I’m a big advocate of science-backed supplements to optimize mental and physical performance. These articles represent my own distilled research on effectiveness, risk, and other things to consider before supplementing. To see what supplements I am currently taking, definitely check out the “My Current Supplements” article at the top of this section. Most of the sources are dervived from Examine.com, which is a great resource, but my intent is to distill it down and add my own research + anecdotes.
Vitamin D is recognized as one of 24 “essential vitamins” along with vitamins A, C, K, and B12, just to name a few. Fun fact - it is actually classified as a steroid that regulates the expression of close to 1000 genes in the body (1⁄24 of the genome), which makes it fairly important.
A report by the US Nutritional Health and Examination Survey in 20092 found that 75% of Americans are Vitamin D deficient. The survey naturally blames staying indoors, the use of sunscreen, and changing of American diets to the sharp increase in Vitamin D deficient adults. Plus we are discovering that biological optimal ranges of Vitamin D occur outside “historical normal” values, which means the medical guidance is showing most people are now deficient.
The first step to figuring out if you need to supplement Vitamin D is to get a routine blood test to check for active Vitamin D levels. Your PCP can order this, or you can use a service like WellnessFX to self-service the blood test at a premium. Vitamin D production and absorption is impacted by several genetic markers, so there is no clear cut advice for everyone. When in doubt, the FDA recommends 1000IU-2000IU daily is safe for most of the population. Remember, you may need more or less given 1) how much Vitamin D is in your blood already and 2) your genetic markers for Vitamin D.
Once you have your blood test data back, you can compare your results against the table below. This table is roughly accurate with the most recent research on the topic of optimal Vitamin D blood serum levels.14
If your blood test comes back wildly deficient, then the highest safe dosage of Vitamin D is 10,000IU daily for three months. It is recommended to get your blood tested again and revise the dosing if necessary.
Timing wise, Vitamin D is best taken in the morning with a fatty breakfast. Taking Vitamin D at night can disrupt circadian rhythms15 and lead to poor sleep quality. If you don’t eat breakfast, then Vitamin D can be taken with Fish Oil to increase absorption. They also make Vitamin D capsules that have olive oil / other fats in them, which also can make a difference.
Gwern (an independent biohacker) also validated this timing evidence through his own experiment with taking Vitamin D at night.16
Now the fun part - toxicity! The National Institute of Health states that a consistent Vitamin D blood serum level of 200ng/ml is potentially toxic. The only way to get blood serum levels that high is to take 10,000-40,000IU supplements daily for close to three months. So yeah, super low to no toxicity, unless you are really trying. And fun fact - you cannot get Vitamin D toxicity naturally - food doesn’t have enough to get to those levels, and the skin regulates Vitamin D production automatically.17
Your genetics play a large role in Vitamin D synthesis, usage, and storage. SNPedia keeps an up-to-date list of what genetic markers are known to positively or negatively impact Vitamin D levels - SNPedia Link. If you have done 23andme or Ancestry.com genetic testing, then you can export that data in Promethease to check for these SNPs directly.
Since I’ve started tracking my own Vitamin D levels, I can say that I’ve never been clinically low in Vitamin D. I have always supplemented with 2000IU Vitamin D since college, so that has contributed to my relatively stable 60ng/ml blood levels. I have experimented with going up to 5000-10000IU daily with no success in impacting my blood levels, but that may be due to genetic and other health factors. I want to try and get closer to 75ng/ml overall, since that is the current guideline for long term bone and heart health.
Vitamin D is extremely cheap to supplement. High quality 5000IU capsules cost about $0.06 per day on average, which is a cheap price to pay for a staple nutritional supplement.
You should take 2000IU or more Vitamin D daily. There is virtually no downside and it costs about $0.06 a day to do it.
Recommended Brand: Nutrigold 2000IU
The brand above has a great score on LabDoor in regards to quality. Link to LabDoor Vitamin D Page