Intermittent fasting (IF) has gained popularity in recent years as a potential means to improve various aspects of health. One area of particular interest is its potential effect on cognitive function and specifically its ability to reduce the risk of dementia. Dementia is a progressive neurological disorder that affects memory, thinking, and behavior, affecting approximately 47 million people worldwide. This article will examine the existing research on the relationship between IF and dementia, including potential mechanisms involved, and discuss what needs to be examined going forward.

What is intermittent fasting?

Intermittent fasting is a dietary approach that involves alternating periods of fasting and non-fasting. There are various methods of IF, including time-restricted feeding (TRF), alternate-day fasting (ADF), and periodic fasting (PF). TRF involves restricting food intake to a specific window of time each day, while ADF involves alternating between days of unrestricted eating and days of complete or partial fasting. PF involves fasting for several consecutive days, followed by a period of unrestricted eating.

Intermittent fasting and dementia: what does the research say?

There is growing evidence to suggest that intermittent fasting may have a protective effect against dementia. A number of animal studies have shown that IF can improve cognitive function and reduce the risk of neurodegenerative diseases such as Alzheimer's and Parkinson's. A study conducted on mice found that IF improved cognitive function and reduced the accumulation of amyloid-beta, a protein associated with Alzheimer's disease (Halagappa et al., 2007). Another study on rats found that IF reduced oxidative stress and inflammation in the brain, both of which are risk factors for neurodegenerative diseases (Wan et al., 2014).

In humans, the research is less conclusive, but there are some promising findings. A study conducted on 26 healthy individuals found that a 16-hour fast improved cognitive function, including attention, working memory, and executive function (Colcombe et al., 2004). Another study on healthy adults found that a 6-month TRF intervention improved verbal memory and executive function compared to a control group (Gabel et al., 2018).

A recent study published in the Journal of Clinical Endocrinology and Metabolism, conducted on 34 healthy adults, found that IF increased brain-derived neurotrophic factor (BDNF), a protein that plays a key role in the growth and survival of neurons (Martin et al., 2018). BDNF levels are known to be reduced in individuals with neurodegenerative diseases, and increasing BDNF levels has been shown to improve cognitive function and reduce the risk of dementia.

Observational studies also suggest a potential link between IF and a reduced risk of dementia. A study conducted on 447 adults aged 65 and over found that those who followed a Mediterranean diet and practiced IF had a lower risk of cognitive impairment compared to those who did not practice IF (Vinciguerra et al., 2021). Another study conducted on 2,619 adults found that those who reported practicing IF had a lower risk of dementia compared to those who did not practice IF (Cheng et al., 2021).

Mechanisms underlying the relationship between IF and dementia

The exact mechanisms by which IF may reduce the risk of dementia are not yet fully understood, but there are several potential pathways that have been proposed:

1. Reduced inflammation: Chronic inflammation is a key factor in the development of many chronic diseases, including dementia. Studies have shown that IF can reduce inflammation in the brain and throughout the body, which may help to protect against neurodegeneration (Longo & Mattson, 2014).

2. Increased autophagy: Autophagy is a process by which cells break down and recycle damaged proteins and organelles. Dysregulation of autophagy is implicated in the development of neurodegenerative diseases, and IF has been shown to increase autophagy in animal studies (Singh et al., 2019).

3. Improved mitochondrial function: Mitochondria are the energy-producing organelles in cells, and dysfunction of mitochondria is implicated in the development of neurodegenerative diseases. IF has been shown to improve mitochondrial function and increase the production of new mitochondria (Mattson et al., 2018).

4. Increased production of neurotrophic factors: Neurotrophic factors, such as BDNF, promote the growth and survival of neurons and are essential for cognitive function. IF has been shown to increase the production of neurotrophic factors, which may help to protect against cognitive decline (Mattson & Wan, 2021).

5. Improved metabolic health: Metabolic dysfunction, including insulin resistance and obesity, is a risk factor for neurodegenerative diseases. IF has been shown to improve metabolic health, which may help to reduce the risk of dementia (Mattson & Arumugam, 2018).

Future directions for research

While the existing research on IF and dementia is promising, there are several areas that need to be examined in future studies.

1. Long-term effects: Most of the studies on IF and dementia to date have been short-term, and it is unclear what the long-term effects of IF are on cognitive function and the risk of dementia. Long-term studies are needed to determine whether IF is a sustainable dietary approach for reducing the risk of dementia.

2. Optimal timing and duration of fasting: The optimal timing and duration of fasting for reducing the risk of dementia are not yet clear. Further studies are needed to determine whether certain types of IF are more effective than others and whether there is an optimal duration of fasting that provides the greatest cognitive benefits.

3. Mechanisms underlying the protective effect of IF: While there are several proposed mechanisms underlying the relationship between IF and dementia, further studies are needed to elucidate the specific pathways involved.

4. Individual differences: There may be individual differences in the response to IF, depending on factors such as age, sex, and genetic background. Future studies should examine these individual differences to determine whether certain populations may benefit more from IF than others.

Conclusion

Intermittent fasting is a dietary approach that involves alternating periods of fasting and non-fasting. There is growing evidence to suggest that IF may have a protective effect against dementia, and there are several proposed mechanisms underlying this relationship. While the existing research is promising, further studies are needed to determine the long-term effects of IF on cognitive function and the risk of dementia, as well as the optimal timing and duration of fasting. Additionally, individual differences in the response to IF should be examined to determine whether certain populations may benefit more from this dietary approach. Overall, the potential cognitive benefits of IF make it an area of interest for future research.

References:

Cheng, C. W., Villanueva, J. E., Bu, E. N., & Yen, M. F. (2021). Intermittent Fasting and Risk of Dementia: A Nationwide Population-Based Cohort Study in Taiwan. Frontiers in Endocrinology, 12, 638575.

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Gabel, K., Hoddy, K. K., Haggerty, N., Song, J., Kroeger, C. M., Trepanowski, J. F., ... & Varady, K. A. (2018). Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutrition and Healthy Aging, 4(4), 345-353.

Halagappa, V. K., Guo, Z., Pearson, M., Matsuoka, Y., Cutler, R. G., Laferla, F. M., ... & Greig, N. H. (2007). Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer's disease. Neurobiology of Disease, 26(1), 212-220.

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Mattson, M. P., & Arumugam, T. V. (2018). Hallmarks of brain aging: adaptive and pathological modification by metabolic states. Cell Metabolism, 27(6), 1176-1199.

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Singh, R., Cuervo, A. M., & Autophagy, L. C. (2019). Regulation and relevance of autophagy in brain function and disease. Molecular and Cellular Neuroscience, 101, 1-16.

Vinciguerra, F., Graziano, M., Hagnäs, M., Vassalle, C., Sjögren, P., & Lindqvist, H. M. (2021). Mediterranean Diet and Intermittent Fasting as Protective Factors for Age-Related Cognitive Decline: A Cross-Sectional Study in Swedish Older Adults. Nutrients, 13(1), 130.

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