Lactose Intolerance: Symptoms, Causes, What to Eat and More

By: Sharmin Sampat

Think you might be lactose-intolerant? You're not alone; about 65 percent of the world's population suffers from the symptoms associated with being unable to properly digest milk sugar, known as lactose.

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Our bodies produce an enzyme called lactase, which digests lactose. But after early childhood, many people produce less lactase. When that happens, your body doesn't have enough of the enzyme it needs to digest lactose, which can lead to the symptoms we associate with lactose intolerance—such as abdominal pain, bloating or diarrhea.

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Symptoms of Lactose Intolerance

Lactase is produced by cells in the lining of the small intestine. When your body doesn't break down milk sugars, the undigested lactose moves through the large intestine, causing symptoms including:

Abdominal pain or cramps
Nausea
Bloating
Diarrhea

Most people who are lactose-intolerant begin to experience symptoms between 30 minutes and 2 hours after eating lactose-containing foods. That's not always the case though, as only about one-third of people who are lactose-intolerant have noticeable symptoms.

Causes of Lactose Intolerance

A decreased ability to produce lactase can be genetic, or may be caused by residual damage to the small intestine following a viral or bacterial infection. Where you're from makes a difference too; lactose intolerance is most commonly found in people of East Asian descent, as well as in people of West African, Arab, Jewish, Greek and Italian descent. Only about 5 percent of people of Northern European descent are lactose-intolerant.

What Should You Do If You Are Lactose-Intolerant?

Tomato-Cheddar Cheese Toast

Pictured Recipe: Tomato-Cheddar Cheese Toast

Avoiding lactose often means steering clear of many, but not all, dairy products. That can pose a problem, as dairy products are important sources of protein, calcium and vitamins A, B12 and D. Many Americans already fall short of the daily recommended amount of calcium; if you avoid dairy products, you're even more likely to be calcium-deficient. You may have to try a little harder but there are plenty of nondairy sources of calcium (see below).

Luckily, being lactose-intolerant doesn't mean that you have to give up all products that contain milk. Simply employ a few different tactics that can help you enjoy dairy products without the undesirable side effects.

Consume foods low in lactose: Hard cheeses like Parmesan and Cheddar contain little to no lactose and usually can be digested easily.
Eat probiotics: Consuming probiotics from fermented dairy, such as yogurt or kefir, can be helpful, as they contain certain types of beneficial bacteria that aid lactose digestion.
Try lactose-free dairy products: Explore lactose-free or reduced-lactose milk; the lactose is predigested (lactase enzyme has been added by the manufacturer), which makes it more easily digested.
Take lactase enzyme pills: Lactase enzyme tablets are designed to help digest the lactose in dairy and may help alleviate symptoms, though it's suggested you check with your health care provider before beginning use.
Try introducing lactose slowly: People with lactose intolerance can generally tolerate about 12 g of lactose at a time (that's the equivalent to the lactose in 1 cup of milk), or 18 g of lactose spread throughout the day. Some research also suggests that people become more tolerant of lactose when they consume it more regularly.
Have lactose-containing foods with meals: Lactose is better tolerated when consumed with other (solid) foods.
Give chocolate milk a try: The cocoa in the chocolate helps reduce the symptoms and effects of lactose in milk. Milk chocolates are usually well-tolerated and do not induce symptoms, although many dark chocolates are dairy- and lactose-free.

Good Dairy-Free Calcium Sources

Roasted Root Veggies

Pictured Recipe: Roasted Root Veggies & Greens over Spiced Lentils

If you decide to go dairy-free, it's important to be sure you're getting enough of the vitamins and minerals you would otherwise find in dairy products. Incorporate plenty of nutrient-rich fruits, vegetables and whole grains. Be sure to look for recipes high in calcium in order to reach the recommended daily amount of calcium, which is at least 1,000 mg (teenagers and pregnant, nursing and postmenopausal women need more). Here are some good nondairy sources of calcium:

Calcium-fortified foods: Many foods—including fruit juices and nondairy milks—contain added calcium. Shake the carton well before use, as the calcium can settle at the bottom. Fortified tofu and whole-grain cereals can also help you meet your calcium needs.
Fish with bones: Fish with small edible bones, like sardines and anchovies, are high in calcium.
Dark leafy greens: Kale, chard and collard greens all deliver calcium—not to mention other vitamins and minerals.

Is It a Milk Allergy?

Lactose intolerance is very common, but its symptoms are sometimes confused with those of a milk allergy, which is far less common. A milk allergy is a reaction to the protein in cow's milk, and has nothing to do with the amount of lactase in the body. Milk allergies are most often seen in children under the age of 3—and many children outgrow them by age 5. Some of the symptoms are similar, so it's important to find out if you're actually allergic to milk or lactose-intolerant by checking with your doctor. Nearly 20 percent of people with lactose intolerance are also allergic to milk.

Bottom Line

It's not always necessary to eliminate dairy from your diet if you are lactose-intolerant. Most people can tolerate some amounts of lactose—and if avoiding lactose is tough, it's worth experimenting with small amounts. The good news is that it's perfectly possible to go dairy-free and maintain healthy levels of calcium. Just be sure to eat balanced meals and include calcium-rich food sources in your diet. And it's always best to consult your doctor or dietitian before making drastic changes in your diet, and especially if your symptoms persist.

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Related:
How to Start Eating Dairy Free
Dairy-Free & Lactose-Free Recipes
Buyer's Guide to Non-Dairy Milk