Supplementing vitamin D [my n = 1 experiment]

Updated: Oct 2, 2019

I'd been unintentionally neglecting my bones for a while. Sounds odd, right? Isn't your skeleton sort of just there, doing its thing holding your body together? Not quite. But 15 year old me (even 25 year old me) didn't have any idea of the common risk factors for compromised bone density - starting the OC pill < 2 years after my first period, chronic stress, low body mass, hormonal imbalances, under eating, nutrient deficiencies ... my bone building to bone loss ratio had come under fire from all angles.

Sometimes concrete data makes you stop and think. My DXA bone mineral density scan demonstrated that I had osteopenia of the spine. I didn't need to be a genius to figure out that osteopenia probably isn't the ideal bone status for a 28 year old. After seeking guidance from Victoria Felkar, I realised that my OC pill and menstrual cycle history also meant that estrogen and progesterone hadn't been working together properly to mitigate bone loss like they should. 

So, I looked at vitamin D and vitamin K, and plenty of other things, too. Vitamin D and vitamin K work together in calcium metabolism and bone mineralisation. You need vitamin K to transport the calcium you eat in your foods into bone. This is obviously just a small fragment of the full picture, but it's an important one.

I became a walking data collection machine. I amassed hundreds of pages of notes, comments, objective metrics and repeat labs. If I took a supplement, I tracked it. And yes, I'm usually that meticulous about my body, whether it's for physique, performance or health purposes.

Here's a recap of my personal supplement protocol and the results in relation to vitamins D and K. This is just what worked for me and I'm not suggesting that it's right for you. I am all for information, and I see my experiences as my n = 1 experiments. And like all experiments, all I can do is share my insights and (I hope!) inspire you to pay attention and track your data. I really think that more people should do that because if you're focused on your health and performance, it's golden information.

No nutrient is a lone ranger

Vitamins and minerals are interconnected. They rely on one another.

For example, vitamin D enables your body to absorb calcium and phosphorus in the gut and use these minerals to keep your bones, teeth and muscles strong. If you're deficient in vitamin D, your body can't maintain an adequate concentration of calcium in the blood to support bone formation. You'll notice that in the first blog in this series on Vitamin D [Nutrient feature!], I mentioned that vitamin D is the master controller that regulates the concentration of calcium in your blood stream. Vitamin D dramatically increases the amount of calcium that you absorb from your diet. You need calcium in bones and other tissues that use it as a cofactor to catalyse different metabolic reactions. Dr Rhonda Patrick explains that if you have sufficient vitamin D (> 75 nmol/L), you'll absorb about 40 % of the dietary calcium you eat. But if you are vitamin D deficient (< 50 nmol/L), you'll only actually absorb around 10 to 15 % of your dietary calcium. So, it's not just all about calcium for healthy bones, because calcium requires its vitamin D side kick.

There are also other vitamins and minerals that vitamin D relies on to help it perform its functions, such as magnesium, vitamin K, zinc, boron and vitamin A.

And that takes us to vitamin K. Vitamin D and vitamin K work together in calcium metabolism and bone mineralisation. You also need vitamin K to transport the calcium you eat in your foods into bone. This is really just scratching the surface of the nutrients and hormones related to bone health. But the basic message here is that it's not just about milk for strong bones

A ridiculously quick primer on vitamin K

Your body needs vitamin K for a couple of main reasons: 

  1. To help your blood clot so that injuries can heal; and

  2. To keep your bones strong and healthy.

Vitamin K has 2 biologically active forms. 

  • Vitamin K1 is found in plants (leafy greens like kale, chard and spinach). K1 travels directly to the liver to activate proteins that play a key role in blood clotting. After completing that job, the remaining vitamin K1 enters circulation to trigger other proteins that prevent calcification. If you don't have enough vitamin K, you don't make these proteins. [A]

  • Vitamin K2 is found in organ meats (like liver) and fermented foods (like Natto, a Japanese fermented soy bean product). It is also made in our gut by bacteria (if you have the right bacteria, that is). K2 does not go to the liver as readily to influence blood clotting like Vitamin K1 does. It stays in the blood vessels and can activate the proteins that move calcium out of the blood stream and shuttle it to bone and other tissues. Even though K1 can do this too, it is only available for this job after making sure that there is enough K1 to maintain blood clotting. So, as Dr Ames explains, eating or supplementing K2 can bump up vitamin K in a form that better supports this nutrient's longer term building projects, including its role in preventing calcification and protecting bone, to bypass the triage effect of too little K1 [B].

How does all of this relate to taking vitamin D? Well, the Vitamin D Council explains that to maximise the benefit of supplementing vitamin D while minimising the possible risk of toxicity at higher dosages, you could take vitamin K in addition to vitamin D to help direct calcium out of the blood stream to the places it's supposed to be (bone) and stop it from setting up shop in undesirable places (arteries). One of the major signs of vitamin D toxicity is too much calcium in the blood (called hypercalcemia). All sorts of bad things can happen if calcium sits in your blood vessels and goes to places in the body that it shouldn't be hanging around, in serious cases creating plaques that can cut off circulation to the brain or the heart.

Supplementing vitamin D and K together

One of the speakers at the SWIS 2018 Symposium, Doug Caporrino, a leading authority on fitness and nutrition, made a comment about vitamin D supplements in his seminar on Hormonal and Micronutrient Testing that peaked my attention. He said that taking vitamin D3 and K2 together promotes assimilation, compared to just D3 alone, and remarked that if you take D3 and K2 together 'you'll see a huge difference'. This prompted me to assess my data, seeing as I've tried both options in recent times. And while I can't come to a generalised conclusion, I can say that I've noticed that to be true for me.

My n = 1 experiment 


In Australia, 25-hydroxy vitamin D (used to indicate vitamin D status) is measured in nmol/L. My 25(OH)D levels looked like this:

  • Early December 2017: 102 nmol/L

  • Late July 2018: 110 nmol/L

  • Mid December 2018: 156 nmol/L

Based on the leading research and recommendations, I aimed to increase my vitamin D status to around 125 to 150 nmol/L. Even though I didn't start out 'deficient' based on the current reference range in Australia, I considered that 100 nmol/L to be an adequate baseline but that it could be a little higher. (If you haven't already, read my blog on Vitamin D [Nutrient feature!] for a recap on vitamin D status and suggest dosages.)

Supplement protocol

December 2017 to July 2018

Even though my 25(OH)D barely changed in this time, I'd actually been supplementing in this period. From December 2017 until May 2018, I took 2000 IU of vitamin D3, but not consistently. I'd say I took it every second day. It was summer in Melbourne, and I was out in the sunshine (and more importantly, UVB radiation) more often, so I figured I'd see if that did the trick.

I also trialled 10 000 IU of D3 daily in April 2018 for 7 days and from mid May to early June 2018 for 21 days as I felt that based on the research (and in particular the Endocrine Society's Clinical Practice Guideline on Vitamin D Deficiency), I may not have been taking enough across the prior 4 months. I did not supplement at all from early June 2018 up until my blood tests in late July 2018, although at the time I lived in the tropics and had some incidental time in the sun most days.

I did not supplement vitamin K in this time frame.

Recap: I took about 1000 IU daily on average in the summer and  early autumn, and then a high dose protocol for a total of 28 days (7 day trial, then another 21 consecutive days). I didn't supplement vitamin K at all. The results? I found it quite interesting to note that 8 months later, my blood test results for vitamin D hadn't really changed in this time.

Late September 2018 to December 2018

From 22 September 2018 until mid December 2018, I supplemented 6000 IU of vitamin D3 and 225 mcg of vitamin K2 daily for about 3 months. I also supplemented other nutrients in that time frame too, like calcium, magnesium and zinc. I've used a combination of Thorne Vitamin D/K2 liquid and vitamin D -1000 or -500 capsules as required to titrate the dosage.

In this time, I travelled to Canada and the US (its fall) for a month. On returning to Australia, I started sun baking more often (about 3 to 5 days a week for 15 to 30 minutes) from early December 2018 for about 2 weeks' before my repeat blood test. Although at this time I lived in a different latitude, my exposure to UVB radiation should have been more or less the same as in the prior Melbourne summer. [C]

Recap: I consistently supplemented 6000 IU of vitamin D3 and 225 mcg of vitamin K2 daily for about 3 months. In this time, I increased my vitamin D level from 110 nmol/L to 156 nmol/L - that's 46 nmol/L in 3 months, taking me to the upper end of the vitamin D range indicated from recent research.

Test and retest

If you don't test, you're not going to be able properly predict your vitamin D status due to the multitude of factors that influence it. If you don't measure it, you can't manage it. Retest at least 1 or 3 months after starting to supplement (and not just for vitamin D, but any nutrient or substance you take).

Note! The information presented in this article is to be used for personal education purposes only. If you have any medical issues or queries, you should consult your doctor. Please enjoy my information in the spirit that it's intended - as a practical, user-friendly synthesis of scientific concepts and carefully researched information, for you to ponder and apply as desired to suit you and your body.



Vitamin D Council, The synergistic relationship between vitamin D and vitamin K

Dr Bruce Ames speaking in this excellent episode of Dr Rhonda Patrick's podcast on Triage Theory and micronutrients

Dr Rhonda Patrick, The most popular questions about vitamin D.


[A] Proteins that are vitamin K dependent include: Matrix gla protein, a protein that binds calcium phosphate crystals in the blood to prevent it from forming an atherosclerotic plaque; Osteocalcin, lives in bone and makes strong bones that don't break easily.

[B] If you haven't yet come across Dr Bruce Ames and his ground-breaking Triage Theory, read my earlier blog [Read: Is your diet accelerating aging and disease? Dr Ames explains why micronutrients matter more than you think.]

[C] Confused about latitude? Osteoporosis Australia has published this great map of the Recommended sun exposure for vitamin D based on location in Australia.