Dear Doctor: I recently fainted in my kitchen and later learned it was because I was dehydrated, something I knew nothing about. I'm well into my 80s and in good health, but I never seem to get thirsty. How much should I drink? Can other liquids take the place of water?
Dear Reader: You've brought up an important topic that doesn't get a lot of attention. That is, the risk of dehydration in older adults.
Our bodies are up to 60% water, so proper hydration is essential for all of us. The water in our bodies serves as a transport vehicle for nutrients and waste, it's a medium for countless chemical and electrochemical reactions, it acts as a lubricant and a shock absorber, it helps to regulate blood pressure and it plays a key role in regulating body temperature.
Dehydration can cause an array of problems, including dizziness, weakness, cognitive impairment, heart arrhythmia, urinary tract infections and other serious conditions. Severe dehydration is a medical emergency.
Several factors put older adults at greater risk for dehydration than those who are younger. You've already mentioned one of them in your letter, which is that you never seem to get thirsty. This is due in part to physiological changes associated with aging, which alter the body's electrolyte balance and mute the sensation of thirst. Changes to cognition can also lead to an impaired sense of thirst. Certain medications, including diuretics and laxatives, can accelerate fluid loss. And because we lose muscle mass as we age, older adults tend to have smaller fluid reserves.
Older adults must make a deliberate effort to stay adequately hydrated. The actual amount of water needed is up for debate. The often-repeated advice that we should drink six to eight 8-ounce glasses of water per day is not based on scientific findings; the amount of water someone needs actually varies from person to person. Body weight, activity level and even the daily weather play a role. The needs of an active person outdoors in a warm climate will be different from those of a sedentary individual spending time inside.
Many foods -- most notably fruits, vegetables and leafy greens -- contain water that contributes to hydration. So do the coffee, tea and fruit juices we consume.
Considering your run-in with dehydration, it would be wise to check in with your health care provider for guidance on your daily water needs. Until then, as someone who is in good health, the recommended six or eight glasses per day are a reasonable goal. (Individuals living with heart or kidney problems who have to monitor fluid intake must check with their doctors for the safest way to get the fluids they need.)
Water, which has no added sugars and zero calories, remains the best option. You can bump up the flavor with lemon, lime or a slice of cucumber. As we mentioned earlier, tea and coffee do count. We urge you to steer clear of sodas, including artificially sweetened ones. The important thing is not to try to fulfill your quota all at once, but to consume fluids gradually throughout the day.