The cheapest Covid-19 (Coronavirus) therapy in the world is...THE SUN:
What he does not mention is that your body cannot build ANY vitamine D in the winther months, depending on your latitude, so you MUST take it in another form in the winter months, for example as vegan vitamine D3 capsules. ALWAYS combine D3 with K2 for optimum metabolization. Always pick the vegan form, the non vegan D3 is connected to animal cruelty, as the non vegan D3 is made from merino wool sheep. The vegan form can be cheaper too, compare prices!!
Oh and he also does not mention that the body cannot make ANY vitamine D if you are behind glass, as glass totally blocks the necessary UV rays. 

What the real problem is regarding what they tell us about Covid-19 (Coronavirus):

He also made a Covid-19 archive of various videos, which I did not watch:

Videos by "Dr. Eric Berg DC". 
(I do not agree about the keto diet, you can try it, but watch your health closely, I think a diet mainly based on plants is better, but pick what works BEST FOR Y O U !!!).