A recently-published large study that examined the dietary habits of over 100,000 Americans revealed an unexpected result. It showed a link between a high consumption of citrus fruits (especially orange juice and whole grapefruits) and greater risks of pigment-related melanoma skin cancer.
The Brown University researchers learned that about 1,800 of the study volunteers developed melanoma. The cancer type produces the dark pigment melanin.
Cancer patients who consumed one serving of citrus juice or fruit 1.6 times every day had a 36 percent higher cancer risk than those who consumed it less than twice weekly, according to The Week. One serving was either one orange, half a grapefruit, or a 6-ounce (177 ml) glass of juice.
The study's authors have a theory that the link is related to high levels of "furocoumarins" contained in citrus fruits such as tangerines, limes, and lemons, according to The Washington Post. Plants produce the substance as a defense mechanism.
Furocoumarins are photoactive. This means that higher levels of ultraviolet radiation cause their toxicity to increase.
Medical researchers have discovered that the substance causes skin to be more sunlight-sensitive. This connects it to melanoma skin cancer.
Dr. Shaowei Wu is the study's lead author and a Brown University research fellow. He noted in a released statement that the findings imply that people who consume large amounts of orange juice or grapefruits should try to avoid much sun exposure.
Marianne Beriwick of the University of New Mexico pointed out in a commentary that the study participants were all in the health profession, so they did not represent the general population. They could also easily spot cancer tumors.
Beriwick also mentioned that the study only included higher cancer risks linked to the consumption of orange juice and whole grapefruits. Whole oranges and grapefruit juice were excluded.
Another recent cancer study in JAMA Internal Medicine linked Viagra use to melanoma. It concluded that men who used the sex enhancement drug had a 84 percent higher risk of developing the type of skin cancer.
The new findings linking citrus fruits and melanoma skin cancer were published June 28, Monday in the Journal of Clinical Oncology.