Johns Hopkins Health Alert
Are You Thirsty Yet?
Dehydration can sneak up on you, especially during exercise. Here's advice to help you get the 48 ounces of liquid you need, today and every day.Thirst is the body’s way of telling you that you need more fluids. Water is required for virtually every bodily function, from respiration to the most minute biochemical reaction. However, the thirst response system diminishes as we age; older people may not feel thirsty even as dehydration sets in.
This was illustrated in a clinical trial that compared the fluid intake of men aged 51–60 with that of men aged 20–28 after a strenuous, 10-day hill walking trip. As reported in the Journal of Applied Physiology, the older men experienced less thirst and became progressively dehydrated while the younger hikers kept drinking plenty of fluids.
The age-associated risk of dehydration may be attributable to age-related diseases, such as kidney disease, diabetes and thyroid disorders. All these conditions can cause the body to excrete more water and increase the risk of dehydration. Older people also are more likely to take medications that cause dehydration. These include antihypertensives, such as diuretics and angiotensin-converting enzyme (ACE) inhibitors and antipsychotic drugs and cholinesterase inhibitors, which are used to treat Alzheimer’s disease and other dementia-related illnesses.
Researchers at Tufts University have devised a food pyramid for older people which recommends at least eight 6-oz. servings (48 oz.) of any liquid per day. Hydration can therefore come from a variety of sources, including fruit or vegetable juice, nonfat milk and low-sodium soup. Even coffee, tea, beer, wine or mixed-alcohol drinks are acceptable in moderation, since all contain large amounts of water. Drinking straight hard liquor, on the other hand, can cause dehydration and is not recommended. Many fruits and vegetables, such as watermelon, berries, grapes, peaches, tomatoes and lettuce, are almost 100 percent water. Even meat is chock full of water. Water from foods typically accounts for 20 percent of your recommended total fluid intake.
Most people get enough water from the foods and drinks they enjoy without having to worry about dehydration, but certain situations call for more care. Instances where you should increase your fluid intake beyond the recommended eight servings to avoid dehydration include:
- While you exercise. For an hour of light to moderate exercise, 2–3 cups of fluid are recommended to stave off dehydration.
- If it is unusually hot. You will naturally lose more fluid and will require extra replenishing.
- If you’re constipated. Increasing fluid intake adds moisture to the large intestine, which helps your body eliminate waste. Also, laxatives can cause dehydration.
- If you’re prone to urinary tract infections and kidney stones. Fluids may prevent urinary tract infections and stop kidney stone formation.
- If you’re sick. High fever, vomiting, and diarrhea can cause rapid dehydration, a condition that can be life threatening.
Warning signs of dehydration: If you notice that you’re urinating less than usual or if you don’t feel thirsty very often, check the color of your urine. It should be the color of straw if you are properly hydrated. If it’s much darker, it’s a sign that you need more fluids. Other warning signs of dehydration include dry mouth, decreased salivation, dizziness, sunken eyes, rapid pulse and a loss of skin elasticity.
Posted in Healthy Living on December 29, 2006
Reviewed June 2011
Medical Disclaimer: This information is not intended to substitute for the advice of a physician. Click here for additional information: Johns Hopkins Health Alerts Disclaimer
Notify Me
Would you like us to inform you when we post new Healthy Living Health Alerts?
Comments
Health Alerts registered users may post comments and share experiences here at their own discretion. We regret that questions on individual health concerns to the Johns Hopkins editors cannot be answered in this space.
The views expressed here do not constitute medical advice, and do not represent the position of Johns Hopkins Medicine or Remedy Health Media, LLC, which has no responsibility for any comments posted on this site.
Male, 67 yr 160 lbs 6 ft tall. I tend to drink less water during the day, 1 to 1.5 liters, because it comes out when I'm sleeping, not when I'm awake. I am voiding completely each time at night, which usually is 5 times from 10 pm to 6 am. During the day, it can be up to 10 hrs between voids. IN-OUT logs suggest that I produce 2 to 5 times as much urine when nap/sleeping as when awake/up/working. Fluid retention is not visible in arms & legs. My bladder max capacity is 325 cc, normal capacity is 200 to 250 cc. This problem lead to discovery of prostate cancer, but eight months after EBRT, I still void frequently at night. My DRE's for as long as I can remember, have been slightly hard on one side, i.e. no enlargement. Taking a prescribed sleep aid every third day helps me get good sleep once in 3 days. Taking the sleep aid more often does not work. My urologist & PCP have no answers. Anyone else have a problem like this?
Posted by: JoeMac | July 26, 2008 12:37 PM
I agree with jdubo above. I've been reading for years and in research books about the subject of water intake and all of the problems associated with insufficient intake. The consensus seems to be about twice the amount professed here and fluids other than water are not counted. The formula is: your weight divided by 2 in ounces. I am surprised at your recommendation here. Also, there seems to be a consensus about feeling thirsty-that dry mouth and feeling thirsty are indicators from your body that you are in crisis mode. It's a last ditch effort to get you to take in water.
Posted by: lucky | April 23, 2010 6:52 PM
Post a Comment
Already a subscriber?
Login
New to Johns Hopkins Health Alerts?
I was suprised to read at my local healthclub that a 200 lb. man needs 100 ounces of water (fluid) each day for optimum hydration.
Now I'm a very healthy 225lb (6'5") person, and, though I know I don't intake enough water, I'm on my first day of trying to drink 10 bottles of water...IT'S A LOT OF WORK!
Your information above states 48 ounces. What's best for me?
Posted by: jdubo | October 22, 2007 1:44 PM