Sunlight prevents cancer, study says
BMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7339.696/d (Published 23 March 2002) Cite this as: BMJ 2002;324:696
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I would like to mention that apart from Malignant Melanoma, U-V
radiation can cause Squamous and Basal Cell Carcinoma, and if not treated
they may become a life threatening condition! I believe that if the author
of the article would have had the number of the excised sun induced skin
cancers, he wouldn't underestimate the risk of excessive exposure to U-V radiation.
Competing interests: No competing interests
The two assumptions in this study: 1) That Northerners and
Southerners eat identical diets and 2) that Southerners receive greater UV
doses are unfounded and lead to an incorrect conclusion.
Regarding assumption 1: One example, consumption of dairy products,
correlates very highly with latitude in the continental U.S. Many
epidemiological studies have shown correlations between the consumption of
dairy products and prevalence of cancers such as prostate, breast and
ovarian. Another, tomatoes. Examination of USDA records will show
correlations of diet and state.
Regarding assumption 2: From skin cancer studies it has been shown
that people from Northern latitudes often receive extremely high
instantaneous (burning) doses of UV during holidays resulting in very high
exposures to Vitamin D. People from SOuthern latitudes tend to take in UV
in much lower instantaneous doses.
Competing interests: No competing interests
Further evidence that UV influences internal cancer; from prostate cancer studies.
Editor,
We read with interest the News Roundup article on the putatively
protective effect of sunlight on development of some internal cancers (1).
In this debate, the suggested link between exposure and prostate cancer
was not emphasised, though studies using a variety of experimental
approaches have suggested its importance (2,3). Thus, latitude and, by
inference, sunlight exposure has been linked with prostate cancer
mortality (3). Recently, we used a validated questionnaire to demonstrate
that increased exposure is protective against prostate adenocarcinoma (4).
Thus, prostate cancer patients had significantly lower mean weeks of
cumulative exposure than controls and, in cancer cases an average lifetime
exposure in the lowest quartile was associated with a significantly
younger age at diagnosis (median 67.7 years versus 72.1 years). We have in
unpublished studies, confirmed these findings in a new group of prostate
cancer patients and controls.
The mechanism whereby sunlight influences prostate cancer risk, is
unclear though 1,25 dihydroxy vitamin D has been implicated (2). The
vitamin has effects on proliferation and differentiation of prostate
tumour cells(2,5). Since increased pigmentation results in reduced vitamin
D synthesis in skin, individual ability to initiate pigmentation after
exposure should influence cancer risk. We examined this possibility by
comparing the frequencies of genotypes of several polymorphic genes
involved in skin pigmentation in prostate cancer patients and controls. We
found that allelic variants in the tyrosinase gene are associated with
reduced cancer risk (5). This gene catalyses rate-limiting steps in the
synthesis of melanin, a major determinant of skin colour.
We believe that these findings add to the growing body of evidence
indicating that sunlight has beneficial effects on the development of some
cancers. These beneficial effects (subclinical vitamin D deficiency is
reported in many countries) need to be considered against its harmful
effects on skin and development of cancers such as malignant melanoma.
Obtaining a better understanding of the beneficial and harmful effects of
sunlight should have considerable benefits for public health.
1. Dyer O. Sunlight prevents cancer, study says. BMJ
2002;324(7339):696.
2. Studzinski GP, Moore DC. Sunlight-can it prevent as well as cause
cancer? Cancer Res 1995;55:4014-4022.
3. Hanchette CL, Schwartz GG. Geographic patterns of prostate cancer
mortality. Evidence for a protective effect of ultraviolet radiation.
Cancer 1992;70:2861-2869.
4. Luscombe, C.J., Fryer, A.A., French, M.E., Liu, S., Saxby, M.F., Jones,
P.W. and Strange R.C. Exposure to ultraviolet radiation: Association with
susceptibility and age at presentation with prostate cancer. Lancet 2001;
358: 641-642.
5 Luscombe, C.J., French, M.E., Liu, S., Saxby, M.F., Jones P.W., Fryer
A.A. and Strange R.C. Prostate cancer risk: associations with ultraviolet
radiation, tyrosinase and melanocortin-1 receptor genotypes. Brit J Cancer
2001; 85: 1504-1509.
Competing interests: No competing interests