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Does Coffee Slow the Progression of Alzheimer’s Disease?

Image shows an overturned coffee mug, with coffee beans spilling out of it. Below the falling coffee beans is a human brain. The background is of a dark blue colour with an out of frame light source shining down on the mug and brain.

Written by Jameson Brown
Illustrated by Aryan Hrishikesh Nair

You are working hard on your assignment that is due at midnight when you begin to feel drowsy. You reach for a trusty cup of coffee and take a nice long sip. Shortly after you begin to feel more alert and ready to finish up that assignment. However, what is it about coffee that makes us feel more alert? Coffee contains the psycho-stimulant caffeine1. A psychostimulant is a molecule that affects the functioning of our central nervous system, which consists of the brain and spinal cord (nervous tissue that lies within the spinal column and transports signals from the brain to the rest of the body and vice versa) by temporarily improving mental or physical function2,3. An example of improving our mental or physical function refers to enhancing alertness3. How does caffeine exert its effects on the central nervous system?

Caffeine and the CNS

Caffeine is a hydrophobic (water-fearing), which allows caffeine to cross the blood-brain barrier that protects the normal functioning of the brain1. The blood-brain barrier selectively filters molecules trying to enter our brain, thereby protecting our brain from viruses and toxins4. The blood-brain barrier is formed from lipids (fats). Due to the fat content of the blood-brain barrier, the barrier possesses similar qualities to the caffeine molecule. The similarity of hydrophobic qualities between the blood-brain barrier and caffeine molecules allows caffeine to cross the barrier. Once caffeine crosses the blood-brain barrier, it performs its function of increasing alertness and reducing fatigue, which causes better performance in certain tasks, such as psychomotor tasks1. A psychomotor activity is a task that requires the combination of precise physical action, attention, and problem-solving skills5. An example of a psychomotor activity is throwing a ball.

Thomas Schreiner and Bogdan Popescu, two researchers at the Carol Davila University of Medicine and Pharmacy in Romania, reviewed data from multiple studies exploring how caffeine affects the brain in individuals diagnosed with a neurodegenerative disease, specifically Alzheimer’s disease (AD)1. A neurodegenerative disease consists of neurons in the brain losing their function and eventually dying. Neurons are cells that send messages throughout the body to perform basic functions such as breathing and complex functions like walking6.

The image shows the blood brain barrier, with "Blood" on the left side of the barrier (in red) and "Brain" on the right (in a pale off white colour). On the left side are two viruses, with one struggling to push through the barrier while the other looks apprehensively at the barrier ahead. Below them is a text which says, "Pathogens such as viruses cannot push through the blood brain barrier". Below the text are 2 caffeine molecules, with an orange arrow indicating their direction of motion. The barrier itself is made up of three yellow cells, with the topmost one largely out of frame The two shown in their entirety each have an orange coloured nucleus. Between adjacent cells are minute gaps labelled "Tight junction". On the "Brain" side of the brain are two more caffeine molecules, and the text below them reads, " Caffeine molecules can pass through the blood brain barrier".
Alzheimer’s Disease and Oxidative Stress

As of 2021, the World Alzheimer’s Disease International Organization reported that Alzheimer’s disease affects 55 million people worldwide7. Alzheimer’s disease causes continuing dementia (a loss of memory and inability to process information properly), depression, and behavioural issues such as irritability.

Bart Rutten and colleagues from the University of Maastricht in the Netherlands suggest that a possible cause of the enhancement of Alzheimer’s disease symptoms is oxidative stress8. Oxidative stress is described as the balance between antioxidants and oxidants lies in the favour of the oxidants8. Oxidants are a free radical8. A free radical is an extremely reactive molecule that will either give an electron or take an electron from molecules8. In contrast to oxidants, antioxidants prevent the damage to important macromolecules that is caused by oxidants8. Macromolecules are molecules in the body that contain many atoms and include fats, sugars, and proteins8. A protein is a macromolecule in the body that is involved in many of body’s functions including the replication of cells4. An increase in the level of oxidants causes the destruction of these important macromolecules, which in turn will disrupt the normal functioning of our bodies and minds8.

Schreiner and Popescu reviewed the effect that caffeine has on oxidative stress as a possible way of slowing the progression of Alzheimer’s disease.

Caffeine’s Role in Oxidative Stress

Through Schreiner and Popescu’s collection of data, they found that caffeine may cause an increase nuclear erythroid 2-related factor (Nrf-2). Nrf-2 is a protein that is correlated with lowering oxidative stress. Schreiner and Popescu highlighted a study performed by researchers at the National Institute of Health Sciences in Tokyo, which showed that mice who had lower levels of Nrf-2 experienced increased levels of oxidative stress9. In contrast, mice that had normal levels of Nrf-2 had decreased levels of oxidative stress9. The result within the animal model has provided promise that caffeine could play a protective manner in preventing the progression of AD1.

Does this Mean Everyone Should Start Drinking Coffee?

While, as seen in the animal models, caffeine can have beneficial effects in reducing oxidative stress that could play a role in the progression of Alzheimer’s disease, there is insufficient evidence to say whether caffeine prevents the onset of Alzheimer’s disease1. In fact, Schreiner and Popescu found that a larger study involving humans produced results indicating an increase in the risk of AD with increased coffee consumption1. Thus, Schreiner and Popescu suggest that while increasing your coffee consumption could increase the risk of developing AD, if a person is already diagnosed with AD coffee consumption may slow the progression of symptoms1.

So next time you are reaching for that cup of coffee, stop to think about the effects the coffee is having on your body behind the scenes as you are feeling more alert.

Sources:

  1. Schreiner TG, Popescu BO. Impact of caffeine on Alzheimer’s disease pathogenesis – protective or risk factor? Life. 2022 [accessed 2024 Nov 1]; 12:330. https://www.mdpi.com/2075-1729/12/3/330. doi: 10.3390/life12030330.
  2. Haleem DJ. Extending therapeutic use of psychostimulants: Focus on serotonin-1A receptor. Prog. Neuropsychopharmacol. Biol. Psychiatry 2013 [accessed 2024 Nov 15]; 46:170-180.
  3. Harrow-Mortelliti M, Reddy V, Jimsheleishvili G. Physiology, Spinal Cord. [Updated 2023 Mar 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.
  4. Patel K. BIO202 Introductory Animal Physiology course notes. Mississauga (ON): University of Toronto Mississauga; 2022.
  5. Harvey PD, Mohs RC. 5 – Memory changes with aging and dementia. In P.R. Hof & C.V. Mobbs (Eds.), Functional neurobiology of aging. Academic Press; 2001. p 53-63.
  6. National Institute of Neurological Disorders and Stroke. Bethesda (MD): National Institutes of Health; [updated 2024 Jul 24; accessed 2024 Nov 15]. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-life-and-death-neuron.
  7. Matziorinis A, Koelsch S. The promise of musisc therapy for Alzheimer’s disease: a review. Ann. N. Y. Acad. Sci. 2022 [accessed 2024 Nov 1]; 1516:11-17. https://nyaspubs.onlinelibrary.wiley.com/doi/10.1111/nyas.14864. doi: 10.1111/nyas.14864.
  8. Yokoo Y, Kijima A, Ishii Y, Takasu S, Tsuchiya T, Umemura T. Effects of Nrf2 silencing on oxidative stress-associated intestinal carcinogenesis in mice. Cancer Med. 2016 [accessed 2024 Nov 1]; 118(A):747-755. https://onlinelibrary.wiley.com/doi/10.1002/cam4.672. doi: 10.1002/cam4.672.

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