More than one-half of all households in the U.S. contain one or more animals. Pets are more common in households with children. Pets are known to provide companionship, warmth and unconditional love, and help prevent loneliness. In addition to the millions of birds, small mammals, reptiles and fish, household pets include more than 100 million cats and dogs. Taking care of these pets has a beneficial impact on one's physical, social and psychological health.

A pet appears to provide important social support. Owning a pet can help you relax, and lower anxiety levels. Pets enable people to focus off their own problems and look outside beyond themselves. One study found that people with depression who swam with dolphins for an hour every day for two weeks reported feeling less depressed than those who simply played in the water.

Studies found that people who had a heart attack survive longer if they own a pet. Pet owners tend to have fewer annual visits to the doctor, and tend to have a speedier, easier recovery after illness or surgery. Specially trained animals are being used in clinical settings, in more and more hospitals and nursing homes. Having psychiatric and other patients interact with animals appears to improve their mood and reduce anxiety. Pet therapy may also reduce the level of pain medication required by some patients. Pet owners with AIDS are far less likely to suffer from depression than those without pets.

One five-year study of children, ages three to 18 years, found that slow-learning children with pets had higher levels of self-esteem and better emotional functioning than those with no pets. Children with autism, learning disabilities or behavioral disorders often show immediate improvement when pets are used for therapy.

A dog can become an exercise buddy. Dog owners are more likely to be physically active on a regular basis and better manage their weight. In Columbia, Missouri, they have a "Walk a Hound, Lose a Pound" program in which people of all ages take shelter dogs for a walk every Saturday morning. Walking a dog also helps a person socialize with others and open up lines of communication. A dog is a conversation just waiting to happen. And pet owners have a tendency to want to talk with other pet owners.

Families with allergies can choose pets without fur or feathers such as reptiles and fish. Alternatively, an option for kids with allergies is getting a stuffed animal. A study found that a stuffed puppy helped to ease the stress and improved outcomes for small Israeli children exposed to violence during the Israeli-Lebanon War in 2006.

Before you buy a pet make sure you choose one whose personality, size and requirements fit your needs, abilities, budget and living situation. Pets make great companions and help us live happier and healthier lives, but they are not a total substitute for human friends and family.

Winston Craig, Ph.D., RD, is a professor of nutrition at Andrews University.

Pets are natural mood enhancers.

A pet can improve your health in many ways.