- Default serving250 ml8.5 fl oz · Dairy & milk
- Counts toward goal250 mlthe full serving
- Hydration factor1.50raises the hydration level more than water
- Calories105 kcal42 kcal per 100 ml
Move the slider to see what a bigger or smaller milk does to the numbers. The app uses the same figures.
Work out your daily drinking target with the water intake calculator.
What the trial measured
The figures come from the Beverage Hydration Index trial, run at three UK universities. Each of 72 healthy men drank 1 litre (34 fl oz) of still water and, on separate days, a litre each of three other drinks, over 30 minutes. Their urine was then collected for four hours. The less urine a drink produced, the more of it was kept. (Maughan et al., 2016)
Over the four hours, the men passed 1,337 g of urine on average after still water, 1,052 g after full-fat milk and 1,049 g after skimmed milk. An oral rehydration solution, the salt and sugar drink made for treating dehydration, came in at 1,038 g. Those three were the only drinks that did better than water. Coffee, tea, cola, lager, orange juice, sparkling water and a sports drink were no different from water.
The men were fasted, resting and already well hydrated, and each drink was a single litre. The index compares how much of one large drink is kept over the next few hours.
Why milk is kept longer
The full-fat milk in the trial was 88% water. The rest was fat, protein and milk sugar, and it carried sodium and potassium. Still water has none of these. (Rodriguez-Sanchez, 2016)
A follow-up trial by the same group changed one ingredient at a time in a litre of water. More sugar (10% or 20%) and more sodium (27 mmol per litre or more) both cut the urine that followed. Caffeine up to 400 mg per litre made no difference. The authors credit energy content, which likely slows how fast the water reaches the blood, and sodium, which improves how much of it is retained. (Maughan et al., 2019) Milk brings energy and electrolytes together.
After exercise
In a smaller study, 11 people exercised in the heat until they had lost 1.8% of their body mass, then drank 150% of what they had sweated out. Over the next five hours they passed 611 ml of urine after low-fat milk, against 1,184 ml after water and 1,205 ml after a sports drink. After milk they stayed in positive fluid balance. After the other drinks they were back in deficit within an hour. The authors make one exception: people with lactose intolerance. (Shirreffs et al., 2007)
How a glass of milk counts
WaterChamp counts a 250 ml (8.5 fl oz) glass of milk as 250 ml toward your daily goal, the same as a glass of water. The hydration factor of 1.50 moves the live hydration level half as far again as the same amount of water. It adds nothing extra to the goal: the glass still counts as 250 ml.
The trial tested cow's milk only. The other milks carry estimates: kefir 1.40, oat milk 1.05 and almond milk 1.00. Chocolate milk sits at 1.45 and hot chocolate at 1.35.
Every drink from the trial, with the factor the app uses:
| Drink | In the trial | WaterChamp factor |
|---|---|---|
| Water | The reference drink | 1.00 |
| Sparkling Water | No different from still water | 1.00 |
| Milk | Retained more than water (full-fat 1.50, skimmed 1.58) | 1.50 |
| Cola | No different from still water | 1.00 |
| Diet Soda | No different from still water (diet cola) | 1.00 |
| Black Tea | No different from still water (hot tea) | 1.00 |
| Iced Tea | No different from still water | 1.00 |
| Black Coffee | No different from still water | 1.00 |
| Beer | No different from still water (4% lager) | 1.00 |
| Orange Juice | No different from still water | 1.10 |
| Isotonic Drink | No different from still water | 1.05 |
Questions
Does milk count as water intake?
Yes. Every millilitre of milk counts toward your daily water goal, the same as water.
Is skimmed milk more hydrating than whole milk?
They scored about the same: 1.58 for skimmed and 1.50 for full-fat. Both kept more fluid than still water.
Is milk better than water after exercise?
In one study, people kept far more of the fluid from low-fat milk than from water or a sports drink over five hours after exercise. The authors exclude people with lactose intolerance.
Are oat and almond milk as hydrating as cow's milk?
The trial did not test plant milks. They count at 1.05 for oat milk and 1.00 for almond milk, close to water.
Hydration factors follow the Beverage Hydration Index: Maughan RJ, Watson P, Cordery PA, et al. “A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.” American Journal of Clinical Nutrition, 2016;103(3):717-723. Read the paper on PubMed. In WaterChamp a milk raises the hydration level more than plain water.
