Actually, you’re both partly right. A tan acquired gradually, whether from a tanning parlor or on the beach, does somewhat protect against sunburn, which is good. But even gradually-acquired tans are unhealthy because, in order to tan, a person has had enough exposure to sun to induce changes in the DNA in skin cells, that can lead to cancer.

Even a pro-sun advocate like Dr. Michael F. Holick, the professor of medicine, physiology and biophysics at the Boston University School of Medicine whose new book, “The UV Advantage” touts the benefits of some (albeit minimal) sun exposure to get more vitamin D, put it flatly, “I do not advocate tanning.”

What’s unarguable is that UVB radiation, whether from the sun or tanning bulbs, is linked to two, usually non-fatal, kinds of skin cancer: squamous cell and basal cell carcinomas. Squamous and basal cell cancers may be more tied to cumulative exposure that does not necessarily cause sunburn, said skin cancer specialist Dr. Howard Koh, the former commissioner of public health for Massachusetts and now associate dean for public health practice at the Harvard School of Public Health.

Melanoma is trickier because it often occurs on parts of the body that are not usually exposed to the sun, though it may be tied to “harsh, episodic” ( as opposed to cumulative) sun exposure, Koh said.

Bottom line on tanning parlors? Probably no worse than lying on the beach: Getting a tan is bad, either way. To be on the safest side, said Dr. Barbara Gilchrest, chairman of dermatology at the Boston University School of Medicine, slather on the sunscreen – and in thicker doses than most people do to get the advertised protection. Or, if you really want to look tan yet avoid skin damage and the cancer risk, consider a “sunless tanning” cream, which merely changes the color of the dead, outer layer of the skin. But beware: a “tan” acquired this way will not protect against sunburn or permanent sun damage.