Summary FAQ

Fluids for Optimal Hydration Status

This answer is brought to you by many of the Australian nutrition professionals who regularly contribute to a nutrition email discussion group.

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There is no scientific justification for a general recommendation that everyone should drink two litres (or any other particular volume) of water per day. For most people, and under most circumstances, thirst will indicate if you need to drink. Other relevant indicators are infrequent urination, low volume and dark colour of urine.

Water should be the fluid consumed most often. Unlike water, carbohydrate-containing drinks (such as fruit juice, sports drinks, cordials and carbonated soft drinks) add to kilojoule intake (and therefore may contribute to weight gain or make weight loss more difficult). If used inappropriately, carbohydrate-containing drinks may also cause dental health problems, especially if they are acidic. But one carbohydrate-containing drink, fruit juice, also makes a significant positive contribution through increasing vitamin C intake.

Caffeine-containing and alcoholic beverages are not as efficient rehydration fluids as water, and some (especially those that are very high in alcohol or caffeine) may actually increase the rate of dehydration. This is likely to apply particularly to people who are not accustomed to these drinks. However, drinking a few cups of tea or coffee each day, while not as efficient as water for rehydration, is not associated with any adverse health effects, and tea may even confer health benefits. Alcohol, if consumed at all, should be taken only in moderation.

Water intake should be increased in the following circumstances: when suffering fever or undergoing treatment for kidney stones; when in dehydrating environments (e.g. air-conditioned offices, hot/dry climates or flying long distances); during hot weather (especially if hard physical work is being conducted, leading to profuse sweating); and if constipation is a problem.

Cardiac, renal (i.e. kidney) or liver patients may need to reduce fluid intake (but check with your doctor and/or dietitian first).

For most Australians, there is no nutritional or health advantage to drinking bottled water compared to tap water.

Under conditions of combined hot weather and sustained exercise or hard physical work, carbohydrate-electrolyte ('sports') drinks are believed to be more appropriate than water as the rehydration fluid, but care should be taken to avoid problems with dental health (e.g. by drinking relatively large volumes infrequently and rinsing the mouth with water).

To assist with weight control, eating high-moisture foods (such as soup, vegetables and fruits) appears to be more effective in reducing food intake than drinking water with (or before) a meal.

Drinking very cold water is unlikely to be of any significant benefit in weight control compared to drinking water that is cool or at room temperature.

Choosing low-salt processed foods (sodium less than 120 mg/100 g) and using salt sparingly can reduce the requirement for water intake by up to half a litre per day.

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[Date Issued: December 2002]

Disclaimer: This material is provided on the basis that it constitutes advice of a general nature only. It is not intended to replace the advice of a physician or a dietitian.