Daily coffee consumption may provide protection against malignant melanoma — the worst form of skin cancer — researchers have found in a statistical study involving tens of thousands of java drinkers.

Researchers concluded that people who drank the most coffee — about four cups daily of the caffeinated brew — slashed their risk by about 20 percent for malignant melanoma, the fifth-most common cancer in the United States.

The analysis was conducted by medical researchers at the National Cancer Institute who studied 447,357 people who participated in a diet and health study sponsored by the National Institutes of Health and AARP.

Erikka Loftfield of the cancer institute’s division of cancer epidemiology and genetics led the study.

Loftfield said despite the finding, which she and her team describe as statistically significant, they cannot explain why coffee drinking may guard against melanoma. Results of the study are reported in the current issue of the Journal of the National Cancer Institute.

“The underlying mechanism of how coffee may mediate the risk for malignant melanoma has not been established,” Loftfield said in an e-mail.

Researchers tracked the health of people in the study over a 10-year period. All were cancer-free when the research began. Loftfield and her team examined how much coffee test subjects drank, their daily exposure to ultraviolet light,smoking history, alcohol consumption, age, gender and a host of other parameters.

The finding that coffee-drinking provides protection against malignant melanoma is in line with other research on less serious forms of skin cancer. Coffee drinkers are less likely to develop basal-cell and squamous carcinomas, researchers have found in recent years.

Numerous other questions remain unanswered. For example, the researchers drew their conclusions based on a sample of non-Hispanic whites — the group at greatest risk of skin cancer. However, no one knows whether other groups would experience the same benefit.

In addition, doctors aren’t willing to endorse gulping down extra cups of coffee in the hope of staving off skin cancer. The Skin Cancer Foundation and Loftfield are recommending safe-sun practices.

Dr. Deborah Sarnoff, a dermatologist and senior vice president of the Skin Cancer Foundation in Manhattan, said there are still glaring gaps in the science.

“Researchers have not yet determined what aspects of coffee made the difference and acknowledged that more research is needed, particularly concerning the relationship between caffeine and melanoma reduction,” Sarnoff said.