Lactose is the main carbohydrate in milk. In babies, it provides a significant proportion of energy. In adults, it is mainly provided by milk and dairy products. To be digested, lactose must be hydrolysed by an enzyme called lactase, which some people lack in adulthood. Defects in this genetic programme in most of the world’s population are often the cause of malabsorption. We speak of lactose intolerance when appropriate tests show that malabsorption is the cause of troublesome disorders.
Where does lactose intolerance come from?
Genetic factors
Lactose intolerance can be largely influenced by genetic factors. A genetic variation known as adult-onset hypolactasia is the most common cause of this condition. This variation results from a decrease in the activity of the enzyme lactase after infancy, a natural phenomenon in the majority of mammals, including humans. In certain populations, however, a genetic mutation has allowed lactase to persist into adulthood, an adaptation probably due to the domestication of dairy animals and the consumption of milk in these communities.
This genetic characteristic is encoded by a specific allele located on chromosome 2, and its expression can be either dominant (lactase persistence) or recessive (adult hypolactasia). Individuals who inherit the non-persistence allele from their parents will express a drop in lactase production from childhood, leading to lactose intolerance in adulthood.
Age-related decline in lactase production
Irrespective of genetic factors, a natural decline in lactase production often occurs with age. This phenomenon is observed even in individuals who maintain sufficient lactase activity in their youth. The decline in lactase production with age can lead to increased sensitivity to lactose in adults and the elderly, necessitating dietary adjustments to avoid the symptoms of intolerance.
Variations between different populations
Variations between different populations in the prevalence of lactose intolerance are significant and widely studied. Rates of lactase persistence vary considerably between ethnic groups and geographical regions. For example, a large majority of people of Northern European origin have lactase persistence, which enables them to digest lactose in adulthood. Conversely, East Asian populations and certain communities in Africa and South America have high rates of adult hypolactasia, with up to 90% of adults lactose intolerant.
These variations have important implications for public health and nutritional recommendations in different regions. They require particular attention when planning diets and public health interventions to ensure adequate nutrition without causing discomfort to lactose-intolerant individuals.
What are the mechanisms of lactose intolerance?
Lactose and its digestion
Lactose is a disaccharide naturally present in milk and dairy products. Its correct digestion requires the presence and activity of a specific enzyme, called lactase, which is normally produced in the cells of the mucosa of the small intestine. The main role of this enzyme is to break down lactose into two simpler monosaccharides, glucose and galactose, which can then be absorbed into the bloodstream.
In individuals suffering from lactose intolerance, the amount of lactase produced is insufficient, resulting in incomplete digestion of the lactose. This undigested lactose continues to make its way to the colon, where it becomes the source of various digestive disorders. The process of lactose fermentation by the intestinal bacterial flora produces gases such as methane and carbon dioxide, as well as organic acids that contribute to symptoms such as bloating, abdominal pain and diarrhoea.
What is the role of the enzyme lactase?
The enzyme lactase is crucial for the efficient digestion of lactose. It binds to lactose molecules and catalyses their cleavage into glucose and galactose. This enzymatic reaction is essential not only for the digestion of lactose but also for the efficient absorption of the resulting simple sugars.
In the case of lactose intolerance, lactase deficiency can be genetic or acquired. The genetic form, known as adult-onset hypolactasia, is the most common and is characterised by a reduction in lactase activity after childhood. Acquired intolerance, on the other hand, can result from diseases affecting the small intestine, such as coeliac disease or certain intestinal infections, which can temporarily reduce lactase production.
Understanding the role of lactase and the mechanisms of lactose digestion is fundamental to developing effective management strategies and minimising the symptoms of lactose intolerance in affected individuals. By enabling better dietary management and the use of lactase supplements, people with lactose intolerance can often continue to enjoy dairy products without significant discomfort.
How does the body react to lactose intolerance?
Symptoms of lactose intolerance
The symptoms of lactose intolerance result mainly from the body’s inability to digest and absorb the lactose present in dairy products. When undigested lactose reaches the colon, it is fermented by intestinal bacteria, producing gas and substances that draw water into the colon, which can lead to a series of digestive symptoms.
The main symptoms include:
- Bloating: accumulation of gas in the intestine, often accompanied by sensations of swelling and abdominal tension.
- Diarrhoea: increased water in the colon can lead to frequent, watery stools.
- Abdominal pain: cramps and acute pain can occur as a result of intestinal distension caused by accumulated gas.
- Gas and flatulence: excess gas resulting from the fermentation of lactose by bacteria.
These symptoms generally appear 30 minutes to 2 hours after consuming lactose-containing products and vary significantly from one person to another in terms of intensity and frequency, depending on the amount of lactose ingested and the level of lactase deficiency.
Short- and long-term effects
In the short term, the effects of lactose intolerance are mainly the gastrointestinal discomforts mentioned above. These symptoms can disrupt daily life and affect quality of life, but they are generally not dangerous for overall health.
In the long term, if lactose intolerance is not properly managed, it can lead to nutritional deficiencies, particularly in calcium and vitamin D. Calcium is essential for bone health and muscle function, while vitamin D plays a crucial role in calcium absorption and bone health. Prolonged deficiency of these nutrients can increase the risk ofosteoporosis and bone fractures.
In addition, prolonged avoidance of dairy products without adequate compensation can lead to a deficiency of other essential nutrients such as B vitamins, protein and potassium, which are abundant in dairy products. It is therefore crucial for people with lactose intolerance to find suitable nutritional alternatives or use supplements if necessary to maintain a balanced diet and prevent nutritional deficiencies.
Effective management of lactose intolerance requires a thorough understanding of its effects and the implementation of dietary strategies to avoid symptoms while ensuring adequate nutrition.
How is lactose intolerance diagnosed?
Lactose intolerance is diagnosed in hospital. Self-diagnosis is not sufficient. Many people with functional digestive disorders have normal lactase activity, but complain of milk intolerance. This is probably due to digestive hypersensitivity to fermentations or psychological effects. For example, eating a white product without lactose can induce digestive symptoms.
Self-diagnosis is therefore not sufficient to conclude that there is intolerance. People’s subjective opinions about their possible intolerance prove to be wrong in more than half the cases.
To prove that the clinical symptoms are associated with poor digestion of lactose, a hydrogen exhalation test must be carried out. The higher the level of hydrogen exhaled after ingesting lactose, the less efficiently it is digested.
The Paleo diet: a return to our dietary origins?
The Paleo diet suggests a diet based on that of our Paleolithic ancestors, the period before animals were farmed and their by-products, such as milk, were consumed. The idea is that our bodies may not be fully adapted to digest foods not present in the diet of our ancestors, lactose in particular being a key example. Is this exclusion justified by a biological maladjustment or simply a fad?
Is lactose intolerance a natural phenomenon?
Lactose digestion requires lactase, an enzyme that many adults no longer produce in sufficient quantities, leading to lactose intolerance. This phenomenon raises a fundamental question: is milk consumption unnatural or the result of an evolutionary adaptation specific to certain populations that have domesticated dairy animals?
What are the risks associated with milk consumption?
Milk critics point to a number of potential problems, ranging from lactose intolerance to allergies to milk proteins. In addition, studies suggest that excessive consumption of dairy products may be linked to an increased risk of certain chronic diseases, such as cardiovascular disease and certain types of cancer. Is this evidence enough to call into question our consumption of milk?
How can we compensate for the absence of milk in the Paleo diet?
If you’re following the Paleo diet, it’s crucial to find alternative sources for the essential nutrients generally provided by dairy products, such as calcium and vitamin D. What are the best alternatives for maintaining a nutritional balance without milk?
Is the Paleo diet a viable long-term solution?
In conclusion, adopting a Paleo diet can be beneficial for some people, particularly those suffering from lactose intolerance or milk protein allergies. However, it is important to assess whether the benefits of such a diet outweigh the constraints, particularly in terms of dietary diversity and nutritional balance.
Towards optimal management of lactose intolerance: Practices and myths
Reducing dairy products: a necessity for some people
For people suffering fromlactose intolerance, it is often advisable to moderate consumption of dairy products to avoid digestive symptoms such as bloating, diarrhoea and abdominal pain. However, it is also possible to incorporate small amounts of milk, generally up to 12 grams of lactose (about a quarter of a litre of milk), depending on individual tolerance. Products such as mature cheeses and certain yoghurts, which contain less lactose, can often be consumed without discomfort.
Preventing nutrient deficiencies
Proper management of lactose intolerance also involves preventing deficiencies in key nutrients such as calcium and vitamin D, which are essential for bone health. People with lactose intolerance should look for alternative sources of these nutrients, such as fortified vegetable drinks, green leafy vegetables or food supplements, to reduce the risk of bone disorders andosteoporosis.
The importance of enzyme supplements
Lactase supplements can help intolerant people to digest the lactose contained in food more effectively. They are used as an adjuvant and not as a substitute for dietary restriction. It is essential to note that the use of these supplements must be adjusted according to individual needs and the amount of lactose consumed. Léro lactéase and Biocyte 5 enzymes are options available from our online pharmacy to help you digest lactose more effectively.
The role of lactic ferments in yoghurts
The lactic ferments present in yoghurt facilitate lactose digestion by producing lactase during fermentation. However, contrary to widespread belief, the lactase produced by these bacteria is not active in the human intestine. Nevertheless, the fermentation process reduces the amount of lactose in yoghurt, which may allow people with lactose intolerance to consume these products with fewer symptoms.
