Lactose Intolerance
Bloating, wind and loose poo after dairy, because your gut makes too little of the enzyme that digests milk sugar. Usually you can still have some dairy.
Quick answer: Lactose intolerance means your small bowel makes too little lactase, the enzyme that digests lactose (milk sugar). Undigested lactose causes bloating, wind, cramps and diarrhoea, minutes to hours after dairy. It isn’t an allergy and isn’t dangerous. Most people can still manage small amounts, such as a cup of milk, especially with food. Lactose-free products and lactase tablets help.
How common. Very common worldwide. It’s least common in people of northern European descent and much more common in people of Asian, African, Hispanic and Indigenous American backgrounds.
Causes.
- Primary: lactase gradually falls with age; the commonest type
- Secondary: gut damage cuts lactase for a while, for example after gastro, or with coeliac disease or inflammatory bowel disease; it often improves when the cause is treated
- In babies: some premature babies can’t digest lactose yet; it improves as they grow. Being born with no lactase is very rare
Symptoms. From a few minutes to a few hours after dairy: tummy pain, bloating, wind, rumbling, diarrhoea and sometimes nausea. Symptoms overlap with IBS.
Intolerance vs allergy. Milk allergy is an immune reaction to milk protein, with hives, swelling, vomiting or breathing trouble, and is commonest in babies. Lactose intolerance is a digestion problem only.
How it’s diagnosed. Often by cutting out lactose for a few weeks to see if symptoms settle, then reintroducing it. A hydrogen breath test can confirm it. Your doctor may check for coeliac disease if symptoms suggest it.
Treatment
The goal is less lactose, not zero dairy. Find your own threshold.
- Step 1 · Self-careSmaller amounts, with foodSpread dairy across the day and have it with meals.
- Works
- Most people with lactose intolerance tolerate up to about 12 g of lactose at once (about a cup of milk), and around 24 g spread over a day
- Access
- Free
- Watch for
- Lactose hides in bread, cereals, sauces, dressings, protein shakes and some medicines.
- Step 2 · Self-careLactose-free productsLactose-free milk and yoghurt have the lactase added for you, so they keep the calcium and protein.
- Works
- Lets you keep dairy foods in your diet
- Access
- Supermarkets
- Watch for
- Plant milks vary; choose ones with added calcium.
- Step 3 · PharmacyLactase tablets or dropsTaken just before a dairy meal, or added to milk.
- Works
- Help some people; results vary
- Access
- Over the counter
- Watch for
- Generally safe; not a fix for milk allergy.
- Step 4 · Allied healthDietitianHelpful if you’re cutting out lots of foods, for children, or if IBS is also in the picture.
- Works
- Keeps calcium and nutrition up while finding your limit
- Access
- Dietitian (GP care plan may help with costs)
- Watch for
- Check with your GP before taking dairy out of a child’s diet.
Save your money
Popular, heavily marketed or often asked about, but the evidence is weak or says no.
- IgG food intolerance testsDon’t diagnose lactose intolerance. A trial without lactose or a breath test does.
- Cutting out all dairy for goodMost people tolerate some, and dairy is a major source of calcium.
Living with it
- Try lactose-free versions of your usual foods before giving them up.
- Read labels for milk solids, whey and lactose.
- If you cut back dairy, get calcium from other sources such as fortified plant milks, tinned fish with bones, tofu and leafy greens.
See your GP if
- You think you’re lactose intolerant and want it confirmed
- Symptoms continue even without dairy
- You have weight loss, blood in your poo, or diarrhoea that wakes you at night
- A child has symptoms, before changing their diet
Get urgent help if dairy causes swelling of the lips, face or tongue, trouble breathing, or collapse. That’s an allergic reaction, not intolerance: call 000 (Australia) or your local emergency number. Read more about anaphylaxis.
Outlook. Lactose intolerance is harmless and lifelong for most adults, but easy to manage. Secondary lactose intolerance often goes once the gut heals.
Common questions
What are the first signs of lactose intolerance?
Bloating, wind, tummy rumbling, cramps and loose poo from a few minutes to a few hours after dairy.
Can you suddenly become lactose intolerant?
It can start at any age. A sudden onset is often secondary, after gastro or with coeliac disease, and may improve.
How much milk can I have if I’m lactose intolerant?
Most people tolerate about a cup of milk (around 12 g of lactose) at once, especially with food.
Is lactose intolerance the same as a dairy allergy?
No. Allergy is an immune reaction to milk protein and can be dangerous. Intolerance only causes gut symptoms.
Is lactose-free milk the same as dairy-free?
No. Lactose-free milk is cow’s milk with lactase added. It still contains milk protein, so it isn’t safe for milk allergy.
Evidence and more information
- NHS 111 Wales: Lactose intolerance
- Wilt et al, AHRQ Evidence Report 2010: Lactose intolerance and health
maladywise.com/lactose-intolerance/