https://www.healthline.com/nutrition/vitamin-d-and-vitamin-k
Botox is a pretty powerful tool for doctors when applied locally in small quantities, but often fatal in Botulism. Water is necessary for life, but hyponatremia is a real thing.
It would be correct to think that at 66 degrees north, and a lot of cloud cover, there is significant risk for Vitamin D deficiency. The consequence is near religious attention to taking fish oil supplements. Doctors routinely screen, Vitamin D tablets are prominently on sale in all the supermarkets etc. It's definitely a data point.
To put things in perspective, the US population is 328M.
People bring this up when it comes to smaller countries, but it doesn't take into account population concentration, which is much more important than sheer population size or density.
Iceland has been very effective.
I wonder if any of the results show supplements work as well as diet/sunlight?
Generally it’s recommended that sun > supplements, for a few reasons. But if you can’t get some sunlight supplements are not a bad choice at all.
https://www.outsideonline.com/2410015/sun-exposure-blood-pre...
sun exposure increases nitric oxide which decreases bp
Closer research shows it probably isn't relevant.
https://www.cebm.net/covid-19/vitamin-d-a-rapid-review-of-th...
All I see from that paper is that there is "no evidence" that Vitamin D is beneficial with COVID-19 (and some qualified evidence that it may help other respiratory infections).
They mentions several planned/registered studies on the question, but none that have reported results yet.
Either way, they still recommend supplementing if deficient(which the numbers for people with IVD are quite high in most regions).
My concern is, if the risk of transmission is more indoors than outdoors as this study indicates(https://theprint.in/health/sharing-indoor-space-major-infect...), Is staying at home making people Vit-D deficient coz of less exposure to sunlight?
And If this is true, is it one of the factors responsible for severe Covid19 outcomes?
Is this also the reason why old folks are severely affected from Covid19, coz they may tend to stay indoors more, relative to other age groups?
"Of 49 patients with mild symptoms of Covid-19 in three hospitals in southern Asian countries, only two had low levels of vitamin D; of 104 patients with critical or severe symptoms, only four did not have low levels of vitamin D." https://www.telegraph.co.uk/news/2020/05/03/time-take-seriou...
"The VDI (Vitamin D Insufficiency) prevalence in ICU patients was 84.6%, vs. 57.1% in floor patients. Strikingly, 100% of ICU patients less than 75 years old had VDI. Coagulopathy was present in 62.5% of ICU COVID-19 patients, and 92.3% were lymphocytopenic. Conclusions: VDI is highly prevalent in severe COVID-19 patients" https://www.medrxiv.org/content/10.1101/2020.04.24.20075838v...
"Vitamin D has been shown to have an anticoagulant effect. A decrease in 25-hydroxyvitamin D [25(OH)D] concentration has also been associated with an increased risk of venous thromboembolism. " https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4069050/
There is also other literature suggesting that Vitamin D can reduce the risk for the "cytokine storm" which leads to acute respiratory distress syndrome by reducing the production of pro-inflammatory cytokines (while increasing the expression of anti-inflammatory cytokines). Again, I'm not a doctor but supplementation is likely to be fairly low risk. There is increasing evidence that there's some sort of correlation and it may be worth exploring.