ATLANTA - Just like their parents, youngsters are taking herbal supplements from fish oil to ginseng, a sign of just how mainstream alternative medicine has become.

More than one in nine children and teens try those remedies and other nontraditional options, the government said yesterday in its first national study of young people's use of these mostly unproven treatments.

Given that children are generally pretty healthy, the finding that so many use alternative medicine is "pretty amazing," said one of the study's authors, Richard Nahin of the National Center for Complementary and Alternative Medicine. The sweeping study suggests about 2.8 million young people use supplements.

Their parents' practices played a big role. Youngsters were five times more likely to use alternative therapies if a parent or other relative did. The same study showed that more than a third of adults use alternative treatments, roughly the same as in a 2002 survey.

The researchers used a big umbrella in defining alternative medicine: Acupuncture, homeopathy, chiropractic, traditional healing, yoga, Pilates, deep breathing, massage and even dieting were included.

Vitamin and mineral supplements are not called alternative medicine, nor are prayer or folk-medicine practices.

Herbal remedies were the leading type of alternative therapy for both adults and those under 18. Among children, such therapies were most often given for head or neck pain, colds and anxiety. Body aches and insomnia were other top reasons children got alternative therapies.

Fish oil for hyperactivity and echinacea for colds were the most popular supplements, although there is no proof such treatments work for those conditions, nor have they been tested in children.

Unlike federally regulated medicines, herbal remedies do not have to be proven safe or effective to be sold. And studies that have been done on them have focused on adults, not children.

Some doctors are troubled that parents may be giving children alternative therapies in place of proven clinical treatments, said Wallace Sampson, an emeritus clinical professor of medicine at Stanford University.

"The reality is none of these things work," said Sampson, who was a founding editor of the Scientific Review of Alternative Medicine, "including some of the more popular ones. They're placebos."

The study by the Centers for Disease Control and Prevention is based on a 2007 survey of more than 23,000 adults who were speaking about themselves and more than 9,000 who were speaking on behalf of a child in their household.

Women are the most likely to use alternative medicine, as are those with advanced college degrees and people who live in the West.

For adults, pain was by far the main reason adults tried massage, chiropractic care, and other alternative therapies. Many adults say they had trouble getting back-pain relief from mainstream medicine. "Some facet of conventional care is not satisfying," Nahin said, "and they're looking at other options."