Vitamin D is essential for calcium absorption in the gut. Vitamin D deficiency causes poor bone quality in children and adults and increases the chance of one’s bones breaking (fractures) resulting in osteoporosis.
Vitamin D also protects the lungs against infection. Vitamin D levels in our bodies normally goes up every summer and down every winter due to seasonal variation of sun exposure to our bodies. Hence, we are more susceptible to cold and flu as well as Covid-19 infections of the lungs in the winter months unless we take more vitamin D supplement in the winter (keep reading).
Keeping our vitamin D level above 40 has been shown to decrease incidence of osteoporotic fractures. Keeping our vitamin D level above 55 will reduce the Covid-19 related mortality and severity of illness. Populations with high incidence of vitamin D deficiency have significantly higher mortality rates from Covid-19 than populations with lower incidence of vitamin D deficiency. People with higher vitamin D levels have a significantly lower severity of illness and improved survival with Covid-19 infection. High dose vitamin D therapy early after diagnosis of Covid-19 infection, also significantly reduces severity of the illness and the mortality.
If you do not know your vitamin D level and do not take any supplements, your vitamin D level is likely sub-optimal. If checking your vitamin D level is not feasible at this time, then take 5,000 units (125mcg) of vitamin D3 daily for the next 3 months and then check your level.
How much vitamin D supplement one needs varies from person to person. It is extremely unlikely that one can achieve a vitamin D level above 55 without taking a supplement. Required vitamin D dose varies between 2,000 units and 10,000+ units daily. A baseline vitamin D level is very helpful in determining the daily vitamin D supplement dose one needs. The lower the baseline vitamin D level, the higher the required daily vitamin D supplement dose needed.
If you know your vitamin D level, then you may use this web site to get an estimate of how much vitamin D you need to take daily: