Lactose is the main sugar in milk. It is naturally found in most dairy products, but in very different amounts depending on whether or not they have undergone lactic fermentation: powdered milk (38 g per 100 g) is the dairy product with the highest lactose content, well ahead of skim or whole milk (5%) and frozen breast milk (3 to 8%). Cheeses, which contain between 0.1g and 2g, lag significantly behind.
To be digested, lactose must be broken down into two other sugars, glucose and galactose; it is lactase, an intestinal enzyme, that provides this breakdown. Lactase is produced by cells in the inner lining of the small intestine. After being broken down, these simple sugars are absorbed into the blood through the intestinal wall. When lactase is deficient, lactose cannot be digested and absorbed. The increased concentration of lactose causes fluid to enter the small intestine, causing diarrhea. The lactose then enters the large intestine, where it is fermented by bacteria to form gas, which causes flatulence, bloating, and abdominal cramps.
Symptoms of lactose intolerance
Symptoms of lactose intolerance in children include diarrhea and limited weight gain, while symptoms in adults include abdominal bloating and cramps, diarrhea, flatulence and nausea.
The difference between cow’s milk allergy and lactose intolerance
Type III allergies (aka intolerance) should not be mistaken for classic food allergies (type I).
In type I allergies, the immune system produces IgE antibodies. These antibodies lead to an immediate allergic reaction(a reaction can occur within seconds or minutes).
In type III allergies, the immune system produces IgG antibodies against food proteins. In this case, the body’s reaction is delayed (up to a few days after eating), but these antibodies can cause a chronic inflammatory reaction.
Cow’s milk allergy is different from lactose intolerance.
Unlike lactose intolerance, people with cow’s milk allergy can digest milk normally, but the proteins it contains cause a rapid immune system reaction. Cow’s milk allergy usually affects children. In children, symptoms appear after consuming milk or dairy products. However, these symptoms, such as itching, skin rashes, and/or wheezing, are usually similar to other allergic reactions. Children sometimes have digestive symptoms (vomiting, abdominal pain, and, rarely, diarrhea).
Cow’s milk allergy is rare in adults and may also cause vomiting and esophageal reflux symptoms.
Unlike cow’s milk protein allergy, with which it is often confused, lactose intolerance is not life-threatening. However, it does cause serious digestive problems, sometimes very painful, without affecting other body systems (respiratory system or skin).
The severity of lactose intolerance varies greatly from person to person, but most people with lactose intolerance are still able to digest about 10-12 grams of lactose, or a glass of milk.
It is worth noting that symptoms arising from lactose intolerance are usually mild, unlike celiac disease, intestinal infections and extreme forms of type I allergies (in particular anaphylactic shock, Quincke’s edema).
Europeans are less likely to suffer from lactose intolerance than Asians. Lactose intolerance is rare in infants and usually occurs after weaning, in parallel with the introduction of complementary foods.
Causes of lactose intolerance
There are two pathological causes of lactose intolerance:
– A genetic mutation that causes a lack of lactase, known as primary alactasia;
– Destruction of the intestinal mucosa as a result of various diseases (cancer, gluten allergy, digestive diseases) that can no longer produce lactase. This is known as secondary alactasia.
While in the case of primary alactasia, lactose intolerance and the symptoms it causes are irreversible, in the case of secondary alactasia, the disorder is only temporary and lasts for the duration of the disease responsible for the failure to produce lactase.
– Furthermore, lactose intolerance results from a completely physiological process that occurs to a greater or lesser extent in almost half of all adults: a progressive decrease in lactase activity with age, which responds to the digestive system’s adaptation to a variety of foods. This decrease in intestinal enzyme activity leads to lactose intolerance, which is usually not severe: most adults can drink a cup of milk without showing any digestive symptoms of the disorder.
Diagnosis of lactose intolerance
– Physician assessment of symptoms after lactose consumption
– Sometimes a hydrogen breath test (this is an outdated technique)
– Genetic lactose intolerance test
A lactose intolerance test will determine if you have a genetic mutation that prevents you from producing the enzyme that helps digest lactose.
This test analyzes the LCT gene. The LCT gene encrypts the instructions that our body needs to make lactase. Lactase works by speeding up the process of converting lactose into simpler sugars. A mutation in this gene makes the individual unable to produce enough lactase to break down ingested lactose. The disease can have different severities depending on the amount of lactase produced by their body; it can generally be mild, moderate or severe.
– Test for latent food intolerance
– Because the symptoms of lactose intolerance are not very specific, it may be helpful to consult a gastroenterologist to rule out other conditions, such as irritable bowel syndrome (which it often accompanies intolerance), Crohn’s disease or gluten intolerance.
Treating lactose intolerance
– Eliminating foods with lactose from the diet
Lactose intolerance can be controlled with a diet that eliminates foods containing lactose, mainly dairy products. Yogurt is often tolerated because it naturally contains lactase produced by lactobacilli. Cheese contains less lactose than milk and is often tolerated, depending on the amount consumed. Milk and other lactose-reduced products are available in many supermarkets.
– Patients who have to avoid dairy products should take calcium supplements to prevent calcium deficiency. Lactase enzyme supplements are available without a prescription and can be taken with meals or drinking foods containing lactose.
– Lactase deficiencies can be compensated occasionally by taking supplements containing this enzyme. When taken immediately before meals, the enzyme in the supplements enters the intestines at the same time as dairy products or foods containing lactose, allowing them to be absorbed.
– Finally, there are lactose-free or low-lactose products to replace conventional dairy products