Improved cardiovascular health and decreased likelihood of liver cancer, Parkinson’s disease and Type II diabetes are all potential benefits of regular coffee consumption, according to the Mayo Clinic. But a new Yale study may have recognized another health benefit: skin cancer protection.

The study, which examined almost half a million people over the course of a decade, found that participants who drank four or more cups of coffee every day were significantly less likely to develop invasive melanoma, a particularly dangerous type of cancer that kills 9,500 Americans every year. Subjects who drank more than four cups a day were 20 percent less likely to develop malignant melanoma than those who drank less than one cup per day.

“A few other observational studies have reported a similar inverse association between coffee drinking and melanoma, but overall previous results have been inconsistent,” said Erikka Loftfield GRD ’15, the study’s author and a doctoral student at the Yale School of Public Health. “We had good statistical power and were not surprised to find that higher coffee drinking was associated with lower risk of melanoma.”

Melanoma differs from other skin cancers in that it forms in pigmentation cells called melanocytes, responsible for producing the molecules that color skin. The melanin-producing cell often mutates into a cancerous cell due to excessive sunlight and ultraviolet light damage, although several genetic causes have been recognized in past studies.

Red-haired, pale-skinned people with frequent exposure to the sun are most likely to develop melanoma because they have less pigment to block DNA-damaging ultraviolet light, said Harriet Kluger, clinical research program leader of the Melanoma Program at Yale.

“One hypothesis would be that there is something in the coffee that protects the cells from developing the mutations that enable them to invade,” she said. “That would be the hypothesis that one could generate from the study.”

The study did not establish any possible causes for the relationship between coffee and melanoma, but it did find that the effect was present only with malignant melanoma and not melanoma in situ, a less harmful type of the cancer. This ineffectiveness, the study noted, would suggest that coffee consumption prevents this cancer from invading deeper into the skin and becoming more harmful — not from forming in the first place.

Kluger said that for an in situ cell to turn into a malignant cell, there must be additional mutations, and coffee may help prevent those mutations.

Both Kluger and Loftfield warned that coffee should not replace sound health practices, including sunscreen use and limited exposure to ultraviolet light, particularly through tanning booths.

“The most important thing that individuals can do to reduce their risk of melanoma is to reduce sun and UV radiation exposure,” Loftfield said. “While our results, and some from other recent studies, may be encouraging to coffee drinkers, they do not indicate that individuals should alter their coffee intake.”

More research is needed to determine whether this 20 percent reduction in malignant melanoma incidence is due to coffee consumption, but past studies seem to be pointing in that direction. For instance, several studies recognized that in lab rat testing, multiple acids and compounds present in coffee, such as caffeine and nicotinic acid, led to a decrease in melanoma in the rats.

While this relationship is present in caffeinated coffee, the 20 percent reduction in malignant melanoma incidence was not found in decaffeinated coffee, suggesting either some effect of caffeine on skin melanoma or some related behavioral trend.

The study does not suggest that coffee should replace good sense, but the reduction in melanoma incidence is significant. If supported by further research, it could be one more long-term health benefit of coffee consumption, alongside the significant decrease in mortality already recognized by research from the Mayo Clinic.

According to the National Cancer Institute, melanoma rates have been rising at roughly 1.8 percent per year for the last decade, while deaths due to melanoma have remained relatively constant.