Do you get diarrhea after drinking milk? Learn about this digestive problem that troubles 90% of Chinese people

Preface

Lactose intolerance is a common nutritional absorption disorder in the world, and its incidence varies significantly among different populations. Data show that the global prevalence of lactose intolerance is about 65%, while in Asian populations, this proportion is significantly higher, close to 90%. In China, especially among adults, the incidence of lactose intolerance is even higher, as high as 85% to 95%. Although lactose intolerance is usually not life-threatening, it has a significant impact on the quality of daily life, especially in the early stages of breastfeeding, when infants may experience digestive symptoms related to lactose intolerance, leading to difficulties in breastfeeding.

In recent years, lactose intolerance and fructose intolerance are often mentioned in parallel, collectively referred to as "disaccharide intolerance", which affects the digestion and absorption of lactose and fructose respectively. This article will introduce the definition, epidemiology, clinical manifestations, diagnosis and relief methods of lactose intolerance in detail, and refer to many authoritative SCI papers and clinical experience, in order to provide treatment suggestions based on scientific evidence.

1. Definition and epidemiology of lactose intolerance

1. Lactose intolerance is caused by insufficient activity or quantity of lactase in the body, which leads to inadequate digestion of lactose and causes gastrointestinal discomfort. As we know, lactase is usually located on the brush border of the small intestine and is responsible for the breakdown of lactose. As people age, the lactase activity of most people will gradually decrease, especially in countries where non-dairy products are the staple food.

2. Global epidemiology: Current studies show that about 65% of the world's population has decreased lactase activity. However, the incidence varies greatly in different regions. For example, the incidence of lactose intolerance is low in the Nordic population (5% to 20%), while it is relatively high in the African and Latino populations in Asia, Africa, and the Americas, exceeding 80%.

Situation in Asia: In Asia, especially in East Asia, the incidence of lactose intolerance is much higher than in Europe and America. The adult lactose intolerance rate in countries such as China, Japan and South Korea is close to 90%. This is related to genetic factors, gene evolution, dietary habits and decreased lactase activity.

Situation in China: China is a country with a high incidence of lactose intolerance. The activity and quantity of lactase in most Chinese populations gradually decrease after puberty, resulting in a high proportion of lactose intolerance in adults. However, due to the popularity of breastfeeding, lactose intolerance in infants in China is relatively low, but it can still manifest at the end of lactation or after weaning.

3. We know that lactase not only differs in activity, but also in quantity and production. Because lactase is an enzyme secreted by the epithelial cells of the small intestine, its main function is to break down lactose into glucose and galactose so that it can be absorbed. When the quantity, production or activity of lactase is insufficient, lactose cannot be completely broken down, resulting in symptoms of lactose intolerance.

Lactase levels: Lactase levels vary from person to person due to genetics and age. Lactase activity is usually highest in infancy because the lactose in breast milk is the main source of energy for infants. However, as people age, they gradually lose the ability to produce lactase, resulting in a decrease in lactase levels. This phenomenon is common in many adults in Asia, Africa, and South America, but less common in some people in Northern Europe.

Lactase production: In addition to changes in quantity, lactase production is also affected by eating habits. People who do not consume dairy products for a long time will have lower lactase expression levels, while people who regularly consume dairy products will have relatively higher lactase production.

The relationship between activity and quantity: Even if the amount of lactase is sufficient, if its activity is insufficient, lactose cannot be effectively broken down. The activity of lactase is affected by multiple factors, including gene mutation, intestinal microenvironment, and inflammation.

In summary, the activity, quantity and production of lactase jointly determine a person's tolerance to lactose, which is of great significance in the treatment and management of lactose intolerance.

2. Disaccharide intolerance: the difference between lactose and fructose intolerance

"Disaccharide intolerance" is the collective name for lactose intolerance and fructose intolerance. These two intolerances are related to defects in lactase and fructose transporter respectively. The two have different mechanisms, but both lead to carbohydrate digestion disorders.

1. Lactose intolerance: refers to the lack or insufficiency of lactase, which results in the inability to effectively break down lactose into glucose and galactose. Lactose cannot be absorbed into the blood, but enters the colon, where it is fermented by bacteria to produce gas and short-chain fatty acids, which usually cause symptoms such as bloating, abdominal pain and diarrhea, and in rare cases, severe constipation.

2. Fructose intolerance: Fructose intolerance is due to the lack of activity or absence of the fructose transporter (GLUT-5) on the surface of small intestinal cells, which leads to the inability to effectively absorb fructose, thus causing gastrointestinal discomfort. Although both are forms of carbohydrate intolerance, lactose intolerance involves enzyme deficiency, while fructose intolerance is more related to abnormal transporter function.

3. Symptoms of lactose intolerance

The clinical symptoms of lactose intolerance are related to the fermentation of inadequately digested lactose in the colon. These symptoms include:

Abdominal distension: Due to the fermentation of lactose, gas is produced, causing the patient's abdomen to bloat.

Abdominal pain: Gas buildup in the colon and intestinal spasms cause abdominal pain.

Diarrhea: Unabsorbed lactose attracts water into the intestines, causing watery stools.

Nausea and vomiting: Some patients may feel nauseous or even vomit after consuming dairy products.

Increased bowel sounds: Due to the increase in gas in the intestines, patients will feel increased intestinal peristalsis sounds.

The intensity of lactose intolerance symptoms varies from person to person. Some people tolerate higher amounts of lactose, while others experience significant discomfort even with small amounts.

4. Diagnosis of lactose intolerance

The diagnosis of lactose intolerance is usually confirmed by clinical presentation and some laboratory tests.

Common diagnostic methods include:

1. Lactose load test: The patient takes a lactose-containing solution orally on an empty stomach, and then measures the blood sugar level. If the lactase activity is normal, lactose will be broken down and absorbed, and the blood sugar level will rise. If the blood sugar level does not rise enough, it indicates lactose intolerance.

2. Breath hydrogen test: When lactose is not digested, it will ferment in the colon and produce hydrogen. By testing the concentration of hydrogen exhaled by the patient, the lactose digestion ability can be indirectly assessed.

3. Fecal pH test: For people with lactose intolerance, lactose is fermented in the colon to produce acidic products, which leads to a decrease in fecal pH.

5. Management and relief of lactose intolerance

Treatment of lactose intolerance mainly involves dietary management and enzyme replacement therapy. Common relief measures include:

1. Limit lactose intake: Avoiding or reducing the intake of dairy products is the most effective way to relieve symptoms. Patients can choose low-lactose or lactose-free alternative products, such as lactose-free milk, yogurt, hard cheese, etc.

2. Lactase supplements: Oral lactase supplements can help patients break down lactose when they ingest lactose and reduce discomfort symptoms.

3. Probiotic supplementation: Some studies have shown that taking specific probiotics can improve lactose digestion. Certain probiotics, such as Lactobacillus acidophilus and Bifidobacterium, may help improve lactose tolerance.

4. Calcium supplementation: Since lactose intolerant people usually reduce their intake of dairy products, this may lead to insufficient calcium intake. Therefore, it is recommended that lactose intolerant people supplement calcium through other means, such as consuming green leafy vegetables, nuts or calcium supplements.

6. Management of fructose intolerance

For people with fructose intolerance, treatment focuses on reducing the intake of high-fructose foods, such as certain fruits, sweeteners, and processed foods. Avoiding foods that contain large amounts of fructose and fructose-glucose mixtures can effectively reduce symptoms.

at last

Lactose intolerance is a common carbohydrate malabsorption disease (disease or malabsorption state) with a high incidence rate worldwide, especially in Asian and Chinese populations. Although lactose intolerance is usually not life-threatening, it has a significant impact on the quality of daily life. Especially for infant feeding, lactose intolerance is a common problem for parents. Scientific diagnosis and management can help patients effectively control symptoms and improve their quality of life.

As research progresses, treatments for lactose intolerance may become more diverse and precise, especially in the application of enzyme replacement therapy and probiotics. At the same time, more scientific research support is needed for the prevention and early intervention of lactose intolerance in infants during breastfeeding.

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