Vitamin D for dementia ... but how much?

Back in September, we wrote about research finding that supplementation with vitamin D was shown to reduce the risk of developing dementia.  My own primary care provider had recommended that I take vitamin D, so I had been taking 50mcg a day of vitamin D-3.

So what are these units?  It turns out that supplements and medications are measured in different ways.  "Mcg" stand for microgram, or one millionth of a gram.  And a gram is 1,000th of a kilogram.  But these are also often measured in "international units," or IU.  Fifty mcg turns out to be 2,000 IU.  

As we noted in the earlier post, vitamin D isn't really a vitamin, it's a hormone.  Hormones only signal different parts of the body to do certain things.  The hormone insulin signals cells to take up glucose from the blood.  It does not actually participate in metabolism of glucose.  Vitamin D signals the initiation of a number of processes throughout the body, including the processes associated with bone development.

Vitamin D is normally produced in the body when the skin is exposed to sunlight.  During winter months, and when people otherwise don't get out in the sun enough, we don't have enough vitamin D to prompt the various processes that it controls.  Including, apparently, some processes that defend against dementia.  The concept here is that the supplements will make up for the missing exposure to sunlight.

So there are different kinds of vitamin D with different numbers associated with them.  Kind of like the B vitamins.  But the B vitamins are not hormones, and it makes a big difference if you have B-12 or vitamin B-6.  However, the research we reviewed in September wasn't able to find a big difference between how different D vitamins function.  So it seems which vitamin D you take doesn't matter.  So I get vitamin D-3 at Costco at a reasonable price.

But what's an appropriate dose?  There are warnings about overdosing, and some recommended supplement doses are quite low.  Fortunately, there is some new research leading to a conclusion that 2,000 IU per day is the sweet spot.  And, as it turns out, that's often the dose of commercially available supplements.  Like the Costco gel cap that I take.

The research was published in the journal Nutrients, with the title "Vitamin D Supplementation: A Review of the Evidence Arguing for a Daily Dose of 2000 International Units (50 µg) of Vitamin D for Adults in the General Population."  (Note µg = mcg.)  It claims to have weighed the dose required to produce positive results in a number of bodily process against doses that might be harmful.

While the September article explicitly discussed influence of vitamin D on dementia, the study in Nutrients did not.  It did, however, discuss influence on the development of diabetes, which is difficult to separate from Alzheimer's disease.  Because lifestyle has so much to do with how both Type 2 diabetes and Alzheimer's disease develop, Alzheimer's disease is sometimes called Type 3 diabetes.

Both vitamin D and vitamin K2 contribute to similar functions in the body and my act synergistically.  According to this study (and a few others), the results with respect to health from supplementation with both together is greater than what would be expected as the sum of both.  So you will see vitamin D and vitamin K2 offered together in the one supplement.  Some say they should still be taken separately.  I take them separately, but I haven't seen research demonstrating that as necessary.