Diarrhea: When Dairy Is the Problem

Medically Reviewed by Carol DerSarkissian, MD on August 26, 2021
3 min read

Milk may do a body good, but not if you’re one of the millions of people who are lactose intolerant.

If you are, you can’t digest the natural sugar (called lactose) found in milk and milk products.

Lactose intolerance symptoms include:

But there are ways to manage lactose intolerance while still getting the nutrition of dairy foods.

Lactase, an enzyme in the small intestine, breaks down the sugar in dairy products. If your body doesn't make enough lactase, you may get diarrhea and an upset stomach when you eat or drink dairy products.

You may have mild, moderate, or severe symptoms, depending on how much lactase your body makes.

Most people develop low lactase levels during childhood (about age 5). In some people, those low levels continue into adulthood.

Low levels of lactase also can be caused by:

Genetics: It’s rare, but some people are born with a gene mutation that prevents them from making lactase. Babies with it usually have diarrhea from birth.

Premature birth: Babies born early may not make enough lactase at first. They’ll make more as they get older.

Other health conditions: Things such as celiac disease, irritable bowel syndrome, cystic fibrosis, and Crohn’s disease, as well as injuries to the small intestine, can lead to less lactase.

If you’re lactose intolerant, you can have symptoms from between 30 minutes to 2 hours after eating or drinking dairy products.

You can control your symptoms with changes to your diet, like avoiding dairy foods. But you might find that you can have some types of dairy. For example, you may learn that some cheeses, like Swiss, cheddar, feta, or goat, don’t bother you, while others trigger symptoms. Or you may be able to have one glass of milk but not more.

You could also:

  • Eat and drink lactose-free milk or dairy-free substitutes like soy, rice, almond, or hemp milk.
  • Pair a solid food with a dairy product (like cereal with milk)
  • Take a lactase enzyme when you eat dairy. You can get these as over-the-counter tablets or liquid.

Although milk is most associated with lactose intolerance, any dairy product may cause diarrhea and other symptoms. Lactose can also be found in:

  • Yogurt
  • Cheese
  • Cream cheese
  • Cottage cheese
  • Ice cream

Milk and dairy products aren’t the only offenders. Lactose may be found in foods you don’t expect, including:

  • Calcium-fortified breads
  • Cereals and baked goods
  • Powdered meal replacements
  • Instant potatoes, soups, and breakfast drinks
  • Pancake, biscuit, and cookie mixes
  • Margarine
  • Salad dressings
  • Products labeled “non-dairy,” like whipped toppings and creamers, which may include milk-derived ingredients

If you are lactose intolerant, the best way to avoid symptoms is to read food labels. Steer clear of products with:

  • Whey
  • Curds
  • Milk by-products
  • Nonfat dry milk powder
  • Dry milk solids

Lactose also is found in more than 20% of prescription drugs and in some over-the-counter medicines. Birth control pills may contain lactose. Even things lactose-intolerant people may take for relief, such as tablets to reduce stomach acid and gas, can contain lactose.

Ask your doctor or pharmacist if a medicine has lactose before you take it.

If you cut back on dairy, it’s especially important for you to get enough calcium. It’s one of the body’s essential nutrients. You need it for healthy bones. It also holds off osteoporosis, a condition that leaves bones thin and easily breakable.

If you’re lactose intolerant, a number of non-dairy foods can help you get enough calcium. They include:

  • Dark, leafy greens and vegetables like broccoli, spinach, and kale
  • Salmon and tuna
  • Beans and legumes
  • Calcium-fortified soy milk and cheeses
  • Almond milk
  • Oranges

You may also be able to eat yogurt that has active cultures. Some studies have found the active cultures in yogurt produce those important lactase enzymes, which can help you digest the lactose in the yogurt. Probiotic yogurts also provide good bacteria without dairy.

If you avoid milk, you also need to make sure you get enough vitamin D. It works with calcium to keep bones strong, and milk is a major source of vitamin D. If you are lactose intolerant, ask your doctor if you should take a calcium and vitamin D supplement.