Could Fasting Help Prevent Alzheimer’s and Parkinson’s Disease?


by Nils Osmar. September 10, 2022. Medical Disclaimer

There’s evidence that taking breaks from food – in the form of either fasting or caloric restriction – might possibly help protect the brain against Alzheimer’s, Parkinson’s and other conditions. Both short and extended fasts have been shown to promote neurogenesis, and to clean mis-folded proteins from the body and brain.

A recent study

According to a 2019 study called “Fasting as a Therapy in Neurological Disease”:

Fasting induces an altered metabolic state that optimizes neuron bioenergetics, plasticity, and resilience in a way that may counteract a broad array of neurological disorders. In both animals and humans, fasting prevents and treats the metabolic syndrome, a major risk factor for many neurological diseases.

In animals, fasting probably prevents the formation of tumors, possibly treats established tumors, and improves tumor responses to chemotherapy. In human cancers, including cancers that involve the brain, fasting ameliorates chemotherapy-related adverse effects and may protect normal cells from chemotherapy.

Fasting improves cognition, stalls age-related cognitive decline, usually slows neurodegeneration, reduces brain damage and enhances functional recovery after stroke, and mitigates the pathological and clinical features of epilepsy and multiple sclerosis in animal models. 

From an article in New Scientist,

Could fasting boost your brainpower? A stomach hormone that stimulates appetite seems to promote the growth of new brain cells and protect them from the effects of ageing – and may explain why some people say that fasting makes them feel mentally sharper...

There is also evidence that ghrelin can enhance cognition. Animals that have reduced-calorie diets have better mental abilities, and ghrelin might be part of the reason why. Injecting the hormone into mice improves their performance in learning and memory tests, and seems to boost the number of neuron connections in their brains.

As a side note, fasting has been shown to dramatically increase the life span in both animals and insects, in laboratory studies…”

From the Johns Hopkins Medicine website:

A growing body of research, much of it led by Mark Mattson, adjunct professor of neuroscience, indicates the regimen offers a host of benefits, such as helping adherents shed pounds, lower blood pressure and cholesterol, slow the progression of Parkinson’s and Alzheimer’s diseases and reduce cancer risk.

In December, Mattson and Rafael de Cabo of the National Institute on Aging put much of that information in one place, publishing a widely publicized research review in the New England Journal of Medicine.

The catalyst for intermittent fasting’s health benefits, they say, is metabolic switching, which occurs when cells transition from using glucose for energy to using ketone bodies, and then back again.”

From the Alzheimer’s Prevention Registry website:

Intermittent fasting in animal studies has … been shown to reduce brain inflammation. There is strong evidence that forms of intermittent fasting can delay the onset and progression of Alzheimer’s disease and Parkinson’s disease in animal models…

“In animal studies, intermittent fasting has been shown to increase longevity, improve cognitive function and reduce brain plaque as compared with animals fed a regular diet,” said Allan Anderson, MD, Director of the Banner Alzheimer’s Institute in Tucson. “One hypothesis is that intermittent fasting enables cells to remove damaged proteins….”

“The animal research is stunning,” concluded Dr. Anderson. “But we don’t know yet if this will have similar benefits in humans.”  There are no substantial human trials of intermittent fasting related to brain function. Some studies of caloric restrictions in humans have shown improvement in memory function and overall thinking ability, but these studies included small numbers of patients.  Many scientists believe a large, well-conducted study of intermittent fasting in humans to determine brain benefits is warranted at this time.

Caveats and cautions

Animal studies can be interesting, but of course aren’t a substitute for human studies. The author of the above article ends it by cautioning against trying even short-term intermittent fasting without consulting with a doctor:

Personal Note

I started fasting a few years ago because I was experiencing some health issues (I was feeling sick and low energy, with no obvious cause).

I started by doing some intermittent fasting and time restricted eating, then went on to do several prolonged (several day) water fasts and fasting mimicking diet. Speaking anecdotally, both my health and my feelings improved rapidly once I started fasting.

Some people may find it hard to start fasting, particularly if they normally eat a diet high in carbs. I find it easier to fast when I’ve been eating a low carb or ketogenic diet for a few days before starting a prolonged fast. (People on ketogenic diets are using ketones, not glucose, as a fuel, so don’t experience sugar cravings.)

I’ve tried different fasting regimens, from IF (intermittent fasting) to ADF (Alternate Day Fasting) to doing occasional 3 to 5 day water fasts or Fasting Mimicking Diets. All have been beneficial. The alternate day fasting regimen was the easiest one for me to follow. But there are some possible benefits to longer fasts that people who are only doing ADF won’t experience.

Risks vs. benefits

It’s important to be aware that, like other interventions, fasting can have both benefits and side effects. When we fast, we’re depriving our bodies (and brains) of nutrients. Dr. Valter Longo and others have cautioned people against doing prolonged fasts, particularly water fasts, without medical supervision. (Longo developed his Fasting Mimicking Diet in an attempt to come up with a protocol which would provide the benefits of prolonged fasting while lowering the risks.)

If you’re new to fasting, or have health issues that might make it a bad idea, I recommend reading Dr. Jason Fung’s book, “The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting” or watching some of Dr. Fung’s videos before trying it.

This post is not intended as, and should not be taken as, medical advice.

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