Does fasting improve brain and mental health? The importance of BDNF

Have you seen the candy bar commercial where a hungry, irritated person becoming normal again after eating the candy bar? It is commonly known that hunger makes a person angry, agitated and unable to think clearly. As the commercial implies, sugar is the cure. However, the data that is emerging shows that sugar is the drug for the brain and that once past the hungry phase, fasting will eventually help with memory, cognition and mood!

Even though glucose is the source of energy for our body and especially the brain, one of the most active organs, a diet high in sugar is detrimental to our health. Besides causing excessive weight gain and leading to metabolic diseases like diabetes, a high sugar diet can worsen mental health and functioning! 

Fasting eventually leads the body to burn fat for energy by converting the fat into ketones, or ketone bodies. Ketosis activates the “clean up” process - autophagy, when cells get rid of the dysfunctional organelles and proteins, then recycle them and thereby become more efficient. Recent researches show that the brain can actually undergo a “regeneration” process, regulated by many proteins and hormones. Brain Derived Neurotrophic Factor (BDNF) is one of these tightly regulated proteins.  BDNF plays a key role in neurogenesis, neuroplasticity and neuroprotection(1), which are essential in learning, memory, mood and a lot of cognitive functions. BDNF has been shown to affect neurodegenerative disorders such as Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, and Huntington’s disease(2). Ketosis is one of the many ways to increase BDNF and too much glucose decreases the level of BDNF. 

Neurogenesis is the formation of new brain cells or neurons. We used to believe that neurons cannot regenerate, that once they are injured they will “die”. Neurogenesis occurs mainly in the developing brain of children but recent studies in animals have shown neurogenesis can occur in certain areas of the adult brain as well. The formation of new brain cells is important in memory and learning. It has been shown in animal studies that fasting upregulates BDNF production, leading to more neurogenesis once the fast is over and nutrients are given to the brain(2). 

Neuroplasticity is the “re-wiring” of the brain. The brain has many “pathways” making connections among brain cells.  The more “pathways” there are, the more ways for the brain cells to send signals to one another and to retrieve information, which then helps with memory and learning. BDNF is one of the proteins involved in making new “pathways”. It has also been shown that in animals that neuroplasticity is important in countering depression as well(3). 

Neuroprotection is the “survival” mode of the brain. BDNF has been shown to improve the brain recovery after oxidative stress or injury like stroke. It is also important in protecting the brain from neurodegenerative diseases. 

The level of BDNF decreases with aging, However, there are many ways to increase its level:

Fasting, specifically during ketosis

Exercise

Healthy diets like the Mediterranean diet

Sleep

Sunlight

Reducing Stress

Social activities

Certain food - dark chocolate, blueberries 

Sugar and saturated fats decrease the level of BDNF.

A healthy brain is one of the most important elements for an active, independent life. Besides staying socially connected, exercising regularly, and eating healthy, intermittent fasting is one way to increase the level of BDNF, keeping the brain “young”.

*Even though intermittent fasting is relatively safe, it may not be suitable for everyone. Do consult with a physician whether this would be recommended for you.

References:

1. Elesawy BH, Raafat BM, Muqbali AA, Abbas AM, Sakr HF. The Impact of Intermittent Fasting on Brain-Derived Neurotrophic Factor, Neurotrophin 3, and Rat Behavior in a Rat Model of Type 2 Diabetes Mellitus. Brain Sci. 2021 Feb 15;11(2):242. doi: 10.3390/brainsci11020242. PMID: 33671898; PMCID: PMC7918995.

2. Gudden J, Arias Vasquez A, Bloemendaal M. The Effects of Intermittent Fasting on Brain and Cognitive Function. Nutrients. 2021 Sep 10;13(9):3166. doi: 10.3390/nu13093166. PMID: 34579042; PMCID: PMC8470960.

3. Mattson M.P., Moehl K., Ghena N., Schmaedick M., Cheng A. Intermittent metabolic switching, neuroplasticity and brain health. Nat. Rev. Neurosci. 2018;19:81–94. doi: 10.1038/nrn.2017.156.

4. Abdulsada MM, Wilhelm ZR, Opekun AR, Devaraj S, Jalal PK, Mindikoglu AL. The effect of four-week intermittent fasting from dawn to sunset on circulating brain-derived neurotrophic factor levels in subjects with metabolic syndrome and healthy subjects. Metabol Open. 2020 Dec 4;9:100070. doi: 10.1016/j.metop.2020.100070. PMID: 33376976; PMCID: PMC7758552.