What we need to understand about vitamin D is basically that there is a lot more to vitamin D than meets the eye. I'll attempt to explore and explain some of the reasons behind that statement, in this post. But this discussion probably barely scratches the surface, because this is a rather complex issue, where many factors depend on many other factors, and many of them are not well-defined.
We all know that IBDs tend to deplete vitamin D levels, and we also know that a vitamin D deficiency predisposes to the development of IBDs and other autoimmune diseases. What we don't know is how much Vitamin D is ideal, and how to determine whether we are taking the right amount of vitamin D supplement. The fact that we have an IBD, means that most of the information published about vitamin D testing and supplementation probably is not valid for us.
Chris Kresser brings up some interesting facts in a blog that he wrote back in 2010, concerning the effects of vitamin D with regard to autoimmune disorders, and much of the info in this post is based on information in that blog. But most of the interpretations (of how that information relates to us, as IBD patients) is mine, so please don't blame Chris if you dispute any of this information.
In the article he acknowledges that people who have an inflamed small intestine, or a leaky gut, have a limited ability to absorb vitamin D from their food and oral supplements. And he points out how both stress and corticosteroid medications, raise cortisol levels, which depletes the body's cholesterol supply. Since cholesterol is the feedstock for vitamin D production in the skin (together with exposure to sunlight), lower cholesterol equals lower vitamin D production by natural means.
Being overweight can tie up vitamin D, because it tends to be taken up by fat cells. And since vitamin D is a fat-soluble vitamin, obviously the lower fat diet recommended by most GI docs for MC patients, further reduces the likelihood that vitamin D will be adequately absorbed by the bloodstream. But more than that, anyone who has an IBD, has a fat malabsorption problem as part of the symptom set, and this drastically reduces our ability to absorb vitamin D. Also, as we get older, we become less capable of producing vitamin D from sunlight. And as our inflammation level increases, our body's ability to utilize vitamin D becomes increasingly compromised.
But before the vitamin D that we already have available can provide any benefits, it must activate nuclear hormone receptors for vitamin D3 , also known as vitamin D receptors (VDR). Unfortunately, autoimmune diseases tend to be associated with a genetic issue (known as polymorphism) that compromises the expression and activation of VDR, so that problem significantly reduces the potential activation of vitamin D. As he points out in the article, a high percentage of patients who have Hashimoto's disease, for example, have VDR polymorphism.
So according to Chris Kresser's interpretation, if we have a VDR polymorphism (which is often associated with Hashimoto's and possibly other autoimmune issues), then we can't necessarily rely on a normal vitamin D blood test result that shows that we have plenty of vitamin D in our bloodstream (because we may not be able to utilize the vitamin D, if we have a VDR polymorphism). This implies that our vitamin D level would have to be much higher than "normal", in order to provide us with enough vitamin D for normal daily functioning, due to our compromised ability to utilize vitamin D. IOW, we might be functioning on the same level as someone who is vitamin D deficient, even though our vitamin D test result showed that we have plenty of vitamin D in circulation.
Obviously there's no simple way to approach this issue, because (as usual) we are all different.
And to add insult to injury, there's the effect of stress, which is always a wild card with anyone who has an IBD. By actual measurement, one of our members, Gabes, found that during an extremely stressful period of only approximately 3 months, her blood level of vitamin D dropped from 116 ng/mL to 56 ng/mL (290 to 140 nmol/L, in international units). That's a drop of 60 ng/mL in approximately 90 days. What makes this truly incredible is the fact that she continued to take 3,500–5,000 IU per day, of sublingual vitamin D3, during that 3-month period. Clearly, when we are subjected to severe chronic stress, our body is capable of consuming vitamin D at almost unbelievable rates.And while most studies do show that a 35 ng/mL level of vitamin D, based on a 25(OH)D blood test, is adequate, issues such as these illustrate why Dr. Cannell (of the Vitamin D Council) recommends a minimum level of 50 ng/mL (in direct contradiction to most other "authorities").
But to complicate the issue, some recent studies have shown that higher isn’t necessarily better when it comes to vitamin D, because having too much D3 in circulation can be harmful, also. Chris mentions a study published in the American Journal of Medicine that established that maximum bone density occurs at 25(OH)D levels between 32-40 ng/mL for most people, and when the levels are increased to above 45 ng/mL, bone density starts to decrease. Along a similar line, a study published in the European Journal of Epidemiology showed that residents of Southern India who had 25(OH)D levels above 89 ng/mL were approximately three times more likely to have cardiovascular disease.
But . . . did the subjects involved in those studies have an IBD or any other autoimmune disease (IOW, could they have had VDR polymorphism)? You can bet that they did not, because most carefully controlled medical research studies are designed to rule out people who do not meet the criteria of a profile that is considered to be "normal" for that particular study. So it is highly likely that the conclusions of that study do not apply to us, since we would almost surely not meet the subject profile requirements of those studies.
To further complicate the matter, research by Chris Masterjohn indicates that a deficiency in vitamins A and K2 apparently play a role in higher-level vitamin D toxicity. IOW, if vitamins A and K2 are deficient, then the potential toxicity of high levels of vitamin D can be amplified. Since this effect has been confirmed by other researchers, we need to be aware that if we choose to maintain higher levels of vitamin D3, then we need to be sure that our vitamin A and K2 levels are not in the deficient range. Even so, there doesn't appear to be any valid research that confirms that higher levels of vitamin D3 are safe when levels of vitamin A and K2 are sufficient, so these are pretty much uncharted waters until appropriate research is done.
But here again, the odds are extremely high that we would be exceptions to the accepted subject profile qualifications that were used in those studies, so the results may not/probably do not apply to us. But we don't know that for a fact — we can only guess, due to the lack of available data. We have to always remember that we will never fit into a "normal" profile, from a medical viewpoint, unless the subject being discussed is "normal" MC patients.
So how do we know if we're taking too much vitamin D, and thereby possibly increasing our risk of damaging our cardiovascular system, or even risking triggering an adverse cardiovascular event? According to Chris Kresser, our serum calcium level can tell us when we've gone too far. If blood calcium levels are up in the 11–12 mg/dL range, our vitamin D level is dangerously high, and we're risking cardiovascular damage. At least he claims to use this gauge in his own practice.
Actually, the cardiovascular risk is more likely to be due to the elevated calcium level, rather than due to the vitamin D level per se, but theoretically, in this situation, lowering the vitamin D supplementation should lower the blood calcium level, if too much vitamin D is the reason why calcium is elevated in the first place. Of course again, this is unsubstantiated by carefully-controlled medical studies, so we can only hope that this assessment of the relationship between calcium and vitamin D levels is valid. My lab uses a normal range for calcium of 8.6–10.1 mg/dL, and I would assume that's probably reasonably representative for the industry, but individual labs may use slightly different numbers for the "normal" range. In International units, a calcium level of 2.8-3 mmol/L would be indicative of vitamin D toxicity.
My last CBC was done last October, and it showed a calcium level of 8.8 mg/mL. My last vitamin D test was done 6 months prior to that (in April), and at that point my 25(OH)D level was 55 ng/mL. I've increased my vitamin D supplement rate since October, so I need to order a test one of these days, to check my current level. All in all, though, there's a heck of a lot more to this vitamin D thing than meets the eye, that's for sure.
The Role of Vitamin D Deficiency in Thyroid Disorders
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I think I'll go back and add that a little later — I need to run an errand first.
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