Hot Water vs Cold Water: What Does Science Say?
A review of research on water temperature and its effects on digestion, hydration, and metabolism.
The debate between hot and cold water is more cultural than scientific, but some research offers insights:
**Hydration** — Temperature does not significantly affect hydration rate. Cold water (5–10°C) is absorbed slightly faster in the small intestine, but the difference is marginal. Drink at the temperature you prefer — you will drink more that way.
**Digestion** — Limited evidence suggests warm water may aid gastric motility and help break down fats during meals. A small 2016 study found warm water improved bowel movements in post-operative patients. Cold water may slow gastric emptying slightly, but clinical significance is unclear.
**Metabolism** — Cold water does cause a small thermogenic effect as the body warms it to core temperature, burning an estimated 8–10 extra calories per glass. This is negligible for weight management.
**Comfort and Compliance** — The strongest argument for hot water is behavioural: many people find it more pleasant to sip throughout the day, leading to better overall hydration. In TCM terms, this aligns with the principle that the body prefers warmth.
**Verdict** — Drink water at the temperature that encourages you to drink more. If hot water feels better and you drink more of it, that is reason enough.