On day 14 of my 366-day self-care challenge, I explored ways to ensure that I was drinking enough water.
Well, even if you aren’t you should probably drink some water.
But just how much water? We now know that thirst is not the best indicator of hydration, especially as we age. Nevertheless, you’ll be hard-pressed to find a one-size-fits-all recommendation.
In fact, this is the vague guidance provided on the USDA website:
“Individual water requirements vary from person to person, and can depend on many factors such as activity level and environment. Most healthy people need to make sure they are drinking enough water, but drinking too much water is usually not an issue.”
Right. So just make sure I drink enough water. Got it.
Similarly, the Institute of Medicine’s (IOM) Dietary Reference Intakes (DRI) established an Adequate Intake (AI) level for water, but because this level is based on survey data, the IOM clearly states it “should not be interpreted as a specific requirement.” While it’s not a recommendation, per se, the AI for most adult women is 2.7 Liters per day (about 11 cups), and for most adult men 3.7 Liters per day (about 15 cups). It’s important to note that the AI is based on total water intake, which also includes food sources that can account for 19 to 25% of our daily fluids (see page 163 of the DRI guide).
It’s been suggested that 6 to 8 glasses per day is sufficient for most people (though how many ounces in that “glass” is still left open to interpretation). Nevertheless, the simple 8×8 rule (eight 8-oz glasses per day) still holds true in some circles.
In a clinical setting, fluid needs are often estimated as approximately 30 cc’s per kilogram of body weight, with actual recommendations being tailored to individual needs. I tend to prefer this method because I’ve found it to be pretty accurate in practice. As a registered dietitian, I’ve used it to calculate fluid needs for patients who rely solely on artificial nutrition support (feeding tubes and parenteral IV’s) to deliver fluid and nutrients.
Clearly there are many ways to look at requirements.
But even after you’ve determined your individual fluid needs, there’s the question of which type of fluid? What about caffeine, for instance?
Surprisingly, the widely accepted notion that caffeine is dehydrating is somewhat of a myth – the research simply isn’t as strong as you might think. The truth is that habitual caffeine drinkers are less prone to caffeine’s diuretic effects over time, and even those who are sensitive don’t suffer from actual dehydration – at least not from consuming natural sources of caffeine, such as with coffee and tea. With that in mind, it seems plausible that caffeinated beverages might contribute to daily fluid intake after all.
But all of that aside, we can’t ignore the fact that some medical conditions (like liver or kidney disease and congestive heart failure) are worsened with large amounts of fluid. In some cases, it can even be fatal. As cliché as it may sound, talking with your health provider is the best way to determine your individual fluid needs. (Add that to your list of questions to ask at your next check-up.)
The giant mason jar I’m holding in the photo above holds 16 cups of water (1 gallon) – roughly a 2-day supply for me personally (using the formula I mentioned above). However, using the IOM’s AI the jar would only contain a 1-day supply (with no food sources being considered).
This lack of consensus within the public health community can make it difficult to set personal goals around fluid intake, but not impossible. Because hydration is one of the most important aspects of our health, taking time to understand your unique needs is time well spent.