Sandy is absolutely correct. Vitamin D normal range is set by statistical sampling of a reference population and observations made related to preventing rickets.
Any level below 20 ng/ml Rickets begins, lower cognition and potential for depression. Above 100 ng/ml hypercalcemia in the blood is observed (in some people).
So the question is what is normal vs what is "optimal". Optimal levels of vitamin D in the blood contributes to immune function, cognition and bone formation. We all want to see an optimal level - not just normal. Doctors focus on normal - I focus on optimal.
https://www.zrtlab.com/blog/archive/vitamin-d-reference-ranges-optimal/
Research has shown that peak immune function occurs when vitamin D levels are above 50 ng/ml and peak around 70 ng/ml. And this includes anti-cancer immune function. T-cells are loaded with vitamin D receptors (VDR). When a foreign virus protein is detected, the first thing T-cells do is find vitamin D and attach it to their vitamin D receptor in order to activate and attack the virus. This is why I believe pandemics - which always seem to occur in winter - are almost certainly associated with low vitamin D status of the patient. I wish they would collect data on this with all of the patients in hospitals having Covid-19.
https://www.ncbi.nlm.nih.gov/pubmed/23785369
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One area of my own personal research is in the role T-cells have in causing inflammation. Multiple sclerosis, for example, is a condition where T-cells attack the body. A delicate balance exists between T-cells expanding to meet a foreign threat and then have to shrink back when the threat is over. Sometimes they don't do that. Covid-19, for example, causes an enormous T-cell response in the lungs leading to over-inflammation, cytokine release leading to enormous amount of fluid filling the lungs. T-cells - can cure and they can kill. Amazing biology goes on in the T-cell.
High levels of vitamin D 'arm' T-cells to do their job. https://www.everlywell.com/blog/inflammation/vitamin-d-and-inflammation-...
And there is research that vitamin D helps in the fight against inflammation. But can high vitamin D levels for long periods of time also lead to some T-cells run amok? And produce inflammation in the longer term rather than lessen it in the short term. I don't know.
My thinking is to let nature guide me in the absence of data. What I observe in nature - It is normal for our vitamin D level to rise and fall with the seasons. And in areas where the seasons are steady (equator), it is normal for our skin to darken in order to lessen the amount of vitamin D created. I am not sure that keeping ones vitamin D at a 'permanent' high level (i.e. 70 ng/ml) is necessarily optimal. Letting it fall back to 40 and then rise again may be more optimal. It may allow T-cells to return to barracks and reload sort of speak. Or more likely, signal genes to de-activate T-cells in order to enable new ones. What is key is this is a longer term process over many months as the sun rises in the summer sky and falls in the winter. It is also interesting that vitamin D is stored by the body with a very long half -life of months. It take months to deplete your vitamin D levels and likewise months to increase it (should be done gradually). Natures way of following the sun? Perhaps.
One final comment - On a bright sunny summer day, after a few hours in the sun (e.g. at the beach) our bodies will produce the equivalent of 10,000 IU's vitamin D. This is a normal high level production that our bodies will do naturally. And they don't produce any more - once this level is reached, other mechanisms shut down vitamin D formation even if you remain out in the sun. Following nature, I never take more than 10,000 IU's in any given day. Keep that in mind. If you have to increase your vitamin D status, do so by taking no more than 10,000 IU's per day over many days-weeks and raise your D status slowly. Raising it suddenly is not good.
