Water on waking

Do this

• Drink 500 ml to 1 L (16–32 oz) of plain water within half an hour of waking. Electrolytes are optional.
• Use the bathroom first, then drink. He links the pair to the body's wake-up signal.
• Aim for roughly 2.4 L (80 oz) across the day, most of it before late afternoon.
• Drink less in the evening so a full bladder doesn't wake you.

Why it works

Even mild dehydration dulls attention and mood. In the episode he adds a second claim: that drinking after waking helps the morning cortisol rise, through signals that travel from the gut and bladder up the vagus nerve to the brain.

What the research says

Good support for the idea that mild dehydration hurts mood and concentration. The claim that morning water raises cortisol has no direct human trial behind it that this app could find, so treat it as his hypothesis.

• Ganio et al., British Journal of Nutrition, 2011Mild dehydration impairs cognitive performance and mood of menLosing about 1.6% of body mass in water worsened vigilance, working memory, tension and fatigue.
• Armstrong et al., Journal of Nutrition, 2012Mild dehydration affects mood in healthy young womenA 1.4% loss lowered mood and concentration and made tasks feel harder.

Watch out

80 oz is a rule of thumb. Needs change with body size, heat and exercise. If you have a heart or kidney condition, or take diuretics, ask your doctor about fluid targets.