Intermittent fasting and the brain-derived neurotrophic factor

In our toolkit for fighting and even preventing Alzheimer's disease, physical exercise is our most effective weapon.  This has been validated repeatedly by scientific investigation.  But why?  As we explained in Beating the Dementia Monster, sustained physical exercise -- aerobic exercise -- promotes generation of BDNF, the brain-derived neurotrophic factor.  This is a protein secreted by neurons, and it can prompt stem cells in the brain to form new neurons.

But is aerobic exercise the only way to induce brain cells to generate BDNF?  Well, it's probably the best way, but it's not the only way.

If you are a dedicated reader of this blog (thank you), you will recall that I began intermittent fasting in January of 2020.  I was encouraged to do this by an article I read in the New England Journal of Medicine (NEJM) from December 2019.  When I began, I immediately noticed that my arthritis was reduced.  This is attributable to the ability of intermittent fasting to reduce inflammation throughout the body.  Since then, my doctors find that my memory and cognition have been stable, but it's hard to say if the fasting has been responsible for any of that.  I have been applying all of the tools from "The Dementia Toolkit" we describe in Beating the Dementia Monster, and I don't really know the relative power of each tool.  I just know that, taken together, the results have been great.  (The experts will give the most credit to physical exercise.)

Since January 2020, intermittent fasting has become a fixture of my lifestyle, and I have posted on it periodically.  But I was recently encouraged to take another look at why intermittent fasting would be helpful to brain health.  The NEJM article stated that one effect was that fasting increased the production of BDNF, but I wondered why.   So I recently began reading more research reports on investigation of BDNF and brain health.

With respect to BDNF, most commonly noted was that the switch from a glucose metabolism to burning ketone bodies for energy (metabolic switching) placed stress on neurons.  Metabolic switching occurs during intermittent fasting when the body has consumed its supply of glucose and must turn to other sources of energy.  When neurons were stressed, they generated more BDNF.  Sustained exercise also produces stress.  So this seems to be one reason why intermittent fasting helps with brain health.  But is that all?

In Beating the Dementia Monster, we identified both oxidative stress and inflammation as causes for the propagation of Alzheimer's disease and mechanisms by which the disease kills brain cells.  Diet and exercise go a long way in fighting these, but intermittent fasting also goes after both.

So the theory is that intermittent fasting calms both oxidation and inflammation while prompting the formation of new neurons via the production of BDNF.  (BDNF also helps with the repair of damaged neurons.)  Here is another writer's take on this.

How much confidence do we have with these claims?  Much of it is based on experiments done with mice, and we've said before that mice are not people!  Innumerable times promising research done with mice has failed to produce similar results in humans.  So why do we still use mice so often?  Because often the results can only be developed from an autopsy.  Which complicates things.

One thing worth noting is that autopsies of elderly humans find that those who died with dementia had significantly lower levels of BDNF in their brains than those who did not.

One last comment.  There are supplements out there that are reputed to increase BDNF, and maybe they do.  However, I have not found any research that I find compelling that demonstrates that increasing BDNF through any method other than exercise and fasting actually resulted in improved memory and cognition.