Hey PM,
You're not the only CH'er to comment about the noticeable correlation between taking vitamin D3 and experiencing a cessation of your CH... or stopping this regimen and having your CH return...
You're also not the only CH'er to comment on experiencing the obvious health benefits of taking vitamin D3...
The statistically significant numbers involved in both cases favor causality rather than coincidence, so it's "not in your head" or mind games if you'll forgive the doubletalk...
That said, there is an apparent adaptation... at least with respect to the loss of effectiveness of this regimen... It's also likely that this adaptation did take place in your head... and elsewhere in your body... I'll try to explain...
I've been exchanging survey data with Dr. Stasha Gominak, MD, a neurologist in Tyler, TX. She's been treating her patients with a vitamin D3 regimen similar to what we've been taking, except she's been doing this for over 6 years... She's also added another vitamin supplement.
She discovered an interesting phenomenon where some of her patients who were completely pain free on this vitamin D3 regimen experienced a gradual return of their neurological symptoms after two to three years. There were no obvious changes in dose or life style... The regimen apparently just stopped working and the symptoms returned.
It took a while then one of her patients called to say the regimen was once again working as it had in the past. After a series of Q & A, Dr. Gominak focused on vitamin B12 and the rest of the vitamin B complex this patient had started taking.
Lab tests confirmed nearly all of her patients who experienced a relapse while on the vitamin D3 regimen were deficient in vitamin B12 and likely most of the other B complex vitamins. She also found that patients who didn't respond to this regimen did so after adding vitamin B 50.
She started prescribing the vitamin B 50 complex to address the apparent deficiencies... and the vitamin D3 regimen started working once again!
A few months later there was another setback... If her patients stayed on the vitamin B 50 for more than three months... the neurological symptoms returned once again... After some additional tests, Dr. Gominak confirmed that too much B 50 becomes counter productive. She eventually settled on a three month course of treatment with vitamin B 50...
Rather than trying to explain her theory on the mechanism of action involved with vitamin B 50... it involves friendly colonies of flora and fauna living in our GI tract... watch the videos of her presentation on "Sleep, Chronic Pain and Headaches" at the following link:
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or

When you finish that, read the article, "The human microbiome - Me, Myself, Us" at the following link then you decide:
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The bottom line... adding a three month course of the vitamin B 50 complex isn't for every CH'er... If the present anti-inflammatory regimen is preventing your CH... it's not broken, so don't try to fix it...
If, on the other hand, the anti-inflammatory regimen hasn't resulted in a CH pain free response with your 25(OH)D between 70 and 80 ng/mL, (175 to 200 nmol/l) or this regimen worked great for a couple years then stopped working... then the three month course of vitamin B 50 may be just what you need... Talk with your PCP or neurologist.
Take care and please keep us posted.
V/R, Batch