Definition
Lactose intolerance is a malabsorption of lactose caused by a deficiency in lactase, the enzyme responsible for its digestion. Lactose is a disaccharide composed of two monosaccharides, glucose and galactose. During digestion, lactose is split into its two components by the action of the enzyme lactase. In case of lactase deficiency, lactose cannot be digested or absorbed and remains intact in the intestine. This causes a significant influx of water into the intestine, followed by bacterial fermentation of lactose and gas production (hydrogen, carbon dioxide, and methane) leading to flatulence and abdominal pain.
Classification
There are three types of lactase deficiencies:
- Congenital lactase deficiency (e.g., rare lactase deficiencies).
- Primary or acquired lactase deficiency. This is the most common form of lactase deficiency. It is due to a decrease in lactase levels with age.
- Secondary lactase deficiency. This is a lactase deficiency that can be caused by a disease affecting the intestinal mucosa (e.g., celiac disease), by an intestinal infection (e.g., gastroenteritis), or by surgical intervention on the intestines.
Symptoms
Symptoms of lactose intolerance may include abdominal pain and cramps, bloating or abdominal distension, flatulence or gas, diarrhea, nausea, and borborygmi (rumbling caused by gas movement in the intestine).
Intolerance versus allergy
It is important to differentiate lactose intolerance from milk allergy. Lactose intolerance is poor digestion of lactose due to lactase deficiency and accompanied by symptoms (e.g., diarrhea, flatulence, abdominal pain). Milk allergy is an immune system reaction to proteins present in milk. Individuals allergic to milk can normally digest lactose; it is the milk proteins that trigger the allergic reaction.
Individual tolerance
The degree of lactose intolerance can vary between individuals. Indeed, depending on individual tolerance, the rate of gastric emptying, intestinal transit time, and the colon's absorption capacity can differ from person to person. Finally, factors such as age (decrease of lactase enzyme with age), ethnicity (e.g., over 90% of Asians are lactose intolerant), and the form of the food (e.g., milk versus yogurt, naturally lower in lactose) can also influence the degree of lactose intolerance.
Nutritional treatment
Lactose intolerance can be managed through a lactose-free diet. However, as mentioned above, the degree of lactose malabsorption can vary from one individual to another. Moreover, many people with lactase deficiency can tolerate up to 250-375 mL of milk before experiencing symptoms. Consequently, nutritional recommendations should be personalized according to the needs and tolerance of each individual. In general, strategies that can be implemented to prevent symptoms of lactose intolerance include:
- Consuming small amounts of lactose at a time.
- Consuming milk or dairy products with other foods during meals and/or snacks.
- Favoring dairy products containing less lactose, such as yogurts and hard or aged cheeses.
- Choosing lactose-free or reduced-lactose milk and dairy products.
- Taking lactase enzyme tablets as needed.
It is also important to ensure that individuals with lactose intolerance meet their calcium and vitamin D needs. This can be done through diet and/or supplementation. Finally, the strategies listed above are general recommendations; it is always best to consult a dietitian for personalized nutritional advice based on your specific needs.
References
Bouthillier, Lise. January 2019. "Digestive Tract Diseases." NUT 2047 – Clinical Nutrition 2. Montreal: University of Montreal.
Article written by:
Marie-Noël Marsan, written in 2021.