Immune Boosters: The Science On Supplements And Immunity

Can herbs and vitamins help strengthen your immunity?
Is it safe to take echinacea or elderberry?
What does the scientific research actually say about coronavirus and vitamin D?
Discover the answers to these and many, many more questions about supplements and your immune system.
"Immune Boosters" began with communication between my family and me regarding supplements that might possibly: 
1.) Help strengthen our immune defenses against viral infections, and 
2.) Reduce inflammation in hopes of lowering the likelihood of runaway inflammation in the event of an infection.
We began exchanging links to articles and scientific papers and, before long, I found myself immersed in online research.
I approached the scientific literature with a specific purpose: to find research on how vitamins, minerals, herbs, and other supplements affect the immune system. But there's a lot of research out there and reporting all of it, or even most of it, would require a book many times this size. 
So I tried to achieve the same balance as the research itself. I didn't report every positive or every negative finding. But if the preponderance of the research I saw seemed to find a positive effect, that is reflected in the chapter. 
For most of the supplements there was at least one review paper that described results of prior research. So it was possible to get an idea of the prevailing scientific opinion on whether the supplement was a net plus, minus, or neutral when it came to supporting the immune system.
There is very little supplement research that directly addresses the new coronavirus and COVID-19. 
But there is a lot of research that scientifically addresses the question of whether certain supplements and herbs can support the healthy function of the immune system to fight off an infection or come through it faster, with reduced symptoms.
Supplements are not cures. They're not a sure thing. They don't provide invulnerability against infection. They are never a substitute for qualified medical care. The best they can do is strengthen the body's natural defenses. They can't promise more against a virus than maybe ever-so-slightly nudging the odds towards our favor. Sometimes, as it is with other things in life, that can be enough.