Citrus Fruit Consumption May Up Risk of Melanoma

Frequent consumers of citrus fruits were found to have an elevated risk of malignant melanoma, according to a study published in the Journal of Clinical Oncology.

More than 100,000 men and women-63,810 women in the Nurses’ Health Study and 41,622 men in the Health Professionals Follow-Up Study-were followed for 24 to 26 years. Those who consumed citrus products ≥ 1.6 times per day had a 36% relative increase in melanoma risk compared with those who consumed the least amount of citrus. A serving of citrus was defined as half of a grapefruit, one orange, or a 6-oz glass of grapefruit or orange juice. Of all citrus products, grapefruit showed the highest association with melanoma, independent of other dietary habits and lifestyle factors. Participants who had a prior history of cancer were excluded from this analysis.

Those who consumed citrus products 1 to 1.5 times per day had a 27% increased risk of melanoma; those who consumed citrus 5 to 6 times per week had a 26% increased risk and those who consumed citrus 2 to 4 times per week had a 10% increased risk.

Those who consumed grapefruit three or more times per week had a 41% higher risk of melanoma compared with those who never ate grapefruit (P < .001).

The two cohorts were followed with the use of mailed questionnaires that included information on medical history and lifestyle factors every 2 to 4 years. A total of 1,840 of the participants were diagnosed with melanoma.

The link between citrus consumption and melanoma demonstrated in this study is not direct, and further studies are needed to validate these results and to identify the potentially carcinogenic source in citrus fruits. One possibility is furocoumarins, a type of psoralen found in citrus fruits in relatively high amounts, noted study authors led by Shaowei Wu, PhD, a research fellow at the Warren Alpert Medical School of Brown University in Providence, Rhode Island. Prior research has shown that furocoumarins sensitize the skin to ultraviolet light from the sun.

The authors noted that the link between citrus consumption and risk of melanoma was most apparent among those who were more susceptible to sunburn during childhood, spent more time in direct sunlight, and lived in locations where the range of ultraviolet exposure was greatest throughout the year.

“While the findings are intriguing, it’s far too soon to recommend any broad changes to grapefruit or orange consumption. Until conclusive data are available, we should continue to be cautious about protecting our skin from sun exposure,” said Gary Schwartz, MD, of Columbia University Medical Center in New York, who was not involved in the study.