Overview

• Germany’s nutrition society recommends about 1.5 liters of fluids per day for healthy adults, including fluids from food, with higher needs during heat, exercise or illness.
• Thirst can be unreliable in older people or during stress or sickness, so use practical checks like urine color and, for athletes, pre- and post-exercise weighing.
• For training, the American College of Sports Medicine advises 0.5–0.6 liters two to three hours before plus 200–300 milliliters shortly before, then roughly 0.5–1 liter per hour depending on conditions while keeping losses under about 2% of body weight.
• After workouts, replace approximately 0.5 liters per 0.5 kilogram lost within two hours and add 20–25% to cover ongoing losses.
• Choose water for most situations and opt for isotonic or electrolyte drinks during longer or sweat-heavy sessions to lower hyponatremia risk, with water-rich foods such as strawberries, radishes, tomatoes, grapefruit and nectarines serving as helpful supplements.