Approximately 20% of the population has an adverse food reaction during their life. The European Academy of Allergy and Clinical Immunology (EAACI) in 1995 proposed several definitions for adverse reactions to foods based on the pathophysiological mechanisms involved. An adverse reaction is a generic term used to describe any unfavorable reaction that occurs after ingestion, contact or inhalation of food or one of its components. Among the adverse reactions are non-toxic reactions, the cause being the ingestion of a non-toxic substance. They are not dose-dependent and only affect susceptible people. Among the non-toxic reactions, there are intolerances in which the immune mechanism does not mediate (as it does in allergies), and may be due to a metabolic, pharmacological cause or indeterminate reactions.
In Spain between 20 and 40% of the population is lactose intolerant. The normal condition in mammals is that a decrease in lactase production is experienced after the end of the lactation period, it is still unknown what this decrease is due to. In societies that do not consume dairy products, their lactase production usually decreases by approximately 90% during the first 4 years of life, although this decrease varies over time. On the other hand, in populations where the consumption of milk and dairy products has been common for years, a mutation has been detected in chromosome two that allows maintaining sufficient lactase concentrations to maintain correct lactose absorption. Approximately 30% of the population maintains lactase activity in adulthood. As a result, the prevalence of lactose intolerance globally varies widely by ethnicity.
Lactose is the predominant sugar in milk. its intolerance appears when our body does not produce either by total or partial absence, primary or secondary, the enzyme lactase (protein), causing us not to metabolize lactose correctly. Lactase is found in the cells that line the small intestine (the enterocytes) and is synthesized if there are at least one of the 2 genes that code for it. Only when the expression of both is altered is lactase synthesis reduced, which in turn reduces lactose absorption. Its function is to hydrolyze (separate) lactose into its two constituents, glucose and galactose. This process takes place in the middle jejunum, where there is a low concentration of bacteria, so only a small amount of lactose is fermented.
There are three types of lactose intolerance:
Congenital lactase deficiency occurs from birth and is diagnosed in childhood. It is an extremely rare alteration. Its treatment is to avoid lactose intake from birth.
Primary (persistent) lactose intolerance occurs when the child grows up in a society that does not consume dairy products. It is what we find in various Asian and African cultures because the consumption of industrialized and commercial dairy products is rare.
Finally, secondary or acquired (reversible/temporary) intolerance, caused by some pathology that damages the mucosa of the small intestine (gastroenteritis, Crohn's disease, gluten intolerance, etc.), so, once the cause is treated primary and the intestinal mucosa is regenerated, remits. Also, the use of drugs (non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, etc.) can affect the intestinal mucosa.
Lactose intolerance was already described by Hippocrates in 400 BC, but the concomitant symptoms have not been identified until 50 years ago. Symptoms appear after ingesting dairy products or foods that contain lactose in their composition. Depending on the lactase deficiency and the amount of food eaten, the magnitude and symptoms may vary from person to person or even in different situations. The typical clinical picture of lactose intolerance may include crampy abdominal pain, bloating, flatulence, weight loss, malnutrition, growth retardation, diarrhea, steatorrhea, acid stools, and occasionally nausea and vomiting. In some cases, intestinal motility decreases causing constipation, probably due to the production of methane. Abdominal pain and flatulence are due to fermentation in the colon of unabsorbed lactose, which is hydrolyzed into glucose and galactose by lactic acid bacteria. Short-chain fatty acids, hydrogen, carbon dioxide, and methane are also produced. The acidification of the stool and the increase in intraluminal osmotic load is due to the presence in the ileum and the colon of undigested lactose, which carries water and electrolytes, accelerating intestinal transit. It is a problem that widely affects the population worldwide, but it is not a serious threat to health.
Some patients do not present these symptoms with the ingestion of lactose and in some cases, the exclusion of lactose from the diet does not lead to an improvement in symptoms. In these cases, we should suspect another underlying disease, such as irritable bowel syndrome.
Its usual diagnosis is based on clinical improvement after eliminating lactose from the diet. But there are also methods to diagnose lactose intolerance, such as the expired hydrogen test after lactose overload, which is a simple test, but requires collaboration from the patient and the result does not always correlate with the patient's symptoms. Another diagnostic method is the study of sugars and reducing substances in feces. Sometimes tests may be necessary to rule out digestive diseases that may cause this condition in a secondary way.
Treatment consists of minimizing the incidence and intensity of symptoms. The dietary control of lactose intolerance will depend on those affected learning through trial and error how much lactose they can tolerate since lactase production and the amount of lactose that can be tolerated varies from person to person. After an initial period of elimination of lactose, it is advisable to reintroduce it into the diet in small amounts spread throughout the day to check tolerance. Do not neglect the calcium intake.
Lactose is present in conventional dairy products and as a food additive. If you eat foods that contain lactose, it should be done in small amounts spread throughout the day, and it is convenient to eat them together with fatty or sugary foods. Semi-skimmed or skimmed dairy products generally have a slightly higher percentage of lactose compared to the whole.
Continuous consumption of small doses of lactose has been shown to involve a certain adaptation process, thereby reducing the amount of hydrogen exhaled and the severity of gastrointestinal symptoms. In cases where only small amounts of milk are tolerated, you can consider taking those that are enriched in calcium and vitamin D.
The best-tolerated dairy products are cream, butter, aged cheeses and ice cream, due to their lower lactose content and/or higher amounts of fat and sugars.
In the case of yogurt, the bacteria it contains ferment the lactose, reducing its content by 25-50% and improving its tolerance. But, you have to be careful since after the fermentation process some yogurts are added milk, as happens with those that do not require refrigeration, so tolerance is worse.
As milk substitutes, lactose-free or low-lactose dairy products should be taken, it is important to check that they have adequate calcium content.
As an alternative source to milk, there are vegetable drinks made of soy, oats, rice, almonds, etc., but you have to be careful with the usual intake of these products because most do not have calcium and have an imbalance in their composition that most are not nutritionally adequate.
In addition, it is essential to always check product labels as business terminology varies according to language and region. In non-dairy products, lactose can be present in processed meats, margarine, breakfast cereals, dried fruits, processed foods, medicines, pre-cooked meals, bars, protein supplements, etc. On the label, it may appear as whey, whey, milk solids, milk modifying ingredients, etc.
In severe or total cases of lactose intolerance, if not detected early and diagnosed correctly, the digestive problems it causes can damage the mucosa and intestinal flora and, in the long term, alter intestinal permeability, which in turn It can lead to allergic or inflammatory problems, as well as deficiencies of essential nutrients for our body. Therefore, good dietary control of lactose and a good review of the labeling of the products will be essential for the treatment.
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