Strong inverse correlations between solar ultraviolet-B (UVB) and many types of cancer have been found in numerous ecological studies in the United States12345 and a case-control study based on death certificates6.
The United States is a particularly useful country to conduct ecological studies since dietary factors are largely shared and solar UVB doses in summer are asymmetrical, being much higher in the west than the east at the same latitude due to higher surface elevation and thinner stratospheric ozone layer, thus permitting use of an index other than latitude, which could have other bases such as temperature. Solar UVB in summer can increase serum 25(OH)D levels by 40 nmol/L according to a study of 45-year old residents of the UK7, and, likely, higher increases in the United States. Most of the recent ecological studies used indices for other risk-modifying factors such as alcohol consumption, smoking, Hispanic heritage, poverty and urban/rural residence345, limited dietary factors4, and air pollution from coal-fired power plants5. Thus, such studies largely overcome the concern regarding confounding factors.
Latitude and annual sunlight doses have been used as indices of solar UVB doses and vitamin D production in a number of single country and multi-country ecological studies. Use of latitude in single-country studies other than the United States is generally useful since many confounding factors such as alcohol consumption, dietary factors, genetic background, pollution levels, and smoking prevalence tend to be fairly similar at all latitudes. In multi-country studies such factors should be included if the data are available. Representative single country studies include those in Australia89, China10, France11, Japan12, and Spain13. A representative multi-cancer, multi-country study is one for Europe14.
The Garland group at University of California San Diego has done a series of global studies finding that cancer incidence rates: bladder15, brain15, breast16, endometrial17, lung16, pancreatic15, ovarian2 and renal cancer18. In these studies, confounding factors such as selected dietary factors, alcohol consumption, and smoking were included as deemed appropriate. All of these papers feature the distinctive “smiley” parabolic curve since cancer incidence rates have minima near the equator and maxima at high latitudes.
No factor other than UVB production of vitamin D has been proposed to explain the latitudinal dependence of cancer rates in general. However, it has been proposed that a genetic factor explains much of the geographical variation for prostate cancer. In the United States, prostate cancer mortality rates19 are highly correlated with ancestry, with higher rates in northern states with more northern European descendents while the southern states have more white Americans with Hispanic heritage20. This finding, plus the fact that cholesterol is an important risk factor for prostate cancer21 led to the hypothesis that an important risk factor for prostate cancer was the apolipoprotein E4 allele, which increases cholesterol production in the liver. A multi-country ecological study was conducted in support of this hypothesis22. However, vitamin D does hinder the progression of prostate cancer23.
The relationship between sun exposure and non-Hodgkin’s lymphoma (NHL) was studied in a pooled analysis of 10 studies participating in the International Lymphoma Epidemiology Consortium (InterLymph) covering 8,243 cases and 9,697 controls in the USA, Europe and Australia. Risk of NHL fell significantly with the composite measure of increasing recreational sun exposure, pooled odds ratio (OR) = 0.76 (95% CI 0.63-0.91) for the highest exposure category (p for trend 0.01)24.
Another index of UVB irradiance at the personal or population level is incidence or death from non-melanoma skin cancer (NMSC), either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC). SCC is a bit problematic since smoking is also a risk factor for it25. NMSC mortality rates were found inversely correlated with 15 types of cancer in an ecological study of cancer mortality rates in Spain13. A cancer registry study found standardized incidence rates of 0.79 (95% CI, 0.68-0.91) for all solid tumors except lip and skin after diagnosis of SCC in sunny countries (Australia, Singapore and Spain) and 0.86 (95% CI, 0.80-0.92) after diagnosis of BCC26.
A recently found paper reporting a study of cancer incidence in regions of Rhineland-Palatinate, Germany with various amounts of land devoted to winegrowing found that while NMSC plus melanoma rates were higher in the regions with >5% of the land in winegrowing compared to regions with <5%, incidence rates for many types of cancer were significantly lower in the winegrowing regions: stomach; colon, sigmoid & rectum; trachea, bronchus and lung; urinary tract for males, leukaemia, cervix uteri, ovary and other unspecified female genital organs27. This study was touted as strong support for the UVB-vitamin D-cancer hypothesis28.
Page last edited: 04 May 2011
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- Garland, C. F. Garland, F. C. Gorham, E. D. Lipkin, M. Newmark, H. Mohr, S. B. Holick, M. F. The role of vitamin D in cancer prevention. Am J Public Health. 2006 Feb; 96 (2): 252-61.
- Grant, W. B. Garland, C. F. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res. 2006 Jul-Aug; 26 (4A): 2687-99.
- Grant, W. B. An ecological study of cancer mortality rates including indices for dietary iron and zinc. Anticancer Res. 2008 May-Jun; 28 (3B): 1955-63.
- Grant, W. B. Air pollution in relation to U.S. cancer mortality rates: an ecological study; likely role of carbonaceous aerosols and polycyclic aromatic hydrocarbons. Anticancer Res. 2009 Sep; 29 (9): 3537-45.
- Freedman, D. M. 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 Apr; 59 (4): 257-62.
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- Chen, P. Hu, P. Xie, D. Qin, Y. Wang, F. Wang, H. Meta-analysis of vitamin D, calcium and the prevention of breast cancer. Breast Cancer Res Treat. 2010 Jun; 121 (2): 469-77.
- Grant, W. B. An ecological study of cancer incidence and mortality rates in France with respect to latitude, an index for vitamin D production. Deramato-Endocrinology. 2010 Apr; 2 (2): 62-67.
- Mizoue T. Ecological study of solar radiation and cancer mortality in Japan. Health Phys. 2004 Nov; 87 (5): 532-8.
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- Grant, W. B. The likely role of vitamin D from solar ultraviolet-B irradiance in increasing cancer survival. Anticancer Res. 2006 Jul-Aug; 26 (4A): 2605-14.
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- Mohr, S. B. Garland, C. F. Gorham, E. D. Grant, W. B. Garland, F. C. Could ultraviolet B irradiance and vitamin D be associated with lower incidence rates of lung cancer?. J Epidemiol Community Health. 2008 Jan; 62 (1): 69-74.
- Mohr, S. B. Garland, C. F. Gorham, E. D. Grant, W. B. Garland, F. C. Is ultraviolet B irradiance inversely associated with incidence rates of endometrial cancer: an ecological study of 107 countries. Prev Med. 2007 Nov; 45 (5): 327-31.
- Mohr, S. B. Gorham, E. D. Garland, C. F. Grant, W. B. Garland, F. C. Are low ultraviolet B and high animal protein intake associated with risk of renal cancer?. Int J Cancer. 2006 Dec 1; 119 (11): 2705-9.
- Devesa, S. S. Grauman, D. J. Blot, W. J. Pennello, G. A. Hoover, R. N. Fraumeni, J. F. Jr. Atlas of Cancer Mortality in the United States, 1950-1994. NIH Publication No. 99-4564. 1999 November 8, 2008;
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- Grant, W. B. A multicountry ecological study of risk-modifying factors for prostate cancer: apolipoprotein E epsilon4 as a risk factor and cereals as a risk reduction factor. Anticancer Res. 2010 Jan; 30 (1): 189-99.
- Holt, S. K. Kwon, E. M. Koopmeiners, J. S. Lin, D. W. Feng, Z. Ostrander, E. A. Peters, U. Stanford, J. L. Vitamin D pathway gene variants and prostate cancer prognosis. Prostate. 2010 Sep 15; 70 (13): 1448-60.
- Kricker, A. Armstrong, B. K. Hughes, A. M. Goumas, C. Smedby, K. E. Zheng, T. Spinelli, J. J. De Sanjose, S. Hartge, P. Melbye, M. Willett, E. V. Becker, N. Chiu, B. C. Cerhan, J. R. Maynadie, M. Staines, A. Cocco, P. Boffeta, P. Personal sun exposure and risk of non Hodgkin lymphoma: a pooled analysis from the Interlymph Consortium. Int J Cancer. 2008 Jan 1; 122 (1): 144-54.
- De Hertog, S. A. Wensveen, C. A. Bastiaens, M. T. Kielich, C. J. Berkhout, M. J. Westendorp, R. G. Vermeer, B. J. Bouwes Bavinck, J. N. Relation between smoking and skin cancer. J Clin Oncol. 2001 Jan 1; 19 (1): 231-8.
- Tuohimaa, P. Pukkala, E. Scelo, G. Olsen, J. H. Brewster, D. H. Hemminki, K. Tracey, E. Weiderpass, E. Kliewer, E. V. Pompe-Kirn, V. McBride, M. L. Martos, C. Chia, K. S. Tonita, J. M. Jonasson, J. G. Boffetta, P. Brennan, P. Does solar exposure, as indicated by the non-melanoma skin cancers, protect from solid cancers: vitamin D as a possible explanation. Eur J Cancer. 2007 Jul; 43 (11): 1701-12.
- Seidler, A. Hammer, G. P. Husmann, G. Konig, J. Krtschil, A. Schmidtmann, I. Blettner, M. Cancer risk among residents of Rhineland-Palatinate winegrowing communities: a cancer-registry based ecological study. J Occup Med Toxicol. 2008; 312.
- Grant, W. B. Cancer risk ecological study in Rhineland-Palatinate, Germany, provides strong support for the ultraviolet B-vitamin D-cancer hypothesis. J Occup Med Toxicol. 2010 19 July 2010; 19 July 2010