Being big-hearted may improve the heart's health, a study has shown.
Scientists found that voluntary work reduced biological markers linked to heart disease.
After 10 weeks, levels of inflammation, cholesterol and body mass index (BMI) were lowered.
Researchers tested 106 teenagers from Vancouver, Canada, who were split into two groups.
One gave up an hour a week for 10 weeks helping young children in local after-school programmes. The other group was kept on a waiting list for volunteer activities.
Measurements were taken of BMI and blood markers before and after the study. The young people also underwent psychological assessments of self-esteem, mental health, mood and empathy.
Study leader Dr Hanna Schreier, from the University of British Columbia, said: "It was encouraging to see how a social intervention to support members of the community also improved the health of adolescents.
"The volunteers who reported the greatest increases in empathy, altruistic behaviour and mental health were the ones who also saw the greatest improvements in their cardiovascular health."
Although the participants were young, early signs of heart disease can start to appear during adolescence, the researchers pointed out.
Previous studies have shown that psychosocial factors such as stress, depression and well-being can affect heart health.
The findings appear in the journal JAMA Paediatrics.