PHILADELPHIA (CBS) – With the heat ramping up, it’s important to stay hydrated. That’s why the results of a new report will probably have parents concerned.

According to a new study, the majority of teenagers and children in the United States are not properly hydrated.

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Harvard researchers looked at data from 2009-2012 on more than 4,000 kids between 6 and 19 who participated in the National Health and Nutrition Examination Survey, which is given each year.

More than half of those surveyed were not getting enough hydration, with boys 76% more likely than girls to be inadequately hydrated.

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Doctors say that even mild dehydration can cause headaches, irritability, poor physical performance and an inability to think.

They also say that water is the best way to hydrate.

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The research is published in the June 11 issue of the American Journal of Public Health.