A common question- asked by almost everyone, athlete or not. Water is fundamental to our body. It hydrates our cells but importantly, allows nutrients to flow through our system.
About 50-60% of the human body is made up of water. That is roughly about 40-45 liters in an average man who weighs 70 kg.
Loss of water is common, particularly in athletes and is called dehydration. Human body can lose 2-3 liters of water in a day based on the intensity of the exercise via sweat as well as through urine. But even without that hard work, the body still needs replenishment of water to function. Hence this question comes up often- how much water should a person drink in a day?
If you are struggling with how much water to drink in a day, use a stepwise approach to first estimate your basal intake of water. Note that someone working out in the heat will lose more water and will need to drink more as compared to someone who is older and relatively sedentary most of the day.
However, a general rule of thumb still applies- one generalized approach is using a benchmark of about 60 fl. oz of water every day if your body size is average and precluding any serious workout or exercise.
Add 16 fl. oz for any additional workout lasting up to 30 minutes and at least another 12 fl. oz for additional 30 minutes of activity.
Thus, in a healthy adult without any significant medical condition, it is common to hydrate with at least 80 fl. oz of liquid (mostly water).
Many individuals still struggle to know exactly how much water they should be drinking on a daily basis, particularly if they workout.
One approach is to use this simple calculation: use your weight in pounds, divide it into half and multiply that number by 0.8 to get your basal recommended volume of water. This is the minimum amount of water you should drink unless you need to restrict it due to a medical condition.
For example, a man weighing 160 lbs, would need 80 (half the weight) x 0.8 = 64 fl. oz or roughly 2 liters of basal water intake. This is about 8 glasses of 8 fl. oz each in a day that he needs to have at a minimum (hence called basal). If he works out, he will need to supplement additional hydration accordingly- adding 16 fl. oz of additional water for a 30 minute exercise brings this to about 80 fl. oz of water a day.
Most athletes will use the exercise related water supplementation to be mixed with some form of electrolyte mix.
Women may have different water needs than men. In general, women have about 50% of their body weight in water as opposed to men who typically have about 60% of it. Drinking adequate water has been shown to help in weight loss in women as well as prevent bladder infections.
There are some occasions when water intake needs to change based on environmental factors and an individual may need to drink more. These include:
Water intake allows significant benefits in adults as listed below:
While a basal intake of water is easy to calculate, it is vital to understand that the overall goal of fluid intake differs markedly in individuals.
Some individuals with a heart condition may need to restrict water intake to < 1.5 liters a day. Similarly, another individual of the same age, with urinary tract infections and kidney stones may need to double that volume per day.
Younger athletes can drink up to 100-110 fl. oz of fluid daily due to their physical activity and water loss. Lastly, it may be difficult to drink 100 fl. oz of water alone, particularly by athletes whose hydration needs are higher and electrolyte losses are significant. In these cases, an electrolyte powder such as MAGNAK® Endurance Mix can replenish both water as well as those lost electrolytes allowing a shorter recovery time. Electrolyte water allows fluid to be retained in the body improving hydration and reduces fatigue.
