re: 500 mg of D3 daily and big doses of C for Covid 19?

The only person I have heard mention strengthening the immune system is Rogan. Many doctors have talked about Vitamin D and Zinc.

And I'm guessing the reasoning behind not mentioning healthy immune systems as a way to fight it is because it's not guaranteed to stop the virus, but what could it hurt? It blows my mind that risk factors for this thing include obesity and diabetes, yet nobody is saying to the population that we need to lose weight and eat properly.

It's mind boggling.