How Much Water Should We Drink in a Day?
There are many recommendations and formulas to determine how much water we should drink. So which one is right?
There actually is no recommended daily allowance (RDA) for water due to the extreme variability in individual metabolism, activity rates, and environmental conditions, according to the National Institutes of Health (NIH)(1).
Instead, the Mayo Clinic defers to The U.S. National Academies of Sciences, Engineering, and Medicine which suggests that the median water intake of adults is an Adequate Intake (AI):
Males- 3.7 L/day (120 oz)
Females - 2.7 L/day (86 oz)
Although the AI is slightly higher, it is also appropriate for women to follow the age old advice of drinking 8 glasses of water per day (10 oz. glasses) if this is easier to remember. Men would need twelve 10 oz. glasses of water. This applies for an average adult on a mild day who is not participating in moderate to intense exercise.
When to Increase Your Water Intake
However, under the following circumstances, the amount of water should be increased to avoid thirst and maintain hydration:
hot day
following a workout or moderate to intense activity
if a fever, vomiting, or diarrhea is present
if lactating
if drinking alcohol
if used a hot tub, sauna, steam room, or had a massage or Epsom salt bath within the past 24 hours
Competitive athletes will need more water and a sports drink to maintain electrolytes based on weight loss during their activity.
How to Know if You're Hydrated Enough
One quick check to know if you're hydrated enough is the urine test:
clear/light yellow urine= hydrated
medium-dark yellow urine= drink more water
Another way to know if you're hydrated enough is the thirst test:
If you're thirsty, you're already dehydrated. It's important to have a glass of water.
Why Drinking Water Is So Important
Water maintains body temperature and pH, metabolism, and the transportation of hormones, oxygen, and nutrients. Water also keeps mucosal cells moist (like nose and eyes), lubricates joints, helps the kidneys and liver flush out waste, and helps prevent constipation.
Effects of not drinking water regularly include:
kidney stones
constipation
increased risk of stroke and recovery time after stroke
slower metabolism
overeating and weight gain
fine lines and wrinkles
Symptoms of Dehydration
Symptoms of dehydration can include fatigue, fever, nausea, headache, stomachache, and in extreme cases, lightheadedness, dizziness, and confusion. Dehydration can put the cardiovascular system in danger.
Is Water the Only Thing You Should Use to Hydrate?
Water is the best source of hydration. However, if you're at the end of the day and just missing your water intake goal, consider if you've had any water-dense fruit or vegetables, herbal teas, milk, or 100% fruit juice. These all count towards hydrating the body.
Water dense fruits and veggies include:
lettuce
watermelon
strawberries
spinach
apples
peaches
pineapple
grapes
tomatoes
cucumbers
Sugar-sweetened beverages, sodas, and sports drinks are not ideal fluids to hydrate with. They contain calories, sugar, and often sodium (which is dehydrating).
Do Caffeinated Beverages Count as Fluid Intake?
Caffeinated beverages may or may not count towards your fluid intake.
Caffeine is a diuretic, which means it increases water loss through urination. If caffeine is not part of your daily regimen, it will work to dehydrate a person. It should not be counted as fluid intake. Instead, for every cup of coffee or tea drank, an extra glass of water should be consumed.
However, if a person drinks caffeinated coffee or tea daily, the body becomes immune to the diuretic effects of the caffeine. Studies show that regular consumption of caffeinated coffee and tea is not dehydrating and these beverages can count towards fluid intake. Water is still the best beverage and is needed on a daily basis.
Is Beer Hydrating?
Beer is mostly water. However, even a low-alcohol beer is dehydrating. According to the National Institutes of Health, "Alcohol suppresses the release of vasopressin, a hormone produced by the brain that sends signals to the kidneys causing them to retain fluid. As a result, alcohol increases urination and excess loss of fluids."
Beer, cocktails, wine, and liquor all lead to dehydration. For every alcoholic beverage consumed, a glass of water should be drunk to prevent dehydration (as well as a hangover!).
Can You Drink Too Much Water?
Yes, a person can drink too much water. Drinking too much water can result in a condition called hyponatremia. ("Hypo" means too little and the "na" represents "Na" or sodium on the Periodic Table of Elements).
Hyponatremia occurs when the concentration of salt in your blood gets too low (2). This can happen from drinking too much water and causing your cells to swell. This swelling can cause many health problems, from mild to life-threatening. The symptoms of hyponatremia mimic the symptoms of dehydration.
Hyponatremia is extremely rare. Most cases are the result of athletes proactively hydrating prior to a game or race, but drink excessive fluids. While it is rare, if someone close to you experiences nausea, lightheadedness, confusion, or seizures after drinking a lot of water, get them help right away. Hyponatremia needs to be treated at a hospital.
How to Track Your Water Intake
If you are trying to improve your water intake this summer, especially if you're spending time outside in the heat or increasing your physical activity, you may want to track the number of ounces you drink.
You can track your water intake with any measuring device such as a measuring cup or a water bottle that you know the volume of.
You can also use a nutrition app like MyFitnessPal or FitBit to record the ounces of water you drink throughout the day.
Today, there are even "smart" water bottles, apps, and other devices that signal when it's been too long since you've taken a sip of water.
After tracking for a week or two, you may be able to get into a routine of drinking water so you don't need to continue keeping records of how much water you drink.
If you don't like water...
For people who can't stand the taste of water, ease into drinking it by trying these tap water alternatives:
unflavored carbonated water (like seltzer or make t yourself with a Soda Stream)
flavored bottled still water (like Hint)
flavor your tap water with fruit like lemon, lime, or strawberries
dilute up to 8oz of juice per day with water
break up your 8 glasses of water with a cup of unsweetened herbal tea
References:
(1) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. (2005). Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington, D.C. The National Academies Press.
(2) Mayo Clinic. (2020). Hyponatremia. https://www.mayoclinic.org/diseases-conditions/hyponatremia/symptoms-causes/syc-20373711
(3) Wu, F. F., Hung, Y. C., Tsai, Y. H., Yang, J. T., Lee, T. H., Liow, C. W., Lee, J. D., Lin, C. J., Peng, T. I., & Lin, L. C. (2017). The influence of dehydration on the prognosis of acute ischemic stroke for patients treated with tissue plasminogen activator. BMC cardiovascular disorders, 17(1), 154. https://doi.org/10.1186/s12872-017-0590-6
(4) Arca, K. N., & Halker Singh, R. B. (2021). Dehydration and Headache. Current pain and headache reports, 25(8), 56. https://doi.org/10.1007/s11916-021-00966-z