Lactose intolerance

Reference: six-minute clip from R4’s Inside Health.

What is lactose?

Credit: Huffington Post

Lactose is the sugar naturally found in milk. It is a disaccharide (read: two + sugar) which means it is made up of two, simple sugar molecules – glucose and galactose:

Credit: Yikrazuul 


What is lactase?

Lactose is broken down into glucose + galactose by the enzyme lactase. These smaller sugars are then absorbed into your blood to be used by your body for energy.

How does it give me symptoms?

If it is not broken down into these smaller sugars then bacteria in the gut (they’re normal!) feast upon it and give you symptoms of loose stools and a loud tummy (in medicine we call this audible, loud grumbling borborygmi!)

How likely is it that I am intolerant?

20% of the population believe they are lactose intolerant; only 20% of those people actually lack the gene that makes lactase (the enzyme that breaks down lactose). These people have lactose malabsorption; the term ‘intolerance’ describes being symptomatic, whether or not you lack the enzyme.

So why do I feel like I am lactose intolerant?

  • You may be having too much lactose in your diet (lots and lots of milk chocolate, lots of cups of milky tea, lots of cream-based foods)
  • It could be functional (read: your brain makes your body feel something)
  • You may have an intolerance to something else in dairy foods- like whey protein in shakes, for example
  • You may have IBS (irritable bowel syndrome) without being lactose intolerant – the symptoms can be very similar!

How to test for it

Your doctor can test for it with a breath test: detecting hydrogen gas after giving someone some lactose suggests an intolerance. Remember: if you give anyone too much lactose, you will detect hydrogen gas and they will get loose stools! (Also note that some people who test positive for hydrogen gas production don’t actually have symptoms – this is malabsorption (positive test) but not intolerance (symptoms). Read here for more.)

We are all on a spectrum of lactose intolerance

You can test it yourself by cutting out milk for a few weeks. Dieticians suggest soya milk is the best replacement because it contains similar amounts of calcium (fortified) and is a good protein. Then: reintroduce it- this is the real test.

My advice

My advice would never be to cut something out completely, because you risk cutting out important vitamins and minerals from your diet. (Disclaimer: I’m training to be a doctor, not a dietician! So, if you want, ask your GP to refer you to an NHS dietician.)

Most people with lactose intolerance can tolerate some milk in their tea – one or two cups a day is fine, but you may start to notice more after that. See the table below; pick foods low in lactose 

  • Try to keep it in your diets in small amounts- like a small yogurt pot, one cup of tea with milk or some cheese.
  • Most yogurts and cheese actually have very little lactose
  • Limit your intake of butter

I hate to say it (actually, I love to say it): it’s all about having everything in moderation!

Research shows that most people with perceived or real lactose intolerance can tolerate about 12g / day.

Lactose content of milk, dairy products and some manufactured products
Reference: Dr Lomer from King’s College, London
Food Type Per cent lactose
  1. * Cow’s milk.
Milk Skimmed* 4.8
Semi-skimmed* 4.7
Whole* 4.6
Condensed, whole, sweetened* 12.3
Dried skimmed* 52.9
Evaporated, whole* 8.5
Goat 4.4
Human 7.2
Sheep 5.1
Cream Single 2.2
Double 1.7
Sour 2.7
Crème fraiche 2.1
Crème fraiche half fat 3.0
Imitation cream, e.g. Elmlea, Tip Top, Dream Topping 2.3–6.8
Cheese Brie/camembert Trace
Cheddar 0.1
Cheese spread 4.4
Cheese spread, reduced fat 7.3
Cottage cheese 3.1
Cottage cheese, reduced fat 3.3
Cream cheese Trace
Danish blue Trace
Stilton 0.1
Edam/gouda Trace
Feta 1.4
Goats cheese 0.9
Mozzarella Trace
Parmesan 0.9
Processed cheese slices 5.0
Yogurt Plain 4.7
Fruit 4.0
Drinking yogurt 4.0
Fromage frais plain 4.0
Fromage frais fruit 3.0
Tzatziki 0.3
Puddings Milkshake average 4.5
Ice cream nondairy vanilla 4.8
Ice cream dairy vanilla 5.2
Choc ice 4.7
Rice pudding 3.9
Custard made with whole milk 5.2
Chocolate mousse 3.

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