NutritionLogic

Your Water Balance

As I said in my first article on diets, drinking enough water is an important skill for staying trim.  Sounds ridiculous put like that doesn't it?  How much skill does it take to drink water?

It is pretty tricky to determine the right amount of water to drink every day and then get yourself in the habit of actually drinking it.  Google searches and conversations with doctors or nutritionists give you a range of advice from drink "lots", 2 L (8 cups) per day, 3 L (12 cups) per day or 3 L (12 cups) per day and an extra glass for every caffeine or alcohol serving.

That is a lot of variability and even the low end represents a pretty challenging habit to establish.  Just try drinking two liters of water per day, let alone three and another 250 mL every time you encounter caffeine or alcohol.  You'll need to set up some kind of reminder system and start organizing your day around water drinking times, and that doesn't allow for the time to respond to the insistent need to eliminate all the water you poured in.

Where does this advice come from anyway?  Should we re-prioritize our days to follow it?

The goal of this advice is to get you to drink enough to maintain your water balance without putting undue strain on your system.  Water balance means what you ingest should balance out what you lose being alive.  You lose water through:

• urine
• feces
• "insensible" loses (perspiration, respiration, direct evaporation through skin)

On the flip side, you gain water from:

• drinking it
• the food you eat
• your metabolism

The second item is pretty obvious but not something you tend to think about.  Just look at spinach's water content, which is 91.4% by weight or a chicken breast's, which is 75.8%.  You drink water when you eat.

Water from food metabolism is a less obvious source.  Turning food into energy produces water.  This is a major input for some animals but a small one for us.  To better understand the concept, consider sugar metabolism where (CH₂O)_n (sugars are water bonded to carbon; cool, isn't it?) combines with O₂ to create CO₂ and H₂O.  Fats, starches and proteins have more complex reactions but do something similar, yielding water for use by your body.

The input and output complexity suggests simple rules like "drink 2 L of water per day" to maintain health are coarse at best.  The following all vary how much water you need:

• your mass changes the waste volume you eliminate
• environmental conditions change the insensible losses
• your food's water content changes the inputs
• the food amounts and types you eat vary metabolic water production
• your activity level changes your insensible losses

If a simple rule doesn't really work, what is the alternative?  We'll cover that next week.