed they were symptomatic and those who
believed lactose intake did not induce symptoms. Both
groups reported only minimal symptoms after intake of
regular or lactose-free milk, reaffirming that most selfdescribed lactose-intolerant subjects can easily tolerate
2 cups of milk daily when consumed in divided doses
with breakfast and dinner.2,32
The high incidence figures for primary lactose
maldigestion among groups grossly overestimate the
number who will clinically react after drinking a glass of
milk with a meal. Randomised, double-blind, controlled
clinical trials have demonstrated that by using a few
simple dietary strategies, those who maldigest lactose
can easily tolerate a dairy-containing diet that meets
calcium intake recommendations. Health professionals
can help these patients and the general public understand how to improve calcium nutrition by overcoming
the enormous barrier of lactose intolerance and in so
doing reduce the incidence of calcium-related chronic
diseases in high-risk populations.12,33
Lactose intolerance may offer protection
against large-bowel diseases
Research has found a reduced incidence of ‘developed
society’ large-bowel diseases such as diverticulitis, colorectal adenomas and carcinomas, ulcerative colitis and
Crohn’s disease in African black people. This disparity
exists despite an adopted urbanised lifestyle and
changes in dietary patterns including decreased fibre
intake (from 30-35 g to 12-14 g daily). It is hypothesised
that the increased concentration of substrate available
for fermentation in the colon due to carbohydrate malabsorption in the group, compensates for the low
dietary fibre intake. This would be protective of the
118
large bowel, and helpful in the prevention of largebowel disease in the African population.34
Controversial areas
Symptoms of irritable bowel syndrome (IBS) resemble
the non-specific reactions of lactose intolerance.
Subjects with IBS tend to self-diagnose lactose intolerance and eliminate dairy without evidence that the
foods are solely responsible for symptoms. Research
suggests that a lactose-restricted diet should be
reserved only for patients who demonstrate symptoms
of diarrhoea, abdominal pain and flatulence during
hydrogen breath testing, irrespective of what was previously reported. Certain individuals may benefit occasionally from a reduced lactose load; however, this
should not be general practice in IBS patients. These
patients should be reassured that small amounts of lactose are unlikely to cause abdominal symptoms even in
lactose-intolerant individuals with demonstrated symptoms.16,35
Infantile colic has been linked to lactose intolerance;
however, research remains inconclusive. Although
there is no consensus as yet about its aetiology, it is
likely to be multifactoral. Two randomised controlled trials found no benefit from lactase treatment of breast
milk or cow’s milk formula. One double-blind placebocontrolled study found a modest but variable benefit
from pre-incubation of foods with lactase. As yet, low
lactose or lactose-free formulas or pretreatment of
feeds with lactase are not recommended as treatment
for colic.4
Inflammatory bowel disease (IBD; Crohn’s disease and
ulcerative colitis) are commonly treated by exclusion of
dairy products; however, most affected people are able
to consume a glass of milk daily without discomfort.
The prevalence of lactose intolerance tends to be
greater in Crohn’s patients with small-bowel involvement than those with colon involvement or ulcerative
colitis. In the latter colonic conditions, lactose malabsorption is as a result of ethnic risk, based on genetic
factors. Bacterial overgrowth and/or small-bowel transit
time may also be responsible for lactose malabsorption
in Crohn’s disease.36
Despite these findings, dairy avoidance in these
patients is extensive and can be attributed to patient
misconceptions, as well as poor medical advice and
minimal nutritional consultation. It is suggested that all
IBD patients receive hydrogen breath tests to ensure
better nutritional management, and avoid unnecessary
dairy elimination and prescription of commercial lactase
preparations.36
Conflicting evidence exists regarding links between lactose intolerance and an increased risk of cataract formation, development of diabetes and ovarian cancer.12
TO SUMMARISE IN PRACTICE
Each lactose-intolerant person, with the help of a qualified dietitian, should determine his or her own threshold and adjust the amount of lactose that can be
consumed comfortably at any one time. Strategies to
help with the inclusion of milk and other dairy products
in the diet without experiencing symptoms include:2,6
• Low amount of lactose consumed. The larger the
amount consumed, the greater the risk of symptoms. Most lactose-intolerant individuals can safely
tolerate 1 cup of milk (12 g lactose), especially if
taken with a meal or other foods, or 2 cups milk per
day in divided doses at breakfast and dinner.
• Consumption of a meal or solid food. Consuming
lactose with a meal or solid food may improve tolerance as it slows gastric emptying and delivery of lac-
Current Allergy & Clinical Immunology, August 2005 Vol 18, No.3
tose to the colon, allowing more opportunity for any
available endogenous lactase to digest the lactose.
• Correct types of dairy food. Certain dairy foods are
better tolerated than others; e.g. full cream milk is
better than lower fat milk. Chocolate milk may also
be better tolerated than unflavoured milk, but the
mechanisms by which cocoa reduces intolerance are
unknown.
Other dairy products with lower lactose content than
milk may be better tolerated, e.g. cheeses (Cheddar,
Swiss, Parmesan, cottage cheese) and ice cream.
Harder cheeses tend to have even less lactose, as
the lactose-containing whey is removed from the
curd during the cheese-making process. Lactose
totally disappears in mature ripened cheeses.
Fermented/cultured dairy products with beta galactosidase are better digested. Yoghurt, sour milk, and
amasi are among these. Yoghurt should contain live,
active cultures as pasteurisation reduces the beneficial effects of the bacterial cultures on lactose digestion.
• Lactose-reduced or lactose-free dairy foods or lactose digestive aids. For the rare cases in which a
patient is unable to tolerate even small amounts of
lactose, or when large amounts of lactose-containing
foods are eaten, commercially available lactosereduced milk and other dairy products are available.
A lactase preparation (liquid) can also be added at
home to regular milk and left overnight. An oral
enzyme replacement tablet, that can withstand the
stomach’s acidity, can be taken at the beginning of a
meal. These products are expensive and are unnecessary if the equivalent of 1 cup milk/ day can be tolerated.
• Gradual increase of intake of dairy foods. Tolerance
to lactose can be improved by gradually increasing
intake of lactose-containing foods. Lactose tolerance
threshold can also be determined in this way.
Elimination of lactose from the diet may actually
worsen lactose intolerance in people with primary
lactase deficiency.
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