lactose intolerance · a plain-English guide

Lactose intolerance symptoms: what they are and how to ease them

Bloated, gassy or running for the loo after a latte or a pizza? That pattern is the classic sign of lactose intolerance. Here’s what’s going on, how to tell, and what people do about it.

What is lactose intolerance?

Lactose is the natural sugar in milk and in foods made from milk. To digest it, your small intestine makes an enzyme called lactase, which splits lactose into two simpler sugars your body can absorb.

If you don’t make enough lactase, some lactose passes undigested into your large intestine. Bacteria there ferment it, producing gas and drawing in water. That’s what causes the symptoms.

It’s very common. Most adults around the world make less lactase than they did as babies, and it’s more common in people of African, Asian, Middle Eastern and South American heritage.

Symptoms of lactose intolerance

• Bloatinga swollen, tight tummy, often the first thing people notice
• Windoften smelly, and hard to hold in
• Stomach crampsusually low down, coming in waves
• Diarrhoeacan come on quickly
• Rumbling stomachloud enough for others to hear
• Feeling sicksometimes with vomiting

Symptoms can be mild or quite severe. They usually depend on how much lactose you had: a splash of milk in tea might be fine, while a milkshake or a creamy pasta sauce isn’t.

When do symptoms start?

Because of that delay, it’s easy to blame the wrong thing. Keeping a short food and symptom diary for a week or two often makes the pattern obvious.

Is it lactose intolerance, or something else?

Several conditions cause similar symptoms, including irritable bowel syndrome (IBS), coeliac disease and a cows’ milk allergy. If you think you’re lactose intolerant, it’s worth seeing a GP rather than guessing. They may ask you to cut out lactose for a couple of weeks to see if things improve, or arrange a hydrogen breath test.

How to ease lactose intolerance symptoms

There’s no cure for primary lactose intolerance, but most people find a way of eating that keeps symptoms down without giving up everything they like.

Find your own limit

Very few people need to cut lactose out completely. Many can handle a small amount, such as milk in a cup of tea. Try small amounts and build up slowly to see what you can manage.

Have dairy with food, and spread it out

Lactose eaten as part of a meal, in small amounts through the day, tends to cause fewer problems than a big dose on its own.

Choose lower-lactose foods

Hard cheeses like cheddar and parmesan contain very little lactose. Live yoghurt is often easier than milk too. Milk, ice cream, cream and milky sauces are usually the biggest culprits.

Swap to lactose-free versions

Lactose-free milk, yoghurt, cheese and cream are now in most supermarkets, as are plant-based drinks. If you cut back on dairy, choose ones with added calcium so your bones don’t miss out.

Check labels for hidden lactose

Milk turns up in bread, biscuits, cakes, ready meals, soups, sauces and some processed meats. In the UK milk must be highlighted in the ingredients list. Look out for whey, milk powder, milk solids and skimmed milk powder.

Types of lactose intolerance

• Primary (the most common): your body gradually makes less lactase after childhood. This is usually lifelong.
• Secondary: a gut problem such as gastroenteritis, coeliac disease or Crohn’s disease damages the lining of the small intestine and lowers lactase for a while. It often improves once the gut heals.
• Congenital: a very rare inherited condition where a baby makes little or no lactase from birth.

Common questions