Lactose Intolerance 101 — Causes, Symptoms, and Treatment

What is lactose intolerance?

Lactose intolerance is a digestive disorder caused by the inability to digest lactose, the main carbohydrate in dairy products. It’s very common, affecting around two-thirds of the world’s adult population at minimum ( 1 ）。

This condition occurs if your body doesn’t make enough of the enzyme lactase, which you need to digest lactose ( 1 ）。

People with lactose intolerance experience digestive problems when they consume dairy, which can negatively affect their quality of life.

These symptoms include bloating,diarrhea, and abdominal cramps.

您可以随着时间的流逝而产生乳糖不耐症吗？

Lactose is found inbreast milk, and almost everyone is born with the ability to digest it. However, you can develop lactose intolerance at any age, even well into adulthood ( 1 ）。

Several types of lactose intolerance exist, and they may be caused by different factors. However, all lactose intolerance is characterized by a deficiency in the enzyme lactase.

Summary

乳糖不耐症是无法消化乳糖，这是乳制品中的主要碳水化合物。这是由于肠道中酶乳糖酶的产生降低而引起的。

Symptoms of lactose intolerance

If not managed properly, lactose intolerance may cause severe digestive problems. These symptoms may appear as quickly as 30–60 minutes after eating.

The most common symptoms are ( 1 ）：

• bloating
• abdominal cramps
• gas
• diarrhea
• nausea

Some people also experience an urgent need to go to the toilet, vomiting, lower belly pain, and constipation.

Diarrhea occurs due to undigested lactose in your small intestine, which causes water to move into your digestive tract ( 2 ）。

Once it reaches your colon, the lactose is fermented by the bacteria in your gut, formingshort-chain fatty acids(SCFAs) and gas. This causes bloating, gas, and pain ( 2 ）。

症状的严重程度取决于您可以忍受多少乳糖以及食用多少。

Fortunately, these symptoms last only briefly. You’re also typically not affected unless you consume large amounts of lactose or have another condition that’s worsened by the digestive irritation caused by lactose intolerance.

summary

乳糖不耐症可能导致消化问题,including bloating, gas, abdominal cramps, and diarrhea.

Causes and types of lactose intolerance

Lactose is made up of the simple sugars glucose and galactose.

You need the enzyme lactase to break lactose down into glucose and galactose, which your body then absorbs into your bloodstream for energy.

Without sufficient lactase, lactose moves through your gut undigested and causes digestive symptoms. Still, there are multiple causes of lactase deficiency ( 1 ）。

这是乳糖不耐症的不同类型。

原发性乳糖不耐症

原发性乳糖不耐症— the most common type — is caused by a decrease in lactase production with age. As such, you lose the ability to absorb lactose over time ( 1 , 3 ）。

这种乳糖不耐症的形式可能部分是遗传性的，因为它在某些人群中比其他人群更为普遍。

Studies estimate that this condition affects under 10% of Northern European people, around 50% of Latin and Middle Eastern people, and 80–99% of African and Asian people ( 1 ）。

Secondary lactose intolerance

Secondary lactose intolerance develops as a result of another condition that affects the small intestine, where lactase is produced. This is because inflammation in the wall of your gut may lead to a temporary decline in lactase production ( 1 , 4 ）。

Possible causes of secondary lactose intolerance include Crohn’s disease,腹腔疾病, chemotherapy, ulcerative colitis, and aging ( 1 ）。

Congenital lactose intolerance

Congenital lactose intolerance ispresent in newborns. It’s a rare, inherited type of this condition, and both parents must possess the particular gene mutation for congenital lactose intolerance for the infant to be born with it ( 1 , 5 ）。

These infants are unable to nurse due to the lactose content of breast milk, and this condition may even be fatal if not caught quickly. Side effects may include severe diarrhea and high calcium levels ( 1 , 2 ）。

This condition is also lifelong ( 1 , 2 ）。

Developmental lactose intolerance

Developmental lactose intolerance occurs in infants, too. It’s typically only seen inpremature babies, who are born before their digestive system is fully developed, and it causes symptoms like digestive distress ( 2 , 5 ）。

This condition typically resolves on its own as the baby grows, but in the meantime, your infant may need lactose-free formula rather than breast milk ( 5 ）。

Risk factors

Some people may have an increased risk of lactose intolerance. Risk factors to look out for include having the following ( 1 ）：

• Asian or African heritage
• 病史消化问题或疾病
• relatives who are lactose intolerant

summary

乳糖不耐症通常被归类为原发性，这是由于您的年龄或次要的乳糖酶水平下降而引起的，这是由另一种影响您小肠的疾病引起的。在极少数情况下，这种情况也会影响婴儿。

Tests for lactose intolerance

Here are the ways that your doctor can test you for lactose intolerance ( 1 ）：

• Hydrogen breath test.This test measures hydrogen in your breath after lactose intake. High amounts of hydrogen suggest digestive problems that may be related to lactose intolerance but also caused by other issues.
• Lactose tolerance test.该测试可测量乳糖摄入后的血糖。如果您的乳糖不耐症，您的血糖水平不会受到影响，因为您的身体无法分解乳糖。
• 基因检测。This test checks for genetic causes of lactose intolerance, but people with secondary lactose intolerance may receive a false negative.
• Lactase activity at jejunal brush border.This invasive and expensive method requires a biopsy of the jejunal brush border, which is part of your small intestine, but is a definitive way to assess lactase activity.
• Stool acidity test.Often used for babies and infants, this test measures stool acid levels, which have a lower pH in cases of lactose intolerance ( 6 ）。

你也可以做elimination testby yourself if you think you have lactose intolerance. To do it, eliminate lactose from your diet for at least 2 weeks, then reintroduce dairy to see whether you experience any digestive symptoms.

While an elimination test may help you understand whether you have trouble digesting lactose, seeking an official diagnosis from a healthcare professional may help you avoid unnecessarily eliminating dairy from your diet if your symptoms are caused by another condition.

summary

Your doctor may choose among several tests to check for lactose intolerance. Otherwise, you can try an elimination test yourself.

How to get dairy’s nutrients without consuming dairy

Dairy products, which include milk and all products made from milk, are highly nutritious.

In fact, dairy intake is linked to higher bone mineral density, which may help reduce your risk of bone fractures as you age ( 7 , 8 ）。

However, people with lactose intolerance may need to reduce or eliminate their dairy intake, potentially depriving them of key nutrients like calcium.

乳制品are excellent sources of calcium, but eating dairy isn’t critical for your health. You can follow a very healthy diet without dairy — as long as you eat other foods that are high in calcium.

一些好的nondairy sources of calciuminclude:

• 钙结合食品。Calcium-fortified foods include juices, breads, and nondairy milks like almond, soy, and oat milk. Just 1 cup (240 mL) of calcium-fortified orange juice provides 27% of the Daily Value (DV) for this mineral ( 9 ）。
• Boned fish.带有骨骼的鱼类罐头，例如沙丁鱼，鲑鱼或白饵，钙含量很高。仅3盎司（85克）用骨头的罐装鲑鱼提供DV的14％（ 9 ）。
• High calcium plant foods.许多植物食品，例如羽衣甘蓝和西兰花，都含有合理数量的钙。仅1/2杯（113克）煮沸的菠菜为钙提供9％的DV（ 9 ）。

对于钙结合果汁和非乳制奶，请确保在使用前摇动纸箱，因为钙可以放在底部。

此外，请记住，由于存在，植物食品的钙通常由于存在antinutrients像植酸和草酸盐（ 9 ）。

summary

有很多方法可以在不食用乳制品的情况下获得足够的钙。钙结合食品，骨骼罐头鱼和深色叶状蔬菜都提供钙。

Which foods contain lactose?

Lactose is found in almost all dairy products, as well as foods that contain dairy.

乳制品

以下乳制品含有乳糖（ 10 ）：

• cow’s milk (all types)
• goat’s milk
• cheese (including hard and soft cheeses)
• ice cream
• 酸奶
• 奶油
• 半半
• butter

Some of the foods above contain more lactose than others. For example, the lactose content of cheese varies significantly depending on the type. Soft cheeses like brie tend to be high in lactose, while hard cheeses like Parmesan contain only small quantities ( 11 ）。

Foods that sometimes contain lactose

Foods that include some form of dairy as an ingredient may also contain lactose, including:

• dishes made with a creamy sauce, such as pasta alfredo
• biscuits and cookies
• chocolate and packaged treats like boiled sweets and candies
• breads and baked goods
• cakes
• breakfast cereals
• instant soups and sauces
• processed meats，例如明确的火腿和香肠
• ready-made meals
• 意大利面调味料和肉汁
• 薯片，坚果和调味玉米饼
• desserts and custards

As such, it’s best to仔细检查成分列表of any packaged food if you have lactose intolerance.

Other names for added dairy

You can check whether a product contains dairy by reading the ingredient list. Added milk or dairy products may be labeled as:

• milk
• 乳固体
• milk powder
• 乳清
• 乳清protein
• 牛奶酪蛋白
• 凝乳
• 乳糖
• buttermilk
• cheese
• malted milk
• dry milk solids
• sour cream
• 乳清protein concentrate
• milk byproducts

Lactose-free alternatives

Lactose-free alternatives exist for most foods that contain lactose.

Some dairy products can be made lactose-free by removing the lactose, which is usually broken down during manufacturing into glucose and galactose ( 11 , 12 ）。

On their own, these simple sugars are naturally sweeter than lactose, givinglactose-free milksa slightly sweeter taste than conventional versions ( 12 ）。

大多数无乳糖的乳制品都被标记为“无乳糖”。乳酸只是一个备受推崇的品牌。

计划t-based dairy products — such asalmond milk, coconut yogurt, soy ice cream, and cashew cheese — are also naturally lactose-free.

summary

All conventional dairy products contain some amount of lactose. If you’re lactose intolerant, it’s also important to check the label of manufactured foods.

Treatment options for lactose intolerance

If you don’t want to give up dairy, a few natural treatments may alleviate lactose intolerance.

Enzyme supplements

Enzyme supplements may help your body digest lactose.

However, the effectiveness of these products may vary widely, from no discernible effect to reduced lactose intolerance symptoms with more favorable hydrogen breath test results ( 2 , 10 ）。

其他人可能会出现降低的症状，而其氢气测试结果没有改变，表明其安慰剂作用（ 2 , 10 ）。

As such, it may be best to consult a doctor before trying these supplements.

Lactose exposure

If you are lactose intolerant, regularly consuming lactose may help your body adapt to it ( 13 ）。

So far, studies on this strategy are limited, but initial results show positive signs.

Through regular lactose exposure, your gut microbiota may be able to produce enough lactase on its own to ease lactose intolerance symptoms — despite your body itself having a lactase deficiency ( 14 ）。

Consistency is key with this method, and high fat milk like whole milk may be the best choice because your body digests it more slowly, potentially giving your gut bacteria more time to digest the lactose ( 2 , 14 ）。

Still, further research is necessary.

益生菌和益生元

益生菌是可提供健康益处的微生物，而益生元是纤维的类型，可作为这些微生物的食物，从而喂养肠道中的有益细菌。

Bothprobioticsand prebiotics have been shown to reduce symptoms of lactose intolerance, although most studies are small ( 2 , 15 ）。

Some types of probiotics andprebiotics可能比其他人更有效。认为最有益的益生菌被认为是双歧杆菌and乳杆菌strains, which are often found in probiotic yogurts and supplements ( 2 ）。

summary

你可以尝试一些策略来减轻乳糖我ntolerance, including enzyme supplements, lactose exposure, and probiotic supplements. Yet, more research is needed on each of these strategies.

您还能吃乳糖不耐受的乳制品吗？

所有乳制品都含有乳糖，但这并不意味着如果您的乳糖不耐症，它们就完全不受限制。

Most people with this condition can tolerate small amounts of lactose. For example, some people can stomach a splash of milk in tea but not the amount you would get from a bowl of cereal.

It’s thought that people with lactose intolerance can tolerate up to 18 grams of lactose throughout the day. In fact, research reveals that many people can tolerate up to 12 grams in one sitting, which is approximately the amount in 1 cup (240 mL) of milk ( 2 , 16 ）。

在通常的部分食用时，一些乳制品也自然含量很低。例如，黄油仅包含痕量的乳糖（ 11 ）。

Certain cheeseslike Parmesan, cheddar, and Swiss likewise have less than 1 gram of lactose per 1-ounce (28-gram) serving. Generally, firm cheeses are lower in lactose than soft cheeses ( 11 , 17 , 18 , 19 ）。

Interestingly,酸奶tends to cause fewer symptoms than other types of dairy in people with lactose intolerance. This may be because the probiotics — or beneficial bacteria — in yogurt possess the lactase enzyme, helping your body break down lactose ( 20 , 21 ）。

summary

大多数患有乳糖不耐症的人可以忍受少量的乳糖。您的身体可能比牛奶更容易消化黄油，酸奶和硬奶酪等乳制品。

底线

乳糖不耐症是由乳糖酶缺乏引起的一组症状，该酶破坏了称为乳糖的牛奶糖。如果您患有这种情况，则在食用乳糖后会出现症状，这在dairy productslike milk, yogurt, and cheese.

These symptoms, which may arise shortly after eating, include abdominal pain and diarrhea.

Many people are lactose intolerant, and there are many ways to轻松调整饮食to avoid or limit lactose. These strategies include buying lactose-free foods.

If you’re concerned that you can’t tolerate dairy, rest assured that there are numerous foods and beverages you can have, along with a number of treatment options to help prevent or alleviate symptoms.