The age-old advice about drinking eight 8-ounce glasses of water daily just doesn’t hold water for everyone, although it can be a reasonable starting point. According to the US National Academies of Sciences, Engineering, and Medicine, men need about 15.5 cups of fluid daily while women need 11.5 cups.
But what if the man weighs 150 pounds and a woman weighs the same? In that case, their fluid needs should be about the same. Therefore, body weight can be a more helpful determining factor for the amount of water needed.
The weight-based recommendation is one-half to one ounce of water for every pound of body weight. For that 150-pound person, that would be 75 to 150 ounces a day, depending on the dryness of the climate they live in and level of physical activity.
Regardless of which approach you use, factors such as age, activity, health status, and fluids from foods should also be considered.
Why Does Your Body Need Water?
Your body depends on water for many different processes and functions, some of which you probably don’t even realize until something goes wrong. Here are a few examples.
- Saliva production. Water is a primary component of saliva, which is essential for oral health and breaking down food. Saliva is involved at the very beginning of your digestive process and helps your body know which digestive enzymes to send.
- Endurance. Being adequately hydrated has an impact on physical endurance and strength. This is especially important for anyone who is very physically active, such as athletes, construction workers, road crews, and other laborers.
- Body temperature. Your body is constantly losing water through urination, sweating, and respiration. When you sweat, the moisture cools your body, but you need to replenish that lost water to keep your body temperature stable. If you become dehydrated, you can overheat, resulting in a higher than normal body temperature.
- Lubrication. Your joints, tissues, and spinal cord need water to stay lubricated and provide protection against stress.
- Intestinal health. Water is necessary to keep your intestinal tract healthy and to avoid constipation.
- Kidney function. Drinking enough water is necessary to help your kidneys perform their essential function of filtering toxins and other waste via urination.
- Electrolyte balance. Your body needs to keep fluid levels relatively stable in your blood, the space around your cells, and the space within your cells. Electrolytes help maintain water and acid-base balance in your blood and are also critical for muscle and nerve function. Thus, consuming enough water is essential for electrolyte balance and overall health. Drinking too much water can flush out electrolytes, so the right balance is key.
- Weight loss. Drinking more water while you exercise and choosing nutrient-dense foods, especially those with high water content such as fruit and veggies, may help you lose extra pounds. Consuming water before a meal can reduce your calorie intake as well.
- Nutrient absorption. Vitamins, minerals, and other nutrients require water to help them dissolve and thus get them ready for use by your body.
- Better circulation. Water is the vehicle that carries oxygen and nutrients throughout your entire body. In one study, when participants drank 16 ounces of water, their metabolic rate increased by 30 percent, which can help with weight loss. This increase lasts for about 60 minutes.
- Better brain. If you skimp on water intake, it can have a negative impact on your ability to focus, remember, and stay alert, and may even give you a headache. Research indicates that being just 2 percent dehydrated can cause problems with cognitive functioning.
- Helps skin. Drinking enough water will help hydrate your skin and may even promote the production of collagen. Water is an important part of the recipe to keep your skin looking younger and being more elastic.
Can You Drink Too Much Water?
Yes, you can. Generally, if you consume 1 liter or more of water within a few hours for several hours, you can experience water intoxication (aka, water poisoning). This condition is characterized by muscle weakness, head pain, nausea, vomiting, fatigue, and cramping. The kidneys in healthy adults can eliminate only about 1 liter of water per hour. Among older adults and children, this elimination amount is lower.
Staying hydrated is about more than drinking enough water. Because water and fluids play such a critical role in so many bodily functions and activities, you need to pay attention to your water intake as well as your physical activity, the heat in your environment, and your age.