Vitamin D & PCa Risk

[pjoshea13]

This is a paper presented at AACR 2018 in Chicago on April 16 [1].

First, I should reveal a bias against Nordic vitamin D studies. (They are perhaps a little more useful than studies conducted on Santa's elves at the North Pole.)

From a 2013 Danish paper [2]:

"Two-thirds of the included patients with LBP {low back pain} had normal Vitamin D levels of >50 nmol/L."

50 nmol/L = 20 ng/mL.

In the U.S., 0-20 ng/mL is deficient, but 20-32 is considered to be insufficient. Some experts believe that one should aim for 50 ng/mL for sufficiency.

In the low back pain study: "Vitamin D levels appear to be normal" - i.e. only two-thirds not deficient being par for a Danish course.

The new study included 246,858 individuals who did not have diagnosed cancer (any type) at the time of the blood test.

Cancer risk factors were calculated for each 10 nmol/L increase in 25-D levels - i.e. each 4 ng/mL increase.

For lung cancer there was a 5% risk reduction, but for PCa there was a 5% risk increase.

"The population analyzed in the study ... had a mean level of 25OH vitamin D of 50.2 nmol/L" i.e. the mean was 20.08 ng/mL. Almost half the tested population was deficient at the time of the test.

A few things come to mind:

i) study [2] suggests that a third of the Danish population is "normally" deficient, whereas population [1] was 50% deficient. Makes sense: doctors might do the test if deficiency is suspected.

ii) blood tests are not passive events. They are usually followed by corrective action, if they reveal a problem. So, we know that half the men were deficient when the test was performed, but not necessarily thereafter.

iii) the possible protective role of vitamin D seems to be well-known among PCa cases. Dr. Myers was an early promoter & has an old vlog post on the topic. Many men now seem to aim for 50-75 ng/mL & have blood tests to monitor levels. It seems reasonable to think that men who believe themselves to be at risk for PCa (due to familial PCa or rising PSA) might be using D supplements. That might affect the analysis.

In Danish men who attained sufficiency, one should suspect supplement use & investigate the reason when doing this kind of study. D uptake via natural means is limited by lattitude. Examples of lattitude:

- Manhattan 40.7831° N

- Toronto 43.6532° N

- Copenhagen 55.6761° N !!!

-Patrick

[1] abstractsonline.com/pp8/#!/...

[2] bmcmusculoskeletdisord.biom...

[herb1]

hI pATRICK; i SAW AN ABSTRACT ON ANOTHER SITE AND RESPONDED BY TARGETING THE SAME ASPECT--APPARENT LOW D IN SWEDISH MEN.

[pjoshea13 in reply to herb1]

Herb,

Those northern lattitudes are brutal. Meager 25-D reserves built up during summer months are not sufficient to carry Scandinavians through the winter months. The angle of the sun needs to between 50 & 90 (overhead) degrees. Below that, as it is for many months, vitamin D cannot be made via the skin.

Cod liver oil can only be taken at low doses of vitamin D, owing to the presence of vitamin A. & too much A will interfere with D uptake.

Which leaves food fortification & supplements.

One problem with Nordic studies is that they do not address the prevalent problem of severe deficiency for one or more months of the year. It's all very well to adjust for the month in which blood was drawn, but can 6 good months really compensate for 6 bad months?

Is it any coincidence that Mediterranean countries have much lower rates of PCa?

-Patrick

[j-o-h-n in reply to pjoshea13]

So Sven, is that the moon or the sun? " Sorry I don't know, this isn't my neighborhood".

Good Luck and Good Health.

j-o-h-n Friday 04/20/2018 5:25 PM EDT