Parents looking for an easy, low-cost way to improve their children’s physical, emotional, and mental functioning should start by making sure they drink more water.

A majority of US children and teens are not drinking enough water to keep them adequately hydrated, according to the annual National Health and Nutrition Examination Survey of the health of the US population conducted by the Centers for Disease Control and Prevention.

Researchers sought to determine whether children were, in fact, adequately hydrated. They collected urine samples from 4,000 children and teens ages six to 19 and measured how concentrated the samples were.

To encourage kids and teens to drink more water, try flavoring it with fruit, like lemons, oranges, or strawberries, or freeze fruit in ice cubes and use them to chill water. Buy a special cup or water bottle that’s only for water.

Researchers at the Harvard T. H. Chan School of Public Health found that slightly more than half of the kids were not getting enough hydration. Boys were more likely than girls to be under-hydrated; African Americans were more likely than non-Hispanic whites to be deficient in hydration.

Nearly a fourth of the children and teens in the study said they never drank plain water.

According to a statement by lead author of the study, Erica Kenney, “These findings are significant because they highlight a potential health issue that has not been given a whole lot of attention in the past. Even though for most kids this is not an immediate, dramatic health threat, this is an issue that could really be reducing quality of life and well-being for many, many children and youth.”

Water is an essential nutrient and is important for such body processes as temperature regulation, circulation, waste removal, and metabolism. Severe dehydration can lead to serious health problems and can require medical attention. Mild dehydration can cause headaches, impaired physical performance, irritability, and difficulty concentrating.

To encourage kids and teens to drink more water, try flavoring it with fruit, like lemons, oranges, or strawberries, or freeze fruit in ice cubes and use them to chill water. Buy a special cup or water bottle that’s only for water. Pack a thermos with cold water before you take off on an outing.

Water is an essential nutrient and is important for such body processes as temperature regulation, circulation, waste removal, and metabolism.

Most importantly, remove all the sugary cola, fruit punches, and sports drinks from the house, leaving water as their only beverage choice — other than milk.

“If we can focus on helping children drink more water — a low-cost, no-calorie beverage — we can improve their hydration status, which may allow many children to feel better throughout the day and do better in school,” said Steven Gortmaker, senior author of the study, in a statement.

The study is published in the American Journal of Public Health.