New study below.
I am posting this because of some negative PCa studies conducted on populations that are largely vitamin D deficient for much of the year. Inexplicably, sufficiency (>32 ng/mL) has been associated with increased risk. Essentially, the risk was U-shaped, with the lowest point somewhere in the insufficiency range (20-32 ng/mL).
The new study population (11,022) was from Olmsted County, Minnesota - where it is difficult to attain D-sufficiency during the winter except through supplementation.
25-D readings were adjusted for month of measurement. I'm not sure what that means - was the adjustment intended to obtain an average for the year or a high summer equivalent?
In an earlier study [2], the team had been concerned about the risk of toxicity with 25-D levels above 50 ng/mL. "The age- and sex-adjusted incidence of 25(OH)D values >50 ng/mL increased from 9 to 233 per 100,000 person-years from 2002 to 2011 .., respectively, and was greatest in persons of age ≥65 years ... and in females". Presumably indicative of the greater awareness of the importance of D, & the increased availability of high-dose supplements.
"Serum 25(OH)D values were not significantly related with serum calcium values or with the risk of hypercalcemia. Medical record review identified four cases (0.2%) where 25(OH)D values >50 ng/mL were associated temporally with hypercalcemia, but only one had clinical toxicity associated with the highest observed 25(OH)D value of 364 ng/mL."
Hypervitaminosis D is inferred from 25-D & hypercalcemia. The remedy? Vitamin K! Without K for calcium transport to bone, excess calcium in the blood must be dumped by the kidneys. (K deficiency is associated with calcification of the arteries.)
Back to the new study:
"Unadjusted all-cause mortality hazard ratios (HRs) ... for 25(OH)D values of less than 12, 12 to 19, and more than 50 ng/mL were 2.6 .., 1.3 .., and 1.0 .., respectively, compared with the reference value of 20 to 50 ng/mL."
"In white patients, adjusted HRs for 25(OH)D values of less than 12, 12 to 19, 20 to 50, and greater than 50 ng/mL were 2.5 .., 1.4 .., 1.0 (referent), and 1.0 .., respectively."
"In patients of other race/ethnicity, adjusted HRs were 1.9 .., 1.7 .., 1.5 .., and 2.1 ...
"White patients with 25(OH)D values of less than 20 ng/mL had greater all-cause mortality than those with values of 20 to 50 ng/mL, and white patients had greater mortality associated with low 25(OH)D values than patients of other race/ethnicity."
"Values of 25(OH)D greater than 50 ng/mL were not associated with all-cause mortality."
Cause-specific mortality is covered in the full text, so I don't know for sure that 25-D > 50 ng/mL is not associated with greater PCa mortality in this study. But, as I have mentioned elsewhere, supplementation at high levels can be due to a perceived risk for PCa & such cases need to be excluded.
-Patrick
