How much water should you drink each day?
It’s a simple question, right? I’m not only a physician, but also a physiologist. The answer to this question is not simple. There are no easy answers. It also depends on who you ask. Research studies have produced many recommendations over the years, but in truth, your water needs depend on many factors, including your health, how active you are and where you live.
Water is essential to good health, but how much you should drink varies individually. These suggestions below can help ensure you drink enough fluids. Although no single formula fits everyone, knowing more about your body’s need for fluids will help you estimate how much water to drink each day.
What are the functions of water in the body?
Water is your body’s principal fluid component and makes up about 60 percent of your adult body weight. The amount of water in humans also depends on age – the younger you are, the higher the percentage of water in your body. Senior adults have about 50% of their weight as water. Every system in your body depends on water. Lack (or loss )of water can lead to dehydration. This can cause your body to have difficulty carrying out normal functions. Even mild dehydration can drain your energy and make you tired and/or give you headaches.
So how much water do we actually need?
Ideally, you want to replace the water you lose each day so your weight stays the same. Every day you lose water through your breath, perspiration, urine and bowel movements. For your body to function properly, you must replenish its water supply by consuming beverages and foods that contain water. So how much fluid does the average, healthy normal adult living in a temperate climate actually need? According to the The Institute of Medicine (IOM), men should drink about 13 cups (3 liters) of total beverages daily, while women about 9 cups (2.2 liters). But, we’ve all heard that we should drink 8 glasses a day or divide our weight in ounces by two and drink that number of ounces daily. The “8 by 8” rule isn’t supported by hard evidence. It remains popular because it’s easy to remember, although it’s just a guideline.
What factors influence our water needs?
Depending on your lifestyle, you may need to modify your total fluid intake. Your activity level, the climate you live in, your health status, and if you’re pregnant or breast-feeding may increase or decrease the amount of fluid you have to drink or eat. For example:
- Exercise – If you exercise or participate in any activity that makes you sweat, you need to drink extra water to compensate for the fluid loss. Intense exercise lasting more than an hour (for example, running a marathon) requires more fluid intake. How much additional fluid you need depends on how much you sweat during exercise, and the duration and type of exercise. Remember to continue to replace fluids after you’re finished exercising.
- Environment – Hot or humid weather can make you sweat and requires additional intake of fluid. Heated indoor air also can cause your skin to lose moisture during wintertime. Altitudes greater than 8,200 feet (2,500 meters) may trigger increased urination and more rapid breathing, which use up more of your fluid reserves. Remember, you lose water during breathing (remember that cold day you could “see your breath?”)
- Illnesses or health conditions – If you have fever, vomiting or diarrhea, your body loses additional fluids, so you must replace them with fluids. In these cases, you should drink more water or oral rehydration solutions. Bladder infections or urinary tract stones may increase your water requirements, but other conditions such as heart failure and some types of kidney, liver and adrenal diseases, may alter and decrease your excretion of water and even require that you limit your fluid intake.
- Pregnancy or breast-feeding – Women who are pregnant or breast-feeding need additional fluids to stay hydrated. The IOM recommends that pregnant women drink about 10 cups (2.3 liters) of fluids daily and women who breast-feed consume about 13 cups (3.1 liters) of fluids a day.
Beyond the tap -other sources of water
When you consume fluids, it’s not just what you drink that counts. In fact, you don’t need to solely rely on what you drink for your fluid needs. You see, on average, the food you eat provides about 20 percent of total water intake. Many fruits and vegetables, such as watermelon and spinach, are 90 percent or more water by weight and this provides another source of fluid. Beverages such as milk and juice are composed mostly of water and this counts too. Although other fluids like beer, wine or soda also contribute to what you consume each day, but they should not be a major source of your daily fluids. Water is still your best bet because it’s calorie-free, inexpensive and readily available.
Staying hydrated, safely
By the time you are thirsty, you are about one to two percent dehydrated. Generally, if you drink enough fluid so that you rarely feel thirsty and your urine is colorless or light yellow, your fluid intake is probably adequate. If you’re still confused or concerned about your fluid intake or have health issues, check with your doctor, health care professional or a registered dietician to help you determine the amount of water that’s ideal for you.
Now, I said stay hydrated safely. Today in the Kansas City Metro area, the swimming beaches at a lake north of Kansas City were closed due to a toxin from blue-green algae. It’s not safe to swim in this water. What’s more important, this is the major source of municipal drinking water for this city where the lake is located. There are a number of pollutants that municipal water sources cannot thoroughly filter. Last summer, Toledo, OH closed their water facility until another dangerous algal toxin (Microcystin) was removed from their water source. Bottled water is not regulated as much as tap water, so this may not be a good source of hydration. I recommend the Puritii Water Filtration Bottle. This water bottle removes 99.999994% of all pollutants including biologicals such as bacteria, viruses, parasites and protozoa. This gives pure, fresh, safe water. We used our bottles when we traveled to Europe last winter without any problems.