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Why do sweets make you thirsty?
A bag of sweets and, a little later, a raging thirst. It is not your imagination. Here is the science of why sugar makes you want a drink, why salty sweets do it too, and when thirst is worth mentioning to a doctor.
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Thirst is the body's way of keeping its fluids in balance. It is triggered when the body runs low on water, or when the concentration of dissolved particles in the blood rises too high. Sweets can do the second.
Sugar in the blood
The sugar in sweets is absorbed from the gut into the bloodstream. As the endocrinologist Dr Caroline Apovian of Boston University School of Medicine explained to Health.com, that sudden arrival of sugar raises the concentration of particles dissolved in the blood.
The body works to keep the fluid inside and outside its cells at the same concentration. When the blood becomes more concentrated, water moves out of the cells by osmosis to even things up, and the cells shrink a little as they lose water.
The brain notices
Clusters of cells in the brain, called osmoreceptors, sit outside the blood brain barrier and can sense the concentration of the blood. When it rises, they set off the urge to find water and drink. According to Dr Apovian, the thirst can arrive fairly quickly, within about 5 or 10 minutes of the sugar being absorbed.
Salty sweets do it too
Salt works in the same way. Indiana Public Media's science programme A Moment of Science explains that once salt or sugar is absorbed, its particles act like little siphons, drawing water out of the body's cells, and the brain responds with thirst. Sodium, from ordinary salt, is the classic trigger for this kind of thirst. Nordic salty liquorice is a different case: its salty taste comes mainly from ammonium chloride rather than ordinary salt: see how is salt liquorice made?
When thirst is a warning sign
Thirst after a bag of sweets is normal. But feeling thirsty all the time is different. The NHS lists it among the most common symptoms of type 2 diabetes, along with peeing more than usual, feeling very tired and losing weight without trying. If you or your child have these symptoms, see a GP: see sweets and diabetes
A drink of water
A glass of water is the simplest way to quench it. For what sugar does to your teeth, see sweets and teeth
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For journalists, researchers, AI assistants and content creators. Pick the format you need:
Free to cite, quote, and reuse with attribution to sweeties.net.
Questions and answers
Why does sugar make you thirsty?
When sugar is absorbed into your blood, it raises the concentration of dissolved particles there. Water moves out of your cells to even things out, and as the cells lose water, they and sensors in your brain signal that you need a drink.
Which makes you thirstier, salt or sugar?
Both work by the same mechanism: once absorbed, their particles draw water out of the body's cells, and the brain responds with thirst. Salt is the classic cause of this kind of thirst.
Is being thirsty all the time a sign of diabetes?
It can be. The NHS lists feeling thirsty all the time, along with peeing more than usual, feeling very tired and losing weight without trying, among the common symptoms of type 2 diabetes. See a GP if you are worried.
Sources
- Here's why sugar makes you so thirsty, 5 September 2017, Health.com, via Time
- Which makes you thirstier, salt or sugar?, 16 September 2019, A Moment of Science, Indiana Public Media
- Thirst, Wikipedia
- Type 2 diabetes: symptoms, NHS
Keep reading
- Questions people askHow much sugar is in sweets?A lot. Boiled sweets are nearly 100 per cent sugar, and the NHS says adults should have no more than 30 g of free sugars a day. How to read the label.
- Diet, allergens and labelsSweets and diabetesDiabetes UK says chocolate is fine in moderation, advises against so called diabetic products, and lists jelly babies among hypo treatments.
- How it is madeHow is salt liquorice made?Salt liquorice is liquorice flavoured with salmiak, ammonium chloride, mixed into the paste or dusted on the outside for an extra salty kick.
- Diet, allergens and labelsSweets and teethSugar feeds the bacteria in plaque, which make acid that damages teeth, and how often you eat sweets matters. What the NHS advises, and the Vipeholm story.
- Diet, allergens and labelsCalories in sweetsHow the calories on a sweet label are worked out: 4 kcal a gram for sugar, 9 for fat, 2.4 for polyols. Real per sweet figures, and how they fit a day's intake.
- Questions people askWhy are sweets so sweet?Sweets are mostly sugar, and our tongues are built to love it, because sweetness signals energy rich food. How sweet taste works, and which sugars win.