Water makes up about 40-62% of your total body weight, and every organ needs water to function properly. After a night of sleep, it’s normal to be slightly dehydrated. Drinking water first thing in the morning supports hydration, which is crucial for overall health.
Dehydration affects blood flow to the brain, which can make it harder to think clearly, focus, remember information, and make decisions.
A 2020 study found that not drinking water for 12 hours can make it harder to think clearly and make decisions. When participants drank 500 milliliters of water before a cognition test, they performed better on tasks that required them think instead of responding automatically.
Another 2021 study showed that not drinking water for 12 hours reduced alertness and reaction time. Drinking 500 milliliters of water before bed and 500 milliliters in the morning improved alertness and reaction speed.
The body produces a hormone called vasopressin when you are dehydrated. This hormone tells the body to retain water, concentrate urine, and regulate blood pressure.
Chronically high vasopressin is linked to higher blood sugar, insulin resistance, and higher blood pressure.
Drinking more water can help lower vasopressin. A 2018 study showed that increasing water intake, especially in people who normally drink very little, reduced copeptin (the marker used to measure vasopressin) by about 41%.
Another 2019 study showed that increasing water intake by 1.5 liters per day for six weeks significantly lowered copeptin levels.
Dehydration causes vasopressin production. Vasopressin tightens blood vessels, which can increase blood pressure if levels are too high. Staying hydrated helps reduce vasopressin production, supporting healthy blood pressure and overall heart health.
A 2024 study showed that drinking 6–8 cups of water per day may reduce the risk of hypertension (high blood pressure) compared to people who consume too little.
Drinking enough water is essential for kidney health. Water helps the kidneys remove waste and toxins and maintain balanced fluids in the body. Staying hydrated helps the kidneys function properly.
Studies suggest that drinking enough water can reduce the risk of kidney stones and urinary tract infections.
Skin hydration is influenced by both internal and external factors. A 2015 study showed that drinking more water can help keep the skin moisturized.
However, another 2024 study found that while drinking enough water supports the skin, using moisturizers is more effective for improving skin hydration and barrier function.
Some evidence shows that water may provide a small benefit for weight management.
A research review found that drinking water may help with weight loss, especially when it replaces sugary beverages. However, the average weight loss was less than 1 kilogram. This means that while adequate hydration can support weight management, it cannot replace following a healthy and balanced diet for weight loss.
Some studies also showed that drinking water before a meal can reduce overall caloric intake in adults.
Your body constantly loses water through breathing, urine, stool, and sweating. Most adults lose about 2.5 to nearly 4 liters of water each day. Water loss is usually slightly less in females and slightly higher in males.
The body produces only a tiny amount of water and cannot store extra, so you need to replace the water you lose every day. Health authorities recommend drinking 2.0–2.7 liters per day for adult females and 2.5–3.7 liters per day for adult males.
