Received this email today from Dr Fung:
Fasting and COVID-19 A lot of people are worried about how fasting affects the risk of COVID-19 virus infection. The truth is there is no good information on this subject at all, so everything is a matter of speculation.
Here’s my take on it:
Fasting mostly affects metabolism and therefore does not directly affect the risk of viral infection or immunity. However, the people at highest risk of severe disease are those with high blood sugars and other medical conditions. If fasting allows you to manage those metabolic diseases better, then it is logical to assume (but not proven) fasting may help in this case.
In any infection, the body has a natural reaction to stop eating. This is called the ‘fasting instinct’ and we’ve all experienced it. When we get a bad cold, the last thing we want to do is eat. Our appetite is naturally suppressed, and we fast. This presumable is part of the body’s protective response to lock down the available blood sugar and to activate the sympathetic nervous system to support the fight against the infection. So, it is logical to assume (but not proven) fasting may help (somewhat) against any viral infection, but at the least it won’t be harmful.
There have been some people who have noticed during longer fasts (>48 hours) cortisol increases and this may suppress immunity. This increased cortisol is part of the general activation of the body, along with other hormones like growth hormone and norepinephrine, so the net effect on immunity is unknown. Further, some have pointed out some of the severity of COVID-19 is due to the overreaction of the body’s own immune system (called a cytokine storm) and a mildly depressed immune response over longer fasting may actually be protective. However, the net effect of all these theoretical concerns is unknown.
So, based on my clinical experience only, since no studies are available, here are my best guesses at what to do about fasting with COVID-19:
Stay safe,
Dr. Jason Fung
Thank you for that.
I’ve read about how a three day fast regenerates the immune system. I’m not sure if that’s good or bad for something like covid-19, which may trigger a cytokine storm. What’s the science for a three day fast?
I’ve often wondered if there is any truth in the old folk-wisdom “starve a fever, feed a cold”, and in particular if there is something to it, could it be actually “starve a bacterial infection, feed a virus”?
My layman-logic being that you’re starving bacteria of easy energy, but viruses hijack our own cells which are still well provided for in fasting, so may not be inhibited by the lack of easy energy.
But there are so many variables . Perhaps fasting causes cells to inhibit nuclear protein building and therefore virus reproduction?, but in that case it also might inhibit the body’s immune system cellular and sub-cellular production.
But… I have no expertise here and am only curious. I’d be inclined to trust Fung’s well-informed speculation in the absence of anything better.