Water makes up about 60% of our body weight and is crucial for almost every bodily function, from flushing out toxins to aiding digestion and regulating your body temperature. But how much water do we really need each day? The answer isn’t as simple as you may think.

how much water do we really need each day?

THE MYTH

One of the most common pieces of advice is to drink eight glasses of water a day, for a total of about 2 litres. This rule is easy to remember and a good starting point, but it doesn’t take into account individual factors in water needs. “No single formula fits everyone. But knowing more about your body’s need for fluids will help you estimate how much water to drink each day.” Below are some things to consider when determining how much water you should be drinking.

BODY SIZE

Simply put: the larger you are and the more muscle you have, the more water you need. This is because muscle tissue contains more water than fat. On top of this, physically active people lose more water through sweat and need to replenish it more frequently. Athletes and those engaging in regular workouts may need significantly more water than the average person, which is why sports drinks crammed with electrolytes exist.

YOUR BREATH

Hot and humid climates also increase your need for water due to higher rates of sweating. On the other hand, dry and cold climates can also increase water loss through the respiratory system: if you can see your breath, you’re losing moisture.

DIET

A diet that’s high in salt, protein, or sugar can also increase water needs: water is required to balance your electrolytes, aid in the proper digestion of protein, and regulate blood sugar (among other functions). Consuming diuretic substances like caffeine and alcohol also requires more water to counteract their effects; our in-home personal trainers in Toronto always suggest pairing every serving of coffee or alcohol with a glass of water.

YOUR HEALTH

Certain health conditions, such as kidney stones or urinary tract infections, may require higher water intake. Medications and illnesses that cause fever, diarrhea, or vomiting also increase your water needs, as these symptoms are very dehydrating.

THE FACTS

Our bodies have a built-in mechanism for regulating water intake: thirst. Thirst is a reliable indicator that it’s time to drink water, but it’s not fool-proof. Older adults in particular may have a diminished sense of thirst: the hypothalamus (which senses thirst) becomes less sensitive with age, kidney function generally declines, and hormone levels shift.

Monitoring the color of your urine is perhaps the simplest way to gauge hydration. Pale yellow urine typically indicates proper hydration, while darker urine suggests the need for water.

THE RISKS

Dehydration, even in its mildest forms, can have significant effects on the body. In the short term, dehydration can lead to headaches, dizziness, dry mouth, and fatigue, affecting cognitive functions like concentration. Physical performance also suffers, as muscles cramp and coordination decreases. Over the long term, chronic dehydration can contribute to more severe health issues like kidney stones, urinary tract infections, and chronic kidney disease. Persistent lack of adequate hydration can also affect your skin health, leading to dryness and premature aging. Lastly, dehydration can impact your cardiovascular health by making the heart work harder to pump blood, potentially leading to high blood pressure and other heart-related conditions. Drinking enough water “helps the heart more easily pump blood through the body. It also helps muscles work efficiently. If you’re well hydrated, your heart doesn’t have to work as hard” (American Heart Association, 2024).

While staying hydrated is crucial, it’s also possible to drink too much water: a condition known as hyponatremia. This occurs when the balance of electrolytes in your body is disrupted by excessive water intake, leading to symptoms like nausea, headache, confusion, and in severe cases, seizures. Athletes are particularly susceptible to this condition during endurance events.

OUR TIPS

Good rules of thumb are to drink water when you’re thirsty, include hydrating foods like fruits and soups in your diet, and adjust your intake based on activity level and climate. For a more tailored approach, consider using this hydration calculator (Very Well Health, 2022) or consulting with a healthcare provider, especially if you have specific health concerns or conditions.

Our in-home and virtual personal trainers also suggest carrying a reusable water bottle with you throughout the day as a constant reminder to drink, and always encourage clients to bring water

to their workouts. You can also set regular drinking intervals, aiming to sip water every hour or with every meal.

FINAL WORDS

Hydration is vital for maintaining health and well-being, but there’s no one-size-fits-all answer to how much water we need. By understanding the factors that influence water needs and listening to your body’s signals, you can ensure you’re adequately hydrated and reaping the benefits.