VDC test kit slider

Newsletter: FAQ’s

Posted on: January 1, 2006   by  John Cannell, MD


This month’s newsletter answers the most common questions that you have asked me via email. I try to personally answer everyone’s email but I have more than 300 unanswered emails in my inbox and the number is growing.

1. How much vitamin D should I take?

Before I answer, I have a few questions for you. Where do you live (latitude)? How much do you weigh? What skin type do you have? How much do you go into the sun? How much do you get in your diet? How much do you get in supplements? What is your 25-hydroxy-vitamin D level? During what season-of-the-year was it obtained?

You see, the answer is different for everyone. The question also assumes we know the ideal vitamin D blood level. We don’t know for sure; around 50ng/ml is the best current guess.

However, an easy answer is: 2,000 units a day. Bio-Tech Pharmacal Inc. sells an inexpensive pharmaceutical grade of vitamin D.  Your local health food store should also carry 1,000 unit capsules. Just be sure they don’t contain any vitamin A. Beta-carotene is OK but preformed retinols (vitamin A) interfere with vitamin D’s function. I do not advise cod liver oil; if you just have to take it, don’t take more than a teaspoon per day. Get your omega-3s from molecularly distilled fish body oils (Trader Joe’s) or by eating wild salmon or sardines; get your vitamin D by taking vitamin D or by going into the sun, or by combining both.1, 2, 3

The government says 2,000 units of vitamin D a day is safe for all adults to take without a doctor’s supervision. Two thousand units a day will get about 80% of Americans to a vitamin D level of 35 ng/ml or higher with no risk of toxicity. The 20% still lower than that are almost all African American.4

“The only blood test that can determine vitamin D adequacy is a 25-hydroxy-vitamin D.”For now, if you take more than 2,000 units a day, you should do so either because you are under the care of a knowledgeable health care practitioner (good luck finding one), or because you know what you are doing. I personally take no vitamin D in the late spring, summer, or early fall because I frequently go into the sun. I take 5,000 units a day in the winter but I know what my vitamin D level is because I get it checked several times a year. If I had cancer or heart disease or Alzheimer’s disease or multiple sclerosis or a hundred other common diseases, I might take more than 5,000 units a day but I’d check my calcium and vitamin D levels even more often. I’d also follow my doctor’s advice about standard medical treatment.

Keep in mind that if you use a sunlamp or a tanning parlor once a week during the winter, you don’t have to worry about blood tests because your body will maintain adequate vitamin D blood levels. Just don’t get burned.

Also, remember to take calcium tablets if you don’t get adequate amounts of calcium in your diet and most people don’t. Trader Joe’s sells a good Calcium/Magnesium/Zinc combination product for next to nothing.

2. What blood test should I have?

The only blood test that can determine vitamin D adequacy is a 25-hydroxy-vitamin D. Whenever I say “vitamin D level,” I’m talking about a 25-hydroxy-vitamin D. Ask your doctor to order a 25-hydroxy-vitamin D blood test.

Unfortunately, many doctors order an “activated vitamin D” level, thinking it better to measure the most active form of vitamin D. It is not. Activated vitamin D, also known as 1,25-di-hydroxy-vitamin D or calcitriol, should never be obtained to determine vitamin D sufficiency. Calcitriol is often elevated in vitamin D deficiency. You cannot tell anything about your vitamin D nutrition by measuring a calcitriol level. If your doctor insists on ordering a calcitriol level to determine your vitamin D nutrition, find another doctor.

(However, serious problems exist with the technology used by some laboratories to measure vitamin D levels. Different labs will report different results when given the exact same specimen of blood. Furthermore, the same lab often reports significantly different numbers when sent the same specimen of blood at different times. In general, low numbers are more reliable than high numbers because interfering substances can easily give falsely elevated results. Prominent scientists have issued urgent calls for standardization. Dr. Graham Carter, one of my personal heroes, has dedicated his life to obtaining a standardized, and accurate, vitamin D levels. His outfit in London is DEQAS or Vitamin D External Quality Assessment Scheme.5, 6

If you take ergocalciferol, or “vegetarian” vitamin D, be warned. Ergocalciferol is not vitamin D, but a vitamin D-like patent drug whose patent has expired. It does not normally occur in the human body and is probably a weak agonist at the receptor site, meaning it may actually partially block vitamin D actions. Ergocalciferol is the villain in most of the reported cases of toxicity in the world’s literature. All bets are off in terms of measuring blood levels if you take ergocalciferol. Some of the labs can pick it up and some can’t. Don’t take ergocalciferol; it is not vitamin D.

If your doctor prescribes 50,000 units of ergocalciferol (Drisdol) once or twice a week, obtain a bottle of 50,000 unit capsules of cholecalciferol from Bio-Tech Pharmacal Inc. of Fayetteville, Arkansas, and take them instead. Take one or two per week until your level is around 50 ng/ml. Then stop taking them and begin maintenance therapy at a much lower dose. You could also take one 5,000 unit capsule every day (also available from Bio-Tech Pharmacal) until your vitamin D level is around 50 ng/ml. Then take enough by mouth during the cold months (and go into the sun during the warm months) to keep your 25(OH)D level around 50 ng/ml. (Keep in mind that labs inside the USA report usually results in ngs/ml; labs outside the USA use nmols/L. One ng/ml is equal to 2.56 nmol/L. So 50 ng/ml is about 125 nmol/L.)

Take enough real vitamin D (cholecalciferol) to maintain your level around 50 ng/ml, year around. A 25(OH)D level is the best, and only, way you have of knowing if you are taking enough. However, do not be satisfied with a 50 ng/ml level unless you know how you are getting enough vitamin D to explain the level (i.e., you go into the sun or take supplements). If your level is 50 ng/ml and you don’t take supplements, don’t go into the sun, don’t use a sun booth, or a UVB lamp, then the level is probably bogus. Repeat the level.

In general, keep your vitamin D level in the upper one third of the lab’s reference range, about 50 ng/ml with the most commonly used test. If you take higher doses, get your calcium checked when you get your 25(OH)D level, just to be safe. If you want to be sure that your hospital is sending their samples to an accurate reference lab, ask the director of the hospital’s lab to contact Professor Bruce Hollis (843) 792-6854 or Professor Reinhold Vieth (416) 586-5920. Both are the world-class authorities in vitamin D measurement technology.

(Although 1,25 dihydroxy-vitamin D (calcitriol) should never be used to diagnose vitamin D deficiency, calcitriol is important in evaluating one cause of high blood calcium, called
vitamin D hypersensitivity. High blood calcium rarely occurs due to vitamin D toxicity, but calcium is elevated in people who have vitamin D hypersensitivity, although their vitamin D level will be normal or even low. Primary hyperparathyroidism is a common cause of vitamin D hypersensitivity, as is sarcoidosis and other granulomatous diseases. It can occasional occur in cancer; about 20% of patients with non-Hodgkin’s lymphoma have vitamin D hypersensitivity. Any competent endocrinologist can treat vitamin D hypersensitivity.)

3. Why don’t you answer all your emails promptly?

I do my best. As the circulation of the newsletter grows and the popularity of the website increases, I am inundated with questions like, “I have prostate cancer, how much vitamin D should I take? My husband just learned he has lung cancer; I heard some researchers at Harvard said he should take vitamin D? My doctor just diagnosed me with multiple sclerosis, what should I do? Would you please email me a PDF of Professor Heaney’s most recent paper? Would you explain to me the difference between calcidiol and calcitriol? How much vitamin D do I need to take if I have the flu? I use full-spectrum light bulbs so I’m getting plenty of vitamin D, aren’t I? Is it true that children with low vitamin D levels are more likely to get lung infections? Are vitamin D levels associated with stroke? What is the Vitamin D Council? Why don’t I get the newsletter; I subscribed? How can I be sure you know what you’re talking about? What is your background? Is it true you are a conservative who used to be a communist? The list goes on.

My answer is that I do my best. During the day I work full-time to support my family. I write, and attempt to distribute the newsletter, on the weekends and evenings. If you don’t get the newsletter, your server is either blocking the mailing or stripping it of its content so you get a blank email. Be sure [email protected] is on your allowed list. If you don’t get the newsletters, you can always read them on our social media pages: facebook or twitter.

I can’t provide personal medical advice. I can’t email you copyrighted material. If you have prostate cancer, or lung cancer, or any cancer, you should take enough vitamin D so you are no longer vitamin D deficient (2,000 to 5,000 units a day, enough to get your vitamin D level around 50 ng/ml and keep it there). If you have MS, the same is true. If I ever got the flu, I’d take one 50,000 capsule of vitamin D as a single dose although you should know that not one scientific study exists to support such a decision.. Full-spectrum lighting has virtually no UVB so it will not generate any vitamin D in your skin.

I try to alert you to all the important studies but I miss a few. For example, a recent study showed children with low vitamin D levels are eleven times more likely to get lung infections! Another recent study showed vitamin D deficiency is a major risk factor for stroke. I spend lots of time learning about vitamin D and I hope I know what I’m talking about. Readers can answer most of their own questions by spending time on the
Vitamin D Council’s website and reading old copies of the newsletters. You can read about the Vitamin D Council’s organization on the website under “about us.”

4. Where does the Vitamin D Council get its funding and what do you do with all the money?

We don’t have any funding. We try to save the little money we have. Unfortunately, the Kettering Family Foundation just turned down our $100,000 grant request. I hoped they would fund us as they generously funded me in the late 1980’s when I attempted (unsuccessfully) to reform testing in America’s public schools. Currently we operate on private donations from readers ($563.00 so far) and a $5,000.00 donation that my wife and I made to the Vitamin D Council last year. The first thing we will do when we get funding is to sponsor a yearly seminar on vitamin D geared towards both health-care-practitioners and interested lay people. We will ask vitamin D experts from around the country to speak in plain language about practical aspects of vitamin D nutrition. If you know anyone who knows anyone with grant money, send him or her along, our address is at the end of this newsletter. I have no doubt that God will provide, should we be doing something worthwhile.

5. If humans make 20,000 units of vitamin D after sunbathing for 20 minutes in the summer, why shouldn’t I take 20,000 units every day?

Because of what we don’t know we don’t know. Someone once said all knowledge comes in three categories: (1) what you know you know, (2) what you know you don’t know, and (3), the largest category, what you don’t know you don’t know. I know I know how to speak English; I know I don’t know how to speak French; I don’t know that I don’t know how to speak a language I don’t know exists.

We simply don’t know the effects of taking 10,000 or 20,000 units a day for year after year. Although light-skinned humans make about 50,000 of units of vitamin D after getting a sunburn (3 times the minimal erythemal dose), we also know they make progressively less and less vitamin D as their skin produces more and more melanin, thereby tanning. My 16-year-old daughter has noticed that she tans much faster when she has been taking oral vitamin D. That is, high blood levels may tell the skin to make more sunblock (melanin). Undoubtedly, other natural mechanisms exist to prevent toxicity, we just don’t know. We do know that when healthy young men took 50,000 units of vitamin D every day for six weeks, average serum blood levels increased by 257 ng/ml. One young man achieved an increase of 400 ng/ml after only six weeks. Although the authors found no evidence of toxicity after this six-week experiment (serum calcium remained normal), 50,000 units a day will eventually turn your internal organs into limestone.7, 8

6. Where do you predict all this vitamin D research is heading?

I predict the final Food and Nutrition Board’s recommendation (in about two decades) will be about 3,000 units a day. I predict that science will eventually show vitamin D deficiency is a major cause of many of the diseases of civilization. I predict that science will eventually show that many of these same diseases of civilization respond favorably to vitamin D treatment. I predict science will eventually prove vitamin D helps prevent and treat some infectious diseases, especially viral respiratory infections like influenza, croup, and the common cold. These are only my attempts to prophesize the future. Remember, only time can tell the difference between and prophet and a madman.

7. What can I do to help?

We need funding of course, so any donations are appreciated. We also need someone who is fluent in German and can translate German medical papers into English. Email me back if you are fluent in medical German and are willing to help translating papers.

8. Is it true that vitamin D improves sexual performance, hair growth, and athletic performance?

Are you asking if one of the most potent steroid hormones in the human body could affect sex, hair growth, or athletic performance? I’ll give you a clue. The literature indicates you are right about one of the three. However, you’ll have to wait for a future newsletter to find out which one.

I hope you have a happy and prosperous new year.

Test Your Vitamin D Levels at Home!

Our in-home vitamin D test kit is easy, affordable, and an accurate way to find out your Vitamin D status.

order NOW

We need your help!

We're spreading awareness on Vitamin D Deficiency
Donate NOW
Latest Articles
4 tips for writing an essay in English

Writing an essay in English can be a challenge, especially if you are beginning to learn the language or do not yet fully master it. But don’t worry, did you know that there are strategies that can make this task easier for you? To help you meet this challenge, we leave you a series of […]

Weekly Newsletter

Our Sponsors

December 21st is DDAY. Click here to celebrate the day with us!