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Interview with Dr. John Cannell of the Vitamin D Council (vitamindcouncil.org)


Naples, Florida
Dr. John Cannell of the Vitamin D Council was kind enough to sit down with me and discuss vitamin D and Crohn's Disease. Dr. Cannell is one of the world's leading experts on Vitamin D so this was very exciting. For more information and discussion on Vitamin D and Crohn's disease, be sure to read this thread.

David: Dr. Cannell, you founded the Vitamin D Council in 2003. Why vitamin D? And what is your background as a medical doctor that led you to be so passionate about vitamin D?

Dr. Cannell: There was a seminal paper that came out in 1999 by Dr. Reinhold Vieth in the American Journal of Clinical Nutrition that basically suggested we’ve been way off on our sun exposure and vitamin D recommendations for fifty years. We should be getting way more sun exposure, way more vitamin D. It was striking and I wanted to do something about it. So I founded the Council.

I have been a physician for almost 35 years, serving as a general practitioner, emergency physician and as a psychiatrist. I have always been interested in nutrition.

David: We've noticed that a majority of people with Crohn's disease who get their vitamin D level tested are deficient. Any idea why that might be?

Dr. Cannell: Most of your vitamin D should come from the sun, but like most humans in the 21st century, we don’t get much sun, so we’re deficient in vitamin D. With fortified foods and multi-vitamins, you might be able to get some vitamin D from foods. But if you have Crohn’s, you might not absorb vitamin D very well, so people with Crohn’s are often severely deficient in vitamin D.

There’s also some thought that vitamin D deficiency might make Crohn’s more severe, suggesting a chicken and egg cyclical type problem.

David: Should we take vitamin D2 or Vitamin D3? Does it matter?

Dr. Cannell: Research shows that D3 is the preferred form. It’s what the human body makes in response to full body sun exposure, it’s absorbed and metabolized better and your body likes it more. D2 is plant vitamin D; not quite the same.

David: What is the RDA of Vitamin D3? Does the RDA vary by geography or season? What dose do you recommend someone with Inflammatory Bowel Disease take?

Dr. Cannell: The RDA is 600 IU for adults, 800 IU for seniors, an almost insignificant amount in my opinion. The RDA does not vary by geography, season or race, although it should. The Institute of Medicine felt there wasn’t enough research to tailor RDAs for specific locations and races at this time.

My recommendation, however, is for all individuals to take enough vitamin D to have a level of 25(OH)D (vitamin D level) of 50 ng/ml. This usually requires about 5,000 IU/day, so that is my simple recommendation. Keep in mind that someone with IBD may have a hard time absorbing vitamin D, so they may require more than 5,000 IU/day to reach a level of 50 ng/ml.

David: Is it possible to take too much Vitamin D as a supplement?

Dr. Cannell: It is. Generally you do not want your vitamin D level to be over 100 ng/ml. You usually have to take more than 20,000 IU/day to achieve this. Supplementing up to 10,000 IU/day is considered safe and is the “no observed adverse effects level” set by the government.

For someone suffering with IBD, 10,000 IU might not achieve as high as level as someone without it; so keep in mind that even 10,000 IU/day may not be adequate for someone with IBD. What’s important is staying under a vitamin D level of 100 ng/ml, not the dose, per se.

David: Should Vitamin D Supplements be taken with or without food? Are there foods / other supplements that should not be taken with Vitamin D?

Dr. Cannell: You best absorb vitamin D supplements with the largest meal of the day. I usually don’t recommend this just because it’s not necessary to take with largest meal, but if you’re suffering from IBD, it should help. Some studies show that absorption is increased by 50% if it is taken with the largest meal of the day.

There are no foods or supplements that shouldn’t be taken with vitamin D.

David: Will very high levels of Calcium in the blood change suggested Vitamin D intake dosage? Parathyroid Hormone? Pregnancy? Breast Feeding?

Dr. Cannell: If you have high serum calcium, you need to work with a doctor before taking vitamin D. They’ll be able to monitor your calcium and vitamin D levels and decide what’s best for you. High serum calcium is rare in Crohn’s, but has been reported in the literature before.

If you have a high parathyroid level, also work with your doctor, particularly if you have primary hyperparathyroidism.

For pregnancy and breastfeeding, I recommend 6,000 IU/day. The breastfeeding infant does not need to supplement if the breastfeeding mother takes 6,000 IU/day, as she will have all the vitamin D the infant needs in the breast milk (assuming her vitamin D level boosts up to 45 ng/ml).

David: Will Kidney Failure or Liver Disease affect the recommended intake of Vitamin D?

Dr. Cannell: If you have kidney failure, you need to work with a doctor. Not because your vitamin D intake should change, but because you may also need to take “activated vitamin D,” which is called calcitriol, if you are on dialysis. This is because the kidney usually produces some calcitriol, but no longer does in severe kidney failure.

Vitamin D metabolism is not affected by liver disease, unless the liver disease is very advanced, so no special requirements there.

David: Will high doses of Prednisone for long periods affect my Vitamin D levels? If someone is actively on Prednisone, should they change their dosage of Vitamin D?

Dr. Cannell: Prednisone, a type of corticosteroid, might have a small effect on vitamin D levels, by lowering them. If you’re taking a steroid, you may want to get your vitamin D level tested and see if your vitamin D is lowered. If so, then increase your dose.

David: How soon after a person begins to supplement should they have their vitamin D level retested?

Dr. Cannell: I recommend three to four months.

David: When supplementing vitamin D, are there any other tests besides serum vitamin D that someone with Inflammatory Bowel Disease should have conducted to make sure the vitamin D supplementation is proceeding as desired with no negative side effects?

Dr. Cannell: Good question, but no, just a vitamin D level [25(OH)D] will do. In rare circumstances, if a patient has high serum calcium, a doctor will run a few more tests such as a 1,25OH₂D and PTH.

Also be warned, some doctors will administer a 1,25OH₂D on accident, instead of a 25(OH)D. This is a mistake, as a 1,25OH₂D does not tell you whether or not you have vitamin D deficiency or sufficiency.

David: What are cofactors and what are the vitamin D cofactors?

Dr. Cannell: Cofactors are nutrients that work together to make sure that every nutrient you intake is acting as best it can in the body. For example, I recommend vitamin K2 as a cofactor, at least 80 ug/day, because it helps place calcium in the right spots in the body. So if you’re taking vitamin D for better calcium absorption, you should take K2 to make sure that calcium is going to the right spots.

The same applies for all the other vitamin D cofactors: magnesium (about 500 mg/day), zinc (about 10 mg/day) and boron (about 2 mg/day). These all interact with vitamin D in the body in various ways.

David: Do you have a specific vitamin D supplement you recommend and why that one?

Dr. Cannell: Any reputable brand from your local drugstore will do. Just be sure it is at least 5,000 IU/day. I also have no specific recommendations for cofactors.

David: What is your feeling on Cod Liver Oil as a source of vitamin D for someone with Inflammatory Bowel Disease?

I don’t think cod liver oil is good to consume. While it may have some vitamin D in it, I think it has too much vitamin A, maybe even to a toxic extent.

David: Some of our members are taking white tablet forms of vitamin D. Is that ok? Are there any forms of vitamin D our members should avoid? Are there any additives or formulations members should watch out for?

Dr. Cannell: To date, no studies have shown that tablets or gel capsules or liquid drops are better than the other.

I’m not against calcium supplementation, but avoid getting a calcium and vitamin D combo-supplement where you have to take too much calcium just to get enough vitamin D.

David: What level of vitamin D should someone with Crohn's disease, Ulcerative Colitis, or other form of IBD aim for? And how many IU of vitamin D should they take per day to get that level?

Dr. Cannell: I consider the optimal and normal range to be 40-80 ng/ml. For healthy individuals, it usually takes 5,000 IU/day to achieve these levels, but with IBD, again, you may have a harder time absorbing the supplements, so it might take more. The key thing is to test every three to four months, adjust your dose and then test again in three to four months.

After you know what dose it takes for you to achieve a level in the 40-80 ng/ml range, then stick with that dose and test once per year.

David: If someone has had a portion of their small bowel removed, does that affect how much vitamin D they should take?

Dr. Cannell: Good question. I don’t believe it’s known what the effects are on vitamin D absorption. I suspect you may need to supplement higher, but I can’t say for sure. Supplementing and testing every three months to start is a good way to ensure that you’re adequately supplementing.

David: Do you feel that supplementing vitamin D may help a person with IBD enter remission or maintain it? Could Vitamin D Deficiency be preventing remission? If so, what level of D3 in the blood may cause this (what is the cutoff for "D3 Deficiency" that is clinically relevant for IBD)?

Dr. Cannell: There are several clinical trials underway right now examining that very question: can vitamin D help IBD? If researchers are studying it, then you know they feel that it can possibly help. But to date, we still don’t know if it can help with IBD or not, as the results have yet to be released.

As being a proponent of vitamin D, I believe it may help with IBD, by either remitting it or maintaining it or by helping with some symptoms. We know vitamin D is immunomodulatory, and vitamin D deficiency is a risk factor for several autoimmune diseases. We also know that in many autoimmune diseases, correcting deficiency helps with the treatment of the disease.

For Crohn’s, studies have been done where they looked at vitamin D levels and disease activity. Sure enough, those with lower levels had more disease activity than those with higher levels. Vitamin D supplementation could potentially help by improving the barrier function of the intestine.

David: Are there extraintestinal manifestations of Crohn's disease that vitamin D supplementation may help alleviate or exacerbate?

Dr. Cannell: Yes. Vitamin D isn’t a cure all, but 38 tissues use vitamin D to help maintain a healthy body. There’s been research into vitamin D’s potential beneficial role in osteoporosis, rheumatology, deep vein thrombosis, seizures, stroke, myopathy, and depression, all things someone with Crohn’s may struggle with.

In listing all these extraintestinal issues people with Crohn’s may suffer from, it may sound like an exaggeration, how can vitamin D help so many things. But researchers do believe that its influence on the human body is this diverse. The reason it its mechanism of action, activated vitamin D is a steroid hormone and like all steroid hormones, it works by turning genes on and off.

Take for example, people with high renin hypertension. The renin gene is down-regulated directly by vitamin D. So vitamin D lowers blood pressure. In depression, the rate limiting enzyme that makes the brains monoamine neurotransmitters, tyrosine hydroxylase, is directly up-regulated by vitamin D. So some, but not all, studies show vitamin D will help depression. The point is that vitamin D has as many mechanisms of action as genes it regulates, and it regulates hundreds, if not thousands, of human genes.

David: Do you have any parting words for the people of Crohnsforum.com?

Dr. Cannell: Remember that you make vitamin D from the sun. We advocate safe sensible sun exposure. The sun may do things for you that vitamin D alone cannot do. This has been shown in an animal model of another autoimmune disorder, multiple sclerosis. So don’t forget to sunbath sensible in the spring and summer. However, since we don’t get much sun exposure in the 21st century as we need, we also need to be supplementing. It’s safe, and while it may not cure Crohn’s or ulcerative colitis, it may help.

Please follow the Vitamin D Council. I am sure we will have some information to report on vitamin D and Crohn’s this year. We have a great newsletter, a great facebook community and a blog. On the blog, some articles are free, some cost money. It only costs five dollars a month to join. While I know no one likes paying to read full articles, we’re a nonprofit and rely on our blog member base to keep us alive and spreading awareness.

Visit us at http://www.vitamindcouncil.org

David: Thank you so much for your time Dr. Cannell. We greatly appreciate it!
Hey David,
Great info...thanks for adding this! My son has been doing well for about one year now...but in last labs we noticed a small decline in vit D ...down to 29 from I think low 30 s. our dr considers it no issue buti would like to see the level higher. What do you think of these vit D lamps? Do you know if sun exposure is just as successful in raising D levels even with strong suntan lotion? My son is so pale we worry about sun exposure.


For info:
ng = nanograms (0.00000001g)
ml = millilitres (0.001l)
IU = International Units. From what I understand this is because not all amounts of substances will give the same amount of vitamin (think like the different types of iron supplements you can get, each with a different strength). Therefore this unit will mean that you will get that amount of the vitamin, whatever the amount of substance you are taking


Well-known member
vit D lamps? Do you know if sun exposure is just as successful in raising D levels even with strong suntan lotion? My son is so pale we worry about sun exposure.
should stay out of the sun after he just went off 6mp, at least for a while, and remain vigilant, 6mp and sun is a really really bad mix, plenty of studies have shown it, getting you the study...


sun warning and 6mp should be a standard warning every single doctor should give to their patients, even after going off 6mp, you need to be careful for a while


Naples, Florida
Hey David,
Great info...thanks for adding this! My son has been doing well for about one year now...but in last labs we noticed a small decline in vit D ...down to 29 from I think low 30 s. our dr considers it no issue buti would like to see the level higher. What do you think of these vit D lamps? Do you know if sun exposure is just as successful in raising D levels even with strong suntan lotion? My son is so pale we worry about sun exposure.
I'm afraid sunscreen almost completely negates vitamin D synthesis from the sun. :( Sunscreen is actually really bad stuff for a variety of reasons. It's all about managing exposure.
What do you think of his D levels being at 29? This despite taking citracal which I believe has 1000 IU of D3.....plus in last 4 months it is declining from low 30 s.
I'm considering adding an additional D3 without the calcium..but it's very difficult finding info on how much is too much for pediatric especially since his GI is not concerned about the level being 29....


Naples, Florida
I don't know that I'd call it a double edged sword. We all just need to change our perspective of how we interact with the sun. We want to be able to go out in the sun for two hours from 11-1 and play frisbee with no repercussions but that's never how it has worked. You have to consciously manage the amount of time you spend in the sun based upon how used to it you are. I work outside daily, often in the 10-2 time period when the sun is most intense yet I never get burnt. I manage my time in the sun. I'll spend 10-15 minutes in it, then do something in the shade for awhile. Then back in the sun I go. My vitamin D level last time I was checked was 82 and I don't supplement at all.

As long as he has been off the 6-MP long enough as kiny alluded to, your son may need to start by spending just 5 minutes in the sun with his shirt off somewhere between and 11am and 1pm time period. As he slowly builds up a tan, he may be able to spend longer time periods in it. I would treat this as part of his treatment regimen: as important as taking his normal medication.

I couldn't disagree more with your GI regarding his level being at 29. If you want to be conservative, put him on another 1000iu of vitamin D. If it was my kid, I'd probably start him another 2000iu of vitamin D and also some magnesium then retest in about 6 weeks to make sure the number is heading up. If it is, then retest on schedule with what Dr. Cannell suggests and adjust the dosage as necessary. All the while getting him out in the sun for a slowly increasing amount of time each day.
Thanks David....I am going to definitely do the additional 1000...and consider the 2000. As far as the sun....tough call here...he is so pale, I'm not sure he's capable of a tan....but I think your concept of building up time is a good one.
Thank you so much for such an informative article!! I have recently been diagnosed with extremely low Vitamin D levels & have started to take a supplement. Now I understand my doctor's concerns. I will also be telling him about this article when I see him tonight. Thanks again!!!
Thanks for this informative article. I was recently advised that I am low in vit D which might possibly be linked to my Crohn's as I am low in Iron and B12 as well. Having said that, low vit D might not be a surprise as the UK has seen very little sun in the last year.

The thing is, 3 years ago I had Sarcoidosis, which I understand causes the opposite problem - too high levels of vit D. This was finally treated with a long course of stereoids (about 9 months) but only after I developped hypercalcaemia and ended up in hospital.

I am surprised therefore to now be taking vitamin D tabs with calcium due to deficiency!

Is there any connection between Sarcoidosis, Crohn's and vit D and calcium?
Update....I did put Matt on 2000 IU of vit D.....tested after about 6 weeks and he is now at 50 (up from 29). My GI was not concerned with 29.....but I feel much better in the 50s. I'm thinking of reducing the supplement to 1000 day....and see of it Maintains or keeps climbing
Being stuck in an office all day - I rarely get much sun.

I have certainly found that supplementing with Vitamin D3 to be immensely helpful for UC.

My doctor never mentioned it. My naturopath got me on it. I had a blood test and found I was deficient. Then after supplementing, I had another test and now have good levels.

The main issue I have is with appropriate dosages.

My doctor put me on a very low dose (800 IU daily) which did nothing.

My naturopath said he was wrong and his information was out of date. She put me on a much higher dose (5000 IU daily ) - which worked.

I am now maintaining levels with 2500 IU daily.

There is much argument over what the safe dosage is meant to be. Which is very confusing for the consumer.


Naples, Florida
The biggest problem is the FDA still says 400iu per day. So some doctors are weary to go too much above that despite the mounting evidence that such amounts is nearly useless for many.
Hi David

My VitD started at 18, moved to 110 (my drs office accidentally put me on 50,000 every day)
Once he saw that he moved me to 5000 a day and 50,000 one day a week. I then tested a few months later at 56 4 months later 33. He won't change anything, just recheck again in
A few months.

I am on short term disability and have spent a lot of time by the pool in the last 3 months.

Any suggestions?

Thanks in advance