Adequate hydration supports numerous bodily functions, including temperature regulation, nutrient transport and joint lubrication. The information below is based on the Nutrient Reference Values for Australia and New Zealand, published by the National Health and Medical Research Council (NHMRC).
Daily Fluid Intake Recommendations
The NHMRC suggests the following Adequate Intake (AI) levels for total water from all sources (food and beverages combined) per day:
| Group | Approximate Daily Total Water (litres) |
|---|---|
| Adult men (19–70 years) | 3.4 L |
| Adult women (19–70 years) | 2.8 L |
| Pregnant women | 3.1 L |
| Breastfeeding women | 3.5 L |
| Adolescents (14–18, male) | 2.7 L |
| Adolescents (14–18, female) | 2.2 L |
These figures include water obtained from food (approximately 20–30% of total intake for most people). Actual needs vary based on climate, body size, activity level and individual health conditions.
Hydration During Exercise
During physical activity, fluid losses through sweat increase. The rate of sweat loss varies widely between individuals and is influenced by exercise intensity, duration, ambient temperature and humidity.
General Hydration Strategies for Exercise
- Before exercise: Drink approximately 400–600 ml of water in the 2–3 hours before activity.
- During exercise: For sessions lasting less than 60 minutes, water is generally sufficient. For prolonged or intense sessions, a drink containing electrolytes may be appropriate.
- After exercise: Aim to replace approximately 125–150% of fluid lost during exercise over the following 4–6 hours. Weighing yourself before and after exercise can help estimate fluid loss.
Electrolyte Balance
Electrolytes — including sodium, potassium, magnesium and calcium — play a role in muscle contraction, nerve function and fluid balance. For most people consuming a balanced diet, food provides adequate electrolytes. However, during extended exercise (over 60–90 minutes), especially in hot conditions, additional electrolyte intake may be warranted.
Common signs that may indicate dehydration include increased thirst, dark-coloured urine, fatigue, dizziness and dry mouth. Severe dehydration requires medical attention.
A Note on Overconsumption
While dehydration is a common concern, overhydration (hyponatraemia) is also a recognised risk, particularly during endurance events. Drinking excessive amounts of plain water without electrolyte replacement can dilute blood sodium levels. Follow thirst cues and avoid forcing fluid intake beyond comfort.