The Vitamin D that I take:
Vitamin D has major effects on nearly all cells of our immune system, including dendritic cells, macrophages, and T and B lymphocytes. All of these immune cells have a receptor that binds to vitamin D, called vitamin D receptor (VDR). When vitamin D binds to VDR, it then influences the expression of certain genes. It essentially tells the cell to start making more molecules that play a role in fighting off infection.
It tells the cell to start making certain cytokines, and groups of molecules called cathelicidins and beta-defensins. LL-37 is the one and only active cathelicidin in our body. It’s been shown to disrupt the membrane of the influenza virus, and inhibit the production of new viral particles for some types of viruses. It also alters cytokine production. Our immune system also has Beta-defensins, which is another group of molecules that help fight infections. β-defensin 2, in particular, has been shown to have anti-viral properties against influenza. Vitamin D in combination with the VDR increases gene expression of β-defensin 2, meaning it increases β-defensin 2 levels inside certain cells of our body, such as immune cells and alveoli. But it also tells the cell to decrease its production of certain molecules that play a role in the cytokine storm. Pulmonary epithelial cells, including alveoli, contain high levels of the 1 alpha-hydroxylase enzyme, which allows for local production of 1α,25-dihydroxyvitamin D, which is the active form of vitamin D, aka calcitriol. Calcitriol inhibits the production and secretion of many cytokines and chemokines, including RANTES aka CCL5. Its also known that Vitamin D deficiency impairs the ability of macrophages to mature, and impairs hydrogen peroxide production, which is important for killing off viruses and bacteria. Vitamin D also play a role in maintaining tight junctions in between lung cells, which is important to act as a barrier against infection. In rats, and possibly in humans, vitamin D causes a decrease in angiotensin II in the lungs, which is a good thing.
An interesting study published in the prestigious NEJM, which coincidentally was published in December 2019, the same time the COVID outbreak started in Wuhan, China. In this study, they looked at people who were critically-ill in the ER, and measured their vitamin D levels. If they were deficient, they gave them big doses of vitamin D, to half the patients. The other half got a placebo. They moved the patients to the ICU. They of course treated them for whatever illness they had, in addition to giving them the single dose of 540,000 IU of vitamin D. This was a randomized, double-blind, placebo-controlled, phase 3 trial. The primary endpoint was 90-day all-cause mortality. Over a thousand patients in the study and they had levels less than 20 ng/ml. For the ones who received the vitamin D, their levels on average, came up to 50 ng/ml. The placebo group’s levels remained low, with an average level of 11. The 90-day mortality was 23.5% in the vitamin D group and 20.6% in the placebo group. So the vitamin D3 did not provide an advantage over placebo with respect to 90-day mortality in critically ill, vitamin D–deficient patients.
About 40% of Europeans are vitamin D deficient, and 13% are severely deficient. Vitamin D deficiency is more common in the subtropical and midlatitude countries than the tropical and high latitude countries: And severe vitamin D deficiency was found to be nearly 0% in some high latitude countries. There are probably less people with vitamin D deficiency in these areas because of fortification in foods, and I’m guessing more consumption of fish, which is one of the few foods that has vitamin D. So looking at the demographics, there seems to be a lot of geographic overlap between severe COVID cases and areas with vitamin D deficiency. So RCT are desperately needed, and as of right now, there are 3 that are taking place, or about to take place. Given the fact that low dose vitamin D is pretty darn safe, it seems quite reasonable for people to take a low dose supplement, especially if they think they might not be getting enough from sunlight or their diet. Of course, ideally, you want to have a discussion with your doctor if possible. Personally, I take 1,000 IU per day. I know that I’m not going to run anywhere near toxic levels of vitamin D with that dose, while at the same time, I know that I won’t be vitamin D deficient.
