You would not have thought it possible, no? Oranges are healthy, they are fruit, for goodness’ sake, and fruit’s good for you! But actually, if you look at the science, the thought that oranges or more specifically, citrus fruit can increase your risk of skin cancer is plausible.
Why?
This is because citrus fruits contain chemicals called psoralens. Psoralens are used in photochemotherapy, a whole area of specialised dermatology. They increase a skin’s responsiveness to the sun. Dermatologists commonly use oral psoralen and UVA radiation to treat widespread inflammatory skin diseases. However, psoralens are also photocarcinogenic ie increase the risk of skin cancer when combined with sun exposure.
Therefore the hypothesis that eating citrus fruits may increase a person’s risk of developing skin cancer or more specifically melanoma could be seen as a valid question that needs exploring.
It is therefore interesting to read a paper that looked at this in further depth in the August edition of the British Journal of Dermatology.
[Marley AR, Li M, Champion VL et al. The association between citrus consumption and melanoma rise in the UK Biobank. Br J Dermatol 2021;185: 353-62.]
What did the study look at?
The UK Biobank is a large health resource in the UK which was established in order for us to better improve the diagnosis, treatment and prevention of various major illnesses such as cancer, heart disease, stroke etc. There are more than 500,000 participants, aged between 40-69 years, who were assessed at 22 centres throughout the UK where they all provided personal information, biological samples and measurements. These participants were followed up with online questionnaires every few years.
The authors therefore had access to over half a million participants (a very large sample size) who provided data on how much and what type of citrus fruit they ate from April 2009 and then with sequential online questionnaires up to June 2012.
The authors then looked at melanoma incidence along with many other factors such as sex, skin type, education, income level, sunburn episodes, time spent outdoors etc.
What did they find?
They found that those with the highest consumption of orange and orange juice (>1 serving per day) had a significantly increased risk of melanoma compared to those with who ate no oranges. This effect was even more pronounced in those with fair skin type, compared to those with an olive complexion.
Is this true for all citrus fruits then?
Surprisingly, they found no link between grapefruit consumption and melanoma. This is surprising because grapefruit has a much higher psoralen level then oranges, orange juice or satsumas.
However, the authors state that grapefruit consumption levels were low in the population under study and maybe if more people ate more grapefruit then the results may have been different.
So I need to cut out oranges to reduce my risk of skin cancer?
Maybe so. This was a large, well conducted study. There have been previous studies which have shown similar results.
[Wu S, Han J, Feskanich D et al. Citrus consumption and risk of cutaneous malignant melanoma. J Clin Oncol 2015; 33: 2500.]
[Mahamat-Saleh Y, Cervenka I, Al-Rahmoun M et al. Citrus intake and risk of skin cancer in the European Prospective Investigation into Cancer and Nutrition cohort (EPIC). Eur J Epidemiol 2020; 35: 1057-67.]
The future?
The authors advise caution in generalising the results to other populations in other countries. However as the UK has less ambient sunshine than other areas in Europe, and also the USA and Australia, the implications could be far more meaningful in those countries with sunnier climates.
As with all studies, further research is needed into this area.
Kind regards,
Sandy
Dr Sandy Flann, Consultant Dermatologist
