Mary Nisi, of Chicago, exercises regularly, between yoga, Pilates and tennis, but she worries about not drinking enough water.
"I can get behind it if it's Evian and it's always with me," said the owner of a wedding DJ business. "But I'd really rather have herbal tea."
Nisi is not alone, according to a study by the Centers for Disease Control and Prevention. Forty-three percent of adults drink less than four cups of water a day. That includes 36 percent who drink one to three cups, and 7 percent who drink none.
Although the CDC does not say how much water is "enough," because our needs vary, less than four 8-ounce cups usually falls short, said Dr. Alyson Goodman, a CDC epidemiologist and lead author of the study.
On the upside, 35 percent of Americans drink four to seven cups a day, while 22 percent drink eight or more.
Water intake varies by demographics. People 55 or older, who are non-Caucasian or who live in the Northeast are more likely to drink four cups or less.
It also varies by health habits. People who drink less water are the same folks who consume a cup or less of fruits and vegetables a day, exercise less than 150 minutes a week, smoke or used to smoke, eat fast food more than once a week, eat fewer than five family dinners a week and do not shop at farmers markets.
"Understanding these associations helps us identify populations that can benefit from interventions," said Goodman.
"Mentally and physically, we're better off being hydrated," said Paula Burke, clinical dietitian at MetroSouth Medical Center in Blue Island. "The human body is about 70 percent water; we need it. It helps our circulation, makes us feel better, helps rid our bodies of toxins and prevents constipation. And drinking water before meals helps you eat less if you're trying to lose weight."
Caffeinated and alcoholic beverages do not count, Burke said, because they increase urination, which means more water is needed to stay hydrated.
Pop can hydrate you, Burke said, but adds sugar to your diet, which has adverse effects ranging from cavities to obesity.
Yet pop tops the list of beverages with calories consumed by adults 19 and older, according to the Dietary Guidelines for Americans from the Department of Health and Human Services. Sports/energy drinks are No. 2, followed by alcoholic beverages, milk, fruit juice and fruit drinks.
The guidelines say most adults need to drink more water, 100 percent juice and low- or fat-free milk, while drinking less pop and alcohol.
So popular are sports/energy drinks, especially among young people, that the American Academy of Pediatrics issued a 2011 report reminding parents to dispense "water, not sports or energy drinks, as the principal source of hydration for children and adolescents."
Habits start young, Goodman said.
"As a pediatrician, I know this is a family issue," she said. "It's up to parents to start children young with healthy drinking habits."
The CDC urges schools, after-school programs and day care facilities to increase children's enthusiasm for drinking water by adding it to their menus, providing cups and pitchers and incorporating water drinking into children's activities and parent communication.
Although the water fountain is a school icon, not all schools have clean drinking water, Goodman said. This despite the federal Healthy, Hunger-Free Kids Act of 2010, which said schools must "make free potable water available where meals are served."
Adults can help by setting good examples and self-discipline, advised Goodman.
"I keep cold, filtered water in the refrigerator at home and a bottle of water with a straw at my desk," said Chicagoan Libby Lowe, who works for a company that educates/coaches employees about healthy-living habits. "I don't know why, but I drink more if I have a straw."