A Multi-country Ecological Study of Dietary Risk and Risk-reduction Factors for Prostate Cancer

A Multicountry Ecologic Study of Risk and Risk Reduction Factors for Prostate Cancer Mortality

OBJECTIVE

The objective of this research is to identify and determine the relative importance of dietary and environmental risk and risk reduction factors for prostate cancer mortality.

MATERIALS AND METHODS

A multicountry ecologic approach was used in multivariate regression analyses with prostate cancer mortality rates and dietary factors and solar ultraviolet-B (UV-B) radiation. Prostate cancer mortality rates for 32 predominantly Caucasian countries for the late 1990s were obtained from the World Health Organization. Dietary supply data were obtained from the Food and Agriculture Organization. Annual solar UV-B dose data were obtained from European ground stations and used to estimate values elsewhere. Linear and multiple linear regression analyses were conducted for all 32 countries as well as the 20 European countries.

RESULTS

The strongest risk factor for prostate cancer mortality was animal products, with the nonfat portion of milk and alcohol being somewhat weaker; the strongest risk reduction factors were onions, other protective vegetable products (excluding alcohol, oils, and sweeteners), and solar UV-B radiation. Dietary data for 1979-81 yielded the highest correlations.

CONCLUSIONS

These results are consistent with insulin-like growth factor-I (IGF-I), being an important risk factor for prostate cancer, with alcohol and calcium being less important risk factors, and with allium family vegetables, and, to a lesser extent, vitamin D being important risk reduction factors. These results should provide guidance for additional studies on dietary and environmental links to prostate cancer.

Ecologic studies of solar UV-B radiation and cancer mortality rates

Solar ultraviolet B (UV-B) radiation (280-320 nm) has been associated with reduced risk of cancer of the breast, colon, ovary, and prostate, as well as non-Hodgkin's lymphoma (NHL) through the production of vitamin D in papers extending back to 1980. Using data on the geographic distribution of cancer mortality rates in the US, another ten cancers have been added to the list for which UV-B/vitamin D is a risk reduction factor (Grant 2002b; submitted). These associations persist even after additional cancer risk and risk reduction factors such as smoking, urban or rural residence, Hispanic heritage, poverty, dietary factors, and use of nonsteroidal anti-inflammatory drugs are added to the analysis. As a further test of the protective role of UV-B radiation, an ecologic study of cancer mortality rates in Europe with UV-B radiation and dietary factors was conducted. Inverse correlations are found for UV-B radiation for a number of cancers, with those for bladder, breast, endometrial, ovarian, prostate, and renal cancer, and multiple myeloma and NHL having the strongest correlations in this and ongoing multicountry ecologic studies. These studies add further support for the role of UV-B radiation and vitamin D in reducing the risk of a large number of cancers.