Drinking enough water every day is important for your health as it keeps your body functioning properly and can prevent health problems. While you may often hear that drinking eight glasses of water per day is recommended, ideal water intake can vary based on age, daily activities, and other conditions. So how much water should you drink? Olivia Marrone, Registered Dietitian at CHA HPMC, explains.

How much water should an adult drink in a day?
Back in the day, the standard rule of thumb was eight 8-oz glasses of water per day. However, how can a nutrient so important be recommended in such a standardized quantity? Surely, water needs vary among different individuals, depending on age, biological sex, body weight, activity level, where they live, diet choices, etc1. More recently, experts from the US National Academies for Science, Engineering, and Medicine recommend 2.7 L per day for women and 3.7 L per day for men.1 Yes, this is a bit more personalized but there are still so many considerations overlooked in this recommendation. I like to take a more personalized approach to making water consumption recommendations for my clients. By calculating 1 mL of water for every calorie consumed, I am able to make a specific recommendation to my clients, based on their own personal attributes. This technique has been verified by countless peer-reviewed research studies and the American Dietetic Association’s Evidence Analysis Library.2 Of course, this doesn’t work for everyone. Some individuals, such as marathon runners, require a much higher intake of water. While others may need to consider medical contraindications for water consumption, such as chronic kidney disease (CKD). I recommend speaking to your doctor if you have any special considerations. Overall, I find this 1mL/calorie rule to be much more accurate, than the standard eight 8-oz cups rule of thumb.

How much water should kids drink in a day?
Water requirements for children increase with age because the larger you are, the more water you need for your body to function properly. A standard recommendation for children is 4 cups per day for ages 1-3, 5 cups per day for ages 4-8, and 8 cups for older children.3 Of course, like in adults, these standardized values do not consider outlying factors, such as body weight, height, BMI, activity level, etc. For example, if your child is running around on the soccer field all day, they will need to increase their water intake to replace all the sweat they lost by drinking extra water. I recommend to use the above values as a base line and adjust based on your child’s situation.

Why is there a recommended amount of water per day?
Health experts make recommendations for water consumption because most adults do not consume enough water on a daily basis. Not only does water make up over 60% of the average person’s body weight, but it also facilitates many important bodily functions that keep us alive.4 Aside from supporting cell function and aiding in digestion, adequate hydration is important in regulating blood pressure, heartbeat, joint function, body temperature, and electrolyte balance.4 Thus, as you can probably imagine, some pretty scary stuff starts to happen when you’re dehydrated. This can be especially dangerous for elderly and other high-risk individuals. Therefore, recommendations for water have arisen to keep people on track and make sure they are meeting their needs. To put it into perspective, most people could survive for weeks without food, but could only last a few days without water.

What are the health benefits associated with proper water intake?
In addition to the physiological benefits mentioned above, adequate water can also help with the following aspects:

  1. Weight loss: High water consumption does not directly cause weight loss. However, drinking water before meals may increase one’s satiety (or feeling of fullness), which in turn reduces the amount of food eaten at mealtimes and promotes weight loss. Others argue that drinking water may slightly increase your metabolism, which could contribute to weight loss. However, the increase in metabolism is quite insignificant and will likely not have a direct impact on weight.
  2. Prevents constipation: Extra fluid in the body keeps the stool moist, soft, and easy to pass.
  3. Reduces risk of UTI: Drinking an adequate amount of water everyday means you are urinating A LOT, which is good news for people prone to UTIs because it will flush harmful bacteria out of the bladder as waste products in the urine.4
  4. Improves skin hydration: Adequate fluid intake ensures every part of your body is properly hydrated, including your skin. Some studies also show that adequate hydration can improve acne and other skin disorders, however more research is needed to confirm these claims.4

What are some things that can happen if you don’t drink enough water?
Not drinking enough water can be very dangerous because, as previously mentioned, the human body is made up of 60% water. Inadequate water intake can cause fatigue, headaches, and affect your mood. In more serious cases, dehydration can quite literally lower the volume of blood in your body, which may lead to lightheadedness, increased risk of fainting, and symptoms of orthostatic hypotension.6

Is it possible to drink too much water? What happens in this case?
Too much of anything is never good. And surprisingly, the same is true for water! The medical community refers to excessive water intake as “water poisoning”. When this happens, the excess fluid flows into our cells, causing them to swell. When the brain cells swell, this can cause an increase in pressure on the brain, which manifests as headache, confusion, and drowsiness. In severe cases, this swelling may lead to seizures, coma, or even death.5

1Gunnars, Kris. “How Much Water Should You Drink per Day?” Healthline, Healthline Media, 5 Nov. 2020, https://www.healthline.com/nutrition/how-much-water-should-you-drink-per-day.
2Vivanti, A P. “Origins for the Estimations of Water Requirements in Adults.” Nature News, Nature Publishing Group, 24 Oct. 2012, https://www.nature.com/articles/ejcn2012157.
3“Choose Water for Healthy Hydration.” HealthyChildren.org, https://www.healthychildren.org/English/healthy-living/nutrition/Pages/Choose-Water-for-Healthy-Hydration.aspx#:~:text=To%20stay%20well%20hydrated%2C%20children,8%20cups%20for%20older%20children.
4“How Much Water Should You Drink?” Harvard Health, Harvard University, 25 Mar. 2020, https://www.health.harvard.edu/staying-healthy/how-much-water-should-you-drink.
5WebMD Editorial. “What Happens When You Drink Too Much Water?” WebMD, https://www.webmd.com/diet/what-is-too-much-water-intake#:~:text=When%20you%20drink%20too%20much%20water%2C%20you%20may%20experience%20water,cause%20pressure%20in%20the%20brain.
6“Signs You Don’t Drink Enough Water.” WebMD, https://www.webmd.com/diet/ss/slideshow-diet-dehydration.
Go to our Blog