Vitamin D3 Supplementation: Yes? No? Why?

Goal: To see why, when, and how vitamin D3 supplements can benefit your health.

Motivation: Doctor prescribed tests for vitamin D3 levels are incredibly common these days, for a reason. Many people live their lives deficient in vitamin D3 levels, which can cause many problems down the road.

Executive Summary: Vitamin D3 is good for you, you’re likely not getting enough because of modern day society, supplements are cheap and effective. Take some Vitamin D3 between 700UI – 4000UI a day (depending on level of deficiency, body weight, sun exposure, etc… see below.)

So what is vitamin D3?
25-hydroxy vitamin D3
Vitamin D3 is a molecule that our body uses for many positive purposes. Some of the beneficial effects include:

* Improves immune responses. (Am J Clin Nutr December 2004 vol. 80 no. 6 1717S-1720S)
* Increases bone density / reduced fracturing in older individuals. (N Engl J Med 1997; 337:670-676)
* Preventing osteoporosis. (Yamaguchi, Vitam Miner 2013, S6)
* Preventing autoimmune diseases. (Ann Rheum Dis 2007;66:1137-1142)
* Preventing Diabetes. (Arch Dis Child 2008;93:512-517)
* Preventing cancer. (Cancer Causes & Control March 2004, Volume 15, Issue 2, pp 149-158)
* And is one of those vitamins that generally decreases in concentration as one ages. (J Clin Invest. 1985 Oct; 76(4): 1536–1538.)

It’s fairly well established that there are lots of good things associated with proper levels of vitamin D3, so I’m not going to go terribly in depth here.

Okay, so then how much vitamin D3 should we be take?
It’s always possible to take too much of a good supplement, so knowing the safe, optimal range is very important. The FDA required amounts of vitamins and minerals typically aren’t terribly optimal. Their job is to be conservative, and many “recommended daily values” are usually just above the amount needed to prevent disease, since that’s an easy black and white cutoff point. Many studies that discuss optimal vitamin D3 levels believe that the recommended amounts is lower than optimal. (The Journal of Steroid Biochemistry and Molecular Biology Volumes 89–90, May 2004, Pages 575–579) For reference, the approximate serum vitamin D3 levels one would maintain if one were to live out in the sun in the way humans evolved would be higher than 100 nmol/L. (Volume 92, Issue 1, September 2006, Pages 26–32) People these days who spend most of their time outdoors have levels higher than 75nmol/L, which is the higher end of “normal”, and is said to be the “target range”. (Volume 23, Issue 6, December 2009, Pages 789–795) In order to get that target, some studies have said to take between 700-1000UI/day of vitamin D3 if you are severely deficient or overweight. Another study says that 1000-2000UI/day is an amount that shows benefits with also being safe. (Volume 32, Issue 3, March 2007, Pages 210–216) Yet even another study says that up to 4000UI/day is also safe and leads to the “normal high” levels of vitamin D3 in blood. (Am J Clin Nutr February 2001 vol. 73 no. 2 288-294) There have also been uses of vitamin D3 in the 50,000UI/week range to treat certain conditions, so the amount needed to be “too much” seems to be fairly wide. All that being said, how much should you take? The studies seem to indicate that between 700-4000UI/day seems to be the safe, effective range. If you live in a dark area, don’t work outside much, have a large body mass, are an older individual, got a test that says you are deficient in vitamin D3, or want to supplement to have serum levels in the higher end of the spectrum, then you should be taking near the 4000UI/day range. I personally take 4000UI. If you get outside a lot, have a small body type, or for whatever reason you believe you may not be terribly deficient but still want to cover your bases, then something closer to the 700UI/day range may be more appropriate for you. If you feel nausea, vomiting, poor appetite, weakness, frequent urination or kidney problems, you may be taking too much. Dial it back a notch.

What kind of vitamin D3 should I be taking?

Cholecalciferol is the hormonally active form, so make sure it says that on the bottle. Anything else may be a related molecule that takes a few steps to be converted into cholecalciferol and wouldn’t be as effective. Simple answer: Make sure the bottle says cholecalciferol or 25-hydroxycholecalciferol. (Same molecule, different name). I take two of the Kirkland Signature Extra Strength Vitamin D3 2000 I.U.. It’s the best bang for your buck.