Five Questions With: Dr. Abrar Qureshi

"In our study fresh grapefruit showed a significant association with melanoma whereas grapefruit juice did not."

Dr. Abrar Qureshi is chief of the Department of Dermatology at Rhode Hospital and chair of the Department of Dermatology at the Warren Alpert Medical School of Brown University. Together with colleagues from the Warren Alpert Medical School and Rhode Island Hospital, and in collaboration with colleagues at Brigham & Women’s Hospital, he recently published a study which found that white people who consumed a lot of grapefruits or orange juice had a small but significantly higher 25-year risk of malignant melanoma.

PBN: What can happen in terms of the ingestion of citrus fruits and skin cancer?
QURESHI:
What we found in two large populations of more than 100,000 white men and women is that high consumption of grapefruit and to a lesser extent orange juice was associated with a somewhat higher risk of malignant melanoma. The results don’t mean that citrus consumption is harmful. Instead, people who eat a lot of citrus might consider taking extra precautions against subsequent sunlight exposure, such as using high-SPF sunscreen and cover skin with protective clothing and broad-brimmed hats.

PBN: How did you measure the association of citrus ingestion and malignant melanoma and what were some of your methods?
QURESHI:
We demonstrated a consistent positive association between citrus consumption and risk of malignant melanoma, a potentially lethal form of skin cancer. The citrus fruits (i.e., orange and grapefruit) examined in the study are the most consumed citrus fruits in the US population. We used a validated questionnaire to collect information on consumption of citrus products and other food items. Melanoma was self-reported biennially and confirmed by pathological reports. Those who consumed overall citrus 1.6 or more times per day had a 36-percent higher risk compared with those who consumed less than twice per week.

PBN: The breakdown according to which type of fruit and whether consumed as juice or not influenced the association. What can you tell readers about that?
QURESHI
: There may be higher quantities of furocoumarins in fresh fruits with peel and pulp than in processed juices. Industrial processing may reduce the quantities of certain chemicals in processed foods, leading to the different associations with health outcomes for consumption of fresh and processed food items. For example, in our study fresh grapefruit showed a significant association with melanoma whereas grapefruit juice did not. However, the consumption level of the food also matters. Although orange juice contains lower levels of furocoumarins, its consumption level is very high in the population—several times higher than other citrus products, thereby explaining its less apparent but still significant association with melanoma risk.

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PBN: What led to the awareness that this association could exist?
QURESHI:
Both biological and epidemiologic studies have demonstrated the photocarcinogenic properties of psoralens (a group of furocoumarins), naturally occurring chemicals rich in certain plants like citrus products. Specifically, both psoralen-initiated photochemotherapy for skin disorders and use of psoralen-containing commercial products have been associated with increased risk of malignant melanoma. However, whether the consumption of psoralen-rich foods (i.e., citrus products) may be associated with an increased risk of cutaneous malignant melanoma has been unknown. Our results showed that consumption of psoralen-rich foods is associated with a modestly increased risk of malignant melanoma in both women and men.

PBN: Should people take these results as reason to avoid the combination of ingesting citrus fruits and spending time in the sun?
QURESHI
: This work does not indicate that we are concerned about citrus consumption. In fact citrus consumption is very important for vitamin C and other very healthy attributes. However, people need to be aware that when they are consuming certain fruits and vegetables that contain these photoactive compounds, they need to be more careful with their sun exposure the next few hours in particular and probably the next day or two. It’s just a matter of being careful with how much ultraviolet radiation they are getting post-consumption.

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