Talk:Vitamin D

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For some, diet may not be enough for Vitamin D

Current recommendations call for people from age 50 to 69 to get 400 international units (IUs) of vitamin D per day and for those over age 70 to get 600 IUs. Many researchers, however, suggest that higher amounts may be needed. [1] Brian Pearson 04:52, 23 April 2007 (UTC)[reply]

Latitude factor

Following this sentence These wavelengths are present in sunlight at sea level when the sun is more than 45° above the horizon, or when the UV index is greater than 3. it might useful to add that the required solar elevation occurs daily within the tropics, daily during the spring and summer seasons at mid latitudes, and almost never within the arctic circles. The point to make apparent is that for many countries there is an annual cycle of boom and bust, which is a huge factor in the health issues associated with vit D.

Suggestion:

At the latitude of Seattle, Montreal, Venice, and Christchurch NZ the sun rises to this elevation during spring and summer, but not during fall and winter, resulting in annual vitamin D cycles.

I picked well-known, longitudinally distant cities at 45 degree latitude; there are few such cities in the southern hemisphere apart from Christchurch. See List of cities by latitude.

From http://www.theglobeandmail.com/servlet/story/RTGAM.20070428.wxvitamin28/BNStory/specialScienceandHealth/home

For the rest of the population, vitamin D levels tend to be lower, and crash in winter. In testing office workers in Toronto in winter, Dr. Vieth found the average was only about 40 nanomoles/L, or about one-quarter to one-third of what humans would have in the wild.

MaxEnt 14:30, 28 April 2007 (UTC)[reply]

60% cancer reduction

This is a shocking number, and hard to believe on face value. Twice the effect as compared to smoking. I did a little arithmetic on that.

http://www.bccancer.bc.ca/HPI/CancerStatistics/FF/AgeStan/Inc/default.htm

Cancer rates for women in BC run about 330/10,000 per year. 1200 women broken into two equal groups and followed for four years gives you 2400 women-years per group. At a rate of 330/10,000 with a 60% reduction in the non-control group gets you incidence rates of 7 and 2.8. How does one measure 2.8 cancers? Quite possibly, the actual numbers were 10 and 4. 14 total cancers in 4800 women-years is a rate of 291/100,000, which is quite realistic. If it breaks down 7 and 7, you have no result. Standard deviation sqrt(14) = 3.7. It looks to me like both sides of the study are within one standard deviation of a possible mean. I don't know off the cuff how to compute the null hypothesis properly, but it's certainly large enough to cast doubt. MaxEnt 16:24, 28 April 2007 (UTC)[reply]

I thought about this some more. My calculation above assumed age-standardized rates. For a study of this size, it's extremely hard to achieve statistical significance with a mean rate this low. Almost certainly the population was biased toward older age groups to achieve a higher mean rate. Women over the age of 65 have a mean rate four times as high. http://www.bccancer.bc.ca/HPI/CancerStatistics/FF/Rates/incidence.htm If the mean rate for the age-skewed study group was 800/100,000, then 20 cancers are expected in the control group, and the 8 observed cancers in the experimental group (-60%) comes out 2.7 deviations below the mean. The study is much stronger if the experimental population was tilted toward advanced age. MaxEnt 17:47, 28 April 2007 (UTC)[reply]

I would like to know if there has been less tanning recently than in years past when people seemed to believe tanned people were nicer looking and possibly more "healthful" looking. Brian Pearson 03:03, 6 May 2007 (UTC)[reply]

I am confused. The article history shows that the results of this study were (first) added to the article by you. Are you disputing information that you - yourself - added?--DO11.10 00:28, 30 April 2007 (UTC)[reply]

I don't think he is disputing it so much as he is wondering aloud how a reduction of that magnitude is possible. WatchAndObserve 14:56, 6 May 2007 (UTC)[reply]

How can a 60% reduction of cancer be possible? And what is the biologic mechanism that links vitamin D with cancer? A year ago I would have said there cannot be such a link because vitamin D affects calcium and bone cell metabolism which have no connection to most cancers. Or so I thought until I read an article in the November 11, 2006 issue of Science News by Janet Raloff, The Antibiotic Vitamin. The article says that vitamin D hormone 1,25-D is necessary for macrophages to produce antimicrobial peptides in the cathelicidin group to combat virus, fungus, and bacteria infections. The link with cancer is that macrophages also destroy damaged cells and cell fragments such as DNA. By the time a cell becomes malignant, its chromosomes and DNA are a chaotic mess. (See Scientific American, May 2007, pages 53-59.) Most chromosomes in cancer cells are mere fragments or completely missing, some are duplicated, and the DNA is rearranged and mutated. The genetic mechanisms that control growth and prevent unlimited growth, such apoptosis, telemere shortening, and intercellular communication are gone or inactivated. Hence, the macrophages, which kill malignant cells and destroy cell fragments, are the last defense against cancer. Since vitamin D is necessary for phagocytosis, vitamin D deficiency can allow malignant cells to multiply unchecked. Greensburger 17:37, 6 May 2007 (UTC)[reply]

At the very least the astonishing correlation in this study suggests that further research is justified. Staypuft9 16:06, 20 August 2007 (UTC)[reply]

Reference questioned

I am taking issue with the following statement:

One recent consensus concluded that for optimal prevention of osteoporotic fracture the blood calcidiol concentration should be higher than 30 ng/mL (US units), which is equal to 75 nmol/L (System International units).

The reference given is http://dietary-supplements.info.nih.gov/factsheets/vitamind.asp, but I don't see this information anywhere on the page. If nobody objects, I will be removing the reference from this statement and adding a 'citation needed' tag.WatchAndObserve 14:59, 29 April 2007 (UTC)[reply]

I have changed the citation.--DO11.10 00:28, 30 April 2007 (UTC)[reply]

I have a doc that states it pretty clearly: [[2]] . Also, if you want you can watch worldwithoutcancer video on google videos, it's a pretty old movie that has had quite some controversy, but it also advocated (somesort of) D Vitamin. Cheers: Mr soros 02:16, 22 July 2007 (UTC)[reply]

Vitamin D; spelling of Mittelstaedt, Martin

Please note that the article entitled "Vitamin D" includes a citation by one Martin Mittlestadt. See citation no. 39. The name is incorrect. The correct form of his name is Martin Mittelstaedt. Cf. http://www.theglobeandmail.com/servlet/story/RTGAM.20070428.wxvitamin28/BNStory/specialScienceandHealth/home Boytinck 17:45, 1 July 2007 (UTC)[reply]

Done--DO11.10 02:29, 3 July 2007 (UTC)[reply]

External Link Video Add

I'd like to add a video in which Dr. DeLuca from University of Wisconsin discusses the history of the discovery and applications of Vitamin D. The link is http://www.researchchannel.org/prog/displayevent.aspx?rID=3751&fID=345 (this does not automatically open the video). Please let me know what you think. (ResearchChannel 19:42, 17 July 2007 (UTC))[reply]

While the content of this video is great, (from what I saw... the history part was fascinating) the streaming quality was –well– bad. I tried the video in both WMP and Quicktime. In WMP the video paused to buffer seven or eight time in the first minute, and didn't get any better when I skipped around. The Quicktime version was better, no buffering issues, but when I tried to skip I lost the sound(?). Given that the video is 1 hour 18 minutes long both issues will probably hinder it's usefulness here. Granted it could be my settings or something (probably not my connection speed though, I am running at over 2,000 kbps). If it is possible to address these issues, I think that the video is certainly relevant and I would like to add a link. --DO11.10 18:30, 20 July 2007 (UTC)[reply]

Vitamin D in milk

I cannot find this information on the milk page: it is my understanding that Vitamin D is fat-soluble. Does this mean that skim milk cannot be fortified with it? Staypuft9 16:07, 20 August 2007 (UTC)[reply]

Mortality benefit

In a meta-analysis of 18 studies, vitamin D (mean dose 528 IU) reduced the mortality risk by 7%. Exact mechanisms remain unclear, and more trials are needed. URL JFW | T@lk 21:43, 10 September 2007 (UTC)[reply]

In the Time.com article that discusses this meta-analysis, there is this sentence: " 'Throughout human evolution when the vitamin D system was developing, the 'natural' level... was probably around 50 ng/mL or higher,' writes Dr. Edward Giovannucci. Only in human evolution? Don't other animals need vitamin D too? If so, how do they make it if their skin is covered with fur? Greensburger 23:53, 13 September 2007 (UTC)[reply]

Some of the light will still reach their skin even with fur; and in many cases not all of their skin is covered with fur. Besides, a fair number of animals (particularly furry ones) tend to be carnivorous, and they can extract it from their prey's liver.WolfKeeper 04:27, 14 September 2007 (UTC)[reply]