Are you taking too much?
Few people now question the importance of this vitamin, and with the benefits being touted in the media (without mention of potential problems), many consumers, and doctors, now think that the more they take the healthier they will be. I want to caution you of the risk regarding excessive intake. Vitamin D taken in high amounts can cause excessive calcification of bone, calcification of soft tissues, kidney stones, headaches, weakness, nausea, and vomiting. Are there currently unknown long term effects of daily high dose use? Does the production of this vitamin through sun exposure influence the body differently than through pill intake?

Testimonial of side effects received by email
According to my blood work my vitamin D3 level was considered deficient (11 ng/ml). My doctor prescribed me to take 50,000 IU once a week for 8 weeks. After taking the high dosage she instructed me to follow up with taking 2,000 IU daily. I've been feeling horrible lately. I'm tired, have a restless sleeping pattern, dealing with muscle (spams also) and bone pain, my joints pop when I move, brain fog, dehydration, dry eyes, blurred vision, bouts of anxiety and depression (which I've never had before). Ever since then I've stopped taking the vitamin. I'm currently at 38 ng/ml. I was a healthy 38 year old woman until I started taking the high dosage of vitamin D3. P.S. I was taking a chelated magnesium supplement (100 mg) for the muscle spams on a nightly basis but I noticed the following morning I would awaken depressed.

I am from Pakistan. Here people think that their vitamin d3 is low and if tested it also proves it (even the country is situated near equator). I is common that without consulting a doctor to take injection of Vitamin D3 or capsules. Secondly in the market, 200,000 iu / 5 mg Vitamin D3 injections and softgel capsules are available which are common. I have taken one of these capsules (200,000 iu) without doing a blood test as in our family everyone is on the lower end. It's almost a 24 hours and I am having restless night with pain in my both hands, legs and back. For a few days I was also taking Surbex everyday.

My current recommendations (I may change my mind as more research is published)
Some people may not need to supplement since their diet includes plenty of the vitamin and they get a lot of sun exposure. In a study with Asian subjects, 45 min sunlight exposure at noon of a casually clothed individuals exposing about 30 percent of their body to sun, 3 times a week for 6 weeks, led to an average increase in the blood level of about 8 ng/ml. Am J Clin Nutr. June 2013. Efficacy of a dose range of simulated sunlight exposures in raising vitamin D status in South Asian adults.Most people may benefit from taking 400 units to 1000 iu a day either as a separate pill or as part of their multivitamin product (in addition to their diet and some sun exposure which could be several hundred units a day).
A few people -- those who do not consume much of this vitamin in their diet, live in Northern latitudes, or some elderly who get little sun -- may benefit from taking 600 to 2000 units daily. More is needed in the winter season and less in the summer season.
Those who have hardly any sun exposure, or have certain chronic medical conditions, may need 2000 to 3000 units a day for a few weeks or months and then down to 1000 to 2000 units daily.
The vast majority of people do not need to be monitored by blood tests. Just take 1000 units a day if you are not sure if you are getting enough and don't waste time and money on regular blood tests.There is no need for the vast majority of Americans to take more than 2,000 units a day for the long run.
There could be a detriment to taking 5,000 or 10,000 units a day. Many people are taking an unnecessary gamble taking these very high amounts.
I do not think that the average person with a good diet and some regular sun exposure needs to take more than 1000 iu a day as a supplement. I have received emails from some doctors who claim I am being too cautious. I would rather err on the side of taking less until long term studies are published regarding the safety of supplementing with 5000 units or more taken daily for a decade or several decades. If such studies do get published in the next few years that show the safety of high dose supplementation, I will change my recommendations. At this time I certainly do not think the 5000 iu pills being promoted are appropriate for the vast majority of the population, and certainly not the 10,000 iu pills. Could people taking these high dosages end up dying sooner due to excessive calcification of their blood vessels and soft tissues? There is some early indication that high dosages of vitamin D could cause calcification of vessels in the brain leading to mental decline. Could excess intake lead to calcification of various tissues in the body including the sinus node and atrial node responsible for heart rhythm maintenance? What about interactions with other medications and supplements? Could taking high doses of calcium along with these excessive doses of vitamin D make matters even worse?As with many natural vitamins and supplements, too low a dosage can be detrimental to health and too high an intake can have adverse effects.

Side effects, caution, safety, danger, toxicity, harm of taking too much
High dosages of vitamin D may cause short term or long term side effects. Excess intake makes the intestines absorb too much calcium. Headache, nausea, vomiting, loss of appetite, dry mouth, abdominal or bone pain, muscle pain, fatigue and dizziness are some of the symptoms of vitamin D toxicity. Itching, impaired kidney function, calcification of organs and blood vessels, osteoporosis, and seizures are other signs that develop at the later stages.
   The vitamin D receptor is now known to be present in dozens of tissues. It is possible that taking high dosages can reduce cancer incidence, but it could increase the incidence of other medical conditions. Until more research is published regarding the influence of high dose intake over a decade or more, I prefer keeping dosages to below 2000 units a day unless a person has a severe deficiency. High dosages could cause atrial fibrillation or cause other types of cardiovascular problems.

Sun exposure a few minutes a day
A few minutes a day of midday summer sun can raise most fair-skinned people's vitamin D levels to sufficient, but not optimal, levels. Those with darker skin need longer time of exposure. The skin's production of vitamin D upon exposure to ultraviolet B radiation in sunlight is the body's predominant source for the hornone. Dr. Lesley E. Rhodes of Salford Royal NHS Foundation Hospital in Manchester  exposed 109 fair-skinned men and women to light equivalent to 13 minutes of midday summer sun three times a week for six weeks. Study participants wore shorts and T-shirts during their brief sun baths. The study was done during the winter months, when people would be getting very little vitamin D from sunlight, to focus on the effects of the sun baths. All of the study participants had low vitamin D intakes, and none were taking vitamin D supplements. Participants' average blood level of vitamin D rose from around 18 nanograms per milliliter to 28 nanograms per milliliter. Some doctors think 20 nanograms per milliliter and above is sufficient, and 32 nanograms per milliliter and above is optimal whereas other doctors think people should have a minimum of 40ng/ml. Based on the results, Dr. Lesley E. Rhodes predicted that with this amount of sun exposure, 90 percent of white adults in Manchester under the age of 65 would have sufficient vitamin D levels, while 26 percent would have optimal levels. Depending on latitude, the average amount of sun exposure required for similar effects in North America would range from nine to 16 minutes. Journal of Investigative Dermatology, online January 14, 2010.
   
How it is made
When humans are exposed to sunlight, 7-dehydrocholesterol in the skin absorbs UVB (290–315 nm) radiation resulting in the production of vitamin D3, also known as cholecalciferol. Vitamin D3 is found naturally in cod liver oil and oily fish such as salmon. Vitamin D3 is also made by irradiating 7-dehydrocholesterol obtained from lanolin from sheep’s wool with UVB radiation. Vitamin D2, known as ergocalciferol, which comes from the UV irradiation of ergosterol obtained from yeast, has been the mainstay for the prevention and treatment of vitamin D deficiency in children and adults.
   Both vitamin D2 and vitamin D3 when ingested undergo metabolism in the liver to form 25-hydroxyvitamin D [25(OH)D; D represents either D2 or D3] and in the kidneys to 1,25-dihydroxyvitamin D. Both vitamin D2 and vitamin D3 are available in supplements, but only vitamin D2 is available as a pharmaceutical preparation because its use predated the Food and Drug Administration and, thus, was grandfathered as a pharmaceutical drug. Vitamin D3 was commercially developed in the 1950s and has not been approved as a pharmaceutical agent in the United States but is used in food supplementation and vitamin supplements.

During sun exposure, the solar ultraviolet B photons (290-315 nm) penetrate the skin where they cause the photolysis of 7-dehydrocholesterol to precholecalciferol. Once formed, precholecalciferol undergoes a rearrangement of its double bonds to form cholecalciferol. Those who are dark skinned and older make less. Application of sunscreen reduces production.

Through windows and glass
Because windowpane glass absorbs ultraviolet B radiation, exposure of sunlight through glass windows will result in little or production of cholecalciferol.

Note: Dozens of studies have shown that people with high levels in their blood have lower rates of diseases and a lower death rate. However, that doesn't prove that people can lower their risk of illness by taking a supplement to raise their vitamin D level. Perhaps sun exposure itself, being active outside, or other factors associated with high blood levels of vitamin D in the blood, influence disease risk. Previous research had suggested that high levels of beta carotene were associated with lower rates of cancer, but when people took beta carotene supplements as part of a clinical trial, they were more likely to die from cancer. Thus far it appears that those with low levels of this hormone can improve their health by taking supplements, but more evidence is needed to prove this likely hypothesis.

Cancer prevention
Cancer researchers are urging people to take a vitamin D supplement to lower their risk of colon, pancreatic, prostate, breast and ovarian cancer, saying studies showed a clear link.

Breast cancer prevention or treatment
Supplementation appears to reduce the risk for breast cancer.

Breast cells have receptors for vitamin D, raising the possibility that the nutrient could help regulate the division and proliferation of these cells; there's also growing evidence that vitamin D could help protect against other types of cancer. Laura N. Anderson, a doctoral student at Cancer Care Ontario in Toronto, sought to separate out the effects of vitamin D and calcium on breast cancer risk by surveying 3,101 breast cancer patients and 3,471 healthy controls about their intake of food and supplements. No relationship between overall vitamin D intake and breast cancer risk was found; nor was there any association between overall calcium intake and risk of the disease. However, women who reported taking at least 400 international units of vitamin D every day were at 24 percent lower risk of developing breast cancer. American Journal of Clinical Nutrition, online April 14, 2010.

Bladder cancer prevention
Nutrition. 2016. Comparative efficacy of vitamin D status in reducing the risk of bladder cancer: A systematic review and network meta-analysis. Ensuring sufficient serum 25-hydroxyvitamin D concentrations might play an important role in decreasing the risk of bladder cancer. The serum 25-hydroxyvitamin D concentration ≥74 nmol/L was associated with a 60% lower risk of bladder cancer incidence.

Vitamin D and prevention of breast cancer: pooled analysis.
Inadequate photosynthesis or oral intake of Vitamin D are associated with high incidence and mortality rates of breast cancer in ecological and observational studies, but the dose-response relationship in individuals has not been adequately studied. A literature search for all studies that reported risk by of breast cancer by quantiles of 25(OH)D identified two studies with 1760 individuals. Data were pooled to assess the dose-response association between serum 25(OH)D and risk of breast cancer. According to the pooled analysis, individuals with serum 25(OH)D of approximately 52 ng/ml had 50% lower risk of breast cancer than those with serum <13 ng/ml. This serum level corresponds to intake of 4000 IU/day. This exceeds the National Academy of Sciences upper limit of 2000 IU/day. A 25(OH)D level of 52 ng/ml could be maintained by intake of 2000 IU/day and, when appropriate, about 12 min/day in the sun, equivalent to oral intake of 3000 IU of Vitamin D(3). Intake of 2000 IU/day of Vitamin D(3), and, when possible, very moderate exposure to sunlight, could raise serum 25(OH)D to 52 ng/ml, a level associated with reduction by 50% in incidence of breast cancer, accorMarch; Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick MF, Garland FC. Department of Family and Preventive Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA, USA.
    Comments: Those who had higher levels of vitamin D probably were outside more often, did they exercise more? Did they sleep better due to exercise and sun exposure? Did these influence breast cancer risk also and not just the vitamin D production?

Colon cancer prevention
When epidemiologists began mapping the incidence of colon cancer in the United States back in the 1970s, they noted a curious pattern. People in the South were half as likely to die of colon cancer as those in the Northeast. Could the reason be the sunshine vitamin D?

Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis.
Previous studies, such as the Women's Health Initiative, have shown that a low dose of vitamin D did not protect against colorectal cancer. Five studies of serum 25(OH)D in association with colorectal cancer risk were identified using PubMed. A 50% lower risk of colorectal cancer was associated with a serum 25(OH)D level > or =33 ng/mL, compared to < or =12 ng/mL. The evidence to date suggests that daily intake of 1000-2000 IU/day could reduce the incidence of colorectal with minimal risk. Am J Prev Med. 2007. University of California San Diego, Department of Family and Preventive Medicine, School of Medicine, La Jolla, California, USA.

Dr. Mazda Jenab of the International Agency for Research on Cancer in Lyon, France, reports that among more than 1200 people who developed colorectal cancer and an equal number who did not, those with the highest levels of vitamin D in their blood had a nearly 40 percent reduced risk of developing colorectal cancer compared to those with the lowest levels. Dr. Mazda Jenab cautions that this has to be balanced regarding the potential toxic effects of too much vitamin D and the fact that very little is known about its association with either increased or reduced risk of other cancers. British Medical Journal Online First, Jan 22, 2010.

Lung cancer
Plenty of sunshine and vitamin D may help people with early stage lung cancer survive longer after surgery. Patients who have high levels of vitamin D and had lung cancer surgery in sunny months are more than twice as likely to be alive five years after surgery compared to patients with low levels who had surgery in the winter.

Osteoarthritis, arthritis
J Nutr. 2014. Vitamin d deficiency is associated with progression of knee osteoarthritis.

Pancreatic cancer
Consumption of Vitamin D tablets was found to cut the risk of pancreatic cancer by 40 percent, according to a study led by researchers at Northwestern and Harvard universities. The study, led by Halcyon Skinner, Ph.D., of Northwestern, appears in the September, 2006 issue of Cancer Epidemiology Biomarkers & Prevention. The study examined data from two large, long-term health surveys and found that taking the U.S. Recommended Daily Allowance of Vitamin D (400 IU/day) reduced the risk of pancreatic cancer by 43 percent. By comparison, those who consumed less than 150 IUs per day experienced a 22 percent reduced risk of cancer. Increased consumption of the vitamin beyond 400 IUs per day resulted in no significant increased benefit.

Prostate cancer
Vitamin D supplements may slow or prevent low-grade prostate cancer from progressing, March 22, 2015, presentation, American Chemical Society meeting, Denver.

Depression
Older men and women with lower levels of vitamin D in their blood are more prone to become depressed over time. The study does not prove that low vitamin D levels cause depression; people with low levels of the nutrient might have other characteristics that predispose them to the blues or spending time outdoors. Journal of Clinical Endocrinology and Metabolism, online May 5, 2010.

Vitamin D and depressive symptoms in women during the winter: a pilot study.
Research indicates that vitamin D supplementation may decrease depressive symptoms during the winter months. In this study, nine women with serum vitamin D levels <40 ng/ml were administered the Beck Depression Inventory (BDI)-II. After vitamin D3 supplementation, six of these women completed the BDI-II and had their serum vitamin D levels reassessed. Vitamin D supplementation was associated not only with an increase in the serum D levels by an average of 27 ng/ml but also with a decline in the BDI-II scores of an average of 10 points. This study suggests that supplemental vitamin D3 reduces depressive symptoms. Appl Nurs Res. 2009. Washington State University, Richland, WA, USA.

Fibromyalgia pain reduction
Reporting in the February 2014 issue of the journal Pain, researchers said those who took supplements for a few months reported less pain and morning fatigue over time than those who did not receive them.

Gum disease
People with higher blood levels of vitamin D may be less likely to develop gum disease. Using data from a national U.S. health survey, researchers found that teenagers and adults with the highest blood levels of vitamin D were 20 percent less likely than those with the lowest levels to show signs of gingivitis -- a milder form of gum disease in which the gums become swollen and bleed easily. The study can only show that there's an association between vitamin D status and gum health, and not that the vitamin is providing the benefit.

Heart disease, heart attack, MI, heart failure.
Vitamin D supplementation might protect against cardiac failure in older people but does not appear to protect against MI or stroke. Cardiovascular disease and vitamin D supplementation: trial analysis, systematic review, and meta-analysis. Am J Clin Nutr 2014.

Immune system benefit
T cells of the immune system rely on vitamin D to become active and remain dormant and unaware of the possibility of threat from an infection or pathogen if vitamin D is lacking in the blood. Carsten Geisler of Copenhagen University's department of international health, immunology and microbiology, proposes that when a T cell is exposed to a foreign pathogen, it extends a signaling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D. This means the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won't even begin to mobilize.

In a study of Japanese schoolchildren, vitamin D supplements taken during the winter and early spring reduced seasonal flu and asthma attacks. According to Dr. Mitsuyoshi Urashima of Jikei University School of Medicine, Tokyo, the idea for the study came from an earlier one looking at whether the supplement could help prevent osteoporosis. Dr. Mitsuyoshi Urashima noticed that people taking vitamin D were much less likely to report cold and flu symptoms. American Journal of Clinical Nutrition, online March 10, 2010.

Lupus, systemic lupus erythematosus
Serum concentrations have been found to be inversely related to lupus disease activity.

Multiple sclerosis
There appears to be a higher relapse rate in those with low levels. Perhaps supplementation could reduce the risk for relapse of multiple sclerosis.

Osteoarthritis
Boston researchers report a link between low serum levels of vitamin D and decreased knee function in patients with osteoarthritis of the knee. At the annual meeting of the American College of Rheumatology in San Antonio, researchers presented findings from 221 subjects recruited from the Boston VA Medical Center. All had knee arthritis and reported knee pain on most days in the month before they joined the study. The investigators measured blood levels of vitamin D at the start and again after 15 and 30 months. They compared change in vitamin D levels with changes in knee pain, physical function and muscle strength during the 30-month study period. Low levels were associated with higher levels of pain and disability and to a lesser extent muscle weakness. The researchers also found that about 50 percent of the population were deficient in vitamin D.

Seniors
Older Americans need more vitamin D to help strengthen bones than what current guidelines recommend. Men and women age 50 and older should take about 600 to 1000 international units of vitamin D each day. Sunscreen, protective clothing and time spent indoors already keep most older Americans from getting enough vitamin D from exposure to sunlight's ultraviolet-B rays.

Teenage girls
Many adolescent girls have low vitamin D levels, especially non-white girls. Reduced sunshine exposure is probably more of a factor than dietary intake. Vitamin D deficiency during childhood and adolescence might impair the acquisition of peak bone mass at the end of skeletal growth and maturation, thereby increasing the risk of osteoporotic fracture later in life. A vitamin D supplement could be of benefit.

Deficiency symptoms and signs
Deficiency symptoms refer to various symptoms that a patient notices, and deficiency signs refers to physical signs that can be seen. Deficiency results in lowered absorption of calcium and phosphorous. Prolonged vitamin D deficiency has a negative impact on bone mineralization and leads to several bone diseases including: Rickets: a childhood disease characterized by failure of growth and deformity of long bones. Osteoporosis; and Osteomalacia: a bone-thinning disorder in adults that is characterized by proximal muscle weakness and bone fragility. Osteomalacia can only occur in a mature skeleton. As little as 100 IU vitamin D2 is effective in the prevention of rickets.
   Rickets appears to be the tip of the vitamin D deficiency iceberg. There is evidence that vitamin D deficiency is still common in children and adults even though certain foods have been fortified with the vitamin. In utero and during childhood, vitamin D deficiency can cause growth retardation and skeletal deformities and may increase the risk of hip fracture later in life. Vitamin D deficiency in adults can precipitate or exacerbate osteopenia and osteoporosis, cause osteomalacia and muscle weakness, and increase the risk for certain cancers.
   Children with inflammatory bowel disease have a high prevalence of vitamin D deficiency.
   In all regions of the world, more than half of postmenopausal women with the crippling bone disease osteoporosis are vitamin D deficient.
   Soft drink, juice and iced tea intake are related to a greater risk of vitamin D deficiency. On the other hand, adolescents who drink milk and eat cereal are less likely to be deficient on the vitamin.
   About a quarter of Britons suffer from a winter deficiency of vitamin D, which can increase the risk of muscle weakness, autoimmune diseases, osteoporosis and certain types of cancer. Britain's northern location and lack of sunshine means that during the winter months many people do not get enough vitamin D, which the body makes when it is exposed to sunlight. Foods such as oily fish and egg yoke are rich in vitamin D and breakfast cereals and margarine are fortified with it, but it might not be enough to get Britons through the winter months when their stores of vitamin D diminish.
   Deficiency is widespread in India, Pakistan, and South Asia.
   People taking oral steroids increase their risk for deficiency, which can lead to bone disease or muscle weakness.

Adolescents and teenagers
Vitamin D deficiency may be a common but unrecognized problem among U.S. adolescents. Researchers found that among 11- to 18-year-olds living in Boston, nearly one-quarter were deficient in vitamin D, a nutrient that aids in calcium absorption and is vital for healthy bone development. The problem is preventable with an adequate diet and time outdoors. The body naturally synthesizes vitamin D when the skin is exposed to the sun, and milk and certain other foods, including many breakfast cereals, are fortified with the vitamin. But U.S. children increasingly fill up on soft drinks at the expense of milk, and spend more time in front of the TV or computer than outdoors.

Blood levels and testing
Unless a person has an unusual diet or a chronic health condition that could lead to severe vitamin D deficiency, I don't think testing is necessary before starting a supplement. Some scientists believe that optimal serum 25-hydroxyvitamin D [25(OH)D] level should be greater than 60 nmol/L. Another measurement is serum hydroxyvitamin D level of 40 to 60 ng/ml. In older adults, a serum 25-hydroxyvitamin D concentration greater than 60 nmol/L lowers the risk of fracture. However, I am still not convinced that we know the ideal dosage to supplement with based on blood test results. In January of 2010 I attended Natural Supplements: An Evidence-Based Update, a conference sponsored by Scripps clinic in La Jolla, CA. I asked several doctors who were attending the conference what dosage of vitamin D they would recommend to a patient who had a blood level of 40 ng/ml. The range of responses was from 0 units to 5000 units daily!! Since there is no medical consensus on how much to dose based on blood levels, what's the point of testing? Let's just give everyone 400 to 2000 units a day based on the patient's desire and sun exposure. Those who are overweight or obese tend to have lower blood levels.

Reasons not to test
There are hundreds of blood tests available to check levels of different vitamins, minerals, amino acids, hormones, cholesterol, various lipids, inflammation markers, liver function studies, kidney studies, etc., etc.. At some point one has to balance the costs and inconvenience of testing versus the potential benefits they provide.  There is no proof at this time that testing, and rechecking levels a few times a year, improves health or increases longevity. In the USA we already spend more than 7000 dollars a year per person for healthcare. Do we really need to add another few hundred dollars a year per person on regular vitamin D level testing and the doctor visits? I am cost conscious and practical in my approach. I think in this country we are going overboard in terms of testing, and for the amount of money we spend on diagnostic testing and health care we are not even close to being one of the healthiest nations on the planet. We do so many diagnostic tests in this country without knowing whether people are actually healthier or live longer as a result of the testing. The people who end up being better off are doctors and the those who own the labs.
    Those who still insist on testing, I have some questions for you: Would you want to check your folic acid level before taking a supplement? What about your vitamin E level before you take a vitamin E pill? What about your thiamine, riboflavin, calcium, magnesium, selenium, or vitamin C level, etc., before you take a multivitamin?

Unless a person has an unusual medical condition or diet where blood vitamin D levels are suspected to be too low or too high, blood testing does not give us much of a clue on exactly how much to supplement. I think the vast majority of people who don't have an unusual diet or serious and chronic medical condition just take 400 to 2000 units a day they should be fine and they don't have to worry about checking for vitamin D levels. Those who want to take more can try 3000 units a day just as long as they understand the potential long term side effects.

Different labs that test for levels may provide different results. For instance, the same blood sample sent to different labs may show results that could vary as much as 20 percent or more.

The same person may have a different vitamin D level at different times or seasons of the year.

There is no agreement by the medical community regarding the ideal blood level of this prohormone. Therefore, what's the point of testing since we don't know how much to give to achieve an ideal level?

I believe sir that you are about making a sincere effort to inform your readers as best as you and your staff can. That said, I have become a proponent of Vitamin D (and as you know, it is not a real vitamin at all) because of all that I have read about it, starting with Dr. John Cannell MD at his web site vitamin d council. All the up to date information and research you could ever hope to find is on this site and Dr. Sahelian I know Dr. John Cannell would love to hear from you about your concerns for taking Vitamin D3. Like you, he is very concerned with getting out factual information to as many people as possible. I ask that you and or your staff please have a thorough look at his vitamin d council site and all the information there.
   This Vitamin D Council site appears to be overly enthusiastic about the benefits of this natural hormone and appears to recommend that most everyone get blood levels checked as if there is unlimited health care money in this country to do so and without proof that such testing will help improve health and increase lifespan.

Lifeguards, certain farmers and sailors and others who work outside and who are out in the sun all day can make 10,000 of units of vitamin D a day. Doesn't this prove that this supplement is safe in 10,000 unit dosages?
    Firstly, the amount of vitamin D made by sun exposure is done gradually throughout the day as opposed to taking a 10,000 unit pill that raises blood levels excessively high right away. Second, is there any evidence that people who are exposed to such high amounts daily are healthier and live longer? Thirdly, Is it possible that a daily intake of 1000 units is just as beneficial as taking 10,000 units and probably with fewer side effects?

I read your email updates with interest. I am a Pediatric Oncologist from Minnesota with an interest in vitamin D. I screen all my patients with 25-hydroxy vitamin D levels done by Mayo Medical Laboratories (Cost 179 dollars). I recommend supplementation if they are under 32 ng/mL. I have found about 90% of my patients are <32 ng/mL especially in the winter. A study from Germany which is about the same latitude as Minnesota found that the peak 25 hydroxy vitamin D levels are in August and the nadir in February. I have enclosed a copy of 2 reviews written by Dr Greg Plotnikoff who directs the complimentary medicine center at Abbott Northwestern Hospital in Minneapolis. He makes a point that you cannot ensure vitamin D adequacy without checking levels even if you are on supplementation. Also as vitamin D is fat soluble obese children and adults need higher levels. I would not supplement with vitamin D for a level of 40 ng/mL.
    The notion of testing everyone would be partially acceptable if money was no object. But if a person were to get three tests a year to check for vitamin D levels, and add the doctor's visit cost, it would be about 1000 dollars per person. An average family makes 30 to 40 thousand dollars a year. Are we going to spend a thousand dollars a year just on vitamin D testing? Should we be testing once, twice or three times a year for the rest of a person's life? If insurance pays for it then premiums will go up for everyone. Academics in hospital settings can sometimes be out of touch with the reality of economics and limited funds for health care. Furthermore, there are no acceptable guidelines on how much of this supplement to give a person based on a particular blood level and we don't know the long term consequences of excess supplementation. I think my practical approach of giving most everyone 400 to 2000 units a day, unless they have a serious medical condition, works much better in the reality of finances and costs. And those who insist on testing should answer why we should not test for levels of vitamin C, E, selenium, zinc, and a host of other important nutrient levels. Aren't these important too, and isn't it possible that certain people could be deficient? Do we test for vitamin C and E levels before we give someone a multivitamin?

I am a naturopathic doctor and I think all patients should have vitamin D levels tested.
   Please explain how our country can afford a few hundred dollars a year more per person for testing of vitamin D levels when a third of the population does not have adequate health insurance and 20 percent of the population is either unemployed or partially employed and the government is trillions of dollars in debt. What if all doctors ordered vitamin D tests on all Medicare patients where would money come from to treat other medical conditions and emergencies?

There is an enormous amount of evidence that people living the the Northern part of the US and in Canada have low levels of vitamin D in their bloodstream. Low vitamin D levels have been associated by on-line publications with osteoporosis, higher incidence of prostate cancer, and bone fractures. The minimum amount of vitamin D listed on the lab report forms is 30 ng/ml, the upper toxic limit is 100 ng/ml. I took a vitamin mineral supplement for years, and when tested the first time in 7/2008 I had a level of 22 ng/ml. On line articles (I mean peer review journals epublication) associate low vitamin D with atherosclerosis, heart disease, diabetes, and more. Are all these journals, and all published research wrong? The accepted level of 400 IU/day is under attack from many quarters. I stated to you before I take 5000 IU vitamin D3/day. I think vitamin D testing is a good idea, it should not be done excessively, but it should definitely be done.   
    I am a proponent of supplementation but question the need for everyone in the country to get tested. In your opinion, how often should people be tested? What happens if a person does not have insurance and they make an average income of 40,000 a year, is it worth it for them to get their vitamin D level tested 3 or 4 times a year at a cost of 500 to 1000 dollars a year? How much a year would health insurance costs rise each year if each person were tested several times a year? Once testing is done for a year, is it necessary to test again the following year? Is there proof that taking 5000 units a day provides more benefits than 2000 units and still has no risks when taken for decades?

I like your newsletter and always appreciate your erring on the cautious side in your recommendations. I agree that we should be cautious about adding large doses of vitamin D or other supplements. However, I'm not sure where you got your data that vitamin D tests cost very much. If you google "vitamin D test cost" online, you'll find a number of different places that appear to be reputable, offering tests that mostly range anywhere from $25 to $68, and even references to labs that do the test for $10. According to Medscape, "Some health insurances cover vitamin D testing and some do not, and prices vary from $10 to $50..." Other examples: Virginia Hopkins: test cost: $68; Saveonlabs: $44.75; Grass roots health dot net: $60; The website Women to Women describes tests that are available for $25. I also found a statement on Wiki that Medicare pays $40 for vitamin D tests. I think what we're seeing is that as demand for Vitamin D deficiency tests goes up, labs start competing with each other for customers and the tests go down. I purchased four test kits for Vitamin D3 from Dr. John Cannell of the Vitamin Research Council. The tests are by ZRT Labs, and I paid $220 for them. Testing twice a year would cost a family of four $440, which amounts to 1 % of an annual income of $40,000 per year, which sounds affordable to me, especially when you consider that maintaining healthy blood levels of D3 could pay for the cost of the tests in saved medical bills.
    Most people go to their doctor's office to get tested which adds a doctor's visit cost and most physicians are likely to add additional blood tests since the person is getting their blood drawn, anyway, thus adding to the overall cost. There are concerns that different labs are not consistent in the levels they measure and some of the cheap ones may not provide accurate information. When health insurers or Medicare cover the cost, eventually all of us will pay for it through additional premiums or increase in tax rate. I am not sure how reliable the tests by ZRT labs are compared to other tests done in a doctor's office. There are differences in results between different labs. One percent of a family's total income is still very high for just testing a level of one of countless hormones, amino acids, vitamins, minerals, nutrients, fatty acids, etc that are in the body. Omega-3 oils are crucial for optimal health. Why not spend another 1 percent of one's income on testing this? What about vitamin C and E levels; what about testing different hormone levels? Where does one draw the line? Plus, there is no guarantee that those who test for levels will live longer than those who just spend 10 minutes a day in the sun and take 400 to 1000 or 2000 units a day.

Receptors
The vitamin D receptor is now known to be present in over 35 tissues. Bone and vascular smooth muscle have vitamin D receptors, so do heart muscle cells.

Vitamin D in Food and in our diet
Vitamin D is found in milk, yogurt and cheeses, as well as in some fortified orange juice, fish, oysters, and certain fortified cereals. Good sources include fish liver oil, eggs and fatty fish such as salmon, herring and mackerel. People might want to consider a vitamin D supplement to raise their intake to 400 to 800 IUs per day, which is well within the safety guidelines established by the National Academy of Sciences. Taking more could be especially important for people living in northern areas, which receive less vitamin D from sunshine. African Americans, who don't produce as much vitamin D because of their skin pigment, could also benefit significantly from a higher intake.

Animal foodstuffs (e.g., fish, meat, offal, egg, dairy) are the main sources for naturally occurring cholecalciferol (vitamin D-3). The highest values are found in fish and especially in fish liver, but offal (organ meats, entrails) also provides considerable amounts. The content in muscle meat is generally much lower. Concentrations in egg yolks range between the values for meat and offal. If milk and dairy products are not fortified, they are normally low in vitamin D, with the exception of butter because of its high fat content.

Breastfeeding
Breastfed babies living in northern latitudes often lack healthy levels of vitamin D, and may even be severely deficient. In northern latitudes, such as that in Iowa (41 degrees North), sunshine is too diminished in the winter for the infants to generate enough vitamin D on their own. Many infants are vitamin D deficient during winter than during summer. The vitamin D deficiency is less prevalent as babies get older. Many decades ago it was standard practice to give infants a teaspoon of cod liver oil, which averages about 400 units of vitamin D per day. When the use of baby formula became popular, enough vitamin D was added to the formula to prevent deficiency. Then since the 1970s women returned to breast feeding, but they did not think of giving their babies vitamin D supplements. Breastfed infants require about 200 units of vitamin D per day. It may be a good idea for women breastfeeding their infants to give them cod liver oil supplements during the winter months. Pediatrics, August 2006.

Vitamin D and Pregnancy
The children of mothers who had low levels of vitamin D during their pregnancy have reduced bone mineral content during childhood, potentially increasing their risk of osteoporosis in later life.
     High levels of vitamin D during pregnancy may lower the risk of wheezing and asthma in offspring during early childhood. Vitamin D deficiency and asthma are both common in the northeastern part of the United States, suggesting that the two may be related. Moreover, while vitamin D has important effects on the immune system, its affect on asthma is not known. Researchers tracked 1,306 mother-child pairs for more than three years, and used a food frequency questionnaire to assess levels of maternal vitamin D during pregnancy. By age two, there was a clear association between increasing prenatal levels of vitamin D in the mother and decreasing risk of wheezing or doctor-diagnosed asthma in the child. The average total vitamin D intake during pregnancy was 550 international units (IU) per day. In a more thorough analysis, a 100-IU increase in maternal vitamin D intake was associated with an odds ratio of 0.90 for "any wheeze" in the child -- defined as mother-reported wheeze during the first two years of life. When the data were adjusted to account for dietary levels of fruit, vegetables, and fish, the results did not change. A preliminary look at the three-year data show a similar strong association between higher maternal vitamin D levels and lower risk of wheezing and asthma at age three years.

Vitamin D from Sun or supplement pill?
Should you purposely tan for vitamin D? You can get all the vitamin D with a vitamin supplement pill -- you do not have to put yourself at increased risk of skin cancer and photoaging. The public is getting a mixed message on sun and health because advocates of increased UV exposure, like the indoor tanning industry, are advocating sunbathing as a means of getting more vitamin D for everyone, including young light-skinned people who face the greatest skin cancer risk. New research has indeed shown that some groups of people who may get little sun exposure and don't drink much milk, for example frail elderly individuals at risk of bone fractures, will benefit from getting more vitamin D than is currently recommended by the US Department of Agriculture. There's also evidence that people with very dark skin and those who live in northern climes may be deficient in the vitamin. But such deficiencies can be handled with oral supplementation. If you are worried that you're not getting enough vitamin D, take a vitamin D supplement pill.

Vitamin D needed by diabetics
A majority of patients with type 2 diabetes show signs of vitamin D deficiency. Because a lack of vitamin D can negatively affect bone health and have other adverse effects routine vitamin D supplementation with about 400 units a day should be considered for people with diabetes.
   People with a low level of vitamin D in the blood have poorly functioning insulin-producing cells and show a poor response to insulin, even when their blood sugar levels are normal.

D2 or D3?
It appears that both forms of the vitamin are useful

Vitamin D2 Is as Effective as Vitamin D3 in Maintaining Circulating Concentrations of 25-Hydroxyvitamin D.
J Clin Endocrinol Metab. 2008 March; Michael F. Holick, Rachael M. Biancuzzo, Tai C. Chen, Ellen K. Klein, Azzie Young, Douglass Bibuld, Richard Reitz, Wael Salameh, Allen Ameri, and Andrew D. Tannenbaum. Endocrine Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118;
Two reports suggested that vitamin D2 is less effective than vitamin D3 in maintaining vitamin D status. Our objective was to determine whether vitamin D2 was less effective than vitamin D3 in maintaining serum 25-hydroxyvitamin D levels or increased the catabolism of 25-hydroxyvitamin D3. This was a randomized, placebo-controlled, double-blinded study of healthy adults ages 18–84 yr who received placebo, 1000 IU vitamin D3, 1000 IU vitamin D2, or 500 IU vitamin D2 plus 500 IU vitamin D3 daily for 11 wk at the end of the winter. Sixty percent of the healthy adults were vitamin D deficient at the start of the study. The circulating levels of 25-hydroxyvitamin D (mean ± sd) increased to the same extent in the groups that received 1000 IU daily as vitamin D2. Our results suggest a 1000 IU dose of vitamin D2 daily was as effective as 1000 IU vitamin D3 in maintaining serum 25-hydroxyvitamin D levels and did not negatively influence serum 25-hydroxyvitamin D3 levels. Therefore, vitamin D2 is equally as effective as vitamin D3 in maintaining 25-hydroxyvitamin D status.

Source
I have a question regarding the source of Vitamin D. I understand cholecalciferol or D3 has the origin from animal products such as sheep wool and hides. Also, I read somewhere that vegans usually obtain vitamin D from the action of sunlight on the skin or by taking fortified foods such as soya milk, margarine, breakfast cereals and vitamin supplements which are made from yeast or other fungi. Fortified vegan products contain D2 ( ergocalciferol ). Vegans are careful about their source as D3 ( Cholecalciferol ) which is animal-derived.
   It appears to be true that Vitamin D in the form of cholecalciferol is derived from sheep wool. Therefore, this would make it fine for a vegetarian but not for a strict vegan. The sheep are not killed. The wool is sheared, and lanolin from the sheep wool is chemically altered in the lab to produce vitamin D3 or cholecalciferol.

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