I've spent the last year researching supplements in an effort to maximize both my physical, mental, and emotional well-being. I had to understand whether the $32 billion dollar supplement industry was a complete sham, or if it was possible to live healthier through supplementation. The following post(s) are being published as a personal reference guide to Examine.com's excellent "Supplement Guides" - which are awesome, but often tough to dig through for the important information.

What is it?

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 I guess makes it fairly important.

Where is it found?

Three places:

  • Sun exposure - the human body naturally converts cholesterol into Vitamin D3 when exposed to UV-B radiation. AKA sunlight. This is tricky in the modern era, since who goes outside anymore?
  • Diet - Milk (124IU/cup) and fatty fish (500IU/salmon filet). That's about it.
  • Supplements - This is what we are here to discuss!

A report by the US Nutritional Health and Examination Survey in 2009 (Research: 17) found that three quarters 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.

Benefits of supplementation

  • Decrease in general mortality - this may be a bit of correlation vs. causation issue, but the research does back an overall lower risk of death for non-deficient patients (Research: 2,3,4)
  • General bone health - Vitamin D has shown to reduce the risk of bone fractures in every age range (most data is for elderly folks).
  • Lower blood pressure - Linked study found an overall reduction of 5mmHg blood pressure when patients increased blood serum D levels. (Research: 5,6)
  • Higher testosterone (in men) - Single study found raising Vitamin D serum levels also increased testosterone in men (Research: 7)
  • Higher estrogen (in women) - Single study found raising Vitamin D serum levels also increased estrogen in women (Research: 11)
  • Lower cancer risk - There is a strong correlation between Vitamin D deficiency and your risk of developing cancer. The following cancers have research backing this claim: breast cancer, colon cancer, prostate cancer, and pancreatic cancer. One study even claims that supplementation of 2000IU/day saw a 50% reduction of breast cancer incidence. That's crazy. (Research: 9,10)
  • Increased Mental Performance - There is a linear relationship between Vitamin D levels and verbal fluency up to and exceeding 100ng/ml. (Research: 18)

Downsides to supplementation

  • None, seriously. There are no known negative side effects of common sense supplementation of Vitamin D (see next section)

Dosages and Toxicity

Dosing for Vitamin D is tough and nearly impossible to get 100% right. The goal is to get blood serum levels between 75ng/ml and 125ng/ml, which is well within the safe range, but can be classified as on the high side on several scales.

The general rule of thumb is a 2000IU supplement will get 95% of the population within those levels over time. (Research: 14) However, the only way to ensure proper Vitamin D supplementation is to get blood tests regularly to check serum levels. Honestly, if you are the 5% who is truly deficient, then you probably need a doctor to recommend a dosage plan anyway. So yeah, 2000IU is the answer.

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 vitD production automatically. The more you know! (Research: 15)

When and how to take?

  • Oral - Yep, just those Vitamin D pills/gummies you can literally find anywhere.
  • Sublingual - Tougher to find, but for those that don't like pills, they make sprays and sublingual solutions as well.

Best route of administration? Actually, doesn't matter in this case. Both the oral and sublingual methods work about the same over time.

The best time to take Vitamin D is alongside your first meal, usually first thing in the morning with breakfast. (Research: 12) It has been reported that taking Vitamin D at night results in interrupted sleep patterns, which doesn't sound like fun. (Research: 13)


You should take 2000IU Vitamin D daily. There is literally no downside, and it costs about $0.07 a day to do it.

Recommended brand: Nature Made 2000IU Softgel - one of the few independently tested and verified brands. (Research:16)


  1. Examine.com -- since this is a tl;dr of that page.
  2. Independent association of low serum 25-hydroxyvitamin d and 1,25-dihydroxyvitamin d levels with all-cause and cardiovascular mortality http://www.ncbi.nlm.nih.gov/pubmed/18574092
  3. Systematic review: Vitamin D and calcium supplementation in prevention of cardiovascular events http://www.ncbi.nlm.nih.gov/pubmed/20194238
  4. Levels of vitamin D and cardiometabolic disorders: systematic review and meta-analysis http://www.ncbi.nlm.nih.gov/pubmed/20031348
  5. Serum 25-hydroxyvitamin D, ethnicity, and blood pressure in the Third National Health and Nutrition Examination Survey http://www.ncbi.nlm.nih.gov/pubmed/17586404
  6. Effect of vitamin D on blood pressure: a systematic review and meta-analysis http://www.ncbi.nlm.nih.gov/pubmed/19587609
  7. Effect of vitamin D supplementation on testosterone levels in men http://www.ncbi.nlm.nih.gov/pubmed/21154195
  8. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials http://www.ncbi.nlm.nih.gov/pubmed/19307517
  9. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis http://www.ncbi.nlm.nih.gov/pubmed/17296473
  10. Vitamin D and prevention of breast cancer: pooled analysis http://www.ncbi.nlm.nih.gov/pubmed/17368188
  11. Vitamin D is an important factor in estrogen biosynthesis of both female and male gonads. http://www.ncbi.nlm.nih.gov/pubmed/10746634
  12. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. http://www.ncbi.nlm.nih.gov/pubmed/20200983
  13. This one is actually from the blogger and known quantified self geek known as Gwern. He found his sleep quality went down the tubes when he took Vitamin D before bed instead of first thing in the morning. http://www.gwern.net/Zeo#vitamin-d-at-morn-helps
  14. The urgent need to recommend an intake of vitamin D that is effective. http://www.ncbi.nlm.nih.gov/pubmed/17344484
  15. NIH: Vitamin D fact sheet http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
  16. Lab Door tests supplement brands for purity and correct claimed dosages. https://labdoor.com/rankings/vitamin-d
  17. NHES Survey (http://www.scientificamerican.com/article/vitamin-d-deficiency-united-states/)
  18. Vitamin D and executive functioning: Are higher levels better? http://www.ncbi.nlm.nih.gov/pubmed/26708262