Men diagnosed with prostate cancer in the summer and fall have a better chance of survival than those diagnosed in the spring and winter, a recent study of Norwegian men suggests.
"Summer and autumn months correspond to times when vitamin D is highest in Norway). Although the study does not prove vitamin D is the determining factor, it does suggest that this possibility should be studied further," said study co-author Dr. Tomasz Beer, director of the prostate cancer program at the Oregon Health & Science University Cancer Institute.
The Study
A team of American and Norwegian researchers analyzed data for more than 46,000 Norwegian men diagnosed with prostate cancer from 1964 to 1992
Result: Compared with men diagnosed in the summer and fall, those diagnosed in the winter and spring were 20% more likely to die within three years after diagnosis. The study was published in the journal The Prostate.
The researchers also examined whether survival was affected by factors such as eating foods high in vitamin D (such as fatty fish), taking vacations in sunny southern locations, and where the men lived in Norway.
Result: Only age seemed to have an influence—younger men had a slightly better rate of survival. The researchers noted that the capacity of skin to produce vitamin D when exposed to sunshine is about 40% lower in men age 75 and older than in men age 60 and younger.
Theory
Vitamin D, which has been shown to inhibit cancer growth, may also help maintain immune system health and help regulate cell growth and differentiation, Beer said.
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