I am very excited to come across this thread on Vit D3, as it is a subject close to my own heart (liver, pancreas etc etc).
No, I am not a scientist doing any research, but a fellow traveller on the diabetes journey, as often found on the forum.
. But one who has a very big interest in the topic, and has trawled as much info about it online as possible, and have been paying close attention to my own VitD3 story now.
First of all, I just want to remind us all of the wonderful diversity of our planet - both in terms of sunlight exposure (my understanding is the best source of this essential hormone), and among ethnic groups in terms of barriers and protectors and reflectors of sunrays - ie skin lightness or darkness, eye colour and hair colour. I am very aware of this trotting between a subarctic region and a subtropical region as I do, and have done over different periods of my life, and experienced the what I believe now to be the effect of Vit D3 deficiency on my own insulin sensitivity over three decades, at least as a contributing factor.
The internet is global, and the English language is popular and widespread globally. How lucky are we! And it means for us in the internet generally, and in this forum in particular, experience of the sun (and Vit D3!), and health parameters are not the same for us all. Including the info given out by GPs.
I say this, as in Sweden the official parameters of sufficiency, optimal, and potentially toxic might be quite different? As one would logically expect perhaps? Vit D3 not being stored for much longer than 8 weeks, is my understanding. And here the season of extreme lack of sunlight is three months a year. (The darkness is coming!)
On the other hand, as Indy in Australia knows very well, as do I as a Kiwi (I have no idea where CatLadyNZ actually lives), the lighter your skin the more dangerous the sunrays in that part of the world is, and sun exposure and risk of skin cancer is a very real and daily consideration. (It is in Scandinavia too, because of the full-on nature of the summer sunlight levels, but nothing compared to Australia and NZ re UV rays). It is no small matter for people in that part of the world to have to pay very close attention to what time of the day, and exactly how much time to spend in it, depending on your skin's natural protection (ie colour/melanin levels).
Sunlight aside, and onto supplementation and optimum levels.
Here in the subarctic:
levels of 25-74 nmol/L are considered insufficient.
Levels of 75-
250 are considered optimal.
And only over 250 is it considered potentially toxic.
And from my own experience - it is exceedingly hard to get to that toxic level! Complete with daily sunning, when the temperature permits, and high level of supplementation - 6,000 IU daily, and at least three subtropical summers in the last six years. VERY hard, at least, it is for me, to get anywhere near toxic levels.
My own Vit D level is only on the upper end of the 'insufficient' scale, at
68 nmol/L (after months of 6000 iu a day, during two same year winters, and a recent half-a-summer-sunning regime reminiscent of the 1970s!). I do have fat absorption issues, with my gallstone, which apparently affects how much VitD you need to operate efficiently too (as in you need more) if I have understood correctly. But there you are.
Apparently, in western countries, and as diabetics with all sorts of digestion/hormone/ organ functioning issues - the last thing we probably need to worry about is too high levels of vitamin D3! (Region, skin colour, food, skin cancer risk dependent of course.) But of course - get yourself tested, and discuss with your doctor, absolutely. I just wanted to get potential toxicity, with D3 supplementation, into perspective.
And it says something that in Sweden you can get your vit D levels tested on socialised medicine/the state - and one should be able to! (Taxes are, um, rather high here
.) But I believe all diabetics should have access to nutrient-level screening included in their taxes (which is what socialised medicine is after all), as it is such a huge part of treating the dysfunction with diet, after all. Think of how much we save the taxpayer, and ourselves, in untaken metformin! But that's just what I think. (You have to pay for a Vitamin D test in NZ - with NZ's MUCH higher rates of T2D compared to Scando countries. A silly illogical 'saving' on a Government's part, but I digress.)