Why Does Dairy Make Me Bloated and Gassy?Lactose Intolerance Explained

The latte was a mistake, and your stomach has a way of announcing it. Forty minutes after the last sip, there’s rumbling, then pressure, then a decision about whether to leave the meeting.

What’s happening

Lactose is the sugar in milk. The NIDDK¹ says the problem is that your small intestine makes low levels of lactase, the enzyme that breaks lactose down, so it can’t digest all the lactose you eat or drink. Undigested lactose reaches the colon, where bacteria ferment it and produce fluid and gas, which triggers symptoms.

The NIDDK¹ lists bloating, diarrhea, gas, nausea, abdominal pain, stomach rumbling and vomiting, within hours of consuming dairy, with severity depending on how much lactose you had. The NHS² says symptoms start a few minutes to a few hours after, and can also include constipation, headaches, tiredness, and joint or muscle pain.

Why it starts later in life

The most common cause, the NIDDK¹ says, is primary lactase deficiency, also called lactase nonpersistence. The small intestine makes less lactase after infancy, and lactase levels get lower with age. Symptoms may emerge anywhere from childhood to early adulthood.

The NIDDK¹ describes two other types. Secondary lactose intolerance follows damage to the small intestine from conditions such as Crohn’s disease or celiac disease, infections or medical treatments, and may be reversible if the underlying injury is treated. Congenital lactase deficiency, which starts at birth, is rare.

It’s common. The NIDDK³ says about 68% of the world’s population has lactose malabsorption, though only those with symptoms are considered lactose intolerant, and that about 36% of people in the US are affected. It adds that African Americans, American Indians, Asian Americans and Hispanic and Latino people are more likely to have it.

It isn’t a milk allergy

The NIDDK³ says lactose intolerance is different from a milk allergy, which is an immune system disorder. The NHS² says food allergies can cause difficulty breathing, itchy skin and swelling, and can be life-threatening. Those symptoms need emergency care, not a dietary tweak.

How it’s confirmed

Bloating and gas have many causes, so confirmation helps. The NIDDK⁴ says your doctor may ask you to cut out milk and milk products for a period of time to see if symptoms go away, or use a hydrogen breath test: you drink a lactose solution and breathe into a container every 30 minutes. If your breath hydrogen rises and your symptoms get worse, it may be diagnosed. The NHS² lists the elimination diet, blood tests and the breath test.

The NIDDK⁴ also says to see a provider for persistent symptoms because irritable bowel syndrome, celiac disease and inflammatory bowel disease can cause similar ones. Our articles on stress and your stomach, gas and bloating through the day cover the overlap.

What helps

Most people with lactose intolerance can manage some lactose. The NIDDK⁵ says many people can have 12 grams, about the amount in 1 cup of milk, without symptoms or with only mild ones. To improve your tolerance, it suggests drinking small amounts of milk at a time and having it with meals, or trying yogurt and hard cheeses like cheddar or Swiss, which are lower in lactose. Lactose-free and lactose-reduced products are also an option.

The NHS² says taking a lactase supplement before food or drink containing lactose may reduce or prevent symptoms.

Watch for hidden lactose. The NIDDK⁵ lists bread and other baked goods, processed meats like bacon, sausage and hot dogs, and nondairy coffee creamers. Check labels for milk, whey, curds and dry milk solids.

Don’t lose your calcium. The NIDDK³ says that if you limit dairy you may get less calcium and vitamin D, which can affect your bones. It lists canned salmon or sardines, broccoli and leafy green vegetables for calcium, and eggs, certain fish and fortified cereals for vitamin D.

The NIDDK⁵ and the NHS² both say to talk with your doctor or a dietitian before making big diet changes, so you still get enough nutrients.

The play

Try this: a dairy diary

For two weeks, write down what dairy you eat or drink, the amount, whether it came with a meal, and your symptoms with a time.

Notice what’s fine and what isn’t. Small servings with food, yogurt or hard cheese may fall in the fine column.

Take the diary to your appointment. The NIDDK⁴ says to be ready to talk about your symptoms, history and eating habits.

When to get checked

Don’t wait if

1. Emergency

   If you get hives, swelling of the lips or face, or trouble breathing after eating dairy, call 911 right away.

The NHS² says to see a GP if symptoms keep coming back after eating, you notice unusual changes in your bowel habits lasting 3 weeks or more, you see blood in your stool for 3 weeks or more, or you lose weight without trying. The NIDDK¹ says persistent digestive symptoms after dairy deserve an appointment, since other conditions can look the same.

Book an appointment if any of these fit:

• Bloating, gas or diarrhea keeps happening after dairy
• You’ve changed your diet but symptoms haven’t improved
• You have blood in your stool or have lost weight without trying
• Your bowel habits changed and haven’t settled in 3 weeks
• You’re cutting out dairy and worry about calcium

The latte isn’t forbidden. It needs a plan, a lactase tablet or a smaller cup.