Vitamin D - Not a Magic Bullet, but Deficiency is a Poison Arrow

I found this presentation by Karl Pfleger of interest. I think I’ll have my vitamin D levels tested the next time I do bloodwork.

Karl is a well known Ex-Google guy and now a leading Longevity Angel Investor in the Bay Area. He also maintains a good resource list website here:


Vitamin D presentation for personal longevity group.pptx.pdf (1.4 MB)

Link to source document:


What a treasure trove of information, thanks for sharing.

@RapAdmin You need to Karl to add this site to the blogs tab.

I take 6,000 IU/day (D3/k2), at night before bed. My levels are in the 200 nmol/L range. My FMD wants a level at least 175.

What’s fascinating about Vitamin D is you can take one time injections and pretty much cover off your Vitamin D needs for at least 3 months+. Oral compliance, especially older folks, is very low.


I vacillate between using 5000 IU and 1000 IU daily. It seems that public opinion changes from taking more to taking less back to more and so on… Which amount do you think is better in general?

I have also heard that you shouldn’t take D3 and K2 together at the same time as they interfere with each other’s absorption. There should be a 2-hour interval between the two. Is this true? Lots of supplements bundle D3 and K2 together so it seems inherently wrong, but then I have seen some supplement bundling that doesn’t make sense. My solution is to take D3 and other fat soluble vitamins in the morning and K2 at night.


I exchanged some emails with a Vitamin K2 vendor…there is NO impact of absorption on combining.


Thank you MAC. When you read the literature and come across opposing opinions, it’s good to have strong evidence for one or the other. This is strong enough to push me into the other camp of not worrying about when I take K2. Was there any negative to taking the two separately and spaced apart?

Related commentary:

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Karl does a good job picking the holes in the paper.

I checked with Dr Gundry, huge AD prevention patient population…he wants his patients around 100 ng/mL. His own is 120 ng/mL. I need to take some more…I am still in the therapeutic window!


Vitamin D protects against depression: Evidence from an umbrella meta-analysis on interventional and observational meta-analyses


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One thing I measure each week is 25OHD levels. That enables me to see the effects of supplementing with D3 and 25OHD itself. I find if I take 3000IU of capsules of D3 in oil my D3 levels trend down from good to sufficient. I want them to be near the top end of normal so every so often I take some 25OHD to supplement the 3000IU daily of D3.


An N of 1 here - for context, I’ve been using InsideTracker now for a little over a year. It asks you to test vitamin D levels. I live in Australia and my GP has said I don’t need to check this (cause of where I live I.e. Queensland (near the GoldCoast for those overseas)).

My calcium history, while optimal, was low for my age (43 at the time). I start taking a Vitamin D supplement every other day after reading an InsideTracker blog indicating that it can improve Calcium absorption and lo and behold it increases.

I have another blood test or two but still do not get my Vitamin D level checked (as the GP again does not recommend it). A few months later, I use an online doctor for a blood test that includes Vitamin D. It comes back with 40ng/mL……still optimal according to InsideTracker, but on the low side.

Seems to me that many might benefit from a Vitamin D supplement (even those that live in ‘sunny’ environments). Just my ‘two cents’……


It appears people with higher BMI figures process vitamin D less edficiently.

This was posted a few days ago.

Didn’t see that. Thanks.

Vitamin D also reduces risk of suicide.

Hmmm. Or perhaps depressed and borderline suicidal people are less likely to take their meds and supplements on schedule. Correlation or causality or both? At least this study looked at more than just blood levels of D. Newsflash-- people that get out in the sunshine tend to be healthier and more active.

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For those of us at risk for skin cancer, including myself.

Vitamin D sufficiency helps prevent diabetes.

AIUI Vitamin D deficiency is helpful if you don’t have much food and run the risk of starving as it shuts down a number of the genes (depending upon how deficient you are). Running a body on fewer genes will require less energy.

Hence I am not quite sure why anyone today would wish to be Vitamin d deficient.