Nonny Dyer worships the sun.

During her years as a river raft guide she spent her days basking in it, and when a career change and motherhood moved her indoors more, she sorely missed it.

“Depression hit big time,” says Dyer, 45.

So for the past three years, she has made a point of catching a few rays on sunny days and visiting a tanning spa weekly during the darker months, not so much to enhance her appearance but to feel better inside.

“I don’t know why,” Dyer says, “but it always just makes me feel better.”

She may be on to something.

At a time when fear of wrinkles and skin cancer has many people slathering on sunscreen and avoiding UV rays at all costs, a growing body of evidence is suggesting that Vitamin D — a hormone produced primarily through exposure to sunlight — is more critical to health than once believed.

In November, the National Institutes of Health convened a group of scientists for a conference, “Vitamin D and Health in the 21st Century,” aimed at exploring a troubling re-emergence of health problems, such as rickets, related to Vitamin D deficiency.

A recent study in the Journal of the American Medical Assn. found a diet rich in vitamin D protected people from developing colon cancer.

In January, the journal Neurology found that women who took vitamin D supplements were 40 percent less likely to develop multiple sclerosis.

And a number of other recent studies have linked lack of Vitamin D, or regular sunlight, to greater risk for high blood pressure, certain kinds of cancer, rheumatoid arthritis, multiple sclerosis, Type 1 Diabetes and depression.

Such news is no surprise to Dyer, who has been diagnosed with Seasonal Affective Disorder, a depression often linked to Vitamin D deficiency.

“Sun raises my mood. It has all my life,” she says.

But the news does have health professionals taking a closer look at a vitamin long taken for granted. Some local nutritionists are upping their recommendations for daily Vitamin D intake, and pushing supplements. Other health professionals — to the dismay of skin cancer specialists — are reversing conventional wisdom and advising people to get more sun.

“There is a sun phobia out there,” says Dr. Michael Holick, a professor of medicine who heads up the Vitamin D Laboratory at Boston University. His new book, “The UV Advantage” (ibooks, Incorporated, $19.95), hit shelves this month.

“It is now recommended that you should never be exposed to direct sunlight,” he says. “That is a radical and unhealthy position to take.”