I found a good summary with interesting history up to and including April 2013 research about vitamin D by Dr Matt ND, and am providing the link to his website and the entire article below the link so that you will be encouraged to see how he provides references to his work and 'the whole thing'; there are, naturally, other topics at his website of equally well-done quality. I encourage people to connect from here to quality providers and information.

One thing I'd like to add: Since it's ultimately a hormone, I've been educated by ITC Natural Wellness Pharmacy's late, great co-president Gary King, RPh and his still alive-and-kicking partner Allan Jolly, RPh, ND that supplementing some with bone builders through the gut only gets you so much benefit; sublingual drops and the skin of the mouth and throat are a better uptake mechanism, more similar to the sun on our skin. That made sense to me, and the drops I purchase from them have been $19/bottle which would supply an average user for about 3 months; I was tested and needing to take about double what most people need. So I ALWAYS suggest to people to put it at the TOP of their lists to get vitamin D testing done and not to presume based on how much you supplement.   ~~ Mardy 

www.drmattnd.com/articlesinformation/vitamin-indecision.html

Vitamin InDecision:

A Case of Split Personality in Science

When it comes to the story of vitamin D, it all started with a simple misunderstanding, and then things generally went downhill from there. You see, vitamin D isn't really a vitamin at all: it belongs to a class of hormones known as secosteroids, which are produced in the human body when cholesterol in skin is exposed to ultraviolet light from the sun.

Though Adolf Windaus was awarded the Nobel prize for chemistry in 1928 for his work on the discovery of vitamin D, it has taken the rest of us about 75 years to even begin to fully appreciate the role of vitamin D in the body. Far beyond regulation of calcium absorption, we now know that it plays an integral role in the function of the immune system, as well as exhibits clinically significant neurological and endocrine effects.

Vitamin D Insufficiency is Common

A large Brazilian study, published in April 2013, found vitamin D insufficiency increased as a function of latitude. That is to say, the further away from the equator the participants lived, the more likely they were to have low vitamin D levels. But even in tropical regions, vitamin D insufficiency was found to be common. That probably doesn't bode too well to those of us living in Michigan.

Another study of those with sleep disorders found that 54% of the participants had insufficient levels of vitamin D in their blood.

Meanwhile, incidence of skin cancer is on the rise, and public health officials have become quite urgent about reminding us to slather ourselves in sunscreen whenever we walk outside. So what gives? Have we really evolved to require such large amounts of sunshine for optimal functioning, only to risk having our lives cut short by melanoma? I am personally inclined to say no- that's not the way nature intended for it to be. At the very least, we now have sunscreen options that are free from chemicals, such as parabens, for which scientists are currently debating research suggesting a link to breast cancer.

Unfortunately, we just haven't yet quite figured out the vitamin D enigma. On the one hand, we have decisive evidence to support benefits of higher levels in the blood, while on the other we also know that the amount of sun exposure required to maintain those levels, even if possible, would greatly increase our risk of skin cancer. In the meantime, we have dietary supplements.

How Much is Enough?

In a manner, vitamin D was the original dietary supplement, and has been added to milk for decades. However studies have found fortification practices in the United States to be inadequate. In 2011, the Institute of Medicine (IOM) released updated recommendations for vitamin D intake which- while a substantial increase- were met with dissatisfaction by many other experts in the field. Meanwhile, as the academics continue to banter, the public is left scratching their heads.

While current IOM guidelines recommend a daily intake of 600-800 IU for most adults, a randomized clinical trial recently found that supplementation with up to 1000 IU produced no significant change in vitamin D levels in otherwise healthy adolescents. Other clinical trials are finding positive benefits for those with preexisting conditions at levels up to 7000 IU per day.

One controlled study found beneficial effects among elite ballet dancers given 2000 IU per day during the winter, in the form of lower injury and improved muscle performance. While it is still anybody guess where the final consensus will come to rest for general supplementation in otherwise healthy individuals- it is the guess of this author that it will land at the 2000 IU mark.

Supplements and Testing are Cheap and Safe

One redeeming aspect of this neverending story of confusion is that vitamin D supplements are both inexpensive and relatively safe to use. A year's supply for regular use can be had for about thirty dollars, and it appears difficult to imagine an adult getting into toxicity issues on anything less than 10,000 IU a day.

What is more, a recent cost-comparison study found that screening for vitamin D levels ahead of time to determine who required supplementation was even less costly than administering supplements to everybody. Which means that vitamin D testing (currently around $60) is likely to soon be covered by your medical insurance, if not already. And who knows- maybe one day soon it will even cover the supplements!

Considering how safe and inexpensive vitamin D supplements and testing are, one must acknowledge a certain degree of absurdity in spending untold dollars on investigations in order to arrive at a scientific consensus of what should be a simple appeal to common sense. But our curiosity does ever get the best of us, and we humans often enjoy a good debate.

In the meantime, if you just so happen to be a Michigander whose limbs have not seen much sun since October of last year- chances are you could benefit from supplementation with vitamin D. But don't let that stop you from soaking up a little sunshine while out and about. The benefits of fifteen to thirty minutes a day before sunscreen is likely to far outweigh the increased risk of skin cancer, even for the fairest among us. But that is just my opinion- I don't have any scientific evidence to back that one up so you will just have to decide for yourself.

Journal References

Arantes HP, Kulak CA, Fernandes CE, Zerbini C, Bandeira F, Barbosa IC, Brenol JC, Russo LA, Borba VC, Chiang AY, Bilezikian JP, Lazaretti-Castro M. Correlation between 25-hydroxyvitamin D levels and latitude in Brazilian postmenopausal women: from the Arzoxifene Generations Trial. Osteoporos Int. 2013 Apr 30. [Epub ahead of print]

Calvo MS, Whiting SJ, Barton CN. Vitamin D fortification in the United States and Canada: current status and data needs. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1710S-6S.

Chakhtoura M, Azar ST. The role of vitamin d deficiency in the incidence, progression, and complications of type 1 diabetes mellitus. Int J Endocrinol. 2013;2013:148673. doi:10.1155/2013/148673

Kirchhof MG, de Gannes GC. The health controversies of parabens. Skin Therapy Lett. 2013 Feb;18(2):5-7

Lee RH, Weber T, Colon-Emeric C. Comparison of Cost-Effectiveness of Vitamin D Screening with That of Universal Supplementation in Preventing Falls in Community-Dwelling Older Adults. J Am Geriatr Soc. 2013 Apr 30. doi: 10.1111/jgs.12213

McCarty DE, Reddy A, Keigley Q, Kim PY, Cohen S, Marino AA. Nonspecific pain is a marker for hypovitaminosis D in patients undergoing evaluation for sleep disorders: a pilot study.Nat Sci Sleep. 2013 Mar 9;5:37-42. doi: 10.2147/NSS.S42641

Putman MS, Pitts SA, Milliren CE, Feldman HA, Reinold K, Gordon CM. A randomized clinical trial of vitamin d supplementation in healthy adolescents. J Adolesc Health. 2013 May;52(5):592-8. doi: 10.1016/j.jadohealth.2012.10.270.

Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, Durazo-Arvizu RA, Gallagher JC, Gallo RL, Jones G, Kovacs CS, Mayne ST, Rosen CJ, Shapses SA. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011 Jan;96(1):53-8. doi: 10.1210/jc.2010-2704.

Suzuki M, Yoshioka M, Hashimoto M, Murakami M, Noya M, Takahashi D, Urashima M.Randomized, double-blind, placebo-controlled trial of vitamin D supplementation in Parkinson disease. Am J Clin Nutr. 2013 May;97(5):1004-13. doi: 10.3945/ajcn.112.051664.

Wamberg L, Pedersen SB, Richelsen B, Rejnmark L. The Effect of High-Dose Vitamin D Supplementation on Calciotropic Hormones and Bone Mineral Density in Obese Subjects with Low Levels of Circulating 25-Hydroxyvitamin D: Results from a Randomized Controlled Study. Calcif Tissue Int. 2013 Apr 17. [Epub ahead of print]

Wolf G. The discovery of vitamin D: the contribution of Adolf Windaus. J Nutr. 2004 Jun;134(6):1299-302.

Image © User:Hungkero / Wikimedia Commons / CC-BY-SA-3.0