What is lactose intolerance, and how can you manage it?

Lactose intolerance means that your body has difficulty breaking down lactose – a sugar in dairy products.

This intolerance can cause a range of digestive issues, including tummy pain, bloating, wind and diarrhoea. Eating fewer foods that contain lactose can significantly reduce these symptoms.

Lactose intolerance isn’t the same as a milk allergy. An allergic reaction to milk is an immune system response, and it’s rare in adults. Most children who have a milk allergy grow out of it by the time they’re 3–5 years old. 

In this article, we’ll explore the symptoms, causes and treatments of lactose intolerance, including how to manage your symptoms and what to avoid.

Symptoms of lactose intolerance

The main symptoms of lactose intolerance are digestive issues that begin after you’ve eaten foods containing lactose.

You may experience any or a combination of these issues:

• bloating

• tummy pain or discomfort

• excessive wind

• a rumbling stomach

• burping

• diarrhoea

• constipation

• feeling or being sick

These symptoms may begin within a few minutes or hours after you consume a food or drink containing lactose.

Lactose tolerance levels vary from person to person. Many people with an intolerance can still have lower-lactose versions of dairy products, like cheeses such as Swiss, parmesan and cheddar.

It may help to spread your dairy consumption throughout the day, to have smaller amounts or to pair dairy with other foods – slowing the rate at which food leaves your stomach.

Foods that can trigger symptoms

If you have lactose intolerance, your symptoms are triggered by foods and drinks containing lactose.

The main sources of lactose are dairy products, such as:

• milk – from cows, goats or sheep, including condensed or powdered forms

• cream

• yoghurt 

• cheese

• ice cream

• rice pudding

• custard

There’s lactose in many processed foods, too, including:

• breakfast cereals

• chocolate bars

• baked goods, like biscuits, cakes and pastries

• sauces

• salad dressings

• protein shakes

Causes of lactose intolerance

Lactose intolerance stems from lactase deficiency. This means that your small intestine, the upper part of your gut, doesn’t produce enough of an enzyme called lactase. 

The enzyme lactase is responsible for breaking down lactose, the sugar in dairy products.

If lactose isn’t properly digested in your small intestine, it passes into your large intestine (colon), where it causes an influx of fluid. Gut microbes ferment the undigested lactose, leading to symptoms such as diarrhoea, bloating and pain.

There are different types of lactase deficiency with different causes.

Primary lactase deficiency

Primary lactase deficiency, also called lactase non-persistence, is the most common form. It has a genetic basis and is inherited from your parents.

If you have this issue, your levels of lactase drop gradually as you age, and you’ll usually notice symptoms in adolescence or early adulthood.

Around 65% of the world's population has lactose intolerance. It’s most common among people of Asian or African-Caribbean descent and least common among people of European descent.

Secondary lactase deficiency

Secondary lactase deficiency often develops when an illness or injury damages your gut. Depending on the cause, it may be short-term or ongoing.

Causes include:

• a gut infection called gastroenteritis 

• celiac disease

• inflammatory bowel diseases (IBDs), like Crohn’s disease or ulcerative colitis

• an injury to your gut or bowel

• antibiotics

• bowel surgery

• chemotherapy

Congenital lactase deficiency

In people with this rare form of lactase deficiency, the symptoms begin from birth.

The cause is genetic, but scientists don’t fully understand how it works.

Developmental lactase deficiency

Babies born prematurely may have developmental lactase deficiency.

This is due to the gut not being fully developed, and it usually gets better with time.

Risk factors for lactose intolerance

The risk factors for lactose intolerance include:

• getting older

• having a family history of lactose intolerance

• being of Asian or Afro-Caribbean descent

• taking antibiotics

• having an IBD

• having celiac disease

• having a gut injury, infection or surgery

• undergoing chemotherapy

How to manage lactose intolerance

The main way to reduce the symptoms is to consume less lactose.

You might start by following a temporary low-lactose diet, typically for 2–4 weeks, and note down your responses.

Once your symptoms have subsided, you can try adding in different amounts of lactose to see where your tolerance level lies. 

For example, try having 100 millilitres of milk and monitoring your symptoms. If you don’t experience symptoms that day, try 200 ml the next day and 300 ml the next. 

If you'd prefer smaller steps, start with 50 ml, then 100 ml, 150 ml and so on. If you don't experience any symptoms, you can rule out lactose intolerance. 

While you're on a low-lactose diet, make sure you’re getting enough calcium by replacing dairy with a suitable alternative. Fortified plant-based milks are a good option.

The amount of lactose you can comfortably digest varies from person to person. But most people with lactose intolerance can have small amounts of lactose spread throughout the day.

As we mentioned earlier, some dairy products have more lactose than others. Milk, soft cheeses and highly processed cheeses are higher in lactose, while hard cheeses, Greek yoghurt and kefir are lower in lactose. 

You can also try lactose-free versions of dairy products. In this case, manufacturers have removed the lactose by adding the enzyme lactase to their products. Or, they’ve used an alternative to dairy.

Another option is taking lactase supplements. These come as tablets or drops, and you take them before consuming dairy to help your body break down lactose. 

There’s also some evidence that certain probiotics may help ease symptoms of lactose intolerance.

Lactose-free recipes

Consuming less lactose is one of the simplest ways to reduce lactose intolerance symptoms. But you can still enjoy delicious, nutritious meals on a low-lactose diet.

You could start by trying these low-lactose and lactose-free recipes:

Breakfast and brunch

• Speedy everyday oats (with plant-based yoghurt and milk)

• Super veg shakshuka

• Coconut custard and berries toast

Lunch

• Roasted carrot and parsnip soup 

• Roasted Mediterranean vegetable frittata (the parmesan cheese is low in lactose) 

• Sticky miso aubergines with crunchy seeds

Dinner

• Creamy cavolo nero gnocchi (with silken tofu)

• Spicy udon noodles with chilli tahini sauce

• Nourishing veggie, white bean and pesto minestrone

Sweets and snacks

• Dark chocolate and cherry cookies (with plant-based milk)

• Date, fig and buckwheat bars

• Carrot cupcakes (with soya milk and coconut yoghurt)

The dos and don’ts of lactose intolerance

Here’s a round-up of strategies for managing lactose intolerance:

Do:

• Cut out lactose until your symptoms improve, then slowly reintroduce dairy to determine how much you can manage. 

• Spread your lactose consumption throughout the day.

• Opt for smaller servings if you’re consuming lactose.

• Choose lactose-free or plant-based alternatives to dairy products.

• Pair lactose-containing foods with other foods.

• Know your cheeses. Go for hard cheeses, like Swiss, parmesan and cheddar. If you love soft cheeses, certain varieties – like brie, camembert and feta – are lower in lactose.

• Try lactase enzyme supplements to reduce your symptoms when you do eat dairy.

Don’t:

• Consume large amounts of high-lactose foods and drinks, like milk and soft cheese.

• Eat different dairy products – such as milk and ice cream – together or around the same time.

• Forget about ‘hidden’ sources of lactose, like processed foods, cakes, pastries and protein shakes.

Diagnosing lactose intolerance

You should see your doctor if you have symptoms of lactose intolerance and: 

• The symptoms keep coming back.

• You notice blood in your poo.

• You notice changes like pooing more often, looser poo or constipation. 

• You always feel bloated.

• You've lost weight unintentionally.

If your doctor thinks you could have lactose intolerance, they may:

• recommend a lactose-free diet for 2–4 weeks to see if your symptoms improve

• refer you for a hydrogen breath test, which can show how well you digest lactose

• give you a physical examination

• run blood tests

These examinations and tests can help rule out other health conditions with similar symptoms, like IBS, celiac disease, IBDs and small intestinal bacterial overgrowth (SIBO). 

Summary

Lactose intolerance causes a range of digestive symptoms, including bloating, wind, tummy pain, diarrhoea and constipation.

This intolerance results from a lack of the enzyme lactase, which helps digest the lactose in certain foods and drinks, such as dairy products.

Lactose intolerance is usually inherited from your parents, and it tends to develop from adolescence onwards.

It can also stem from a gut injury or illness, as well as from certain treatments, like antibiotics or chemotherapy. In this case, how long the intolerance lasts depends on the specific cause.  

Many people with lactose intolerance can eat small amounts of lactose-containing foods without experiencing symptoms. The right amount varies from person to person. 

To reduce the symptoms of lactose intolerance, doctors recommend consuming less lactose or opting for lower-lactose and lactose-free alternatives. 

To learn more about other gut health topics, visit Symprove’s Gut Hub. 

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