Vitamin D is an essential element in many of the bodies functions, including the immune system and can be found in almost every organ of the body. It is true that the sun is the major source of vitamin D for most people, but it has been shown that solar intensity in Scotland is too low to provide sufficient amounts of the vitamin. There have been several studies in other countries which show that good levels of Vitamin D are beneficial against Covid-19, but the UK government have consistently refused to fund their own study. It is known that a high percentage of the population, particularly among the BAME and the elderly are deficient. BAME people, it is thought because of their skin pigment, the elderly because their skin conversion system weakens with age.
We have been taking supplements since we turned 60. usually only a small 400iu's every couple of days. Then we graduated to 400iu's daily in winter until the advent of Covid. We now take 1000iu's daily and also have a good diet containing vit D. We have looked at the evidence from around the world and whilst there have been no double-blind trials (I don't think the drug companies want the truth getting out), are convinced that a healthy level of D vitamin offers some protection.
Mike.X