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Vitamin D Q&A
How much vitamin D should I take?
I don't know.
How often should I have a 25-hydroxy-vitamin D blood test?
I don't know.
Why don't you know?
Because everyone's situation is either a lot, or at least a little, different. How much vitamin D you need varies with age, body weight, percent of body fat, latitude, skin coloration, season of the year, use of sunblock, individual variation in sun exposure, and—probably—how ill you are. As a general rule, old people need more than young people, big people need more that little people, fat people need more than skinny people, northern people need more than southern people, dark-skinned people need more than fair skinned people, winter people need more than summer people, sunblock lovers need more than sunblock haters, sun-phobes need more than sun worshipers, and ill people may need more than well people.
Regular readers should understand the reasons behind all these statements except for the last one. However, don't feel bad, no one understands it. Vitamin D is used by the body—metabolically cleared—both to maintain wellness and to treat disease. If you get an infection, how much vitamin D does your body use up fighting the infection? Nobody knows. If you have cancer, how much vitamin D does your body use up fighting the cancer? Nobody knows. If you have heart disease, how much vitamin D does your body use up fighting the heart disease? Nobody knows. If you are a child with autism, how much vitamin D does your brain need to turn on the genes that autism has turned off? Nobody knows. If you are an athlete, how much vitamin D does your body use up making you stronger and quicker? Nobody knows, etc.
This is what I'd do. If you live in Florida and sunbathe once a week, year around, do nothing. If you use suntan parlors once a week, do nothing. However, if you have little UVB exposure, my advice is as follows. Well children under the age of two (2) should take 1,000 IU per day, over the age of two, 2,000 IU per day. Well adults and adolescents should take 5,000 IU per day. Around 2–3 months later have your doctor order your first 25-hydroxy-vitamin D blood test. Yes, start the vitamin D before you have the blood test. Then adjust your dose so your 25(OH)D level is between 50 and 80 ng/mL (125 and 200 nmol/L), summer and winter. These are conservative dosage recommendations. Most people who avoid the sun—and virtually all dark-skinned people—may have to increase their dose once they find their blood level is still low, even after two months of the above dosage, especially in the winter.
One more thing. Everyone has different vitamin D machinery. For example, regular run-of-the-mill rickets does not require much vitamin D to be cured. However, two other forms of rickets, both rare, one caused by a defective vitamin D receptor and the other by a malfunction of the enzyme that activates vitamin D, requires either much more vitamin D or activated vitamin D (calcitriol) itself. It seems likely that there is as much variation in the amount and functionality of the enzyme that activates vitamin D as there is in the vitamin D receptor. Furthermore, there are probably tissue variations as well. That is, one vitamin D deficient child gets rickets, another autism, another asthma, and yet another type 1 diabetes because functionality of the vitamin D machinery is genetically variable both between children and within children's tissues. Therefore, some people, who have genetically determined decreased functionality of the machinery in different tissues, will need more vitamin D. How much more, we do not know. However, should you have a child with autism, they will usually need more than a normal child to overcome their genetic defects. None of what I say in this paragraph is proven, it is theoretical.
What blood test should I have?
The only blood test that can diagnose vitamin D deficiency is a 25-hydroxy-vitamin D [25(OH)D]. Get your levels above 50 ng/mL (125 nmol/L), year around. Unfortunately, about 10–20% of the doctors in the USA order the wrong test. They order a 1,25-dihydroxy-vitamin D, thinking that by measuring the most potent steroid in the system, they are getting useful information. They are not. 1,25-dihydroxy-vitamin D is an adaptive hormone; it goes up and down with calcium intake. Furthermore, as 25(OH)D is a weak steroid, when 25(OH)D levels are low, the body compensates by increasing the amount of the potent steroid, 1,25-dihydroxy-vitamin D. Thus, a common cause of high 1,25-dihydroxy-vitamin D is low 25(OH)D or vitamin D deficiency. So these doctors see the 1,25-dihydroxy-vitamin D is normal or high and tell their patients that they are OK when they are vitamin D deficient, advice that may prove fatal. Furthermore, the reference labs in this country know this is occurring but, to date, have not taken steps to educate the doctors ordering the test because the reference labs make more money off a 1,25-dihydroxy-vitamin D than they do from a 25-hydroxy-vitamin D. Although the misdiagnosis of vitamin D deficiency may prove fatal, the doctors, and the reference labs, are ordering and processing the wrong test.
Does it matter what reference lab my doctor uses?
Yes, it might make a huge difference. A number of methods exist to measure 25(OH)D in commercial labs. The two most common are mass spectrometry and a chemiluminescence method, Liaison. The first, mass spectrometry, is highly accurate in the hands of experienced technicians given enough time to do the test properly. However, in the hands of a normally trained technician at a commercial reference lab overwhelmed with 25(OH)D tests, it may give falsely elevated readings, that is, it tells you are ok when in fact you are vitamin D deficient. The second method, Liaison, was recently developed and is the most accurate of the screening, high throughput, methods; LabCorp uses it. Quest Diagnostics reference lab uses mass spec. Again, both Quest and LabCorp are overwhelmed by 25(OH)D requests. The problem is that the faster the technicians do the mass spec test, the more inaccurate it is likely to be. If your 25(OH)D blood test says "Quest Diagnostics" on the top, do not believe you have an adequate level (> 50 ng/mL). You may or may not; the test may be falsely elevated. Let me give you an example. A doctor at my hospital had Quest Diagnostics do a 25(OH)D. It came back as 99 ng/mL of ergocalciferol. He is not taking ergocalciferol (D2), he has never taken ergocalciferol, only cholecalciferol (D3), and he is not taking enough to get a level of 99 ng/mL, 50 ng/mL at the most. His email to Dr. Brett Holmquist at Quest about why Quest Diagnostics identified a substance he was not taking went unanswered other than to say "any friend of Dr. Cannell's is a friend of ours."
Long story short: if your lab report says "LabCorp" on the top, it is probably accurate; if it says Quest Diagnostics, it may be falsely elevated. While LabCorp has also been overwhelmed with 25(OH)D requests, the Liaison method they use is relatively easy to do and does not rely on technician skill as much as the mass spec methods do. I'm not saying this because I'm a consultant for DiaSorin, who makes Liaison, I'm saying it because it is true. If you don't believe me, get Quest to make me an offer to be their consultant at 10 times what DiaSorin is supposed to be paying me and see how fast I turn Quest down. If Quest fixes their test, I'd love to consult. The ironic thing: I've made both Quest and LabCorp lots of money via this newsletter, the website, and by repeatedly telling the press that people need to know their 25(OH)D level, which has contributed to the skyrocketing sales of 25(OH)D blood tests.
Here you can help. Find out which labs in your town use Quest Diagnostics and which use LabCorp. Have a 25(OH)D test at both labs the same day (you will have to pay for them yourself). Then send both results to the Vitamin D Council. If Quest Diagnostics does not fix their 25(OH)D test, the Vitamin D Council will fix it for them.
My doctor prescribed Drisol, 50,000 IU per week. What is it?
Drisdol is a prescription of 50,000 IU tablets of ergocalciferol, or D2. Ergocalciferol is not vitamin D but it is similar. It is made by irradiating ergosterol, which is found in many living things, such as yeast. D2 is not normally found in humans and most studies show it does not raise 25(OH)D levels as well as human vitamin D (cholecalciferol, or D3) does. However, Drisdol is a lot better than nothing. The best thing to do, if you are vitamin D deficient (and human) is to take human vitamin D, that is, cholecalciferol vitamin D3.
Why are you against cod liver oil?
Cod liver oil contains toxic amounts of vitamin A. Vitamin A antagonizes the action of vitamin D. Stay tuned to the press. In several months you will see a clear warning by numerous experts not to take vitamin A or cod liver oil.
I have advanced renal failure and I'm on dialysis, how much vitamin D should I take?
The same as everyone else. Since I have told you about commercial labs ripping you off, let's add some drug companies. Patients with advanced renal failure need activated vitamin D or one of its analogs, available by prescription. This is very important as their kidneys cannot make enough 1,25-dihydroxy-vitamin D (calcitriol) to maintain serum calcium. However, the rest of their tissues activate vitamin D just fine and when those tissues get enough, and when the kidneys get more vitamin D, the calcitriol spills out into the blood, lowering their need for prescription calcitriol or one of its analogs. The companies that make the analogs don't like that, it means reduced sales. So these companies do nothing, the scientists behind these companies say nothing, and renal failure patients die prematurely from one of the vitamin D deficiency diseases.
When I asked my doctor for a 25(OH)D blood test, he just laughed and said it was all idiotic. What can I do?
Help me unleash the dogs of war, the plaintiff attorneys. If you read about past nutritional epidemics caused by society, such as beriberi or pellagra, you will realize that education alone will take decades. Physicians successfully fought against the idea that thiamine deficiency from milling rice caused beriberi for almost a century. However, things are different now. The agents of change in modern America, as obnoxious as they are, are plaintiff attorneys. Once the first malpractice lawsuits claiming undiagnosed and untreated vitamin D deficiency led to breast cancer, autism, heart disease, etc., get past summary judgment—and they will—and end up in front of a jury, things will change rapidly. One of the main reason physicians do what they do is fear of lawsuits. In a matter of months, arrogance and ignorance will give way to 25(OH)D tests and vitamin D supplementation
My blood test came back at 120 ng/mL. Am I toxic?
No, vitamin D toxicity has never been reliably documented with 25(OH)D levels less than 200 ng/mL (500 nmol/L). Ranges for humans living and working in the sun are between 50 and 100 ng/mL (125 and 250 nmol/L). Did Quest Diagnostics do your 25(OH)D?
Page last edited: 08 November 2010