Can prolonged fasting help improve our immune system?

Fasting, like exercise, is often seen just as something that we can use for weight loss purposes. Although fasting has been known and practiced for thousands of years. It has been used as a spiritual practice and for healing from diseases, not for weight loss purposes like we are seeing now. It is a very beneficial and powerful practice, especially for metabolically unhealthy individuals.

To be healthy and to remain so for our lifetime requires a strong immune system. Fortunately, the human body is doing an amazing job at keeping us healthy by cleaning the old cells, removing the toxins and distributing all of the nutrients to the correct places. Our skin, lungs, digestive system, liver and kidneys all play an important role in keeping us healthy. However, we can help our body and make its job much easier by eliminating highly processed foods, added sugars, and industrial oils such as vegetable oils.

How about complete fasting, could that be an effective way of strengthening the immune system? And how is it that consuming no food at all can help us to heal?

Actually, when we stop eating, normally after 24 to 36 hours we will have depleted our glycogen (sugar) in the liver which will force the body to produce a product called ketones. Our brain and nerve systems depend on glucose to function, however in the absence of glucose the body actually makes its own glucose to maintain homeostasis. Exactly how this process takes place will depend on the individual heath markers. If we then continue into a prolonged fast, after 36 hours or longer the body will start the healing process — essential starting to repair and clean our old and damaged cells. When we have no food at all in our digestive tract the body is not using energy for digestion and can instead use it for these other processes. However our immune system will also slow down, due to the body’s break down of immune fighting white blood cells. And the body will begin to conserve energy and will slow down our metabolism too.

When we start our re-feed (i.e. we start eating again after our fast) our immunity and metabolism increases. The body starts to regenerate itself which includes strengthening the immune system and increasing metabolism. Researchers have found that after 72 hours of fasting we can improve our metabolism and trigger stem cell regeneration of new immune cells.

So, actually, once in a while stopping eating could benefit your health. How often you should do it really depends on how healthy you are. Normally, for a healthy individual a fast of 48 to 72 hours, once a month, can be enough. It’s important too during the fast to be sure that you get enough fluid and electrolytes (such as sodium, potassium and magnesium) too. If you are taking medication then of course please consult with your physician and only fast under supervision.

I personally practice fasting on a regular basis, which depending on my current goals can be one 72 hour fast every couple of months, and/or one 24 to 36 fast every week.

Everyone is unique, with personal goals and individual health markers, so do be mindful as to how you start to fast, and importantly how you break the fast too. You should start refeeding after your fast with a small meal and gradually increase to get back to your normal eating patterns. Fasting is not an opportunity to eat more, but it is an amazing healing tool so make sure to watch your body and see how it reacts. You will be amazed at how much energy you will have after the fast.


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Mayo Clinic


Texas A&M College of Veterinary Medicine & Biomedical Sciences

Fasting triggers stem cell regeneration of damaged, old immune system

USC University of Southern California

Prolonged fasting ‘re-boots’ immune system

Medical News Today

Refeeding syndrome: what it is, and how to prevent and treat it

US National Library of Medicine, National Institutes of Health

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