SUNLIGHT AND LYMPHOMA
Scientists have sometimes put forward the theory that exposure to ultraviolet radiation from the sun might be a risk factor for the development of non-Hodgkin’s lymphoma (NHL) (Bentham 1996). Here was yet another argument, they suggested, for avoiding prolonged contact with Old Sol. While blistering sun exposure is undoubtedly associated with an increased risk of several types of skin cancer, a solid link between sunlight and NHL has never yet been proven. And indeed, a recent report from the University of Sydney, Australia, has turned this theory on its head, demonstrating that far from inducing NHL, sunlight may in fact offer protection from the disease.
Published in December 2004, this is the first epidemiological study to examine the association between sunlight and NHL using direct measurements of sun exposure in individual subjects. The study, which reviews sun exposure over a time span of six decades, compares 704 Australian adults (between the ages of 20 and 74) who had a confirmed diagnosis of NHL, to 694 control subjects without NHL. The control subjects were randomly selected and then matched to the NHL patients by age, sex and place of residence. A questionnaire and telephone interview were used to determine the number of hours spent outdoors on working and nonworking days and vacations.
Contrary to expectations, the risk of NHL fell with increasing hours of sun exposure. The chance of getting NHL was 35 percent less in that portion of the study population that had the most sun exposure compared to the portion that had the least. The impact was even greater when the scientists looked at sun exposure on non-working days. People who got a lot of sun exposure on weekends and holidays had less than half the incidence of NHL compared to those who stayed indoors on their days off. It was a remarkable difference.
“Our results provide strong statistical evidence for an inverse association between sun exposure and NHL,” Prof. Anne Kricker and her School of Public Health coauthors wrote in the International Journal of Cancer (Hughes 2004). Since sun exposure produces vitamin D in the skin, these findings suggest that this essential vitamin, best known for preventing rickets (a deficiency disease resulting in a weakening of the bones), may also protect against some deadly forms of cancer, including lymphoma. In scientific terms, the authors say that it makes “UV-mediated synthesis of vitamin D a plausible mechanism whereby sun exposure might protect against NHL.”
These results were anticipated in a previous ecologic study of NHL mortality rates in the US carried out by William B. Grant, PhD, of the Sunlight, Nutrition And Health Research Center of San Francisco (Grant, 2002). (An ecologic study investigates the characteristics of a disease in a whole population.) In that study, NHL mortality rates were also found to be inversely correlated with ultraviolet B (UVB) radiation from the sun. Grant’s most recent work indicates that not only is solar UVB radiation dose an important risk reduction factor, but also that city living is itself a risk factor, attributable to reduced UVB doses received by urban dwellers (Grant and Garland, in preparation). In November, 2004, the results of Dr. Grant’s 2002 published study were confirmed by Japanese researchers who analyzed the effect of sunlight on the incidence of digestive tract cancers (Mizoue, 2004). This adds additional support to the idea that solar UVB radiation, through the production of vitamin D, might be an important
“While NHL is often found associated with basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, the reason for this association is not fully understood,” said Dr. Grant, “although it could be that systemic immunosuppression is involved” (Grant 2004). Nevertheless, the inverse relationship between UVB radiation and NHL indicates that vitamin D most likely plays an important role in preventing cancer.
Grant emphasizes, however, that those who receive excessive UV radiation doses, beyond the amount required for adequate vitamin D production, may be putting themselves at increased risk for NHL. This points to the need for moderation in all things, including sun exposure.
The issue is of considerable importance. There will be 54,370 new cases of NHL in the US in 2004. Although there are some modestly effective treatments available for NHL, the annual number of US deaths from the disease is 19,410 (ACS 2004). Between 1973 and 1996 the incidence of NHL increased by 81 percent.
Nor is the US alone: 286,000 people are diagnosed with non-Hodgkin’s lymphoma worldwide every year and approximately 161,000 die from the disease, according to International Agency for Research on Cancer (IARC) estimates for the year 2000. Non-Hodgkin’s lymphoma is the most rapidly increasing kind of cancer, after lung cancer and non-melanoma skin cancer.
The NCI has attributed this increase variously to genetic and treatment-related immunodeficiencies, exposure to viruses, pesticides and occupational chemicals (JNCI 1999). Should we now add watching TV instead of getting some sun in the park as a new risk factor for NHL?
Unfortunately, while the evidence of the benefits of sunlight daily becomes more persuasive, the dermatology profession continues vigorously to promote a policy of sunlight avoidance. Dermatologists tend to regard unprotected sun exposure as a grave danger, analogous in scale and seriousness to the risks of unprotected sex. The NCI enthusiastically endorses this wrong-headed policy, stating that “[I]n general, increased exposure to the sun-especially without adequate use of sunscreen and protective clothing-increases the chances of getting skin cancer.” While it is true that excessive amounts of sunlight do increase the risk of skin cancer, moderate amounts are not dangerous. The NCI also ignores the bigger point: a moderate amount of sunlight protects against some of the most dangerous internal cancers, including NHL.
The US government has even set a “Healthy People 2010 Target” to increase to 75 percent the proportion of adults who are very likely to use sunscreen with an SPF of 15 or higher, wear protective clothing, or seek shade (NCI 2004). In this topsy-turvy world, the sun (which, after all, is the source of all life on this planet) is seen as a health threat. Since the government cannot ban sunlight, it tells us to save ourselves from the Great Carcinogen in the Sky by slathering on sunscreens and scurrying for the shade.
Yet commercial sunscreens are not without potential dangers themselves.
Most American sunscreens contain synthetic chemicals such as benzophenones (dixoybenzone, oxybenzone), PABA and PABA esters (ethyl dihydroxypropyl PABA, glyceryl PABA, p-aminobenzoic acid, padimate-O or octyl dimethyl PABA), cinnamates (cinoxate, ethylhexyl p-methoxycinnamate, octocrylene, octyl methoxycinnamate), salicylates (ethylhexyl salicylate, homosalate, octyl salicylate), digalloyl trioleate, menthyl anthranilate and avobenzone [butyl-methyoxydibenzoylmethane). According to the skinbiology.com website, most of these chemicals generate harmful free radicals and have estrogenic (i.e., female hormonal) activity. With the exception of avobenzone, they are banned by the European Union. Yet this potential danger does not concern the National Cancer Institute one whit.
Despite increasing evidence that there is no scientific basis for a policy of strict sunlight avoidance, some in the dermatology profession have stubbornly continued to cling to their ‘sunlight is dangerous’ dogma, and to punish those mavericks who have dared to challenge the status quo. Early in 2004, Michael F. Holick, MD, PhD (who has written 210 PubMed-listed articles on vitamin D) was fired from his position in the Department of Dermatology of Boston University for stating that people in northern latitudes could benefit from 15 minutes of unprotected sun exposure three times per week. Prof. Holick’s position was based on the best scientific evidence available today, while his critics are still defending outdated and largely disproven concepts. This firing was an outrage against academic freedom and a stain on the reputation of a great academic institution. Professor Holick’s dismissal, and the whole topic of sunlight’s relationship to cancer, is worthy of a Congressional investigation.
Previous Moss Reports articles on Dr. Holick’s firing:
Acknowledgement: Special thanks to Dr. William B. Grant for his help with the facts in this article. All opinions expressed are my own.
–Ralph W. Moss, PhD
American Cancer Society (ACS), Cancer Facts & Figures 2004. Retrieved December 6, 2004 from: http://www.cancer.org
Bentham G. Association between incidence of non-Hodgkin’s lymphoma and solar ultraviolet radiation in England and Wales. Brit Med J 1996;312:1128-1131.
Grant WB. An estimate of premature cancer mortality in the United States due to inadequate doses of solar ultraviolet-B radiation, Cancer.2002;94:1867-75.
(See, also, Dr. Grant’s website at http://www.sunarc.org) Grant WB, personal communication, Dec. 6, 2004.
Hughes AM, Armstrong BK, Vajdic CM, Turner J, Grulich AE, Fritschi L, Milliken S, Kaldor J, Benke G, Kricker A. Sun exposure may protect against non-Hodgkin lymphoma: a case-control study. Int J Cancer 2004;112:865-71.
JNCI (Anonymous) Stat Bite: U.S. Non-Hodgkin’s lymphoma incidence, 1973-1996. J Natl Cancer Inst 1999;91:1109.
Mizoue T. Ecological study of solar radiation and cancer mortality in Japan. Health Phys 2004;87:532-8.
National Cancer Institute (NCI), Cancer Progress Report-2003.
Reuters. Sunshine may ward off lymphoma. Dec. 3, 2004.
Sorensen HT, Mellemkjaer L, Nielsen GL, et al. Skin cancers and non-hodgkin lymphoma among users of systemic glucocorticoids: a population-based cohort study. J Natl Cancer Inst. 2004;96:709-11.