It is a sign of the times, apparent both on the newsstands and in the mailboxes: The health and fitness boom has infected not just the general consciousness but also the publishing industry.

From slick magazines like American Health to decidedly less colorful newsletters from institutions like Harvard Medical School, all sorts of health publications have emerged to update us on the latest research, the newest diets, the hottest ideas and the most promising cures for whatever ails us.Doctors have always had their own journals - weighty, technical publications all but indecipherable by the lay person. But it's been only recently that consumers have had their pick of so many different health magazines and newsletters, written in their language and for their use.

One consumer-magazine directory lists 35 magazines in its health category. Besides the more well-known ones like Health and Prevention, the list includes special-interest publications like Arthritis Today, Coping (for people with cancer), Generations (about Alzheimer's disease and aging), Paraplegic News and Yoga Journal.

Many of these magazines emerged in the early '80s, following on the heels of the overall health-and-fitness boom, said Marian Confer, research director for the Magazine Publishers Association.

And the magazines tend to be healthy from a business standpoint as well, say industry watchers.

The top seller, for example, is Prevention, a Reader's Digest-sized magazine with a circulation of nearly 3 million. Hippocrates, an intelligent, issues-oriented publication, has built up a 359,000 circulation in just one year.

But along with quantity comes the question of quality. That is vital because when it comes to health care, what's presented to consumers has to be accurate and safe.

We decided to survey the field, looking at a sampling of both health-oriented magazines readily found on newsstands, and newsletters from medical schools and institutions usually available only by mail. To do this, we sought the opinions of a five-member panel of health-and-fitness experts, comprising a doctor with a sports medicine background, a physical education professor and a dietitian and ourselves. (As writers we are part of the burgeoning field of consumer-health reporting.)

The panel looked at the current issue at the time of the survey, which was either the publications' May or June issue. As a result, our opinions may not necessarily reflect the publication's general scope year in and year out, but rather its output that particular month.

With magazines, as in anything, there are different strokes for different folks. Our panelists had different likes and dislikes, different definitions of what's good, what's mediocre, different priorities and preferences.

Just like any reader.

At the one end, for example, there is Hippocrates, a year-old, every-other-month magazine that most panelists found to be written on a higher level than most consumer publications. That is by design: The magazine is trying to reach the college-educated, non-medical professional, said a spokesman for Hippocrates.

"We wanted to produce something between the lay fitness magazines like Health, American Health and Prevention, on the one hand, and the professional medical journals on the other," said John Kiefer, Hippocrates' editorial coordinator.

Panelists found the most variety among the four magazines, rather than the newsletters. That is to be expected because the magazines are more heavily targeted to specific groups of consumers and advertisers. Health, for example, is clearly a "women's" magazine, with most of its features directed at young women and all its illustrations and most of its ads showing young women as well.

The five newsletters, by contrast, were a more homogenous bunch, reflecting their all-information, no-advertising, little-glitz bent.

While all but one of the newsletters generally were found to be sober, reasoned publications, even within this group there are differences. Mainly, it's in focus.

"We're different from Berkeley's, which has more of an emphasis on fitness and wellness," said Dr. Michael J. Hogan, medical editor of the Mayo Clinic Health Letter. "We're a little more similar to Harvard's. We are a little more bent toward . . . well, I don't want to say disease, but we cover more subjects like illness and treatment."

Health newsletters are relatively new, having emerged over the past several years, said Frederick D. Goss, executive director of the Newsletter Association.

"It's generally an offshoot of the national concern over health and fitness," he said.

Newsletters tend to come and go more quickly than magazines, responding to the trends of the day, whether they be solar power, biotechnology or, now, health and fitness, he said.

"Newsletters succeed when they can give specialized information," said Goss. "Newsletter readers tend to be upscale in education and income. They're information-seekers."

And, Goss said, health and fitness are subjects particularly adaptable to a newsletter format.