Last updated: 1/24/12

ABOUT VITAMIN D AND VITAMIN D DEFICIENCY

Please note: the information contained within this informal paper is not intended to treat, diagnose, or otherwise replace the care of a trained physician.  Instead, the information is based on my research in an attempt to educate people about the importance of vitamin D testing and the effect of vitamin D on a person's health.  I have not quoted my sources fully yet, nor have I properly quoted all of the sources that I do quote.  I am working on this.  In the meantime, a long list of references from which I pulled my research is at the bottom of this writeup.

I first learned about the importance of vitamin D from a 72-year-old personal contact who was taking large doses of vitamin D, 10,000 IU's a day.  After a year, her vitamin D blood level was tested, and it was 109 ng/ml, which was close to the statistically-normal range of 30-100 ng/ml.  By estimating how much her level should have risen with this daily dosage, it was projected that she had been severely vitamin D deficient or not as able to absorb the vitamin D due to her age.  Still, the amount that she was taking alarmed me.  In college, I had learned that anything greater than 400 IU’s daily would create vitamin D toxicity.

VITAMIN D AND THE CANCER CONNECTION

For the person described above, the importance of getting her vitamin D to a healthy level was that just a few months after starting to take vitamin D, she was found to have breast cancer, a very small tumor, but one that still required surgery and radiation therapy.  She then learned from Dr. John Cannell’s website, www.vitamindcouncil.org, that vitamin D deficiency had something to do with a greatly increased risk of cancer.  We have since learned that a "natural" vitamin D blood level as seen in monkeys in the wild is 80 ng/ml and that this level "virtually eradicates breast cancer [ref: R. Vieth]."  Perhaps if she had known about vitamin D much earlier, she could have prevented her breast cancer or, at the least, significantly reduced her risk for developing cancer. 

According to scientists, prostate and colon cancer are at the top of the list with breast cancer in terms of vitamin D deficiency and a significantly higher incidence of cancer.  Perhaps my dad would not have died of colon cancer if we had known about vitamin D in 1980 when he started to complain of strange symptoms of chronic fatigue and pain and a constant, flu-like achiness.  Many lab and imaging tests later, none came back with any abnormalities, and my dad was ultimately told that his symptoms were due to stress and depression.  This shocked all of us.  The only time I ever saw my dad seem anything close to depressed was when his father passed away, which was understandable.  He was a professor and loved his job and his students.  It made no sense that his pain, fatigue, and flu-like achiness were from stress or depression.  Three years after these symptoms started, and many doctor visits later, he was diagnosed with colon cancer and died eight months later.  All of his symptoms were consistent with vitamin D deficiency, but no-one ever talked about vitamin D deficiency then.  My dad was an expert in his field, a great humanitarian, positive and ever eager for a new project, an inspiration to all, and his death was truly a great loss. 

At the time my dad was just starting to get sick, this is when John’s-Hopkins’-educated scientists Frank and Cedric Garland were starting to put together the picture that there is a strong association between colon and breast cancer and geographic location [ref: Fox, New York Times, 2010].  The evidence suggested that vitamin D levels were higher and risk of cancer lower in people who lived closer to the equator and that vitamin D levels were lower and risk of cancer higher in people who lived further from the equator. 

Vitamin D, however, appears to be primarily a preventative substance when it comes to cancer and some other diseases, and it has been suggested that vitamin D is most useful when one gets sufficient amounts during childhood, particularly the first year of childhood [ref: Holick].  For someone who already has cancer, it is not yet known if vitamin D will help cure the disease.  As a matter of fact, Dr. Frank Garland, who dedicated himself to vitamin D research, sadly passed away on 8/17/10 of esophageal cancer.  Is this cancer one that vitamin D cannot effectively control, was there a flaw in his genes, was there an environmental toxin that attacked his esophagus, or did Dr. Garland spend most of his life, particularly his childhood, without sufficient vitamin D?  I believe that these are questions that we need to answer to determine just how effective vitamin D is in its apparent anti-cancer actions. 

My dad had colon cancer, which is one of the cancers that is most linked to vitamin D deficiency.  He went through experimental treatments such as monoclonal antibody therapy, and these treatments were unsuccessful.  I imagine that, even as desperate as he and we all were to find a cure for him, if doctors had asked my dad if he wanted to try vitamin D therapy, he probably wouldn’t have taken the suggestion seriously.  What, a vitamin (although we now know it is a hormone)?  For me, I thankfully had a significant source of sun exposure the first 12 years of my life, which I hope will help me and many children whose parents have seen the light, so to speak.  However, for me, I was found to be significantly D deficient in my 40’s, and I am now taking enough vitamin D to keep my blood level at 80-100 ng/ml and keeping my fingers crossed and trying to do other things to help my body like eating right, getting enough sleep, and so on. 

I have now talked to over 100 people in the last year about vitamin D deficiency and the importance of getting tested.  Out of 38 people who have gotten back to me, 33 of them were deficient, which is an 87% deficiency rate.  I have told friends and family, and I approach people wherever I go to ask if they have had their vitamin D tested.  Symptoms and conditions that people have shared with me have ranged from cancer, chronic fatigue, chronic pain, thinning hair and nails, weak legs, restless legs, elevated blood pressure, low thyroid, type I & II diabetes, osteoporosis, multiple sclerosis, foggy brain, insomnia, and more.  Recently, I learned of a baby that was just diagnosed with rickets.  Rickets was first discovered and named in the 1820’s [ref needed].  It was diagnosable and curable then by exposing children to sunlight (i.e. vitamin D) or by giving the children cod liver oil (i.e. vitamin D, but too much vitamin A), and it is diagnosable and curable now.  We are far more medically and technically advanced than to allow the medical profession to allow any cases of rickets to exist in the world today, yet here we are with a case of rickets in 2010. 

Following is an attempt to explain why vitamin D is important, how it might affect you or your family, how to avoid a deficiency, and tips to take to your doctor about getting a vitamin D test and other important tests.  The information below comes from research from top vitamin D scientists and physicians.  I hope that my synopsis will save all of you from having to piece this information together yourselves.  I have included links to websites, video’s, lectures, and vitamin D scientists' contact information adapted from Dr. Cannell’s Vitamin D Council website.  Be sure to visit Dr. Cannell's website and click on the Research link for list after list of research studies, www.vitamindcouncil.org. 

MY CONTINUED QUEST TO LEARN ABOUT VITAMIN D

As a bio-engineering student, I was curious about how something so simple as a vitamin could have such a profound effect on health.  I already knew that vitamin D enabled the absorption of calcium, which is used for proper nerve, muscle, and bone function.  After starting my recent research, I learned that vitamin D was originally called a vitamin because it was isolated from food, although a very short list of food and usually in small amounts.  Because vitamin D was found in food sources, it was put in the same category as other of these "vital amines" that had already been discovered, such as vitamins A, B, and C. Vitamin D was given a "D" in the name because that was the next letter available.  I then learned that vitamin D is actually a kind of hormone, and it is involved in just about every process in the body, from mineral absorption to the direct and indirect regulation of 6,000 genes that control many bodily functions [ref: Holick].  There are vitamin D receptors all over your body [ref: Holick], including in your brain, heart, pancreas, breast and prostate tissue, white blood cells, thyroid, retina, and in your DNA [ref: Holick and others].  You name it, vitamin D receptors are there.

In terms of calcium absorption, I learned that when vitamin D is low, the body can't absorb enough calcium from the diet.  This is where the parathyroid glands come in.  There are four parathyroid glands behind the thyroid in the front of the neck.  The parathyroid glands are biosensors that sense the amount of calcium in the blood.  When calcium is needed, the parathyroid glands secrete parathyroid hormone (PTH), which first asks vitamin D to activate itself and absorb calcium from the digestive system.  If a person's D is low or the person does not ingest enough calcium, PTH then goes to the kidneys for calcium and ultimately to the bones.  Osteoporosis can be one consequence of this system malfunction.  Your brain cannot function without calcium, and this is one reason that PTH will do anything it can to get it, including robbing your bones. 

PTH levels will be high when vitamin D is low because the parathyroid glands are on overdrive.  When a vitamin D deficiency is treated, the PTH should come down.  If this does not happen, medical attention is required, especially if serum calcium is also high.  Sometimes, it can take awhile for the PTH to come down.  For one person I know, it took three months of 9,000 IU's a day of vitamin D before the PTH started to decrease.  Luckily, this person's calcium stayed in the normal range during this time and continues to do so.

I was particularly interested to learn from Dr. Holick that vitamin D directly and indirectly regulates 6,000 genes in the body [ref needed].  This is important because genes are DNA sequences that are recipes that contain the instructions for specific proteins to be produced.  Proteins are the molecular switches that turn functions in your body on and off and allow substances to be carried in and out of the cells and through the blood.  200 of the genes that vitamin D regulates have been discovered to regulate cell proliferation, differentiation, and apoptosis [ref: Holick, Vieth, and others].  One of the implications of this is that vitamin D activates genes that ultimately lead to recognition of cancer cells.  In addition, the action of vitamin D has been found to be able to either turn certain cancer cells into normal cells or cause them to die [ref Holick, regarding leukemia cells].  It is important to note that vitamin D has so far found to be a preventative substance.  That is, vitamin D can help fight cancer cells before they have formed into a tumor.  I have found no research yet that indicates that vitamin D can shrink tumors, where cancer cells have been able to take hold and thrive.

It is well known in the scientific literature that one gene sequence can produce 100's of proteins, and one protein can have 100's of functions.  Imagine the number of functions in the body that are incorrectly turned off or incorrectly left on during a vitamin D deficiency.

In addition to regulating genes and enabling calcium absorption for muscle, nerve, and bone health, vitamin D also enables absorption of magnesium and phosphorus that support muscles, nerves, and bones.  Phosphorus is what allows your energy molecule, called ATP, to provide energy.  Phosphorus is also one of the components of your DNA.  Magnesium is a natural calcium channel blocker and relaxes the muscles.  Research shows that magnesium is especially important for a healthy heart and healthy blood vessels.  When blood levels of magnesium are low, vitamin D absorption is inhibited, and when D is low, magnesium absorption is inhibited.  Alternately, when blood levels of phosphorus are too high, vitamin D is inhibited.  Low levels of these minerals can be either due to a lack of them from the diet, low vitamin D, or from other conditions such as kidney disease and autoimmune diseases like sarcoidosis [ref needed].

One has to consider if it was the chicken or the egg that came first.  In other words, is it low vitamin D that causes the kidneys or immune system and mineral absorption to malfunction, which leads to disease and further abnormalities such as high PTH, high phosphorus, cancer, and diabetes, to name a few, or is it the other way around?  Scientists who have been studying vitamin D seem to indicate that, in most cases, it is low vitamin D, particularly childhood cases of low vitamin D, that came first.  It appears from the research that I have read that all of us have genetic predispositions, and when vitamin D, which regulates genes, is low, this is when the risk of those genetic predispositions increases dramatically and leads to disease.

WHAT IS THE CORRECT BLOOD LEVEL OF VITAMIN D?

Scientists have found that the first 32 ng/ml of vitamin D is reserved for calcium absorption [ref: R. Vieth].  Researchers have also discovered that the body only starts to store vitamin D when blood levels of 50 ng/ml are achieved [ref: Cannell].  Most lab tests indicate that 30-100 ng/ml or 20-100 ng/ml are the normal range.  If the first 32 ng/ml is used for calcium absorption, however, and we do not store any vitamin D until we reach a blood level of 50 ng/ml, it is very misleading that the normal range goes as low as 20 ng/ml, and I hope that this will get corrected someday soon by the people in charge of disseminating this kind of information to the public.  

In autism cases that have recently surfaced, in certain cases, what appears to be a very normal vitamin D level is not.  In a Vitamin D Newsletter from Dr. John Cannell of the Vitamin D Council, one child was reported to have a level of approximately 37 ng/ml, which is well within the normal range of 30-100 ng/ml.  When treated with large doses of vitamin D to bring his level to 80-100 ng/ml, the autism vanished [ref: J.J. Cannell, Vitamin D Newsletter, Feb 2010].  Dr. Cannell’s theory, which he believes will be proven in the next several years, is that children who exhibit autism at vitamin D levels less than 80 ng/ml have an enzyme deficiency that does not allow them to utilize vitamin D at low levels, even if the vitamin D level is within normal range [ref: J.J. Cannell, Vitamin D Newsletter, Jan 2010]. 

Dr. Cannell also theorizes that, while not advised, girls can tolerate a lower vitamin D level because they have more estrogen than boys.  Estrogen can act as a calcium-absorption backup system that is particularly useful in women during pregnancy because pregnant women need to produce more calcium than normal to help build a baby's bones and to assist in nerve and muscle function [ref needed].  This is somewhat of a catch 22 because it seems that not only does estrogen act as a backup system for vitamin D in terms of calcium, but vitamin D also helps produce estrogen [ref needed].  It stands to reason that when vitamin D is low, estrogen will also be low.  Overall, this is a very unhealthy situation, but it still allows females to be able to last longer on low vitamin D levels simply because their bodies are built to make more estrogen. 

Imagine what is going on in anyone's body when vitamin D is less than the "natural" level, or 80 ng/ml, as reported by vitamin D scientists [ref: R. Vieth].  In addition, we are all different, and what is a normal vitamin D level for one person is potentially debilitating for another. 

VITAMIN D, DISEASES, AND OTHER HEALTH CONDITIONS

Successes with vitamin D are not limited to autism.  Vitamin D deficiency has been linked to medical conditions such as cancer, diabetes, osteoporosis, osteopenia, osteomalacia, multiple sclerosis, arthritis, high blood pressure, Crohn's Disease, thyroid disorders, loss of bone density, and nervous system disorders such as schizophrenia and cerebral palsy [ref needed].  An endocrinologist told me earlier this year that the thyroid has nothing to do with vitamin D.  I then found scientific journal articles that clearly show that the thyroid is full of vitamin D receptors.  There must, then, be a strong link between the thyroid and vitamin D.  I believe that a new training system is needed when it comes to medical school training and vitamin D.

The Mayo Clinic ran a study in 2003 and found that effectively 100% of chronic pain patients are vitamin D deficient.  Another Mayo Clinic report states that vitamin D is extremely important in the treatment of chronic pain (http://www.youtube.com/watch?v=JegTunHx6r0).  A recent survey of lymphoma patients showed a strong association between vitamin D deficiency and multiple illnesses in these patients (http://www.youtube.com/watch?v=UgpZ-TylYAM).  More recent news has come out of the Mayo Clinic that treating vitamin D increases chances of survival of lymphoma (http://www.youtube.com/watch?v=UgpZ-TylYAM).  Yet another recent Mayo Clinic Report indicates that vitamin D protects the body "from head to toe" (http://www.mayoclinic.org/news2009-mchi/5417.html). 

UC San Diego has reported a 75% reduced risk of colon cancer if blood levels are maintained between 40-60 ng/ml (100-150 nmol/L) [ref needed].  A recent press release announced virtual eradication of breast cancer by raising vitamin D to "natural levels," or 80 ng/ml (Vieth: www.canadianbusiness.com/markets/cnw/article.jsp?content=20091104_132502_4_cnw_cnw).  Finland reduced its daily recommended intake of vitamin D from 5,000 IU's to 400 IU's.  It was reported that diabetes quadrupled as a result [ref: http://www.uctv.tv/search-details.aspx?showID=16940].

In 1822, it was found that exposure of the skin to sunshine cured rickets in children, a bone development disorder [ref: Weick].  In the early 1900's, it was found that cod liver oil and exposure of the skin to a mercury arc lamp also cured rickets as well as tuberculosis, where tuberculosis sanatoriums were typically located at high altitudes.  In the 1920's and 30's, it was found that vitamin D was the underlying mechanism that cured these disorders.  However, cod liver oil was found to not only contains substantial amounts of vitamin D, it was also found to contain substantial amounts of vitamin A.  Today, it is known that cod liver oil should not be used as a vitamin D supplement as large doses of vitamin A can inhibit vitamin D from functioning and increases the risk of cancer by 16% [Cannell, and government study, ref needed].  The reason that the mercury arc lamp worked was because it is in the same wavelength range as UV-B rays from the sun, where UV-B rays are the rays that produce vitamin D in the skin under the right conditions.  

To reach a large number of children to reduce occurrence of rickets alone, milk was fortified with vitamin D, so why are we still finding cases of rickets in hospitals?  As mentioned earlier, a friend called just yesterday to say that a friend's baby was diagnosed with rickets.  How can this be?  What about tuberculosis?  The National Institutes of Health (NIH) reports that there were 9.2 million cases of tuberculosis and 1.7 million deaths worldwide from tuberculosis in 2006 [need ref].  How?  Bacterial resistance to antibiotics?  Overuse of sunscreen?  Too much time indoors?  Not enough vitamin-D-rich foods in the diet?  Overuse of hats and protective clothing?  No controls over dairies and whether they are fortifying milk appropriately?  Fog and smog that reduce UV-B rays?  Medications or too much vitamin A?  The answer seems to be yes to all of the above.

ONE BILLION PEOPLE WORLDWIDE ARE VITAMIN D DEFICIENT

According to top vitamin D researchers, one billion people worldwide are not getting enough vitamin D [ref: Holick, and many others].  Anyone can be hit with a vitamin D deficiency, including babies, teenagers, and adults of any age.  Particularly hard hit, however, are people with dark skin, people who are overweight, the elderly, and those who live above 34 degrees north and south latitude [ref: Holick, Vieth].  On the West Coast of the US, 34 degrees latitude is approximately the level of San Diego, California.  On the East Coast, this is approximately Atlanta, Georgia.

The NIH states that up to 78% of the US is vitamin D insufficient (<30 ng/ml) and up to 36% is deficient (<20 ng/ml).  Other studies show that 70% of US children are deficient [ref: need ref].  Dr. M.F. Holick says that research points to a lifetime of increased risk of many diseases and conditions when infants do not get adequate vitamin D in the first year of their lives [Holick: www.youtube.com/watch?v=Cq1t9WqOD-0].  Even people who get plenty of sun, drink milk daily, and eat oily fish like salmon can still be vitamin D deficient. 

CAN I GET ENOUGH VITAMIN D FROM MILK AND SUN?

Many doctor TV shows, such as Dr. Oz, The Doctors, and others have reported information about vitamin D.  One report was on the 10/21/09 episode of The Doctors.  In the show it was recommended that ten minutes of sun and drinking milk would provide sufficient vitamin D for everyone.  However, this is not enough information for anyone who is vitamin D deficient (<20 ng/ml) or insufficient (<30 ng/ml), especially for a child with autism, a baby with rickets. or a person with dark skin.

First, researcher and physician, Michael F. Holick tested different brands of US milk.  The brands tested did not have the amount of vitamin D that was advertised on the carton.  Milk should have about 100 IU's per cup.  Not always so.  
[ref: MF Holick, Q Shao, WW Liu, and TC Chen, “The vitamin D content of fortified milk and infant formula,” NEJM, Volume 326:1178-1181, April 30, 1992, Number 18].
 
Second, for vitamin D synthesis from the sun, it is the angle of the sun that determines if vitamin D will be produced in the skin.  In order to know if the angle is high enough, your shadow must be shorter than you are (adapted from M. Mittelstaedt, "The vitamin D miracle: Is it for real? [online]" Globe and Mail, March 8, 2008 at 9:32 AM EST, Available at: http://www.theglobeandmail.com/life/article672998.ece).  This only happens year round if you live near the equator.  Anyone who lives above the latitude of north 34 degrees latitude or below south 34 degrees latitude will only get vitamin D from sensible sun exposure in the late spring, summer, and early fall.  The time of day is only from approximately 10:00am-3:00pm, and these guidelines have to be adjusted depending how far away from the equator the person lives [ref: Holick, Vieth].

Third, skin pigment determines how quickly you synthesize vitamin D from the sun.  According to Dr. Holick, very dark skin is equivalent to SPF 15 sunscreen, which, according to his new book, The Vitamin D  Solution (2010), blocks 95% of vitamin D synthesis.  In his new book, Holick also says that SPF 8 blocks 90% of vitamin D synthesis.  He states that a dark-skinned person needs 5-10x more exposure than a light-skinned person to get the same amount of vitamin D (Holick: www.youtube.com/watch?v=Cq1t9WqOD-0).  One size does not fit all because we all have different amounts of pigment in the skin.

Fourth, researchers have discovered that every 100 IU's of vitamin D that is ingested or synthesized by the sun raises a person's blood level by approximately 1 ng/ml [ref: Holick].  For example, if you are vitamin D deficient with a level of 5 ng/ml, drinking a glass of milk that might contain 100 IU's will raise your blood level by 1 ng/ml.  Your level would then go from 5 to 6 ng/ml, and this is only if you drink one glass of milk every single day, ensuring that it really does have 100 IU's in it, and you will still be deficient. 

Even taking a multivitamin with 400 IU's would only raise your blood level by 4 ng/ml, going from 5 to 9 ng/ml, and, again, you will still be deficient.  To get enough daily vitamin D from milk to go from 5 ng/ml to a bare minimum of 32 ng/ml, one would need to drink 27 glasses of milk a day, every day, but drinking 27 glasses of milk in just one day will result in an overload of calcium and protein and dangerous if not deadly fluid intake levels.

It is even difficult to get enough vitamin D from oily fish because one has to also take into consideration that 1) oily fish is known to have too much mercury to use it as a dietary staple, 2) often, supplies of oily fish like cod and salmon are severely low due to overfishing or other environmental reasons, and 3) even if one ate three servings of oily fish at approximately 300 IU's per serving, this would amount to approximately 900 IU's a day.  A person starting with a level of 5 ng/ml blood level would only increase their level by 9 points, from 5 to 14 ng/ml, which is still in deficiency range.  In addition, there is a difference between farmed and wildcaught fish, where farmed salmon, for example, has 75-90% less vitamin D than wildcaught salmon [ref: Holick].  I wouldn't stop eating Costco farmed salmon because of this, however, because as can clearly be seen, it is really difficult to get enough vitamin D just from food.  

The National Institute of Health’s (NIH’s) USDA Food Database shows that certain salmon have about 750 IU’s of vitamin D per serving.  However, the NIH’s Office of Dietary Supplements has stated, however, that the testing done for vitamin D is not accurate and is under review.  The Office of Dietary Supplements used to have a vitamin D-rich foods that showed that salmon had 300 IU's per serving.  The Office of Dietary Supplements pulled the list off the website sometime between Jan-May 2010 however.  A conference was scheduled for 12/16/09 on this topic.  See links below:
NIH USDA Food Database http://www.nal.usda.gov/fnic/foodcomp/search/
NIH Office of Dietary Supplements: http://dietary-supplements.info.nih.gov/Health_Information/Vitamin_and_Mineral_Supplement_Fact_Sheets.aspx

Fifth, maybe you want to get vitamin D from the sun, but not everyone can tolerate sun exposure.  Some people have skin disorders that prevent them from going in the sun [ref: Holick, UV Advantage, 2003], and there is no way a person who cannot go in the sun can get enough vitamin D from milk, or food, if he/she is vitamin D deficient or insufficient. 

Another example of people who have been reported to not be able to tolerate sun exposure, are people with red hair and freckles.  Per W.B. Grant, people of “Fitzpatrick skin type 1” should never use sunbeds [Grant, W.B., “A critical review of Vitamin D and Cancer,” Dermato-Endocrinology 1:1, 25-33; January/February 2009], and I would assume that this includes exposure to natural sun as well. 

Sixth, for those who can tolerate sun exposure, in order to get a useful dose of vitamin D, per Dr. Holick, one must practice sensible sun exposure when the angle of the sun is optimal, the skin should turn "just pink" but not burned, and then sunscreen should be applied, not before, and the angle of the sun must be optimal as described earlier [ref: Holick, UV Advantage, 2003], in other words, your shadow must be shorter than you are. 

How long one stays in the sun depends on the amount of pigment in the skin.  Sensible exposure of face and hands for a light-skinned person provides about 200-400 IU's, face and arms about 1,000 IU's, and full body exposure about 10,000-20,000 IU's [ref: Holick and Vieth].  Similar to the milk example above, a vitamin-D-deficient person with a blood level of 5 ng/ml will get 1,000 IU's by exposing face, hands, and arms, and this will only raise their level by 10 ng/ml, bringing their level to 15 ng/ml, and they will still be in deficiency range.  Then add to the mix if the person wears sunscreen all the time and if the angle of the sun is too low for vitamin D synthesis. 

Remember, for vitamin D synthesis from exposure to the sun, your shadow must be shorter than you, and the angle depends on the latitude were you live and the time of year and day.

In the end, one cannot just drink milk and go out in the sun for 10 minutes as was advertised on The Doctors show, especially in the case of autistic children, who appear to need a level of 80-100 ng/ml.  There is a lot more to it than that.  The bottom line messages here are: 1)  Deficiency can mean different things depending on your body, such as in the apparent case of autistic children, and 2)  10 minutes of sun and vitamin D from milk and diet will rarely be sufficient for anyone.  In addition, beware of what your doctor tells you about vitamin D as very few doctors are adequately trained in this area at this time.  Do your own research.

WHAT ELSE CAN BE CAUSING WIDESPREAD VITAMIN D DEFICIENCY?

According to research that I have read, age lessens the ability to synthesize vitamin D from the sun by 75%.  Excess body fat affects the availability of D in the body.  Medications such as anti-seizure drugs, thiazides, and glucocorticoids reduce vitamin D in the body [ref is further below].  Some health conditions affect our ability to maintain proper vitamin D, such as primary hyperparathyroidism and sarcoidosis.  Fat malabsorption problems, caused by diseases like Crohn's Disease and celiac disease ("sprue"), can hinder vitamin D absorption from the diet [ref: my endocrinologist].  Gastric bypass surgery bypasses much of the small intestine and vitamin D is primarily absorbed through the small intestines, thus lowering a person's ability to get enough vitamin D from the diet.  Vitamin-D-rich food and supplements do not work well for people with these health conditions, and researchers say that these people must rely on the sun or appropriate use of UV-B tanning beds for vitamin D.  I have heard that doctors may give vitamin D injections in these cases.

Environmental conditions also affect vitamin D levels.  Fog, cloud cover, and smog all lower or eliminate the UV-B rays needed to produce vitamin D in the skin.  Our skin color, age, body fat, use of sunscreen, protective clothing, medications, and medical conditions, and our geographical location all make us different.  We, therefore, all have different vitamin D requirements.  I learned from online University of California "UCTV" video's by Carole Baggerly, breast cancer survivor and avid vitamin D advocate (www.grassrootshealth.net), to think of vitamin D like food.  Do you eat the same amount and same things as everyone else?  No, you have specific needs for your age, weight, height, and genes, and it is the same for vitamin D. 

VITAMIN D SYMPTOMS

Many people who have gotten back to me to tell me that they were found to be vitamin D deficient typically have one or more of the following symptoms, and lab tests usually come back normal: thinning hair and nails, weakening muscles, digestive problems that are often diagnosed as IBS, increasing food allergies, foggy brain, trouble sleeping, trouble staying awake when needed, bladder pain and urinary urgency, an increasing number of infections, agitation that results in yelling and swearing that is not typical of that person, and chronic pain and fatigue.  Some who have gotten back to me have had health conditions such as retinal cancer, high blood pressure, diabetes, and osteopenia, osteomalacia, osteoporosis, and fibromyalgia.  As stated earlier, a case of rickets was recently reported.

A contact of mine said that one of her doctors only runs vitamin D tests on patients who complain of chronic fatigue and pain.  In another case, a contact of mine asked her pediatrician to have her 2-year-old son tested for his vitamin D level, and she was told that since he didn't have bowed legs, which is characteristic of rickets, there was no reason to test for vitamin D.  We both wondered, "Why wait till it gets to that point?  Why not keep track of one's vitamin D as a preventative measure?"  The Bone and Cancer Foundation has stated that all cancer patients will have a low vitamin D level.  What might have happened with these people's lives if they had tracked their vitamin D levels?  Another doctor recently told a friend’s son who asked for a vitamin D test that vitamin D testing is only for women.  Something is very wrong here. 

Vitamin D deficiency is not limited to humans.  Dr. Holick has even treated reptiles and gorilla's in zoo's for vitamin D deficiency [ref: http://www.youtube.com/watch?v=Cq1t9WqOD-0].  Ask your veterinarian for a vitamin D test for your pets.

You do not have to feel ill to be vitamin D deficient.  One person can have a severely low level of 8 ng/ml, and another a very low level of 17 ng/ml.  The person with 8 ng/ml might feel only a little fatigued [ref: personal contact], and the person with a level of 17 ng/ml might be bedridden [ref: personal contact].  We are all different and respond differently.  Don't let yourself, your children, or your elders be victims.  Get tested, and work with your doctor to achieve a healthy vitamin D level.   

HOW DO I KNOW IF I HAVE A GOOD VITAMIN D LEVEL?

Vitamin D scientists and MD's recommend getting your blood level tested.  To do this, you need a 25(OH)D blood test.  Once you get your level tested, the way for your doctor to know how much you need is to follow the "100 IU rule:" every 100 IU's raises the blood level by about 1 ng/ml [ref: Holick]. 

For people who are deficient, the change in vitamin D blood levels seems to vary greatly after starting supplementation.  It is, therefore, very important to get your blood level retested every 4-8 weeks to monitor your progress and make any necessary adjustments until your doctor knows what maintains a healthy vitamin D level for you.  This is all well researched by the scientists and MD's noted below.  In addition, there are other, important blood tests that should be run at the same time as a vitamin D test.  These tests appear in a list further below.

For people whose vitamin D blood level will not rise, these patients will need special treatment.  Per Dr. Michael F. Holick, often the blood test itself is inaccurate.  In other cases, for those who are taking a vitamin D liquid gel cap, Dr. Holick says that the gel cap can be bitten, or emptied into a glass of milk as the gel cap may simply not be broken down by the person's body, and opening the cap may enable proper absorption.  Someone I met recently who tried to give his autistic child vitamin D gel caps had to empty the gel cap into milk because his child would otherwise spit out the gel cap.  As stated above, those who have had gastric bypass surgery may not be able to absorb enough vitamin D through supplementation. 

If you are having problems getting your blood levels to rise, and your doctor cannot help, have your doctor contact one or more of the following vitamin D scientists, many of whom are also physicians.  Or, contact them yourselves if you are not getting answers from your doctor that make sense to you.  Their full contact information appears at the following link: http://www.vitamindcouncil.org/scientists.shtml. 

In brief, these scientists are MD's are:

- Anthony W. Norman, PhD, UC Riverside, anthony.norman@ucr.edu
- Bess Dawson-Hughes, MD, Tufts University, bhughes@hnrc.tufts.edu
- Bruce W. Hollis, PhD, Medical University of South Carolina, Hollisb@musc.edu
- Cedric F. Garland, DrPH, FACE, UC San Diego, cgarland@ucsd.edu
- Christel Lamberg-Allardt, PhD, University of Helsinki, Finland, christel.lamberg-allardt@helsinki.fi
- Edward Giovannucci, MD, SCD, Harvard School of Public Health, edward.giovannucci@channing.harvard.edu
- Frank C. Garland, PhD, Naval Health Research Center, San Diego, (8/17/10 deceased)
- John J. Cannell, MD, Vitamin D Council, info@vitamindcouncil.org
- Michael F. Holick, PhD, MD, Boston University School of Medicine, mfholick@bu.edu
- Reinhold Vieth, PhD, University of Toronto, rvieth@mtsinai.on.ca
- Robert P. Heaney, MD, FACP, FACN, Creighton University Medical Center, rheaney@creighton.edu
- William B. Grant, PhD, SRI International, NASA Langley Research Center, wgrant@sunarc.org

Reports are surfacing that large amounts of vitamin A reduce the activity of D once it's in the body.  Vitamin A, according to Dr. John Cannell [Vitamin D Newsletter, 2/2/10, and www.vitamindcouncil.org], is a co-factor that assists vitamin D, but it is required only in small amounts.  Vitamin A has been well-researched in the literature.  Latest reports indicate that large doses of vitamin A block vitamin D at the receptor level, and government studies reported in 2007 show that large doses increase the risk of cancer. 

A reminder about cod liver oil as a source of vitamin D: cod liver oil is a good source of vitamin D, but it also contains a high amount of vitamin A.  A vitamin D supplement that I saw at Whole Foods has 500 mg of cod liver oil.  According to the NIH USDA Food Database, 500 mg of cod liver oil contains 50,000 IU’s of vitamin A.  According to Dr. Cannell, just 25,000 IU’s of vitamin A is toxic to adults, and 3,500 IU’s is toxic to children.  I strongly encourage everyone to read the label of your vitamin D supplements.

I think that most doctors and nutritionists would agree that we should all make sure to get the USRDA of calcium through the diet or from supplements.  Beware, however, that supplementing with calcium can be detrimental to some people, such as those who have high blood calcium, such as in the case of someone who is immobilized or someone who has an autoimmune disease, kidney disease, or a parathyroid condition.  This is why you want to be seen by a doctor and not self treat.  There is a lot more to it than just taking a supplement.

In addition, Dr. Cannell indicates that zinc, boron, as well as magnesium are co-factors of vitamin D [ref needed].  These minerals can be obtained from the diet or by taking a supplement.  See links given above for the NIH Food Database and the Office of Dietary supplements to find the USRDA for these minerals and talk to your doctor or a nutritionist about what is right for you. 

HOW MUCH VITAMIN D COMES FROM SUN, FOOD, AND SUPPLEMENTS?

Based on research by Dr. Holick (University of Boston Medical Center, book: UV Advantage, 2003) and Dr. Reinhold Vieth (University of Toronto), moderate, sensible exposure to the sun produces the following amount of vitamin D for a light-skinned person when the angle of the sun is optimal.  Reminder: you can measure your shadow and if it is shorter than you, the angle of the sun is optimal for vitamin D synthesis.  As stated earlier, according to Dr. Holick, a dark-skinned person will need 5-10x more exposure, depending on skin pigment.  Per Drs. Holick and Vieth:

For light skin, without sunscreen, till skin turns "just pink," when your shadow is shorter than you are:
•    Face and hands = 200-400 IU's
•    Face and arms or legs = 1,000 IU's
•    Full body = 10,000-20,000 IU's

Researchers have estimated sensible sun exposure as:
•    Red hair and freckles, about 5 minutes (see caution further below)
•    Light skin but no red hair or freckles, about 20 minutes
•    Dark skin, 5-10 times longer than a person with light skin, depending how much pigment is in the skin

Please note that in Dr. Holick's new book, The Vitamin D Solution, and in his earlier book, The UV Advantage, he recommends getting 25-50% of the above exposure times.  Reducing exposure time this way is one way to ensure that one does not get overexposure that would lead to sunburn.  However, this will also lower the above-listed IU values.

According to Dr. Holick, if you have areas of skin that are sun damaged from prior sunburns, sunscreen should be worn on those areas at all times.  Dr. Holick states that the further one lives from the equator, the lower the angle of the sun and the less vitamin D synthesis.  The "vitamin D season" is from about March to October, from about 10:00am-3:00pm.  For areas closer to the North and South poles, this vitamin D window will be shorter, both time of day and number of months.  He states that there is some vitamin D synthesis before 10:00am and after 3:00pm at the right time of the year but that the optimal time is when your shadow is shorter than you are or about 10:00am-3:00pm.

Per Dr. Holick and others, our bodies have a vitamin D biosensor mechanism that protects us from vitamin D toxicity when we get vitamin D from the sun.  The shut-off mechanism is activated when your skin starts to turn "just pink" but not sunburned.  However, this mechanism does not work for vitamin D that is ingested, such as in the form of supplements.  If you take vitamin D supplements, it is recommended to get your blood level of vitamin D tested periodically as you learn how your body responds to vitamin D. 

Recent research indicates that toxicity starts at blood levels of 200 ng/ml, but some people have been reported to have toxicity at 150 ng/ml.  Toxicity results in elevated blood calcium and can be lethal. 

Another word of caution for people with red hair and freckles: according to W.B. Grant, some people cannot tolerate sun exposure without burning and have an increased risk of skin cancers due to the high sunburn risk.  This group of people includes those with red hair and freckles, which is a skin type called “Fitzpatrick skin type 1.”  Many vitamin D researchers suggest that people who have problems absorbing vitamin D from supplements can instead use tanning beds and sun exposure to increase their vitamin D levels.  Dr. Grant says, however, that people with Fitzpatrick skin type 1 should never use sunbeds [Grant, W.B., “A critical review of Vitamin D and Cancer,” Dermato-Endocrinology 1:1, 25-33; January/February 2009].  The key to sensible sun exposure is to never allow the skin to burn.

There is recent research from the University of Wisconsin, the pioneers of current-day vitamin D research, that suggests that sun exposure produces addition beneficial substances other than vitamin D.  These substances are under investigation as potential use for prevention of autoimmune diseases, such as multiple sclerosis.  While vitamin D supplementation is good, perhaps some sensible sun exposure is better.

A small list of foods have vitamin D, and these appear on the Office of Dietary Supplements website: http://dietary-supplements.info.nih.gov/Health_Information/Vitamin_and_Mineral_Supplement_Fact_Sheets.aspx.  There is also an online USDA food database: http://www.nal.usda.gov/fnic/foodcomp/search. 

As stated earlier, if you use the USDA online food database, the Office of Dietary Supplements warns that they do not have a good method of testing for vitamin D yet.  Until they correct their testing methods, I would use the short list on the Office of Dietary Supplements website instead.  A conference was scheduled for 12/16/09 on this topic.

Another reminder about vitamin A:  per Dr. Cannell, vitamin A in large doses causes vitamin D to not work.  In addition, as a reminder, cod liver oil is a good source of vitamin D, but be careful because it also contains a high amount of vitamin A, and vitamin A toxicity and inhibition of vitamin D can occur if you ingest too much cod liver oil.  Just 500 mg of cod liver oil contains 50,000 IU's of vitamin A, twice the level that is reported to cause toxicity in adults and 14 times the level that is reported to cause toxicity in children.

Vitamin D supplements come in two forms, D2 and D3.  D2 is plant based and available by prescription.  D3 is animal based and available over the counter/online.  If you are found to have a vitamin D deficiency, if your doctor knows how to treat a vitamin D deficiency, you will be prescribed 50,000 IU vitamin D2 capsules to be taken once a week for 4-8 weeks, re-tested, and the dosage adjusted accordingly, ensuring that a healthy blood level is maintained.

Taking 50,000 IU's is the same as taking about 7,000 IU's per day.  Dr. Holick writes that he puts vitamin-D-deficient patients on 50,000 IU's of D2 for 4-8 weeks.  He says that once levels normalize, he then puts them on 50,000 IU's of D2 every two weeks for life.  This is the same as taking 3,500 IU's per day for life.  Be sure, though, to get your blood level re-tested.  I know one person who was put on 1,000 IU's after being on the 50,000 IU pill for six weeks.  I met her several months later after she had been on 1,000 IU's for all that time, told her to get re-tested, and her level had already dropped by 10 ng/ml. 

There is controversy about D2 vs. D3.  Some say that D2 is not as effective as D3.  Some say that D2 inactivates D3 in the body.  D3 is the form that your body makes from synthesis of vitamin D sun-exposed skin.  It is up to you (and your doctor) what form you wish to take.  A study evaluated by Dr. Holick showed initially that D2 was not as effective; however, this study did not take some variables into account, and Dr. Holick explains this in the following video: http://www.youtube.com/watch?v=Cq1t9WqOD-0).  Dr. Holick states that D2 in large amounts is equally as effective as D3.  D3 is available online in many dosages, such as 50,000, 5,000, 2,000, 1,000, 800, 600, 400, and 200 IU's.  I have read that certain sundried mushrooms have lots of natural D2 in them, but one would need a regulated and tested source of mushrooms to know how much of the mushrooms to eat.

Per Dr. Holick and in many journal articles, sensible exposure to the sun is said to lower the risk of melanoma-type skin cancers and that people who are low on vitamin D and who get little sun exposure have the highest risk of melanoma.  The exception to this appears to be people with red hair and freckles, known as Fitzpatrick skin type 1, as stated earlier and restated below.

TIPS TO TAKE TO YOUR DOCTOR ABOUT GETTING A VITAMIN D TEST

If you have a doctor who knows how to treat vitamin D deficiency, he/she should know the following (this is an excerpt, sources are noted in brackets, and a list of the sources appears at the end). 

Your doctor should know that:

•    The standard test for vitamin D is the 25(OH)D test (inactive form of vitamin D); there is a second test, called a
      1,25(OH)2D test (active form of vitamin D), and Dr. Holick has written that the second test is never useful; 
      many labs will order the wrong test even if the doctor wrote a lab slip for the right test.

•    Your blood level should be a minimum of 50-80 ng/ml [ref: Dr. J.J. Cannell] and that other reports recommend
     40-60 ng/ml.

•    Vitamin D toxicity occurs at blood levels >200 ng/ml [ref: R. Vieth].  Older reports indicate that toxicity occurs
      at >150 ng/ml. 

•    Latest research as mentioned above shows that breast cancer risk is greatly decreased with a vitamin D blood
      level of 80 ng/ml (www.canadianbusiness.com/markets/cnw/article.jsp?content=20091104_132502_4_cnw_cnw).

•    Every 100 IU’s from sun, food, or supplements raises the blood level by about 1 ng/ml [15].
 
•    Your parathyroid hormone (PTH), calcium [10,16], phosphorus, and magnesium should also be checked
      [17,18,19]; however, note that the blood's job is to maintain all blood components in the normal range; when you
      have a level that is outside the normal range, your doctor will know that this is a serious sign that something
      is wrong; however, with a vitamin D deficiency, the tissue mineral levels can be depleted yet the blood level will
      still be in the normal range; I have read that magnesium is best checked by tissue sample, which is not always
      feasible to do; therefore, vitamin D deficiency therapy should always include magnesium USRDA supplementation as 
      well as calcium USRDA supplementation even if blood levels are normal; most doctors will agree with this; the USRDA
      minimum and upper tolerable intake levels for supplements is available at: 
http://dietary-supplements.info.nih.gov/Health_Information/Vitamin_and_Mineral_Supplement_Fact_Sheets.aspx.

•    You should get vitamin D, PTH, and serum calcium re-tested in 4-8 weeks [3,16] and re-tested periodically to
      determine if adjustments are needed; Beware: if you were D deficient, and your doctor had you on 50,000 IU's of
      D2 once a week for4-8 weeks or so, and he/she drops you to 1,000 IU's a day after your level comes up into normal
      range, your level will drop again, guaranteed.  Prove me wrong and get a retest after another 4-8 weeks on 
     1,000 IU's.

•    Most people should ingest at least the USRDA of calcium daily, which is on the dietary supplements website above;
      however, people with high calcium levels need special medical evaluation as suggested below.

•    Co-factors assist vitamin D, such as vitamin K, zinc, boron, magnesium, SMALL amounts of vitamin A, and a substance
      called genestein (an isoflavone found in soybeans) [18] and should be supplemented or obtained through
      the diet; see the USRDA website above for minimum and upper tolerable intake levels for vitamins and minerals.

•    Vitamin A in large doses (25,000 IU's for an adult, 3500 IU's for a child), block vitamin D from functioning in the body
      [Dr. John Cannell, www.vitamindcouncil.org, Vitamin D Newsletter, Feb 2, 2010]; Beware: just 500 mg of cod liver oil
      contains 50,000 IU's of vitamin A and some vitamin D supplements contain this amount.  Also be aware that there
      are some websites that indicate that if you have a higher vitamin D level, one can tolerate a higher amount of
      vitamin A, but I have found no research to substantiate this.

•    Medications such as many anti-seizure/anti-epileptic medications, thiazides, and glucocorticoids [10],
      low magnesium [17], high phosphorus [10,16], and large doses of vitamin A can inhibit vitamin D.

•    Elevated blood calcium and PTH or abnormally high vitamin D are signs of other, serious health conditions
      [10,19,21]; if you have elevated calcium and/or PTH, ask to see an endocrinologist about a parathyroid condition
      and other conditions that can cause high calcium.  During the 1st month that I was taking the 50,000 IU vitamin D2
      capsule 1x/week, I got very bad muscle cramps and 400-800 mg magnesium/day eliminated them.  I also had in the
      2nd month a slightly elevated calcium level of 10.4 mg/dl, where the high end of normal is ~10.2 mg/dl.  I had
      very elevated urine calcium as well -- it was found that I was ingesting ~2,000 mg calcium/day due to a large
      amount of calcium in our well water as well as additional calcium from dairy products that I ate or drank 3-4 times/day.
      One month after correcting my calcium intake, my blood and urine levels were at a normal level.  If your doctor tells
      you that it's the vitamin D that is causing the high calcium, ask him/her to evaluate your diet and do some deep
      research about vitamin D and hypercalcemia.  Research strongly indicates that the only time that vitamin D can cause
      hypercalcemia is when there is another condition present, such as kidney disease, sarcoidosis, and some other
      conditions that your doctor will be aware of.  Do not let him/her immediately blame vitamin D.  Start
      with having an evaluation of your diet and getting some blood tests to rule out other conditions.


•    Vitamin D lab tests are known to contain an approximate 20% error, so if the patient is at the low or high end
      of normal, this should be taken into account when determining a treatment plan.  For example, a level of ~64 ng/ml 
      is actually ~50 ng/ml after deducting the 20% error.  A level of 50 ng/ml would be 40 ng/ml after deducting the 20%
      error.

•   If your doctor has not been trained in vitamin D, ask your doctor to review the references below and to contact the
     many scientists for more information; many of the scientists are also MD's.

WHERE TO GET YOUR VITAMIN D BLOOD LEVEL TESTED

•    A lab order from your doctor that you can take to the lab covered by your insurance
•    A $60 home test kit (can be done every 6 months until 5-year study ends); go to www.grassrootshealth.net
      (this test used to be $40)
•    A $65 home test kit that can be done as often as you like: go to www.vitamindcouncil.org

WHERE TO GET SCIENTIFIC INFORMATION ABOUT VITAMIN D

A consortium of top vitamin D scientists and physicians has gathered on www.grassrootshealth.net below.  Three of these scientists and doctors have websites of their own and other materials on the web as follows.  You will find list after list of compelling scientific research articles and other information that I hope will encourage you to get your blood level checked and get vitamin D healthy:
•    www.grassrootshealth.net (consortium of the top scientists, founded by breast cancer survivor, Carole Baggerly)
•    www.vitamindhealth.org (Dr. Michael F. Holick)
•    www.vitamindcouncil.org (Dr. John J. Cannell) -- click on the research tab and see endless lists of studies
•    www.sunarc.org (Dr. William B. Grant)
•    www.vitamindsociety.org (Canadian non-profit group)

Journal articles and online video’s

•   NEW! http://www.youtube.com/watch?v=onSPZ0aBUKM (2011 Abbott Labs video on Vitamin D function)
•   http://content.nejm.org/cgi/content/extract/357/3/266 (New England Journal of Medicine, Dr. M.F. Holick)
•   http://www.youtube.com/watch?v=Cq1t9WqOD-0 (Dr. M.F. Holick, including gorilla and iguana vit D deficiency)
•   http://www.youtube.com/watch?v=emjCzaHtSrg (Dr. Robert Heaney lecture)
•   http://www.uctv.tv/search-details.aspx?showID=16940 (Carole Baggerly, founder of Grassrootshealth.net)
•   http://www.uctv.tv/search-details.aspx?showID=15773 (Dr. Michael Holick lecture)
•   http://www.direct-ms.org/Presentations/Vieth/index.html (Dr. Reinhold Vieth lecture, link updated 7/27/11)
•   http://www.youtube.com/vitamindcouncil (Dr. John J. Cannell)
•   www.canadianbusiness.com/markets/cnw/article.jsp?content=20091104_132502_4_cnw_cnw (11/09 Breast Cancer Newswire)

CONVERSION FACTORS FOR COUNTRIES OUTSIDE THE U.S.

ng/ml * 2.5 = nmol/L           //       nmol/L / 2.5 = ng/ml     
IU * 0.025 = micrograms    //         microgram / 0.025 = IU’s

VITAMIN D REFERENCES

[1] National Institutes of Health, "Dietary Supplement Fact Sheet: Vitamin D," Available at: http://ods.od.nih.gov/factsheets/vitamind.asp (Accessed 4 September 2009).
[2] J.H. Tanne, “US Children are not Getting Enough Vitamin D, Studies Conclude,” British Medical Journal, 339, pg. b3277 (2009), Available at:  http://www.pbs.org/newshour/bb/health/july-dec09/vitamin_08-03.html (Accessed 13 September 2009).
[3] M.F. Holick, "Vitamin D Deficiency," New England Journal of Medicine, 357, pp. 266-281 (2007).
[4] J.J. Cannell, R. Vieth, J.C. Umhau, M.F.  Holick, W.B. Grant, S. Madronich, C.F. Garland, and E. Giovanucci, “Epidemic Influenza and Vitamin D,” Epidemiology and Infection, 135 (7), pp. 1-12 (2006).
[5] L. Jeng, A.V. Yamshchikov, S.E. Judd, H.M. Blumberg, G.S. Martin, T.R. Ziegler, and V. Tangpricha, “Alterations in Vitamin D Status and Anti-Microbial Peptide Levels in Patients in the Intensive Care Unit with Sepsis,” Journal of Translational Medicine, 7 (1), pg.28 (2009).
[6] M. Zasloff, “Fighting Infections with Vitamin D,” Nature Medicine, 12, pp. 388-390 (2006).
[7] M.F. Holick, “Evolution and Function of Vitamin D,” Recent Results in Cancer Research, 164, pp. 3-28 (2003).
[8] Sister M.T. Weick, “A History of Rickets in the United States,” The American Journal of Clinical Nutrition, 20 (11), pp. 1234-1241 (1967).
[9] P. Chocano-Bedova and A.G. Ronnenberg, “Vitamin D and Tuberculosis,” Nutrition Reviews, 67 (5), pp. 289-93 (2009).
[10] L. Shinchuk and M.F. Holick, "Vitamin D and Rehabilitation: Improving Functional Outcomes," Nutrition in Clinical Practice, 22 (3), pp. 297-304 (2007).
[11] C.F. Garland, E.D. Gorham, S.B. Mohr, F.C. Garland, “Vitamin D for Cancer Prevention: Global Perspective,” AEP, 19 (7), pp. 468-483 (2009).
[12] J.J. Cannell, Vitamin D Council, “Vitamin D Research,” Available at: www.vitamindcouncil.org/research.shtml (Accessed 25 May 2009).
[13] M.B. Demay, P.N. MacDonald, K. Skorija, D.R. Dowd, L. Cianferotti, M. Cox, “Role of the Vitamin D Receptor in Hair Follicle Biology,” Journal of Steroid Biochemistry & Molecular Biology (2007).
[14] C.A. Baggerly and C.F. Garland, “Is it True? A Public Health Program on Vitamin D and Disease Prevention Sponsored by GrassrootsHealth,” Vitamin D-Action, A Consortium of Scientists, Institutions, and Individuals Committed to Solving the Worldwide Vitamin D Epidemic, Available at: www.grassrootshealth.net/media/download/vit_d_baggerly_tv.pdf (Accessed 25 October 2009).
[15] M.F. Holick, "Vitamin D and Sunlight: Strategies for Cancer Prevention and Other Health Benefits," Clinical Journal of the American Society of Nephrology, 3 (5), pp. 1548-1554 (2008).
[16] M.F. Holick, “The D-Lemia For Preventing Secondary Hyperparathyroidism in Chronic Kidney Disease,” Endocrine Practice, 14 (1), pp. 6-9  (2006).
[17] H. McCoy and M.A. Kenney, “Interactions between Magnesium and Vitamin D: Possible Implications in the Immune System,” Magnesium Research, 9 (3), pp. 185-203 (1996).
[18] J.J. Cannell, “More Vitamin D Questions and Answers, Magnesium and Vitamin D,” Vitamin D Newsletter July 2009, Available at: www.vitamindcouncil.org/newsletter/more-vitamin-d-questions-and-answers.shtml (Accessed 25 May 2009).
[19] V. Reddy and B. Sivakumar, “Magnesium-dependent vitamin-D-resistant rickets,” The Lancet, 1 (7864), pp. 963-965, (1974).
[20] K.A. Touhy and T.I. Steinman, “Hypercalcemia Due to Excess 1,25-dihydroxyvitamin D in Crohn's disease,” American Journal of Kidney Disease, 45 (1), pp. e3-6 (2005).
[21] J.J. Cannell and B.W. Hollis, “Use of Vitamin D in Clinical Practice,” Alternative Medicine Review, 13 (1), pp. 6-20 (2008).
[22] M.F. Holick, “The Vitamin D Epidemic and its Health Consequences,” Journal of Nutrition, 135 (11), pp. 2739S-2748S (2005).
[23] M.F. Holick, “Sunlight and vitamin D for bone heal