When you don't have enough of the digestive enzyme lactase to digest the lactose in dairy, you can experience abdominal discomfort and digestive issues after eating products like milk, ice cream, yogurt, and cheese. This is known as lactose intolerance.
Lactose is the natural sugar in milk and dairy foods. Your small intestine produces an enzyme called lactase to break this sugar down for digestion.
This article discusses the causes and symptoms of lactose intolerance, how it is diagnosed, and different options for managing the condition.
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This video has been medically reviewed by Chris Vincent, MD.
Lactose Intolerance Symptoms
Worldwide, upwards of 70% of adults are lactose intolerant. It's uncommon for children under 5 to have the condition. Lactose intolerance symptoms in adults, which occur only after lactose is consumed, may include:
- Abdominal cramping
- Gas
- Bloating
- Nausea
- Diarrhea
- Abdominal pain
These symptoms usually occur half an hour to a couple of hours after eating dairy products. Typically, the severity of symptoms corresponds with how much of the offending food and/or drink was consumed.
While classic lactose intolerance symptoms are present, these are fairly general symptoms that may also occur because of several other conditions.
Causes of Lactose Intolerance
Your body stops making lactase by age 5. From there, levels of this enzyme decrease. Without enough lactase to break down lactose into glucose and galactose—sugars your body can absorb and use—the lactose sits in your digestive system.
For some, a naturally occurring bacteria called lactic acid bacteria can take over for the missing lactase. But even with that present, that may not be enough to digest lactose.
This causes fluid to flow into your colon, where bacteria feed on it and causes symptoms of lactose intolerance, such as diarrhea and stomach cramps. It is only after this that it eventually leaves the body in feces.
Approximately 30 million American adults have some degree of lactose intolerance by the time they are 20 years old.
The decrease in the lactase enzyme, called lactose non-persistence, is the most common cause of lactose intolerance.
Genetics is the least common cause. Parents may pass an intolerance onto a child, in which case the condition may begin from birth. Infants with this condition may be unable to digest breast milk and require a lactose-free formula.
Others may experience lactose intolerance due to a digestive disorder. Conditions such asCrohn's disease or celiac disease can damage the intestinal cells that produce lactase.
Sudden Lactose Intolerance
For many people, the condition seems to come on suddenly, even if they never had a problem with eating or drinking products with lactose before.
Lactose intolerance may be triggered by an illness, injury, or surgery that affects your small intestine. Conditions such as celiac disease and Crohn's disease fall into this group, as do stomach infection (gastroenteritis), inflammatory bowel disease, or a bacterial overgrowth in your small intestine.
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Lactose Intolerance In Children
Though it's most common in adults, lactose intolerance can also affect children as early as age 2. If you have a child with lactose intolerance, it can be a problem throughout their life, or they may outgrow it.
The symptoms of lactose intolerance in children are the same as those in adults. You may also notice that your child is cranky or has mood swings after they consume dairy products due to the discomfort they feel.
Keep in mind that breastmilk and infant formula made with cow's milk both contain lactose. If your infant consistently becomes cranky and has symptoms of lactose intolerance after being fed one of these, see their pediatrician.
Foods That Trigger Lactose Intolerance
Since lactose is the natural sugar found in milk, cheese, and other dairy products, a person with lactose intolerance will experience symptoms any time they consume one of those products.
Foods that commonly trigger lactose intolerance include:
- Milk
- Ice cream
- Cheese
- Yogurt
- Smoothies
- White, milk-based sauce
- Food cooked with cheese, such as pizza or macaroni and cheese
- Cream dessert filling
- Custard and pudding
- Whipping creams
- Milk-based creamer, half and half
Some people may experience lactose intolerance from consuming certain foods but not others.
Lactose Intolerance or Dairy Allergy?
A dairy allergy is not the same as lactose intolerance. With dairy allergy, the immune system works to fight the proteins in milk, even though they are not inherently harmful.
Symptoms of dairy allergy are different from those of lactose intolerance. If you or your child has an allergic reaction to a dairy product, call 911 or go to the hospital immediately.
Symptoms of dairy allergy include:
- Swelling of the face, lips, tongue, or throat
- Itching or tingling of the lips
- Hives
- Wheezing or coughing
- Shortness of breath
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Diagnosing Lactose Intolerance
If you experience symptoms of lactose intolerance, it is best to speak with your healthcare provider to get a formal diagnosis and advice that is tailored specifically to your health and medical needs.
Many people determine that they or their child has lactose intolerance simply because they experience symptoms after consuming dairy. While your assumption may prove true, remember that other medical problems can produce similar symptoms. Examples include infection, inflammatory bowel disease, malabsorption, and food allergy.
Elimination Diet
An elimination diet may help diagnose lactose intolerance. With this, you eliminate all dairy products to see if the symptoms resolve.
It is important to eliminate only dairy when doing this. Otherwise, you won't be as certain about what foods trigger your symptoms.
Some of the richest non-dairy sources of calcium include:
- Calcium-fortified foods and beverages, such as orange juice, soy milk, cereals, and bread
- Canned fish with bones, such as sardines and salmon
- Leafy green vegetables, including broccoli, kale, and Chinese cabbage
- Milk substitutes such as soy and nut beverages
- Dietary supplements with calcium
Diagnostic Tests
Lactose intolerance can be diagnosed by various tests, including a lactose tolerance test, a breath test, or a stool sample test.
- Lactose tolerance test: This blood test measures your blood glucose (blood sugar) after drinking lactose. If you can't properly break down and absorb lactose, your blood glucose level will not rise as much as expected after consuming the drink.
- Hydrogen breath test: This test measures the hydrogen in your breath after you drink a lactose-containing beverage. High amounts of hydrogen suggest that you may be unable to break down the lactose.
- Stool test: A stool sample is analyzed to measure undigested lactose in the stool. This is often used for infants and young children.
Treatment of Lactose Intolerance
Treatment for lactose intolerance consists of avoiding some or all lactose-containing foods or supplementing your body's supply of lactase enzyme so that you can better digest dairy if you consume it.
When an underlying condition causes lactose intolerance in a child, treating the condition will typically resolve the symptoms within three to four weeks.
Adults are less likely to "cure" their intolerance. Lactase levels can be restored in adults, but the process can take some time and is not always possible. Treatment, therefore, is focused on management.
Diet Changes
You may find that cutting out all dairy makes you feel your best. However, this may not be necessary for everyone.
You may notice that you can tolerate cheese but not ice cream or yogurt but not milk, for example. It is perfectly fine to consume the foods and drinks that don't cause you problems while avoiding the products that do.
It's worth mentioning your diet changes to your healthcare provider so they can check for possible nutrient deficiencies resulting from eliminating foods.
If calcium is a concern, know you can also get this vital nutrient from non-dairy sources, including fortified cereals and orange juice, kale, collard greens, garbanzo beans, and cooked broccoli.
Lactose-free milk and lactose-free ice cream are available in most grocery stores. Like regular milk, these also contain calcium and vitamin D. Most people who have lactose intolerance do not experience symptoms when consuming these lactose-free dairy options.
Supplements
Over-the-counter lactase enzyme supplements can be taken before eating dairy products, but they are only effective if you get the timing right. Be sure to follow the package directions when taking these to have the beneficial effects when needed.
Probiotics—helpful bacteria that naturally live in the digestive tract—may also help ease symptoms in some people with lactose intolerance.
If your healthcare provider suggests probiotics for you, you use probiotic capsules found in the refrigerated section of a health food store. You can also get probiotics by consuming options such as pickles, kimchi, tempeh, sauerkraut, and kombucha.
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Complications of Lactose Intolerance
If you have severe lactose intolerance, some complications can occur. Frequent vomiting or diarrhea can cause dehydration, weight loss, or imbalances in electrolytes—particles that have several roles in the body, including helping your muscles contract and your nerves send signals.
If you have a gastrointestinal (GI) infection, the effects of your lactose intolerance can be more noticeable until the infection resolves. If you have a GI condition such as inflammatory bowel disease or irritable bowel syndrome, it can make your lactose intolerance worse.
Some people who have lactose intolerance avoid all dairy products. As a result, they can become deficient in essential nutrients such as calcium, vitamin D, and protein.
These deficiencies can cause several health effects, such as bone fragility.
Summary
When you are an infant, your body creates the enzyme lactase, which breaks down lactose—the sugar found naturally in milk and other dairy products. Your body stops making lactase after you are 2 to 5 years old, which is why lactose intolerance becomes more common as you age.
Lactose intolerance symptoms like diarrhea, gas, and bloating can begin a half hour or more after consuming a food or drink that contains lactose.
If you are lactose intolerant, you may be able to avoid these symptoms by not consuming lactose or by taking OTC lactase supplements or probiotics.
