The video posted with all of the covid-19 commercials being exactly the same makes you wonder why they all insist on you staying inside your home. Well here is what happens when we get no sunlight and sit all day.
https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/sitting/faq-20058005
When you sit, you use less energy than you do when you stand or move. Research has linked sitting for long periods of time with a number of health concerns. They include obesity and a cluster of conditions — increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol levels — that make up metabolic syndrome. Too much sitting overall and prolonged periods of sitting also seem to increase the risk of death from cardiovascular disease and cancer.
Any extended sitting — such as at a desk, behind a wheel or in front of a screen — can be harmful. An analysis of 13 studies of sitting time and activity levels found that those who sat for more than eight hours a day with no physical activity had a risk of dying similar to the risks of dying posed by obesity and smoking. However, unlike some other studies, this analysis of data from more than 1 million people found that 60 to 75 minutes of moderately intense physical activity a day countered the effects of too much sitting. Another study found that sitting time contributed little to mortality for people who were most active.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4463890/
On the other hand, it is well known that there is a seasonality to influenza that correlates well with the seasonal drop in vitamin D or 25-hydroxyvitamin D (25[OH]D) levels.2 Levels of 25(OH)D are quite low in nursing home residents, and supplementation with 2000 IU of vitamin D can bring levels to normal safely in most patients.3 The use of vitamin D as a prophylactic for influenza has shown promise in prevention of illness and reduction of secondary asthma in children.4 In this study there was benefit for influenza A but not influenza B or the common cold. The mechanism of how vitamin D works for influenza A has been described in the literature.5 Interestingly, the 25(OH)D levels identified in the recent Canadian Household Study have shown a drop in the average vitamin D level in Canadians over the past 5 years from about 67.7 nmol/L to 64 nmol/L, with one-third of those surveyed having levels below 50 nmol/L. Levels in the wintertime were considerably lower and would put the Canadian population at risk of a number of medical conditions.