“D3 at 125 mcg a day is the magi bullet for flu and colds and depression. 22 years experience.”
Studies show D did not impact the frequency of colds.
Studies have shown that D2 the synthetic small portion of natural D does not impact colds at 200 IU a day. D3 is naturally derived from plant and much more complete D and the dose I use is 5000 IU which is 125 mcg, one tiny gelcap. I used to get colds and flu a couple of times a year because my wife was a primary school teacher and she brought them home from school. I started the D3 at my MIL's urging and have not had any virus in 22 years. Colds are virus, you know. My wife started the D3 when she saw me recover from a normally 3 week (for that round) bout of flu in 8 hours. She has been cold and flu free also for 22 years and successfully avoiding the required-at-school flu shots most years.
Every time I see that someone I know and sometimes someone I don't know is starting a cold I give him a bottle of D3 and tell him how to take it. Works every time. The doctors, at least in this area, are starting to recommend D3 as treatment for colds and flu. People in Miami don't need D3 supps unless they work all day inside buildings. Lots of sunshine in Miami and the Keys. Outdoor people do not need the supp when temps permit short sleeves. If you can't get off of what Doctors Say and do your own research, well some folks like the sympathy and attention they get when sick.
It is likely you bridle at what I write but I would hope you would secretly try it. It's cheaper than Nyquil.