Friday, November 26, 2010

Vitamin D Linked to Pancreatic Cancer

Stopped me in my boots, this one:

Circulating 25-Hydroxyvitamin D and Risk of Pancreatic Cancer, American Journal of Epidemiology, 2010

It found:
"A high 25(OH)D concentration (≥100 nmol/L) was associated with a statistically significant 2-fold increase in pancreatic cancer risk."
Cancer risk was higher in Caucasians and those living at latitudes above 35ºN. Interestingly, "few participants residing at low latitudes had 25(OH)D concentrations greater than 100 nmol/L."

That form of vitamin D, 25(OH)D, is an indicator of vitamin D status in the body. It comes from a blood test. It's not the vitamin D we eat, it's not the vitamin D we make in our skin, and it's not the active form of the vitamin. It's an intermediate that we measure to test for deficiency.

While 100 nmol/L is high, it's not that high:
"The range of 25(OH)D3 levels associated with risk in this study was below that considered to reflect hypervitaminosis D (400-1,250 nmol/L)."
This particular study pooled results of several studies, 8 to be exact. The advantage of this ... it covered more geographical regions, had a larger number of cancer cases, and a wider range of vitamin D concentrations than the individual studies alone. You get a better feel for viable associations.

In one separate study of male Finnish smokers, "prediagnostic serum concentrations greater than 65.5 nmol/L were associated with nearly a 3-fold increased risk of pancreatic cancer."1 However, you can't generalize those results to women, to men younger than 50, or to populations outside Finland. Although these results are pretty ominous for men over 50 who smoke and who live at higher latitudes.

"The active form of vitamin D might influence growth factors (ref. given) which promote tumor growth (ref. given)."
Active vitamin D is a steroid hormone. It affects a number of other regulators and hormones. Much of its influence has been discovered in only the last few decades. The manner of that influence is still in many cases a mystery.

Why The Pancreas?

The islet cells in the pancreas (if you have diabetes you may know that beta cells, part of the islet cell group, make insulin) make the particular enzyme that turns 25(OH)D3 into its active form 1,25(OH)D3. Not many cells make this enzyme. I know the kidney makes it. I'll have to be on the lookout for studies linking vitamin D to renal cancer.

"Given the present study's pooled results and research gaps in the understanding of vitamin D's role in carcinogenesis, recommendations to increase vitamin D concentrations in healthy persons for cancer prevention seem premature."
1 A Prospective Nested Case-Control Study of Vitamin D Status and Pancreatic Cancer Risk in Male Smokers, Cancer Research, 2006


Claudia said...

You're not big on supplements, are you.

Bix said...

You know, I'm not. I used to be. I still get drawn in. The pro-vitamin D literature is pretty convincing. But the D in a pill gets handled differently in the body than D we get from sun. And vitamin pills are really just another isolated, manufactured, high-potency drug. ... with fillers and chemicals that health-conscious people wouldn't eat in food (oxidized fat, preservatives).

Much supplemental vitamin D has been irradiated (irradiated lanolin from sheep's wool). I know people who wouldn't touch irradiated food with a 10-foot pole, yet they down handfuls of irradiated vitamin D. Maybe they don't know. But why don't they know? If they knew the problems with pills they might not take them. And supplement makers would not be happy. Supplements are a multi-billion-dollar industry.

It's hard to get at the truth. People are so driven by money and fame (they like to be "right," to be considered an authority, instead of just one among many who study). So many websites exist just to promote someone, to help them sell books or supplements or get speaker fees. Where is the raw curiosity? Where is the exchange of ideas? Instead of an exchange of judgement?

Anne said...

So how do they know that it wasn't the smoking that led to the increased risk of pancreatic cancer and that it was nothing to do with the vitamin D at all ? Also the men weren't taking vitamin D supplements so they must have been getting it from the sun and from fish which is perfectly natural. Not a very convincing study really ! Rather like that one which said that TV ownership was linked to heart disease.

Bix said...

"Residual confounding by cigarette smoking is not likely, because there was no significant interaction of the vitamin D association with smoking status, and positive associations were observed among never smokers."

The data were adjusted for age, race/ethnicity, sex, cohort, date of blood draw, body mass index, smoking (never smoker, former smoker who had quit ≥15 years previously, former smoker who had quit 1–14 years previously, former smoker who had quit <1 year previously or current smoker of <20 cigarettes/day, and former smoker who had quit <1 year previously or current smoker of ≥20 cigarettes/day), and diabetes status, among others.

This was noteworthy:

"Compared with controls, cases more often had a greater saturated fat intake, and consumed less fish, carbohydrate, and folate."

Anonymous said...

Very good post..

Anonymous said...

Thanks a lot for writing this, it was unbelieveably informative and told me a ton

Anonymous said...

Holy sh*t! Everyone I know takes vitamin D!