Hydration
Also known as water intake, drinking water
Necessary but not magic. Being adequately hydrated matters; drinking four litres a day does not make your skin glow.
Free.
How it works
Skin hydration is governed mainly by barrier function and the stratum corneum natural moisturising factor, not by systemic water intake. Severe dehydration does reduce skin turgor and cause a drawn appearance, but once you are adequately hydrated, additional water is simply excreted.
How it's used
Drink to thirst, with pale-yellow urine as a reasonable marker. If your skin is dry, the fix is barrier repair — a moisturiser with ceramides and occlusives — not more water. Adequate hydration does help with energy, training performance and reducing the puffiness that follows a high-sodium day.
Trade-offs
In favour
- Free
- Genuinely important for training performance and general function
- Helps clear sodium-driven facial puffiness
Against
- Marketed far beyond what evidence supports
- Extra water does not improve skin quality in already-hydrated people
- Dry skin is a barrier problem, not a water intake problem
Risks and side effects
- Water intoxication and hyponatraemia from extreme intake — rare but genuinely dangerous
- Excessive intake disrupts sleep through nocturia
How good is the evidence?
Evidence for a direct water-intake-to-skin-appearance relationship in hydrated individuals is weak. Evidence for the importance of avoiding dehydration is strong.
Sources
Sources point to guideline bodies and literature searches rather than single papers, so they stay accurate as the evidence moves.