The benefits of sunlight outweigh the harms

[Neon Beach]

The benefits of sunlight outweigh the harms
18 January 2003 William B. Grant,
Atmospheric Sciences, NASA Langley Research Center (this letter is not related to my NASA work)
12 Sir Francis Wyatt Place, Newport News, VA 23606-3660, USA
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Re: The benefits of sunlight outweigh the harms ( http://www.bmj.com/cgi/eletter-submi...eigh+the+harms )



The recent editorial on preventing skin cancer (1) is, in the author's opinion, too narrowly focused to accomplish the overriding goal of the editorial, namely, reducing death rates in the U.K., especially from cancer. Focusing the discussion of solar ultraviolet-B (UV-B) radiation (280-320 nm) only on skin cancer, especially melanoma, is a very narrow perspective (2).

It is a narrow viewpoint since solar UV-B, which gives rise to tanning, sun burning, and, sometimes, skin cancer, is also the primary source of vitamin D for many people. Vitamin D has many mechanisms involved in reducing the risk of cancer, including increasing cell differentiation and apoptosis, reduction of metastasis and angiogenesis around tumors, and reduction of parathyroid hormone (3-6). A number of epidemiologic studies have shown an inverse correlation between solar UV-B doses for several types of cancer (7-16).

The cancer mortality rates in the U.S. from 1970-94 (17), as well as the map of solar DNA-weighted UV-B (peaking near 300 nm) radiation for the U.S. in July (18), can be used to show that the 50% higher mortality rates for a dozen types of cancer in the NE U.S. compared to those in the SW U.S. are highly correlated with differences in solar UV-B doses for the two regions (16). It should be pointed out that while this study was conducted using only cancer mortality rates in (17) and solar UV-B radiation doses in (18), a more extensive study using additional factors such as diet, Hispanic heritage, other diseases, poverty, and smoking, has been completed and a manuscript on the findings will be submitted for publication shortly. In the new study, a much larger fraction of the cancer mortality rate distributions can be explained with the additional factors, but the fraction attributed to insufficient UV-B radiation and/or vitamin D remains very nearly the same.

Total consumption of vitamin D (dietary plus supplements) is generally significantly inversely associated with cancer, such as colorectal cancer (19-23). Vitamin D also plays an important role in reducing the risk of or severity and progression of a number of other diseases including arthritis, multiple sclerosis, osteoporosis, and rickets (24,25). Vitamin D deficiency is a problem in the U.K., especially among non-European immigrants (26-28) and the elderly (29), as well as for Europeans in general (30,31).

To put UV-B and cancer risk and risk reduction in perspective in the U.K., it is instructive to look at cancer incidence and mortality rates for cancers related to solar UV-B radiation (16). The data for the mid-to -late 1990s are available from (32). The data are based on the best available data as well as modeling efforts. The results are presented in Table 1. The sums of incidence for the cancers for which UV-B radiation and vitamin D are risk reduction factors (7-16) are about 25 times the incidence for melanoma, the predominant form of skin cancer, while the mortalities are 50 times those for melanoma. In the U.S., a conservative estimate is that 8% of the "premature" mortality rates for the sum of these cancers for males can be delayed, as well as 10% of those for females (16). However, the UV-B doses in the U.K. are equivalent to those at the northern boundary of the U.S. Thus, the fraction of premature mortality that can be attributed to insufficient UV-B and/or vitamin D in the U.K. could be 12% for males and 15% for females. These rates imply that the UV-B/vitamin D-preventable incidence of all non-melanoma cancer is 3.5 times the incidence of melanoma in the U.K., while the delay in mortality from all non-melanoma cancer is 7 times that for melanoma, assuming that incidence and mortality have the same relation to vitamin D.

Going further, the increase in melanoma rates in the U.K. may be due only in part to increased UV exposure practices: it could also be due to increasing obesity. Obesity has been linked to melanoma in two studies (33,34). Increases in obesity rates have been reported in the U.K. (35).

So, what should be the responsible policy guideline regarding solar UV-B exposure and vitamin D? First, enjoy the sun in moderation; avoid burning and excessive tanning. Second, consider supplementing with vitamin D, individually or at the population level. However, be careful not to have serum 25(OH)D3 levels rise too high (<50-60 ng/ml). Serum testing for 25(OH)D3 levels is now readily available. See (36) for thoughts on fortification of foods with vitamin D.

References
1. Fry A, Verne J. Preventing skin cancer. BMJ. 2003;326:114-5
2. Dyer O. Sunlight prevents cancer, study says. BMJ 2002;324(7339):696.
3. Feldman D, Zhao XY, Krishnan AV. Editorial/mini-review: Vitamin D and prostate cancer. Endocrinology. 2000;141:5-9.
4. Mehta RG, Mehta RR. Vitamin D and cancer. J Nutr Biochem. 2002;13:252-64.
5. Van den Bemd CJCM, Chang GTG. Vitamin D and vitamin D analogs in cancer treatment. Current Drug Targets. 2002;3:85-94.
6. Ylikomi T, Laaksi I, Lou YR, et al. Antiproliferative action of vitamin D. Vitam Horm. 2002;64:357-406.
7. Garland CF, Garland FC. Do sunlight and vitamin D reduce the likelihood of colon cancer? Int. J. Epidemiol. 1980;9:227-31.
8. Hanchette CL, Schwartz GG. Geographic patterns of prostate cancer mortality. Cancer, 1992;70:2861-9.
9. Lefkowitz ES, Garland CF. Sunlight, vitamin D, and ovarian cancer mortality rates in U.S. women. Int. J. Epidemiol. 1994;23:1133-6.
10. Freedman DM, Zahm SH, Dosemeci M. Residential and occupational exposure to sunlight and mortality from non-Hodgkin's lymphoma: composite (threefold) case-control study. BMJ. 1997;314:1451-5.
11. Janowsky EC, Lester GE, Weinberg CR, et al. Association between low levels of 1,25-dihydroxyvitamin D and breast cancer risk. Public Health Nutr. 1999;2:283-91.
12. John EM, Schwartz GG, Dreon DM, Koo J. Vitamin D and breast cancer risk: the NHANES I Epidemiologic follow-up study, 1971-1975 to 1992. National Health and Nutrition Examination Survey. Cancer Epidemiol. Biomarkers Prev. 1999;8:399-406.
13. Luscombe CJ, Fryer AA, French ME, et al. Exposure to ultraviolet radiation: association with susceptibility and age at presentation with prostate cancer. Lancet. 2001;358:641-2.
14. Freedman DM, Dosemeci M, McGlynn K. Sunlight and mortality from breast, ovarian, colon, prostate, and non-melanoma skin cancer: a composite death certificate based case-control study. Occup. Environ. Med. 2002;59:257-62.
15. Grant WB. An ecologic study of dietary and solar UV-B links to breast cancer mortality rates. Cancer. 2002;94:272-81.
16. Grant WB. An estimate of premature cancer mortality in the United States due to inadequate doses of solar ultraviolet-B radiation. Cancer. 2002;941:867-75.
17. Devesa SS, Grauman DJ, Blot WJ, Pennello GA, Hoover RN, Fraumeni JF Jr. Atlas of Cancer Mortality in the United States, 1950-1994. NIH Publication No. 99-4564, 1999. http://cancer.gov/atlasplus/new.html (accessed January 16, 2003).
18. DNA spectral exposure (kJ/m2) for July 1992 (North America)
http://toms.gsfc.nasa.gov/ery_uv/dna_exp.gif (accessed January 16, 2003).
19. Bostick RM, Potter JD, Sellers TA, et al. Relation of calcium, vitamin D, and dairy food intake to incidence of colon cancer among older women. The Iowa Women's Health Study. Am J Epidemiol. 1993;137:1302-17.
20. Kearney J, Giovannucci E, Rimm EB, et al. Calcium, vitamin D, and dairy foods and the occurrence of colon cancer in men. Am J Epidemiol. 1996;143, 907-17.
21. Martinez ME, Giovannucci EL, Colditz GA, et al. Calcium, vitamin D, and the occurrence of colorectal cancer among women. J Natl Cancer Inst 1996;88: 1375-82.
22. Marcus PM, Newcomb PA. The association of calcium and vitamin D, and colon and rectal cancer in Wisconsin women. Int J Epidemiol. 1998;27:788-93.
23. Grant WB, Garland CF, Evidence supporting the role of vitamin D in reducing the risk of cancer, Comments on "Prospects for chemoprevention of cancer" by RM Tamimi et al., J Intern Med 2002;251:286-300. J Intern Med, 2002;252:178-9.
24. Deluca HF, Cantorna MT. Vitamin D: its role and uses in immunology. FASEB J. 2001;15:2579-85.
25. Holick MF. Vitamin D: A millenium perspective. J Cell Biochem. 2003;88:296-307.
26. Iqbal SJ, Kaddam I, Wassif W, Nichol F, Walls J. Continuing clinically severe vitamin D deficiency in Asians in the UK (Leicester). Postgrad Med J. 1994;70:708-14.
27. Datta S, Alfaham M, Davies DP, et al. Vitamin D deficiency in pregnant women from a non-European ethnic minority population--an interventional study. BJOG. 2002;109:905-8.
28. Shaw NJ, Pal BR. Vitamin D deficiency in UK Asian families: activating a new concern. Arch Dis Child. 2002;86:147-9.
29. Bates CJ, Prentice A, Cole TJ, et al. Micronutrients: highlights and research challenges from the 1994-5 National Diet and Nutrition Survey of people aged 65 years and over. Br J Nutr. 1999;82:7-15.
30. van der Wielen RP, Lowik MR, van den Berg H, et al. Serum vitamin D concentrations among elderly people in Europe. Lancet. 1995;346:207-10.
31. Scharla SH. Prevalence of subclinical vitamin D deficiency in different European countries. Osteoporos Int. 1998;8(Suppl 2:S7-12.
32. J. Ferlay, F. Bray, P. Pisani and D.M. Parkin. GLOBOCAN 2000: Cancer Incidence, Mortality and Prevalence Worldwide, Version 1.0. IARC CancerBase No. 5. Lyon, IARCPress, 2001. Limited version available from: URL:
http://www-dep.iarc.fr/globocan/globocan.htm
Last updated on 03/02/2001. (accessed Jan. 16, 2003).
33. Kirkpatrick CS, White E, Lee JA. Case-control study of malignant melanoma in Washington State. II. Diet, alcohol, and obesity. Am J Epidemiol. 1994;139:869-80.
34. Shors AR, Solomon C, McTiernan A, White E. Melanoma risk in relation to height, weight, and exercise (United States). Cancer Causes Control. 2001;12:599-606.
35. Seidell JC. Obesity: a growing problem. Acta Paediatr Suppl. 1999;88:46-50. 36. Andersen R, Brot C, Ovesen L. Towards a strategy for optimal vitamin D fortification (OPTIFORD). Nutr Metab Cardiovasc Dis. 2001;11(4 Suppl):74-7.

Table 1. Incidence and mortality for cancers linked to UV-B radiationas risk (melanoma, however, UV-A (320-400 nm also plays a very important role)) or risk reduction factors for the U.K. in the mid-to-late 1990s (30).

Cancer Type Incid. Mortal. Incid. Mortal.Males (cases) Females (cases)
Melanoma 2398 769 3375 795
Bladder 9593 3670 3837 1795
Breast 34,815 14,415
Colorectal 17,249 9341 15,924 9,047
Endometrial 5000 1112
Esophageal 4264 4212 2800 2640
Gastric 6178 5101 3579 3199
NHL 4402 2414 3760 2131
Ovarian 6138 4560
Prostate 21,301 10,062
Renal 3356 1891 2007 1179
Totals 66,343 36,691 77,896 40,078

Preventable through UV-B and/or vitamin D - USA rates (16) 5300 2900 7800 4,000
Preventable through UV-B and/or vitamin D - estimated UK rates 8000 4500 12,000 6,000

Source: http://www.bmj.com/cgi/eletters/326/7381/114