Vitamin-D Craze — Fallacy or Function?

Have you jumped onto the popular Vitamin D bandwagon? Most likely, if you have visited your doctor recently and blood tests were ordered, a recommendation was made for this previously less-than-routine lab work (specifically, 25-Hydroxy Vit C, Calciferol, Total D2 & D3). My health care professional passionately suggested it. (She is actually an FNP – Family Nurse Practitioner, and a good team player.) Frankly, Vit D wasn’t more than a blip on my radar, other than for the sufficient sunshine versus risk of sunshine controversy. And I took notice of the small amounts in my regular multi supplement (mine happens to be 400 IU per tab).

So, what’s the scoop? Is it primarily a fad along the lines of a ‘product du jour’? Or is it the panacea it is often made out to be? What’s the back-story? Is it worth another 20 minutes in the sun or another jar in your cabinet?

I feel confident in saying the answers ARE worth knowing.

A few Vitamin D Facts

Let’s start with this one – Vit D is not a vitamin. It’s a hormone (colferol) produced by the skin. Why is it called a vitamin? I am tempted to say “to fool us common folk” but I will graciously assume it was evolving chemical knowledge.

There are technically 3 forms of Vit D:

D1 — found to be a mixture and a distinction little used these days;
D2 — most commonly from fungi and mushrooms;
D3 — primarily from sunlight, but found in fishy oils, and certain animal/plant and “fortified” products. D3 is also known as cholecaliferol.

There are low amounts of Vit D in fortified milk and even in beer (yum). Neither are enough to meet sufficient levels.

Vit D receptors are not the same for everyone.  Darker skin people have a harder time absorbing the nutrient. Not surprisingly, most everyone has higher levels in the summer than winter months.

It appears that those over 70 years old (especially if not getting enough sunlight) and those overweight may need to concentrate more attention on reaching sufficient levels. Meaning, there is a dose-relationship of oral Vit D to age, sunlight exposure and weight.

D3 is the more vital form of the substance, and the one I am referencing from here on.


Always. Never. All. 100%. Everyone. These are words we learn to avoid, right? Panacea should probably join that list as well.

There is a considerable amount of research on Vit D, some of which (as always) introduces an equal number of questions accompanying the answers. Still, there are review studies, which offer more determinant results. One in particular looked at close to 60 randomized clinical trials (over 100,000 people from different genders and varying age ranges, from 18 to 107). Another reviewed 25 trials. Taken as a whole, here are some conclusions from those studies.

  1. Decreased D levels may often be a SYMPTOM (a marker) of other activity or non-activity, or certain genetics.
  2. Lower Vit D levels are seen with inflammation.
  3. Diseases tend to lower Vit D. Example, influenza and colds decrease Vit D. Some advocates and vendors speculate that keeping Vit D levels elevated will help avoid the flu. Clearly a chicken-egg question.
  4. Vit D at sufficient levels may reduce the effects or serious consequences stemming from falls and fractures. [Bone health appears better in people with scores over 75 n mol/L – or 30 ng/ml.] In a study of 675 accident-victim autopsies, in cases where osteomalacia (bone softening) was present, no more than 31% had reached the useful target.
  5. The claims for improvements of osteoporosis or arthritis are not substantiated (perhaps unanticipated given #4 above).
  6. Likewise, the assertion that Vit D helps regulate or lower blood pressure is not conclusive.
  7. Diabetes improvement with the use of Vit D falls a bit flat as well. The Journal of Internal Medicine says that Vit D neither affects lipids substantially nor glucose tolerance. The substance is clearly not a treatment for the condition. Still, a lower than desirable level can create problems related to glucose tolerance or diabetes.
  8. Claims by advocates regarding Vit D as a combatant in fighting depression again appear minimal. Although reports of reduction in stress and anxiety are often described.
  9. Highest levels of Vit D correspond (in general) to less disease. [Note that manufacturers are allowed to promote Vit D products as a support to the immune system.]
  10. The one SHOCKER. These studies DID indicate Vit D’s ability to “prevent mortality.” What? Yes. The bottom line is a (possible) life extension of 11%, or approximately 4.4 years. However, this is NOT a “protective” tablet, and researchers worry it may give a false sense of protection. It is JUST a piece of the puzzle in a good living scenario. Still, it may be one of those coveted corner pieces that complete the picture.

Testing and Desired Levels

Save some money. Interestingly, some researchers say that there is no need to test and retest for Vit D. Routine tests may not be recommended by all physicians for 2 reasons:

  1. The test is not considered very good (whether that statement relates to accuracy or sensitivity I am unsure). Evidently, some labs can show different results on the same day from the same sample. [Let’s point out that the testing industry is making lots of money on it. So not everyone loses.]
  2. It will probably not significantly alter the dose you take.

There is certainly merit to this argument. Nevertheless, I like to have the facts. Hopefully, an occasional test (say 1-2 years to start?) may accurately-enough show you whether you are progressing in a positive direction or showing signs that indicate insufficient levels.

What ARE insufficient levels?

My testing center may not necessarily divide status as all other labs do; but it is in rough agreement with other sources. Here are their ranges. *

ng/ml measurement * n mol/L measurement *
Deficient < 20 < 50
Insufficient 20-29 50 – 72.5
Sufficient 30 -100 75 – 250
Possibly Toxic > 100 > 250

Some labs use 150 ng/ml or 375 n mol/L as toxic levels.

* Note. There are 2 different but common measurements of Vit D amounts. ‘ng/ml’ is the more frequent one used these days; but you may still see ‘n mol/L’. If you need to convert these, you divide the ‘n mol/L’ result by 2.5 to translate it to the lower ‘ng/ml’ number. To calculate vice versa (starting from the ng/ml number) then simply use the same 2.5 figure but multiply.


From a related Harvard Nutrition Department article: Benefit-Risk & Assessment of Vit D Supplement, by Bischoff, et al] there is the suggestion that optimal benefit levels are from 75-110 n mol/L (the ‘sweet spot’). Several advocates strongly support the 110 n mol/L range (or 44 ng/ml) as only a minimum; while others such as the US government might consider the 44 ng/ml a bit high.

Historically speaking, it is suspected that early man most likely met the sufficient levels normally and without effort. Those differences between modern and early man are often attributed to numerous variables: how few clothes were worn, allowing for more Vit D reception; the demand for work outside even in the lesser daylight hours of winter; as well as fewer environmental, food and disease factors.


How to explain “official” recommendations on dosing? Ah yes, — all over the map. [And the different measurement standards don’t add to the clarity.]

Let us start with the question of toxicity. My lab simply states greater than 100 ng/ml can be toxic. According to Robert P. Harney (The Vit D Requirement in Heath and Disease) toxicity would usually develop only with a considerable amount (such as 10,000 IU / day) on a consistent basis; and that still might test only as 100 ng/ml (or 250 n mol/L). Agreement is not clear.

Evidently some of the worry about toxicity stemmed from original studies on vitamin D that used Cod Liver Oil, which has excessive amounts of vitamin A as well. Since Vit A is a fat soluble vitamin (staying in the body longer) you can overdose on it.  Thus it was unclear which substance (or both) stimulated side effects. Still, the concern about Vit D toxicity is a fear about increased Calcium in the blood from excessive D amounts (some list this as above 150 ng/ml others even 300). In the Bishop article reviewing 25 randomized clinical trials, increases in serum calcium were not really seen until about 643 n mol/L (or 257 ng/ml) – quite a big difference from typical amounts. The good news here is that we might wish to go easy on the Cod Liver Oil. [Ah, thank goodness.]

Perhaps not many, but occasionally professionals do recommend a consistent 10,000 IU/day dose. They may do so especially if readings were initially low. Few of us manage getting adequate levels of the sunshine vitamin from the sunshine.

So what oral dose is recommended? …….Hmmmmm.  It depends on your source.

  • U.S. NIH (National Institute of Health) recommends 600 IU for most adults as “adequate intake” — and 800 IU for adults over 70 years old. [You may see older references that tout an even lower 400 IU endorsement.]
  • Some researchers suggest that 1,000 IU/day may bring most people up to 75 n mol/l (or 30 ng/ml)
  • 2,000 IU/day may ‘shift course’ to a more desired range.
  • 3,000 IU/day is often recommended by D-advocates for those people over 70 years old who get little sunshine
  • Doses of more than 3,000 IU are perhaps best for those overweight (more weight meaning more Vit D)
  • 1800-4,000 IU/day might reflect desirable ‘caveman levels’

Because we all react differently, and certain conditions can decrease Vit D, I was happy to be able to evaluate my own score at least one-time (despite any dubiousness of the test’s general accuracy). Without Vit D supplementation, my level was a bit under 50 ng/ml. Still low, according to certain current sources (and my self-evaluation).

In our house, we purchased Costco’s Kirkland brand of D3. A bottle of 600 soft-gel caps at 2,000 IU/cap costs approximately $12. Sure is a lot less than some medications. Certainly, not as tasty as a beer at the local brewery, but you can be more certain of the D levels to be obtained. And while D from the sun is always recommended in small amounts, to garner higher ranges in your scores, we recognize the risk as well. If we encourage each other to wear long sleeve shirts and wide brimmed hats to protect ourselves from common skin risks and conditions, it is doubtful we are going to slip into bikinis to expose more skin — even if it might indeed raise our Vit D levels.

I stick to my proclamation of no panacea. Perhaps that’s a matter of principle. Yet, admittedly, the answer to the title question of Fad or Function is clear. It’s function. For me, I will continue my supplementation. Vitamin D seems to be earning its kudos and is worth its weight in gold-en sunshine.

A Few References

  1. Benefit-risk assessment of vitamin D supplementation. Bischoff-Ferrari HA, Shao A, Dawson-Hughes B, Hathcock J, Giovannucci E, Willett WC. Osteoporos Int. 2010 Jul;21(7):1121-32. doi: 10.1007/s00198-009-1119-3. Epub 2009 Dec 3. Review. PMID:19957164
    Note: Centre on Aging & Mobility, Department of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Gloriastrasse 25, 8091, Zurich, Switzerland.
  2. Harney, Robert P., Creighton University, Omaha, Nebraska (The Vit D Requirement in of Heath and Disease) Journal of Steroid Biochemistry and Molecular Biology Published online before print June 2008, doi: 10.2215/​CJN.01160308
  3. NIH fact sheet on Vitamin D.
  4. Jun Sun, Ph.D. Associate Professor Departments of Medicine University of Illinois at Chicago. Vitamin D/Vitamin D Receptor Regulation of Gut Microbiome in Health and Disease. An in-depth presentation about VDR (vitamin D receptors)


Picture credit:
Sun graphic: And Vit E capsules from public domain Pictures image 18043.   Both via Pixabay


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2 thoughts on “Vitamin-D Craze — Fallacy or Function?

  1. Very informative article. I must confess, I don’t have a good idea of my current levels of Vitamin D, and it has been years since I steadily took a D supplement. (I just dug one out of the fridge). I also note that our bottle of daily multi-vitamins contains 1000 IU which, in light of your dose chart, seems to be on the low end of the scale for the generally office bound.

    • What a good point about “office bound” people perhaps wanting to be more diligent.
      BTW, I wasn’t steadily taking one either. drb

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