Overview

• The Deutsche Gesellschaft für Ernährung reiterates about 1.5 liters of fluids per day for healthy adults, noting the popular two‑liter target lacks strong evidence.
• Experts say most healthy people can drink to thirst, while older adults, the ill or highly stressed should not rely on thirst alone.
• For training, ACSM advises 0.5–0.6 liters two to three hours before exercise, 200–300 milliliters just before, and roughly 0.5–1 liter per hour during longer or hotter sessions, with urine color and body weight as simple checks.
• Overdrinking low‑sodium water can trigger hyponatremia, a rare but serious risk for endurance athletes, so sodium‑containing drinks or foods are recommended during heavy sweating.
• In summer heat, choose water, unsweetened herbal or fruit teas, or diluted juice rather than sugary soft drinks or pure juices, and use water‑rich foods to supplement but not replace fluids.