Claudia's (HI) comments about vitamin D represent a good starting point, BUT are largely inaccurate. I recommend this website: http://www.vitamindcouncil.org/.
Why? Five years ago, I discovered vitamin D because I was a co-teacher of a "Train the Trainer" Osteoporosis Progressive Resistance Training Exercise program that served 17 communities. My objective/ goal was to determine how to prevent & reverse osteoporosis, naturally. What I found was adequate vitamin D and vitamin K in the duodenum were pre-requisites for the rapid transport of calcium to our bones and teeth.
What I also discovered was sarcopenia (age-related muscle loss) is also caused by vitamin D insufficiency. What these twin findings mean is, without adequate vitamin D, aging will result in decreased bone density and progressive muscle loss.
Today, I also teach classes on ARTHRITIS PREVENTION AND TREATMENT, HEALTHY COGNITIVE AGING, -&- VITAMIN D AND HEALTHY AGING. In each of these classes I mention vitamin D (not actually a vitamin, but instead a pro-hormone) regulates/ enables over 10% of our genes. Clearly, we all need to get our vitamin D levels up to at least adequate levels.
The pharmaceutical industry is opposed to this. Why? Because vitamin D adequacy should prevent most chronic diseases (including all cardiovascular diseases, diabetes, -PLUS- most autoimmune diseases & psychological disorders).
And if you don't find my claims credible, I highly recommend going to: http://www.ucsd.tv/search-moreresults.aspx?keyword=vitamin+d&x=15&y=7 to watch their many videos presented by vitamin D experts.
Also, when I look at my deformed knees, my scoliosis as a teen and pre-eclampsia during my pregnancies, I also appreciate that I am probably among the 25% of humans who inherited a mutant vitamin D receptor gene, and consequently am someone who needs more vitamin D than most people.
Finally, recent studies of the vitamin D status of people living in tropical areas found over 50% are vitamin D deficient. WHY? Sun exposure can keep/ get your vitamin D level up ONLY if you don't shower or bathe daily. Personally, I choose supplements!
Diana
Dianaof MA4:49AM May 16, 2010
So-called "vitamin" D is not necessary to consume because the body makes its own, through sun exposure. The two major forms which are ingested are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). They have actions like a steroid and likewise, it has the ability to make us feel good, while we are actually getting sicker. Yes, our bodies can use this ingested molecule, as a precursor to the active metabolite "D", but it is NOT necessary and may cause mischief with the body's immune system!
Calcitirol (1,25-Dihydroxycholecalciferol) is the active metabolite form of vitamin D found in the body. You cannot ingest this - your body must make it, therefore it is not able to be defined as a "vitamin" either. However, the essential activities performed in the body by Calcitirol (1,25D) are MISTAKENLY ascribed to the D2/D3 and this leap of logic makes for bad science. The body has a complicated system to regulate the production, conversion, metabolism and destruction of the various forms of "vitamin D". It can DOWN-regulate the amount of D3 circulating in your blood if there is already too much 1,25D as can be the case in severe inflammatory disease. Hence an apparent "deficiency" of vitamin D (D3) might be wrongly assumed to be the cause of the disease.
Do not jump to conclusions of cause & effect regarding a low vitamin D blood test.
In fact, studies show most chronically ill people with blood tests indicating low or "deficient" Vit D (where only D2/D3 are measured) will prove to have high levels of the metabolite calcitirol - 1,25D! They actually have plenty, often way too much of it, and this causes many of the symptoms they suffer.
Why is this not well known? I suggest several reasons:
1 - Doctors seldom request the 1,25D test. It is cheaper and easier to only order the D2/D3 test. The test for 1,25D is more expensive and difficult to conduct properly; it often returns false negatives (low readings) when blood samples are not properly handled.
2 - There is a lot of commercial push to sell vitamins and an understandable desire by the public to buy them and "take control" of their own health. We want it to be as easy as taking vitamins to make up for a "deficiency". Unfortunately, it's not that simple.
3 - Lazy research and bad science. People make mistakes by jumping to conclusions regarding cause & effect. Vitamin manufacturers jump on the bandwagon and issue press-releases, amplifying the effect of the mistake until even the doctors and scientists believe their own mistakes and it becomes received knowledge; dangerous assumptions.
Here is a link to a page outlining some facts about vitamin D:
http://mpkb.org/doku.php/home:tests:125d
Claudiaof HI2:46AM March 25, 2010
Vitamin D is a highly undervalued vitamin nutrient. The benefits, specifically in the reducing chances for cancer, clearly outweigh the risk discussed in this article.
Otherwise, very interesting article. Thank you
Danof PA7:40PM March 18, 2010
Increased vitamin d and calcium does not cause kidney stones. Low intake of vitamin d causes secondary parathyroidism and it is this that leads to kidney stones. So taking vitamin d reduces not increases the risk.
Without enough vitamin d in the blood you cannot absorb calcium so it does not matter how much you eat it just passes through. With suitable vitamin d intake by whatever means there is probably no need for calcium supplements.
Pete5:59PM March 16, 2010
Dr. Willett:
Quite interesting... thanks. Your article could be enhanced by a close look at the Dairy Lobby's influence on U.S. recommended daily calcium levels.
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Diana of MA 4:49AM May 16, 2010
Claudia of HI 2:46AM March 25, 2010
Dan of PA 7:40PM March 18, 2010
Pete 5:59PM March 16, 2010
Mike of MI 4:38PM March 16, 2010