Harvard Health Letter

The sunshine D-lemma

Sunlight causes skin cancer, but it also produces vitamin D, a substance that seems to prevent some types of cancer and possibly other diseases.

Carcinogen is a word that jumps off the page. It makes us think of nefarious chemicals and noxious pollutants.

So it's startling to see sunlight — or, to be more precise, the invisible, ultraviolet portion of sunlight — labeled a carcinogen, a term that can be applied to anything believed to cause cancer. There are some nuances to the evidence, but overall, there's not much question that exposure to ultraviolet light is a risk factor for all three types of skin cancer: basal cell, squamous cell, and melanoma.

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »