Why are there lactose intolerant people?

Around 65% of the human population is affected by lactose intolerance. It occurs because the bodies of certain people does not create an enzyme called lactase or does not create it in the right amount, so they cannot digest lactose, which is present in dairy, other foods and culinary preparations.

Lactase is responsible for dividing lactose into its two molecules: glucose and galactose, in order to be absorbed. If this does not happen (because there is not enough lactase or directly none), the lactose will go its way without being absorbed, producing fermentation and gases. The symptoms of intolerance will be: abdominal distention accompanied by pain and sounds of intestinal movements that can be associated with diarrhea and, in extreme cases, vomiting and constipation.

Lactase is lost in mammals when they reach adulthood except in areas where milk intake is historically maintained through cows or herds of goats or sheep, such as in European Nordic countries, Mr Federico Argüelles Arias, President of the Spanish Foundation of the Digestive System (FEAD), stated that the populations of North Africa and Arabia and, to a lesser extent, the inhabitants of Southern Europe are scarce.

No. Lactose intolerance occurs when the person has a lactase deficiency that causes the person not to absorb lactose well. When it reaches the colon, the poorly absorbed lactose is fermented by bacteria in the intestine and produces gases, among other things.

Allergies are mediated by an immune reaction via immunoglobulins, the most common is the allergy to cow’s milk proteins and usually induce similar symptoms. However, on many occasions, allergic problems can cause skin, eye and respiratory reactions that do not manifest in the case of lactose intolerance.

It’s not the same. The term malabsorption only refers to the fact that lactose is not absorbed, whereas with lactose intolerance we refer to the appearance of symptoms caused by this malabsorption. In fact there are people who present lactose malabsorption without symptoms.

What does it consist of? Federico Argüelles Arias explains, "There are cases of intolerance to secondary lactose, which means that the intestine has lost the lactase temporarily due to a problem in the intestine. For example, after severe gastroenteritis or celiac disease. In these cases, the villi of the intestine are lost, where lactase accumulates and until they are not replenished the lactase is not re-concentrated. Here the patient can return to consuming lactose gradually. In the rest of the cases, lactic activity does not usually recover, in any case, it can improve the metabolization that colon bacteria make of lactase, for example, by providing probiotics."

Adults with lactase deficiency usually maintain 10% to 30% of intestinal lactase activity and develop symptoms only when they ingest enough lactose to exceed colon compensatory mechanismsFederico Argüelles Arias tells us.

Lactase deficiency is variable among people who are lactose intolerant. Most intolerant patients can support the intake of at least 12 grams of lactose, equivalent to a glass of milk. But in reality, many patients complain of intestinal disturbances with intakes below this amount. Daily lactose intake should be limited to doses that do not produce side effects, says Ángel Ferrer Torres, an allergist at Hospital Quirón Salud in Alicante and a member of Top Doctors. 

Fermented products are better tolerated because the bacteria have hydrolysed lactose. Among the most common are cured or semi-cured cheese or some homemade yoghurts, since the bacteria that ferment them have lactase. Also ice cream and serums processed in a traditional way. Other dairy products such as curds, by having fat and extracting the watery part where the lactose is, can also be perfectly tolerated, as can butter, says Ferrer Torres.

It’s a widespread belief, but is it an urban legend or is it happening? Federico Argüelles Arias tells us that there is no record of this statement.

The fact that a person is lactose intolerant may lead us to think that if they cannot eat the same amount of dairy as someone with enough lactose in their body, they may suffer from calcium deficiency. Well, you don’t have to.

According to Ferrer Torres, adults need 1000 mg of calcium a day. The allergist tells us that dairy contributes almost half of this amount. However, there are other non-dairy foods that provide not negligible amounts of calcium. In fact, they can provide more than the milk itself (100 mg of calcium/100g of milk). Amongst them the specialist highlights sesame seeds (700 mg of calcium/100g of seeds), tofu (250 mg of calcium /100g of tofu), blue fish such as anchovies, or sardines (250 mg of calcium /100g of fish), almonds and pistachios, steamed vegetables such as spinach, broccoli, lettuce, chard, parsley, wakame seaweed, and beans such as chickpeas (150 mg calcium/100g food).

On the other hand, dairy products sold without lactose continue to provide calcium, in fact their nutritional values are exactly the same as those of dairy products used, the only thing they differ from is that they do not contain lactose (they do carry lactose) lactase is added in order to be digested.

Lactose is not only present in dairy products but also in culinary ingredients in which these products or their derivatives are used, such as in pastries made with milk or butter, milk bread or in flaked potato puree. Of course you will have lactose in bechamel, cream pastries, preparations with cream, ice cream, fruit smoothies, and milk chocolate. According to the expert of Top Doctors: The intake of these foods usually produces symptoms associated with intolerance.

Lactose is hidden in small amounts in drugs as an excipient (product specified), food substitutes (bars, powder) and protein supplements. Traces can also be found in products marked with the letter L, processed meats (sausages, pâtés), seasoning powder, margarines, breakfast cereals, prepared meals. As indicated these foods usually contain traces and very rarely the amount ingested comes to produce symptoms in a lactose intolerant person. These indications are specified for patients allergic to cow’s milk proteins, says allergist Ángel Ferrer Torres.

There are lactose intolerants who, for example, take a pill at meals so that they can eat foods that contain lactose without experiencing any symptoms. This pill is basically lactase and can be purchased at the pharmacy without a prescription. However, whether it is good or not to consume it regularly, Federico Argüelles Arias replies: There is no evidence of adverse effects, although it is recommended not to ingest regularly, only on demand when it is known that a meal with a significant amount of lactose is to be made.