Lactose Intolerance: Symptoms, Diagnosis and the Dairy You Can Still Eat
By Alexandria “Alix” Best, founder and head coach of The Swole Kitchen · Certified Nutritionist · B.S. Public Health · Precision Nutrition certified
A latte, a bowl of ice cream or a protein shake, and an hour or two later you are bloated, gassy and looking for a bathroom. If that pattern sounds familiar, lactose may be the reason. It is one of the most common digestive issues in the world.
The good news is that most people with lactose intolerance do not need to give up dairy completely, and hitting your protein and calcium targets is very doable. Here is what lactose intolerance is, how it is diagnosed, how much dairy most people tolerate and how to read labels for hidden lactose.
Key takeaways
- Lactose intolerance means digestive symptoms after eating lactose, the natural sugar in milk, because your small intestine makes too little of the enzyme lactase.
- It is very common. About 68% of people worldwide and about 36% of people in the U.S. have lactose malabsorption, though not all of them get symptoms.
- Most people can still have some lactose. Research suggests many tolerate about 12 g at a time, roughly one cup of milk, especially with a meal.
- Hard cheeses, yogurt and lactose-free dairy are often easy options, and there are plenty of lactose-free ways to get protein and calcium.
- See a doctor before cutting out dairy for good. Celiac disease, IBS and other conditions can cause similar symptoms, and a milk allergy is a different, potentially serious problem.
What is lactose intolerance?
Lactose is a sugar made of two smaller sugars, glucose and galactose. To absorb it, your small intestine uses an enzyme called lactase to split it apart. When you do not make enough lactase, some lactose travels undigested to the colon. Bacteria there ferment it, producing gas and drawing in fluid, and that causes the symptoms.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) separates two terms that often get mixed up:
- Lactose malabsorption means your body cannot break down all the lactose you eat.
- Lactose intolerance means that malabsorption causes symptoms. Only people with symptoms are lactose intolerant.
Why it happens
- Lactase nonpersistence. The most common cause. Lactase production naturally drops after infancy, so symptoms may start in later childhood, the teen years or early adulthood. It is genetic and runs in families.
- Secondary lactose intolerance. Damage to the small intestine from conditions like celiac disease or Crohn's disease, or from some medicines, surgery or radiation. It may improve once the underlying cause is treated.
- Congenital lactase deficiency. A rare condition present from birth.
Who is more likely to have it
Lactose malabsorption is most common in people whose families come from Africa and Asia, and least common in people of northern European descent. In the U.S., NIDDK notes it is more common among African Americans, American Indians, Asian Americans and Hispanic or Latino people.
Symptoms of lactose intolerance
Symptoms usually start within a few hours of eating or drinking lactose. They include:
- Bloating and gas
- Diarrhea
- Abdominal pain or cramping
- Stomach rumbling
- Nausea, and sometimes vomiting
How severe they are depends mostly on how much lactose you had at once. A splash of milk in coffee may cause nothing, while a large milkshake on an empty stomach may cause a lot.
Lactose intolerance vs. milk allergy
| Lactose intolerance | Milk allergy | |
|---|---|---|
| What it is | A digestive problem with milk sugar | An immune reaction to milk proteins |
| Typical onset | Later childhood, teens or adulthood | Usually in the first year of life |
| Symptoms | Gas, bloating, diarrhea, cramps | Can include hives, swelling, vomiting, wheezing and, in severe cases, anaphylaxis |
| Small amounts | Often tolerated | Can trigger a reaction |
| Lactose-free milk | Usually fine | Not safe, it still contains milk protein |
If you have trouble breathing, swelling of the lips or throat, or hives after dairy, that is not lactose intolerance. Get emergency care.
How lactose intolerance is diagnosed
You can notice a pattern on your own, but a doctor should confirm it, because other conditions cause similar symptoms. NIDDK lists irritable bowel syndrome, celiac disease, inflammatory bowel disease and small intestinal bacterial overgrowth as conditions to consider. Diagnosis usually involves:
- A history and exam. Your doctor asks about symptoms, diet and family history.
- A trial elimination. You avoid milk and milk products for a set period to see if symptoms go away, then reintroduce them.
- A hydrogen breath test. You drink a measured amount of lactose and breathe into a container every 30 minutes for a few hours. A rise in breath hydrogen along with symptoms points to lactose intolerance.
When to see a doctor
- Symptoms that are new, worsening or happening even without dairy.
- Weight loss, blood in your stool, ongoing diarrhea, fever or waking at night with symptoms.
- A family history of celiac disease or inflammatory bowel disease.
- You are planning to cut dairy entirely, especially for a child, a teen or during pregnancy.
How much dairy can you tolerate?
Most people with lactose intolerance can have some lactose. NIDDK points to research suggesting many people can have about 12 g, roughly the amount in one cup of milk, with no symptoms or only mild ones. Spreading dairy through the day and eating it with other food usually helps.
| Food | Serving | Lactose (approx.) |
|---|---|---|
| Milk (nonfat to whole) | 1 cup | 12–13 g |
| Lactose-free milk | 1 cup | 0 g |
| Ice cream or frozen yogurt | 1/2 cup | 2–6 g |
| Low-fat yogurt | 6 oz | 4 g |
| Cottage cheese (2%) | 1/2 cup | 3 g |
| Sour cream | 2 tbsp | under 1 g |
| Cheddar or Swiss | 1 oz | under 1 g |
| Mozzarella | 1 oz | under 1 g |
| Butter | 1 tsp | about 0 g |
Values are estimates from a UVA Health handout and vary by brand and recipe. Yogurt with live cultures is often better tolerated than its lactose number suggests, and aged hard cheeses contain very little lactose.
Practical ways to tolerate dairy
- Start small and go slow. Add one food at a time in a small amount and see how you feel.
- Have dairy with meals, not on an empty stomach.
- Choose lower-lactose options like hard cheese, yogurt with live cultures and lactose-free milk.
- Use lactase products if they help. Lactase drops or tablets taken with dairy help many people digest it. Ask your doctor or pharmacist if you are unsure.
Lactose-free protein options
Milk, yogurt and cottage cheese are some of the most convenient protein sources there are, so going lactose-free can leave a gap. These options help you stay on target. For your daily goal, see how much protein you need or use our Macro Calculator.
| Option | Lactose | Notes |
|---|---|---|
| Lactose-free milk, yogurt and cottage cheese | None or very little | Same protein as the regular versions. NIDDK notes they are as healthy as regular dairy. |
| Hard aged cheese | Very low | Good flavor and protein, but higher in calories and fat |
| Whey protein isolate | Usually lower than whey concentrate | Not lactose-free by default. Check the label and test your own tolerance. |
| Eggs, egg whites, chicken, fish, lean beef, turkey | None | Naturally lactose-free. Watch for breaded or processed versions. |
| Tofu, tempeh, edamame, lentils, beans | None | Plant proteins, also good sources of fiber |
| Pea, soy or other plant protein powders | None | Check for added milk ingredients |
For snack and meal ideas, see our high-protein snack guide and what to eat after a workout.
Do not forget calcium and vitamin D
Cutting dairy without replacing it can leave you short on calcium and vitamin D. Good nondairy calcium sources include canned salmon and sardines with soft bones, tofu made with calcium, leafy greens and broccoli, almonds, beans, and fortified soy milk, cereals and juices. Vitamin D comes from fatty fish like salmon, eggs, fortified foods and sunlight. Talk with your doctor before starting supplements, especially high-dose vitamin D.
How to read labels for hidden lactose
Lactose shows up in more than milk and cheese. NIDDK lists baked goods, breakfast cereals, instant potatoes, soups, salad dressings, flavored chips, processed meats like bacon and lunch meat, meal replacements, protein powders and bars, and nondairy creamers.
On the ingredient list, look for:
- Milk, lactose or whey
- Curds
- Milk by-products
- Dry milk solids or nonfat dry milk powder
A small amount in a long ingredient list is usually not a problem for most people. Some prescription and over-the-counter medicines also contain small amounts of lactose, so ask your pharmacist if you are very sensitive. When eating out, our tips on eating healthy at restaurants can help you ask the right questions.
Frequently asked questions
Can you suddenly become lactose intolerant?
Yes, lactose intolerance can seem to appear suddenly. Lactase levels naturally fall with age for many people, so symptoms may start in the teen years or adulthood. Intestinal damage from an illness, celiac disease, Crohn's disease, surgery or some medicines can also cause it, sometimes temporarily. Because other conditions cause similar symptoms, see your doctor if digestive problems start without a clear reason.
What cheese is lowest in lactose?
Hard, aged cheeses are lowest in lactose. Cheddar, Swiss and Parmesan typically contain less than 1 gram per ounce, because most lactose drains off with the whey or breaks down during aging. Mozzarella is also low. Fresh, soft cheeses like ricotta and cottage cheese contain more, and processed cheese products can vary, so check labels and test your own tolerance.
Is Greek yogurt OK for lactose intolerance?
Greek yogurt is often well tolerated by people with lactose intolerance. Straining removes some lactose, and live cultures help break down part of what remains. Lactose content still varies by brand, so start with a small serving with a meal and see how you feel. Lactose-free Greek yogurt is a good option if regular versions cause symptoms.
Is whey protein OK if you are lactose intolerant?
It depends on the type and your sensitivity. Whey protein isolate is usually lower in lactose than whey concentrate, and many people with lactose intolerance tolerate it in a single scoop. It is not automatically lactose-free, though. Check the label, start with a half serving, or choose a plant-based powder such as pea or soy if symptoms continue.
Is lactose intolerance the same as a dairy allergy?
No, they are different conditions. Lactose intolerance is a digestive problem with milk sugar that causes gas, bloating and diarrhea. A milk allergy is an immune reaction to milk proteins that can cause hives, swelling, vomiting or trouble breathing, and it can be life-threatening. Lactose-free milk is fine for most people with lactose intolerance but not for anyone with a milk allergy.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases. Definition and Facts for Lactose Intolerance.
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and Causes of Lactose Intolerance.
- National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of Lactose Intolerance.
- National Institute of Diabetes and Digestive and Kidney Diseases. Eating, Diet, and Nutrition for Lactose Intolerance.
- UVA Health. Managing Lactose Intolerance (2024).
This article is for education and is not medical advice. If you have ongoing digestive symptoms, talk with your doctor before removing foods from your diet.
About the coach
Alexandria “Alix” Best founded The Swole Kitchen and coaches every client personally. She is a certified nutritionist with a B.S. in Public Health and Precision Nutrition certification, and has coached 1:1 nutrition and training for more than ten years. More about Alix