Supplement Series | Vitamin D3

We're going to go for a deep-dive on Vitamin D3 biology, but if you're looking for the cheat-sheet, here's the take home messages:

  • Over-supplementing with Vitamin D can have seriously negative side effects due to calcium issues.  Do not blindly supplement with 5000-10000 IU/day.
  • Take 1000-2000 IU/day of Vitamin D3 or better yet, get 30 minutes of sun exposure 3-5 times a week.
  • Make SURE to eat leafy greens (vitamin K rich) along with colorful fruits and veggies, eggs and butter (Vitamin A rich) to allow for appropriate calcium deposition and metabolism.

Vitamin D is a molecule that is typically made by skin cells, called keratinocytes, when we are exposed to the sun.  It can also be found in relatively high amounts in fish, egg yolks, and cheese. Interestingly, its estimated that a large percentage of the US (and World) population is "deficient" in Vitamin D, more accurately a molecule its converted to called calcitriol, or 1,25 dihydroxyvitamin D. 

Vitamin D has been shown to be important in the optimal function of MOST organ systems, including but not limited to:

  • Appropriate function of the immune system
  • Absorption of dietary calcium
  • Recovery from training
  • Body composition

Needless to say, we want to make sure we're dialed in with our levels.

One of the major issues is that there's very little consensus on what makes someone "deficient" in VD3.  Medically, people think of numbers below 25 ng/ml in blood, however other researchers believe that optimal levels fall below 50-80 ng/ml. Clearly the medical world hasn't quite made up their minds yet.

It's estimated that direct sunlight for as little as 30 minutes, three times per week can induce the production of more than enough vitamin D. However, considering that up to 40% of Americans are deficient, either we're doing a terrible job at getting outside, this amount of exposure isn't cutting it, or there is another underlying biological issue.

The typical response to low VD3 levels is to supplement the crap out of people with 5-10,000 IU/day.  People then come back after a few months and if their blood levels are not improved, the prescription goes even higher.  Someone once told me a fun analogy using the "check oil" light in a car.  If the light kept going on despite filling the oil regularly, would you simply continue to dump more oil in, or would you maybe search for another issue???  Thats probably what's going on here with your low vitamin D3 levels, as we keep adding more and more through supplementation, but not really making an impact.

Additionally, we need to consider if massive supplementation is a really smart idea to begin with. There are a handful of studies that show a correlation with lower VD3 levels and higher risk of basically all mortality.  So thats not good and we should clearly supplement with it, right??


Another set of studies correlate that mortality increases once you VD3 levels exceed 40 ng/ml.  If you're like me you're probably thinking "Jesus, my head hurts... what the hell is going on here?"  Well we're going to get to the bottom of this.

There is a risk factor called hypercalcemia, or high levels of calcium in the blood, thats been associated with fairly strong doses of vitamin D supplementation.  On top of that, looking in the blood alone can be misleading. Calcium based kidney stones, as well as deposition into other soft tissues and... the big problem child, arterial deposition of calcium, have all been reported with Vitamin D3 supplementation as well.

Is this really about Vitamin D or is it about calcium???

So while you're probably ready to throw your supplement in the trash, we need to take a bigger picture look at this and figure out what the real culprit here is.  One strong possibility is that our calcium levels are TOO HIGH, and that as a result, our body is trying to shut down one of the major calcium absorbers (the product of Vitamin D, calcitriol, or 1,25 dihydroxyvitamin D) to normalize out the levels. 

Why might our calcium levels be too high???  Well there's a ton of reasons, but the most obvious ones involve inappropriate levels of other vitamins and minerals.  The big players here being magnesium, vitamin A and Vitamin K. 

Just to give you an example of WHY its important to balance out your micronutrients, lets look at Vitamin K as an example.  Vitamin K does a ton of things in the body, but one of the most critical is to allow for calcium deposition into bone (AKA taking calcium out of the blood stream, arteries, etc).  Fun fact, if you supplement rats with Vitamin K2, it inhibits artery calcification quite nicely.  So the basic idea goes that if you don't have enough Vitamin K, then your blood calcium levels rise. To combat bringing even MORE calcium into your body, feedback mechanisms prevent the conversion of vitamin D3 into its active calcitriol form.  As a result of this, you end up "low" on vitamin D3 when you test for it.  Your doctors see this and just supplement the shit out of you, but this doesn't really solve the problem, if anything it just worsens it.

What SHOULD you do?

OK, so most of you probably don't care about the biology, you just want to know the end game.  Here's the best general recommendations we can make:

1) Try and get some sun when you can.  The body does a good job of shutting off vitamin D production when it doesn't need to make it.

2) Take 1000-2000 IU/day, especially in the winter.

3) Eat some mother trucking veggies.  Vitamin K is found in dark green leafy veggies like kale, spinach and swiss chard.  Vitamin A is found in colorful fruits and veggies eggs and butter.

4) Take a good probiotic (more to come on this later) as Vitamin K conversion happens in the GI tract