Low vitamin D levels “prevalent” in early stage prostate cancer?
Posted Mar 10 2011 12:00am
Vitamin D insufficiency is currently defined as a serum level 25-hydroxy vitamin D that is less than 75 nmol/l. (And there are many who think that a higher minimum level might be appropriate.)
Choo et al. decided to monitor the serum vitamin D levels of a cohort of patients with non-metastatic prostate cancer being treated at their institution in Toronto, Canada. They hypothesized that vitamin D insufficiency might be common in patients with prostate cancer.
They measured their patients’ serum 25-hydroxy vitamin D levels at baseline and annually over a 5-year follow-up period and then analyzed the accumulated data with the following results:
Data from 106 patients with a median age of 66.3 years were available for analysis.
The mean and median 25-hydroxy vitamin D levels at baseline were 72.4 and 70.0 nmol/l, respectively.
64/106 patients (60.4 percent) met the definition of vitamin D insufficiency at baseline.
Season (i.e., time of year) was the only significant variable associated with vitamin D insufficiency.
Of a total 477 measurements of 25-hydroxy vitamin D from baseline and yearly follow-ups, 187 (39.2 percent) met the definition of vitamin D insufficiency.
Choo et al. conclude that “vitamin D insufficiency was prevalent among patients with nonmetastatic prostate cancer.”
Now it might be more appropriate to conclude on the basis of this study that vitamin D insufficiency was prevalent among men with prostate cancer in Toronto, but actually we can’t be sure that even that is the case based on these data. We don’t know, for example, whether this prevalence of vitamin D insufficiency in this cohort of patients is any higher (or lower) than the prevalence of vitamin D insufficiency in a comparable group of men from the Toronto area with as average age of about 66 who do not have prostate cancer.
Vitamin D insufficiency is not uncommon at higher latitudes. People in northern cities like Toronto spend a great deal of their relatively long winter indoors. Before we all jump to the conclusion that vitamin D insufficiency is strongly associated with a diagnosis of prostate cancer, it seems likely that we need some better data on vitamin D levels in a comparable, “normal” group of men.