People have understood that kindness is good for the person who receives help. For example, when we give food to a hungry person, he is lucky. However, scientists have recently begun to study the effect(影响)of the kindness on the person giving it. What they have found is that doing good is good for the doer(行为者).Acts of kindness can improve health, help a person reach goals and even add years to a person's life.
The first study to show the connection between doing good and living a long life was a study on aging(衰老). Beginning in 1956, scientists studied a group of married mothers for 30 years. They thought the women with the most children would die first. But the number of children a woman had did not matter. Wealth did not matter. Education did not matter. What did matter was whether they volunteered. Women that volunteered had fewer diseases during their life.
Many other studies have found the same positive(积极的)effects. Helping other people improves long-term health. The gains are the same for men, women, old people and the young. Those who volunteered had fewer serious diseases than those who did not volunteer. This included diseases such as heart attack, cancer and stroke.
Scientists are studying many possible causes. One possible cause is an increase in antibodies(抗体)，which help fight against disease. One study showed the body produces more antibodies after an act of kindness.
Another one is an increase in Oxytocin(催生素)，it is a chemical that fights the effects of stress from life. Scientists have found a link between being kind to people and an increase in the chemical oxytocin.
