Lactose Intolerance Global Network

Lactose Intolerance

What is lactose?
Lactose is a sugar or disaccharide present in all mammal’s milk: cows, goats, sheep and in breast milk, and it can also be found in many prepared foods. It is known as the sugar in milk, (C12, H22,O11) a natural disaccharide made of glucose and galactose.

What is lactase?
Lactase in an enzyme produced in the small intestine, that plays a vital role in breaking lactose down into its two simple sugars glucose and galactose (process needed for its absorption by our body as it can only absorb simple sugars). If lactase levels are low or this breaking-down work is not done well, lactose becomes difficult to digest.


What is lactose intolerance?
Lactose intolerance means that there is not enough enzyme (lactase) in the small intestine to break down all of the lactose consumed. Partially digested or undigested lactose passes into the large intestine and there it is decomposed by the bacteria of the large intestine, generating waste substances like hydrogen (H2), carbon dioxide (CO2), methane (CH4) and short-chain fatty acids which cause all of your symptoms like: pain, abdominal bloating, diarrhoea, etc. It is also known as an intolerance to dairy products, disaccharide deficiency, lactase deficiency or milk intolerance.

What direct intestinal symptoms does it cause?
The symptoms that frequently arise after ingesting dairy products.

Abdominal pain
Abdominal bloating and swelling
Abdominal gas and flatulence
Acidic diarrhoea
Pasty and floating faeces
Urgent bowel movements
Perianal redness


What unspecific symptoms can it cause?
As there is an alteration in the intestinal mucus, a series of unspecific symptoms can occur in any part of the body.

Pain in extremities
Skin problems
Alterations in concentration
Sleep disturbances

Which races are affected the most?
There seems to be a clear cause-effect relationship with the habit of milk consumption. Towns that have traditionally been “cattle breeders” and have consumed animal milk generation after generation, present less cases of lactose intolerance than other towns unaccustomed to its consumption. The majority of the worldwide adult population has a lactase deficit, except for the population of Northern and Central Europe.


What kinds of intolerances exist?

1. Acquired hypolactasia or genetic primary intolerance (LNP Lactase-nonpersistence)
This causes a progressive decrease in lactase production and therefore the gradual loss of the ability to digest lactose. This usually happens over the lifespan of certain ethnic groups and it has a genetic cause. People with this intolerance notice how consuming milk gives them increasingly more symptoms over time. Over 70% of the worldwide population suffers from this intolerance.When it is of a genetic/primary nature there is no possible cure, as the individual does not recover the enzyme and the symptoms are only eased by removing dairy products from the diet.Lactose intolerance is not dangerous and is very common in adults, the majority of whom show some degree of intolerance by reaching the age of 20.

2. Secondary intolerance
Decrease in lactase production is secondary, as it is caused by temporary intestinal damage due to other causes (see possible causes). Once the person is cured and when the intestinal mucus has regenerated, the lactose intolerance disappears.

Possible causes:
· After weaning, the amount of lactase produced reduces if the child is not continuously exposed to lactose through its diet. Therefore it is important to introduce lactose gradually. In the beginning the baby can only digest colostrum (water rich in protein, mineral salts and immunological factors). Then this begins to enrich with lactose and lipids until it gives way to the definitive milk. The maternal milk becomes more complete according to the baby’s enzymes. Therefore, the body increases or decreases the enzymes depending on its needs, and an imbalance in this process is what causes infant intolerance.
· Intestinal problems caused by virus, bacteria or parasites.
· Celiac disease (enteropathy induced by gluten)
· Intestinal illnesses (Chron)
· Intolerance to cow’s milk protein
· Malnutrition linked to prolonged diarrhoea
· Surgical operations on the small intestine
· Taking certain antibiotics
· Situation of malnutrition (anorexia or bulimia)

3. Congenital hypolactasia or congenital intolerance (CLD Congenital lactase deficiency)
This is a rare form of intolerance caused by a congenital or genetic defect. Very few cases have been detected around the world, the majority of which are in Finland. It is essential to prescribe a dairy-free diet to infants to prevent harm and serious complications in their development.

What diagnostic methods do we have?

A. Hydrogen breath test (most-used method)

The patient is given a solution containing lactose (25-50g lactose in 200-400ml water) and at subsequent 15-minute intervals is made blow into airtight bags/indicator instrument/test tubes to give a sample. When the undigested sugars are transported to the large intestine, the bacteria living there use them as food and create hydrogen as a waste product. The hydrogen is then absorbed into the bloodstream and expelled through respiration. The hydrogen detected in the respiration indicates that the sugar has entered the large intestine without being absorbed by the small intestine. An increase of hydrogen in the respiration after consuming lactose must be proven and the level of tolerance is determined based on this result. This test is done by also evaluating the presence of methane, and thereby avoiding possible false positives.

B. Blood test for lactose overload

Firstly a blood sample is taken from the patient to find his/her basal glycaemia (initial blood sugar level). Then, as in the hydrogen test, the patient is given 100 grams of lactose in a solution with water. Then, after 60 and 120 minutes new blood samples are taken. If no glucose is released -due to the absence of the action of lactase that should be present in the intestine- then no glucose is absorbed into the bloodstream through the intestinal wall and therefore, the blood sugar level does not increase and it can be said that a lactose intolerance exists. The existence of a lactose intolerance can be confirmed if the glycaemia (blood sugar level) after consuming lactose does not raise by more than 14.4mg/dl (0.8mmol/l) with regards to the basal (initial) value. Examples of positive and negative results -courtesy of patients-

C. Biopsy of the small intestine

Gastroscopy (endoscopy) examination
Biopsy samples of the small intestine can be obtained by EGD (esophagogastroduodenoscopy) or other endoscope of the upper gastrointestinal tract. A flexible optical fibre tube is introduced (endoscope) through the mouth or nose towards the upper gastrointestinal tract. Tissue samples obtained during the endoscope are sent to the laboratory for examination. This shows the presence or absence of lactase in the intestinal mucous.

D. Genetic test

Recent studies show that lactase activity is related to the presence of two identical polymorphisms in the gene MCM6. This method consists of extracting and amplifying the DNA of a sample -patient’s blood or saliva- continuing with a hybridization on strip protocol, in order to detect the presence of polymorphisms C/T 13910 and G/A 22018 in intolerant persons. The final practical result is a series of coloured bands on a strip that are interpreted with the help of a template. It can be determined whether or not the patient is intolerant to lactose based on the different combinations found. Example of positive and negative result and related documentation about this diagnosis method compared with the hydrogen test -courtesy of Operon-

Are there different levels of intolerance?

Sensibility to lactose can vary greatly -some people notice the effects immediately after consuming small amounts, whereas others have a higher sensitivity threshold making it more difficult to observe its cause-effect relationship. Depending on the intolerance level, each person can tolerate a higher or lower amount of lactose a day. There are people who remain asymptomatic all of their lives if they don’t exceed a certain amount of lactose a day. In this manner, we find people who tolerate cheese perfectly (which has very little lactose when cured) or yoghurt (where thanks to its bacteria part of the lactose has been converted into lactic acid) but display clear symptoms when consuming a glass of milk. Everyone should be aware of their level of tolerance. See the indicator for the lactose contents of different foods in the Traffic light section. Sensibility can also change over time and with general health conditions. A sever episode of diarrhoea caused by an infection, can temporarily reduce lactase levels making us more sensitive to lactose temporaly.


Why is it important to detect and treat it quickly?
Because lactase is one of the most delicate and vulnerable intestinal enzymes. If we continue consuming lactose, the injury to the intestinal mucous will increase and a vicious circle will arise: injury to the mucous/malabsorption of lactose will be increasingly difficult to solve.

Is lactose intolerance different to an allergy to cow’s milk protein (COMP)?
Although both ailments have the same origin (milk) they are unrelated (COMP allergy is an immune system reaction to milk protein). This explains why on the market you can find products suitable for lactose intolerance (lactose free milk, cheese free milk) which are not suitable for with an COMP allergy.


How to live with an intolerance?
A lack of milk in the diet can result in a lack of calcium, vitamin D (needed to absorb calcium), riboflavin and protein. The most common complications are weight loss and malnutrition. Therefore, it is essential consume other products rich in these substances, such as the recommended daily doses of vitamins A, C, phosphorous, magnesium and potassium (which help calcium absorption).
Alternative sources:
Calcium: Sardines, salmon, tofu, prawns, cabbage, spinach, etc.
Vitamin D: Although this is created by the body when exposed to the sun, a rich source of this is cod liver oil.

And if I don’t want to give up dairy?
If you don’t want to give up the taste and nutritional properties of cow’s milk, for the last few years you can find milk brands on the market whose lactose has been removed or previously partially hydrolysed known as “low in lactose” or fully hydrolysed “lactose free”. An offer that has been complemented with dairy derivatives like different varieties of cheese -Gouda, Emmental, etc.-, grated cheese, yoghurt, flavoured milkshakes, cream, etc. In our country you can also already find lactase supplements in tablet/capsule form that allows you to consume lactose products. These are recommended for occasional use when eating out and when you are unsure whether dishes contain lactose or not, going to business dinners, celebrations, etc. These tablets provide our body with the lactase it needs to breakdown the lactose of a specific meal, and as its effect is instantaneous you have to take it every time you have a meal. The main inconvenience is finding the right dose for you, as it will always depend on the relationship between: Your intolerance level / amount of lactose consumed.