What is your Vitamin D strategy for the winter months?
Below you are looking at a chart of my Vitamin D levels form 2019 to 2023.
As you can see, I recently had a low measurement of 31 nmol/L.
I am here to describe to you how I have been strategizing to avoid the red circles for good in the future.
Maybe it can help you too :)
Kat's Vitamin D levels 2019-2023
Background & Problem Statement:
Expect 7-8 months each year of negligible Vitamin D from sun.
Negligible intake from food.
My previous approach has been to supplement ‘more’ between the months of October-April.
That was NOT quantitative enough resulting in deficiencies end of Winter/beginning of Spring.
For anyone who doesn’t live in the tropics, you will likely experience a fluctuating availability of Vitamin D that you can synthesize from the sun at certain periods of the year. So you would also benefit from formulating your own strategy.
Why I care?
Numerous benefits of optimal Vitamin D levels for Neuroplasticity & neurogenesis as I have written about.
(When it comes to the brain, I leave no stones unturned. 💚)
Questions:
How much body store of Vitamin D can/would I have by the end of summer (August)?
What is the amount of Vitamin D I need to supplement between September-April so I come out of dark season at >65 nmol/L in April?
What we know:
Daily RDA: 600-800 IU/d (15–20 μg/d)
Maximum suggested dose: 4,000 IU/d for healthy adults
Vitamin D supplements exist in large range of doses
Each 1,000 IU of vitamin D3 daily in addition to what you make/eat will raise the serum level by 25 nmol/L (10 ng/mL) after a few weeks
Vitamin D toxicity is documented at 10,000 IU/day and can occur at as little as 2,000 IU a day
(P.S. I have prescription grade Vit D at 50,000 IU ↓ ↓ which I have never taken as I fail to see the benefit of this (for me). Individuals who have gut issues cannot absorb nutrients properly so that is why it can be used clinically, but I do not have this issue. I buy my own at 1,000-2,000 IU per tablet/capsule.)
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Mega-dose of Vitamin D3 Supplementation
What I am asking:
How much Vitamin D can the average adult human store?
In what form?
And for how long?
How much time in the sun produces how much IU of Vitamin D in the body?
How much Vitamin D can I ‘store away’ in my body in July & August assuming average sun exposure time of 15 min/day, 7 days a week?
Finally, I make an estimate of how much Vitamin D I would need to supplement weekly in the months of Sept-May so as to maintain a level of 65 nmol/L+ of serum vitamin D.
These are the answers I found:
Total vitamin D storage capacity in the body for an average healthy adult is not that well characterized. I have seen estimate of ~10,000 to 20,000 IU, I have also seen up to 50,000 IU but this value depends on the amount of body fat you have to store the Vit. D.
The form of vitamin D that is stored in the human body is calcidiol, 25-hydroxyvitamin D [25(OH)D]
There is a difference in the half-life of vitamin D in the blood & in body fat:
Half-life of Vitamin D in the blood:
Calcidiol (25-hydroxyvitamin D), the main circulating form of vitamin D, has a half-life in the bloodstream, estimated to be around 2-3 weeks. This means that it takes about 2-3 weeks for half of the circulating calcidiol to be cleared from the blood.
Half-life of Vitamin D in body fat:
The literature suggests that the storage half-life of vitamin D in body fat can be anywhere between 2-6 weeks or a few months.
In summer & spring, with 22% of uncovered skin, 1,000 IU vitamin D are synthesized in 10-15 min.
Assumptions:
I make 1000 IU per day all of July and August by being in the sun for 15 min. each day
I use 800 IU per day.
Vitamin D that remains:
200 IU x 60 = 12,000 IU
Rationale:
Further assuming I store away all that remains 12,000 IU, this would only last 2 weeks of no sun days in the winter.
Even if I increased my sun exposure in the summer, and manage to store away 50,000 (which I doubt as I am not that big of a person), this wouldn’t last more than 2 months with no newly made Vitamin D from sun.
Beyond that, I am facing the half life of how long Vitamin D can be stored in body fat.
New Strategy:
I may need to rely on daily supplement of 1,000 IU/day as soon as 2 weeks into the winter, and definitely not later than 4 weeks.
This seems logical based on my existing reference points of taking 1,000 IU 2-3 days a week in winters of 2019-2023.
Next Steps:
Measure serum levels again in August 2023, January 2024, and April 2024, with the goal of it being steady between 65-80 nmol/L.
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P.S. I also confirm, for my situation, there is no need for 50,000 dose of Vit. D, I just need to hit the 1,000 IU more frequently, or 2,000 IU every other day.
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For a more general & higher level approach to Vitamin D through sun & food, you can read that here.
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Disclaimer
This information is not medical advice. This content and other content on this website is for informational and educational purposes only and is not intended to be a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
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References
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Jones G. Pharmacokinetics of vitamin D toxicity. Am J Clin Nutr. 2008 Aug;88(2):582S-586S. doi: 10.1093/ajcn/88.2.582S. PMID: 18689406.
Khan QJ, Fabian CJ. How I treat vitamin D deficiency. J Oncol Pract. 2010 Mar;6(2):97-101. doi: 10.1200/JOP.091087. PMID: 20592785; PMCID: PMC2835491.
Hengist A, Perkin O, Gonzalez JT, Betts JA, Hewison M, Manolopoulos KN, Jones KS, Koulman A, Thompson D. Mobilising vitamin D from adipose tissue: The potential impact of exercise. Nutri. Bull. 2019 Feb;44(1):62-69. doi: 10.1111/nbu.12369. Citations: 2.