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Special Reports June 2016 Issue

Drink Up to Stay Healthy and Hydrated This Summer

Water, that is, along with these other smart sipping choices.

Every cell in your body needs water to function. Water transports nutrients and oxygen throughout the body, and carries away waste materials. Water makes up most of your body, ranging from about 75% of body weight in infancy to 55% of body weight at older ages. Your brain and heart are almost three-quarters water, your muscles and kidneys are almost 80% water, and even your bones are about 30% water.

Summer is an important time to keep your body's fluid needs in mind, says Dariush Mozaffarian, MD, DrPH, dean of Tufts' Friedman School and editor-in-chief of the Health & Nutrition Letter. "For older adults, there is the risk of subtle dehydration in hot weather, leading to lightheadedness and falls."

For staying hydrated, Dr. Mozaffarian adds, "Water is king. The best approach is to be sure to eat regular meals - food has plenty of natural and added salt, which you lose when sweating - and drink plenty of water. Fruits like watermelon, grapes, etc. are great options, too."

Sports drinks like Gatorade should be avoided, he says, unless you're engaged in extended vigorous activity in hot weather. And of course sugared sodas, sweetened ice tea and energy drinks are an "absolute no." The added sugars in these beverages come with little or no beneficial nutrients and plenty of risk for weight gain and diabetes.

THINKSTOCK

BEYOND THIRST: As you age, you need to pay extra attention to your body’s hydration needs. Older people often have a reduced sensation of thirst, so it's easier to miss the warning signs that you're becoming dehydrated. Older individuals also tend to have lower reserves of fluid in the body, may eat less regularly (and therefore consume less sodium), and may drink insufficient water following fluid deprivation to replenish the body's water deficit. Because of this, older people may need to pay more attention to their fluid intake, particularly during hot weather, and plan to drink regularly even when not thirsty.

The Adequate Intake (AI) of fluid - water from all food and beverage sources - for men over age 50 is 3.7 liters (almost 4 quarts) a day, which includes about 13 cups from beverages including water; the rest is typically obtained from food. For women over age 50, the AI is 2.7 liters (a little less than 3 quarts) a day, with about 9 cups coming from water and other beverages. So you actually need more than the popular notion of eight glasses of fluids a day - but it doesn’t all have to be water.

In practice, according to national nutrition-survey data, men drink a combined total of about 11 cups of beverages per day, and women drink about 10 cups.

For most people, according to the Institute of Medicine, "fluid intake, driven by thirst... allows maintenance of hydration status and total body water at normal levels" - but keep in mind, as noted above, that as we age natural tendencies may not always be adequate. Despite what you may have heard, the water in caffeinated beverages such as coffee and tea does "count" toward keeping you hydrated, as discussed more below. So does the fluid content of foods, which may add up to about 22% of the average American’s water intake.

In addition to drinking plenty of water and other healthy liquids to avoid dehydration this summer, you can actually reduce your risk by exercising regularly. Fit people of any age do sweat more, keeping the body cool, but also have more diluted sweat, losing fewer electrolytes as they perspire.

FLUID FACTS: So why is it so important to get enough water and other fluids? In summer, it's particularly crucial because of water's role in regulating the body's temperature, through sweating. Another reason older people need to be more aware of their body's fluid needs is that they are less able to compensate for the increased blood thickness that results from the loss of water through sweating.

Then there are the kidneys, which play a key role in regulating the body's fluid balance. Your kidneys work more efficiently when the body has plenty of water. Deprived of adequate fluids, the kidneys must work harder and are more stressed.

Other ways in which your body uses water include:

- Making saliva for food consumption and digestion

- Keeping mucosal membranes moist; these include membranes in your mouth, nose, eyelids, windpipe and lungs, stomach and intestines, and urinary system

- Serving as a "shock absorber" for your brain and spinal cord

- Transporting nutrients and oxygen throughout the body and removing waste

- Lubricating your joints.

Next: Page 2: What We Drink and Reality Check

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