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.)
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.
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.
For a more general & higher level approach to Vitamin D through sun & food, you can read that here.
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.
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.