Today，young people spend about six hours a day in front of a TV or a computer and less than four minutes playing outdoors.It is not healthy for the mind and the body when time spent using technology replaces outdoor time.
Some health experts call green time "vitamin G".Kids who don't get outdoors much are likely to have trouble in school.Doctors believe that is because being outdoors excites the mind more than sitting around indoors.Even those who usually spend a lot of time outdoors notice a difference when they don't get green time.Madelyne P，14，says ， "I feel more tired when I don't get outdoors."
Researchers believe the positive effects of green time come from the physical activity in pastimes such as hiking or boating.Exercise produces brain chemicals that improve learning，mood，and sleep.It also improves learning by increasing connections between nerve cells that are important in learning and memory.Some schools hold classes outside for those reasons.Student Hannah Smith，says she believes the outdoors helps her focus and gets her to learn.Learning in a forest sparked her interest in art and photography，too.
Even doctors are helping give their patients a dose of（一剂）vitamin G.Miller writes "park prescriptions （处方）"for her patients because，being outdoors is good for health.She finds that when she gives patients park prescriptions，they are likely to continue with them.
Getting outdoors can be simple，just like calling together your family for a picnic lunch.All it takes is five minutes or more of green time.
Get outside，and get your vitamin G!
