AUTOPHAGY 102: Why 15 grams of protein is a magic number

This article should not be construed as offering either formal or informal medical advice. The content is intended solely for informational purposes. Any changes in your lifestyle or diet should be done in consultation with your doctor or health care professional.  You can read the full medical disclaimer here

I’ve sometimes mentioned in my articles about autophagy that the body uses about 15 grams of protein to keep basic functions (like the heartbeat) going, and that therefore, amounts below that will not stop autophagy.  I wanted to clarify how this works, and why it matters.

Imagine for a moment that you are a vegan eating an extremely low protein diet (you’re living on lettuce and celery.) (I know that’s not how vegans really eat, but bear with me.)

So, you eat a bunch of lettuce and celery, and get only 10 grams of protein a day. But your body needs 15 grams to keep your heart beating. So –— no problem —— it goes into autophagy to get the other 5 grams it needs to keep the heart beating.  (Which is great for the body, because it gets the building blocks for those proteins by scavenging debris, bacteria and viruses out of the cells.)

So if you were eating a diet that low in protein, you would be in constant autophagy. But if there were days you got your protein ABOVE 15 grams, the body would have all it needed to keep the heart beating, so autophagy would stop till you went under 15 grams of protein again. Then it would resume, cause if the heart’s not beating, life’s not very fun. 🙂

Of course, being in constant autophagy is NOT good. The body loves and needs protein. (That’s why it resorts to autophagy when deprived of it, to make some of its own out of cellular debris). And as Dr. Valter Longo pointed out, it’s not the fast that creates stem cells and give you a new immune system after several days of no food, it’s the re-feed after the fast. (One reason that a week of fasting should ALWAYS be followed by a two week re-feed of very high nutrient food) (But hopefully this clarifies why people who are fasting don’t need to panic if they accidentally ingest a couple of grams of protein. Autophagy will go on.

This is the reason that doctors sometimes create “fasting mimicking diets” that keep the protein below 15 grams, as a way for people who want to experience some benefits of fasting, but not to really fast, to do so.

This also clarifies why it won’t stop your fast if you eat just a little protein when fasting. (Not to say it’s recommended, but it won’t be the end of the world.) Let’s say you add some cream to your coffee. There are 0.3 grams of protein in a tablespoon of cream. (You’d have to drink 45 tablespoons, or 3 full cups of cream in a day to stop autophagy.)

Most people still like to do water-only fast (plus electrolytes). The idea of fasting is to give your body a break from food, so if you can do them, water fasts are the easiest way to go. But hopefully this should clarify why adding a tiny amount of cream to your coffee when fasting, won’t break your fast.