Tuesday June 30, 2015 (foodconsumer.org) -- Drinking citrus fruit juice and excessive sun exposure may increase risk of melanoma, the most deadly skin cancer, a new study published June 29 in the Journal of Clinical Oncology suggests.

The study of more than 100,000 medical professionals led by Dr. Abrar Qureshi from Brown University and colleagues found study participants who drank orange juice once or more times per day were 25% more likely to be diagnosed with melanoma than those who drank the juice less than four times per month.

Similarly, the study also found men and women who drank grapefruit juice at least three times per week were at 41% increased risk for melanoma, compared to those who never drank any.

The study merely revealed an association between drinking citrus juice and elevated risk for melanoma and it did not establish any causal relation between the beverage and the cancer risk.

However, if there is indeed some causal relationship, that is, drinking orange juice or grapefruit juice increases risk of melanoma, then it is possibly the photoactive chemicals in the juice like furocoumarins that cause the problem.  Furocoumarins are known to sensitize the skin and make it more susceptible to the damage induced by UV rays.

In other words, citrus juice per se may not boost the risk of melanoma.

UV rays have been recognized by the U.S. National Toxicology Program as human carcinogens.  That means excessive exposure to the sun can increase risk of skin cancer.  But interestingly, UV exposure does not boost risk of melanoma as much as other types of skin cancer.  Also sun exposure promotes biosynthesis of vitamin D and helps prevent 17 types of cancers including many types of deadly forms of cancer like melanoma.

The take-home message is that the study does not mean you cannot drink citrus juice.   However, as always, one should avoid excessive exposure to the sun.  You do so because over-exposure can increase risk of skin cancer even if you do not drink orange juice or grapefruit. (David Liu)