There is a lot of confusion regarding fasting, its types and effects on the body. Fasting has numerous benefits, which directly improve immunity such as
Less oxidative stress
Lower inflammation
Autophagy or cellular recycling
Growth of stem cells
Improved mitochondrial functioning
Kills pathogens
Resets immunity
This list clearly suggests that fasting is immensely beneficial for the immune system. Valter Longo cites evidence that a 72-hour fast can rejuvenate our entire immune system, with broad anti-ageing benefits[1].
How fasting resets the entire immune system
When you eat, there is a huge spike in the insulin levels. After 12 hours of fasting, growth hormones kick in. After 17-24 hours the magic happens when your body enters, the state of autophagy where body kills damaged cells and pathogens uses them for energy. Autophagy is the best detox you can get.
But due to this effect, after 24 hours of fasting, you lose some of the White Blood Cells (WBC). To quote Longo “When you starve, the system tries to save energy, and one of the things it can do to save energy is recycle a lot of the immune cells that are not needed, especially those that may be damaged,”. The WBCs continue to decrease in number as you fast. However, they come back, and in larger number than before when you re-feed and thus resetting and strengthening the immune system.
Because the WBC count drops when fasting, it is not a good idea to fast especially when you have a viral infection[2]. The case of bacterial infection is exactly opposite supporting the old adage “Starve a fever (bacterial), feed a cold (viral)”.
The study by Yale researchers Wang, Andrew et al. on opposing effects of fasting metabolism on tissue tolerance in bacterial and viral inflammation has concluded
Fasting metabolism is protective in bacterial, but not viral, inflammation
Ketone bodies limit ROS-induced neuronal damage during bacterial inflammation
It is repeatedly shown that fasting-induced autophagy is a great tool against bacterial infections. Studies have shown its efficacy against group A Streptococcus[3], Mycobacterium tuberculosis[4], Salmonella infection[5] etc. You yourself have experienced that you lose appetite when you get a bacterial infection. That is the natural response by your body to fight off the pathogens.
However, some viruses such as γ-herpesvirus (Herpes virus)[6], HIV[7] escape or block autophagy. In some cases, autophagosomes supported the replication of the virus in host cells[8]. Influenza A virus can also replicate itself using autophagy. [9]
So the question arises if autophagy is going to support COVID19 replication? Not exactly. Coronavirus replication does not require autophagy[10].
In another study, it was shown that autophagy reduces MERS-Coronavirus infection[11].
The novel coronavirus (COVID19) is a new one and it is hard to predict if autophagy will help the virus in replication or reduce the infection. Hence, it is better to err on the side of caution. I would not suggest any fast longer than 16 hours as after 24 hours the white blood cells start dropping leaving the body predisposed to infection due to lower immunity.
So what’s the takeaway?
You can still do time-restricted eating or intermittent fasting of 16:8. This will have no effect on WBC count.
It will not trigger full-blown autophagy. However, the basal autophagy because of time-restricted eating will help your immune system to work properly.
Avoid longer fasts (>24 hours).
If you are wondering how to boost your immunity and missed my thread, you can read it here.
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Jagatjit
References