There is no simple answer to how much water you need daily. It’s complicated. What we do know is we need to stay hydrated.
The adult body is about 60 percent water. Water is necessary for many vital functions that must occur daily. Chronic dehydration can raise your risk for many health problems, and it can have negative consequences on cognitive and physical performance.
How much water should we drink? The usual advice, to drink “eight cups a day,” is often questioned and criticized. But it was never gospel. It was simply meant to be a general guideline since an adult can lose over a litre of water daily. This, of course, will vary (remember, it’s complicated). How much water to drink depends on several factors, like age, weight, health, temperature, and activity levels.
There are various other recommendations besides eight cups per day. However, most sources agree adult humans need approximately 12 cups of water daily (three litres), which includes about four cups (one litre) from watery foods. But all advice is approximate, as we each have varying needs. How much you need depends on how much you lose.
Heat and or exercise. We lose water when we breathe and perspire. Thirst mechanisms work well during rest but won’t function well during intense activity.
Research shows when we rely on thirst alone during intense exercise, we tend to consume less fluid, replacing only about half of what we lose.
You can lose 1-2 percent of body weight when exercising intensely in a hot, humid environment. Therefore, it’s recommended to drink at least 12 cups (three liters) of fluid on the days you exercise in addition to any fluid from food.
Diet. The kidneys need more water to excrete excess salt and protein in diets high in salt and protein. Therefore, the more meat, salt and high-sodium restaurant food eat, the more water you’ll need. Same for those with diets high in processed foods.
Highly changed foods have very little water content, but whole, unchanged foods offer plenty. Therefore, if you eat mostly refined, processed foods, you’ll need more water.
Alcohol and caffeine. Alcohol is a diuretic: Drink more water than you usually would when you drink alcohol. Caffeine is also a diuretic, but the amount of water in coffee or tea can offset any fluid loss from the caffeine. However, too much sweetener added to caffeinated beverages will be dehydrating.
Aging. As our bodies change with age, we can’t hold as much fluid. Our thirst mechanisms and sensations may not work as they did in our younger years. And our kidneys may not either. Certain medications may affect our fluid needs and can increase urine output.
If you are over 65, consider drinking an additional 8 to 16 ounces (.25 to .5 litres) of fluid over and above your level of thirst. And know the symptoms of dehydration: dark urine, fatigue, dizziness, headaches, dry mouth.
How can you tell if you are getting enough fluids? Most of us can trust our thirst mechanisms, so drink when thirsty. Urine colour is a helpful measure of hydration, but it isn’t perfect because the colour may be affected by foods, drinks, or medications.
Ideally, for most of us, urine should be light yellow. If your urine is bright yellow, you could be dehydrated; if it’s colourless, you could be overhydrated. A dry mouth may also be a good way to measure hydration, especially if it’s a challenge to form saliva.
Can you drink too much water? Yes. Excess water can disturb your body’s normal balance of electrolytes, just as the balance is disturbed by not drinking enough. However, water intoxication (hyponatremia) is not as common as dehydration is. If you worry you drink too much, cut back – especially if you usually consume far more than the general recommendation! Our hydration needs are constantly in flux, and dehydration can sometimes occur. It’s best to understand dehydration, know your body, and treat it accordingly.
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Eve Lees has been active in the health & fitness industry since 1979. Currently, she is a Freelance Health Writer for several publication and speaks to business and private groups on various health topics.