That is an interesting article. I do not have MAST issues (as far as I know, at least!) but I had problems taking a vitamin d3 supplement (my levels were around 14 the one time I had them checked). I would get very restless, some tachycardia, and muscle spasms that resulted in headaches. I found that if I take it with magnesium, I do not have those side effects. I read somewhere on the internet that vitamin d can use up magnesium stores, I have no idea if that is accurate or not though. What kind of side effects did you experience from taking vitamin d?