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How Much Fluid Do I Need?

June 05, 20233 min read

Whether you’re still in New Year’s resolution mode or not, one question that dietitians are asked on a regular basis is how much water we should be consuming. 

Of course, there is a science behind this with some fancy calculations but to make things easy for all of us, some general rules of thumb will be shared here. 

Why Water is Important to Our Bodies

Our water intake is important because water makes up over half of the human body and our cells are unable to function without it. Our cells make up our organs, muscles and brain. Every system requires adequate fluid to function properly from our memory, circulation and blood pressure, temperature regulation, filtration system, etc.  Every day we lose water through our breath, perspiration, urine and bowel movements, therefore replacing fluids daily is imperative.

How Much Water Do We Need?

So how much water does our body need to perform our daily functions? In general, a minimum of 2-3 liters daily for the average healthy adult.  A popular recommendation is 100 oz per day which would provide just over 3L daily.  If you want to get a little more specific, the average adult needs about 30 mL/kg of actual body weight (1 lb = 2.2 kg). So, a 150 lb (68.2 kg) adult would require approximately 2,045 mL (~2L) daily. 

 

When we factor in climate, overall health, pregnancy/breastfeeding, and activity or exercise, our fluid requirements increase.  Living at a higher altitude or in a more hot or humid climate can increase perspiration and risk for dehydration. 

Health issues such as fever, vomiting, diarrhea, and wounds increase fluid losses.  Women who are pregnant or breastfeeding require more fluids on a daily basis.  Any activity that causes you to perspire will increase your fluid needs. 

Be sure to drink water before, during and after exercise.   Because there are so many factors involved with exercise and body type, it is not plausible to recommend a blanket fluid replacement recommendation for everyone- this is something that should be discussed with your Registered Dietitian, medical provider, or Certified Personal Trainer. 

According to the American College of Sports Medicine (ACSM) a general rule for light to moderate exercise is to drink 16-20 oz of water prior to exercise, drink during exercise according to your thirst, and afterwards drink about 16-20 oz per pound lost during exercise. 

For prolonged exercise, it may be recommended that beverages containing carbohydrates and electrolytes be consumed (please consult your medical or exercise specialist to best fit your needs and optimize performance). 

What Other Liquids Count as Hydration?

Beverages such as juice, milk, tea, and coffee count towards your daily fluid intake.  Even fruits and vegetables such as celery and watermelon that have a high water content can count.  It’s best to avoid a lot of caffeine (for many reasons), and depending on your caloric needs and medical diagnoses/overall health, it may be best to avoid fluids that contain calories or specific nutrients that need to be avoided. 

Water is always the best bet. 

How Can You Tell You're Properly Hydrated?

Your fluid intake is likely adequate if you rarely feel thirsty and if your urine is colorless or a pale yellow.  To prevent dehydration, it’s best to drink a glass of water first thing in the morning, with each meal and between each meal, and before, during and after exercise.  Also, if you’re feeling hungry, try drinking a glass of water first as our bodies can confuse thirst and hunger.

 

If you have any questions, concerns, or specific fluid needs due to a medical condition or athletic performance, consult your Registered Dietitian.

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