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Intermittent fasting for mental health benefits: Fact or Fad?
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What you eat influences your brain health. Exciting evidence is emerging that suggests that your meal timings can also play a role in cognitive performance. High quality animal studies have highlighted mental benefits of fasting. Human studies are upcoming that may solidify benefits of fasting for brain health. The concept of eating at limited times and scheduling meals within a certain time frame is called intermittent fasting. Evidence of its benefits for a wide range of health conditions is adding up, opening doors to its use for brain benefits.
How does your brain fuel itself?
Your brain performs highly sophisticated and important functions, which uses up to 20% of the energy you consume. The food you eat is broken down into glucose which is used as an energy source. The brain needs a constant supply of glucose to do its job. A small supply of glucose is stored to ensure adequate supply when you are not eating. These stores can only last 10-14 hrs of fasting [1]. During this time, you need to replenish your body with food, which most people do when they eat meals at regular times. Depending on your last meal and your energy use, after 12-36 hours of absence of food [2], your body must switch to alternate means to continue providing energy for essential bodily functions.
What happens in your brain during intermittent fasting?
During low food intake, your brain has optimised itself to use other sources of energy for fuel. Once glucose stores run out, it uses stored fats to produce energy. One of the fat sources used for energy are called ketone bodies. These are transported into the brain during the “energy switch” from glucose to ketone bodies. The brain assumes this to be a stressful situation and enters protection mode. It builds up stress resistance and activates the pathway that will help produce new brain cells and new connections. It does this by releasing a protein called BDNF (brain-derived neurotrophic factor) [3].
Can intermittent fasting nourish your memory?
BDNF is one of the most important brain compounds, being extensively studied for learning and memory benefits. It regulates brain cells in the memory and learning centre. The more evolved and intricate your brain network is, the stronger and smarter your brain will be. BDNF promotes production of new brain cells, their branching and strength of connections [4]. Decreased levels were found in Alzheimer’s disease and increased levels were found to support cognitive performance. Animal studies found that 16 hours of fasting for 3 months, where food consumption was limited to an 8-hour slot, activated BDNF and increased brain cells in the memory and learning centre of the brain [3]. Another animal study where feeding and fasting were done on alternate days, there was an improvement in long term memory and new brain cell growth [5].
Can intermittent fasting improve cognitive performance in humans?
In human studies, where ketone bodies were artificially increased after an overnight fast, there was an improvement in cognitive performance among older adults [6]. Participants who fasted for 2 days a week and had regular eating habits for 5 days a week, were studied for 3 years. 24% of those who practised intermittent fasting were classified as successful agers with optimal brain health for their age. This was in comparison to less than 4% of the non-fasting group classifying as successful agers [7]. This opens a possibility of modifying meal timings to gain brain health benefits.
Intermittent fasting for a better brain: The future is exciting!
There is a wealth of evidence on the cognitive benefits of intermittent fasting in animal studies. The mechanism of “energy switch” in the brain is well understood, along with the exciting cognitive benefits it brings. Research evidence on the benefits of intermittent fasting for certain medical conditions exist, with brain health studies still in its infancy. This is an emerging field and there is a growing need for high quality human studies with set fasting time frames to ascertain its benefits for cognitive functions.
References
- Brocchi, A. et al. (2022). Effects of Intermittent Fasting on Brain Metabolism. Nutrients, 14(6), p.1275.
- Gudden, J. et al. (2021). The Effects of Intermittent Fasting on Brain and Cognitive Function. Nutrients, 13(9), p.3166.
- Baik, S.-H. et al. (2020). Intermittent fasting increases adult hippocampal neurogenesis. Brain and Behavior, [online] 10(1), p.e01444.
- Seidler, K. et al. (2022). Intermittent fasting and cognitive performance – Targeting BDNF as potential strategy to optimise brain health. Frontiers in Neuroendocrinology, 65, p.100971.
- Dias, G.P. et al. (2021). Intermittent fasting enhances long-term memory consolidation, adult hippocampal neurogenesis, and expression of longevity gene Klotho. Molecular Psychiatry. [online]
- Reger, M. A. et al. (2004). Effects of beta-hydroxybutyrate on cognition in memory-impaired adults. Neurobiology of aging, 25(3), 311–314.
- Ooi, T.C. et al. (2020). Intermittent Fasting Enhanced the Cognitive Function in Older Adults with Mild Cognitive Impairment by Inducing Biochemical and Metabolic changes: A 3-Year Progressive Study. Nutrients, 12(9), p.2644.
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