8 Ways Decent Dental Care Defies Dementia

Posted on by Jesse Santiano, M.D.

Chewing preserves learning ability and spatial memory to maintain brain health and prevent dementia

There is a special relationship between chewing and brain functions. As people grow older, memory loss can happen. This is not only due to the passage of time but is related to the loss of teeth and subsequent chewing dysfunction.

To better understand the effects of chewing to brain function, it is vital to know the hippocampus.

The Hippocampus: What’s It For?

The word hippocampus is Greek for sea-horse (sea-monster and horse) because of its shape. It is the center for spatial memory and learning. Spatial memory is essential for navigation, whether it is inside a house or going on a long drive.

1511_The_Limbic_Lobe

The dentate gyrus (DG) is located in the hippocampus and is one of the areas where new brain formation or neurogenesis occurs. Neurogenesis happens even in the adult brain and is needed for brain maintenance and optimum function.

The hippocampus works with the HPA or hypothalamic-pituitary-adrenal axis. The HPA is the coordination between the glands regulating the hormones that affect the whole body. The negative and positive feedback interactions between the hypothalamus, pituitary, and adrenal glands are shown below. Whatever happens to the hippocampus can also affect the HPA axis.

1024px-HPA_Axis_Diagram_(Brian_M_Sweis_2012).svg

For this article, we will concentrate on cortisol. Cortisol is the hormone secreted by the adrenal gland that is necessary to maintain life and is secreted appropriately in higher amounts during times of stress to survive the strain of the situation. However, chronic cortisol secretions are terrible for the body because it causes neurodegeneration, hypertension, and osteoporosis.

Now that we know about the hippocampus let us chew on the science of mastication.

What Happens During Chewing?

  1. Chewing Increases Cerebral Blood Flow and is bite related. The harder the consistency of the food, the greater the blood flow (2). The higher blood flow stimulates activity like arousal and wakefulness. This is exemplified by the increased alertness during studying or driving while chewing gum.
  2. Different senses are stimulated in the mouth during chewing.  The gums and inside the teeth have nerve endings for tactile sensation for texture and hardness. The tactile stimuli are needed to know how much pressure should be applied for each bite and chew. Another is position sense (proprioception) to identify the physical relation of the food bolus to the whole mouth. Proprioception is needed for proper placement of the food between the teeth for more efficient chewing. The other senses triggered are the smell and temperature of the food.

    1421_Sensory_Homunculus
    The Cortical Homunculus showing  the Large Part of the Brain That Gets Sensory Signals from the Mouth
  3.  The sensory information from the mouth during chewing are sent thru the olfactory and trigeminal nerve and stimulates the different parts of the cerebral cortex and increases brain activity.
  4. Chewing stabilizes the interaction between the hippocampus and the HPA axis, making the brain, especially the hippocampus, more resistant to excess cortisol. A well regulated HPA axis prevents the damaging effects of too much cortisol resulting in neurodegeneration, hypertension, and osteoporosis (7).
  5. Chewing prevents neurodegeneration by the reduction of pro-inflammatory cytokines like Interleukin-1 beta (IL-1β) secreted by the astrocytes. (1)
  6. Normal neurogenesis of the basal forebrain ensures adequate production of acetylcholine, which is distributed to the whole brain. Acetylcholine is a neurotransmitter. It is necessary for memory, and it decreases in dementia. In molarless or bite-raised animals, the hippocampal acetylcholine release, acetyltransferase, and choline acetyltransferase activity were significantly reduced. That is why donepezil (Aricept) is prescribed in Alzheimer’s dementia patients. Donepezil maintains a higher level of acetylcholine in the brain to improve memory.
  7. Chewing sustains healthy BDNF and trkB levels.   Brain-derived neurotrophic factor (BDNF) and tropomyosin related kinase B (trkB) are essential for nerve transmission and synaptic plasticity by increasing dendritic spines. Dendritic spines are parts of the brain cells that make them communicate with one another. Dendritic spines are needed to retain new information and experiences for learning.

    Spine_Dynamics
    The dendritic spine is the small branch coming off the dendrite, forming the connection or synapse.
  8. The rhythmic movement and motor control of the mouth during chewing stimulate the cerebellum and the hippocampus. “Protein tyrosine phosphatase interacting protein 51 (PTPIP51) is probably a new protein regulating memory formation by influencing dendritic and axonal growth and synaptogenesis” (8).  The expression of PTPIP51 is restricted to the cerebellum and the hippocampus. (9)

Note that the majority of the studies done that are mentioned above, which included molar teeth extraction,  crown reduction or bite elevation, and other oral manipulations and the biochemical and brain effects, are done in animals. However, the observational studies among the human population with regards to chewing dysfunction and memory problems parallel the results of the animal studies.

Human Studies about Health and Cognitive Function

Studies show oral health and cognitive function go together. Natural teeth are essential to maintain the hippocampus to preserve long term memory.

Chewing or even sucking a piece of sugar-free, spearmint flavoured gum was shown to be associated with immediate better cognitive performance, improved the score of word recall, sensitivity index of the spatial working-memory task, and reaction time of the numeric working-memory task in humans (4)

Chewing also alleviates stress, decreases the damaging effect of endogenous steroids on the brain, thus enhancing cognition.

In summary, chewing stimulates the brain with different sensations and increases cerebral blood flow, prevents neurodegeneration, promotes neurogenesis, and mitigates the damaging effects of stress.

Real-Life Applications

  1. Eating vegetables and nuts are good for brain health.
  2. Chewing a piece of gum under stressful situations may be a better alternative than smoking or stress eating.
  3. Take care of periodontal disease. Periodontitis and metabolic syndrome make each other worse. Both should be treated. Metabolic syndrome is a significant risk factor for coronary artery disease and stroke.

I will end with the Home Care recommendations of the American Dental Association

Don’t Get Sick!

Recommended Readings

  1. Christmas Gifts that Prioritize Health
  2. Diseases Associated with the Metabolic Syndrome
  3. Periodontal Disease and Metabolic Syndrome
  4. Exercise and Neurogenesis
  5. The Metabolic Syndrome
  6. The Story of KAATSU. The Incredible Technique for Muscle Toning and Hypertrophy
  7. Sarcopenia: The Scourge of Aging
  8. What is Ischemic Preconditioning?
  9. GERD/Heartburn and Metabolic Syndrome
  10. Where You Live Can Affect Your Health
  11. Are You Ready for Doctor Shortages?
  12. Getting Ready to Celebrate the Holidays

References:

  1. Huayue Chen, Mitsuo Iinuma, Minoru Onozuka, Kin-Ya Kubo. Chewing Maintains Hippocampus-Dependent Cognitive Function. Int J Med Sci. 2015; 12(6): 502–509. Published online 2015 Jun 9. doi: 10.7150/ijms.11911
  2. Onozuka M1, Fujita M, Watanabe K, Hirano Y, Niwa M, Nishiyama K, Saito S.
    Mapping brain region activity during chewing: a functional magnetic resonance imaging study. J Dent Res. 2002 Nov;81(11):743-6.
  3. Listl S. Oral health conditions and cognitive functioning in middle and later adulthood. BMC Oral Health. 2014;14:70.
  4. Hansson P, Sunnegårdh-Grönberg K, Bergdahl J. et al. Relationship between natural teeth and memory in a healthy elderly population. Eur J Oral Sci. 2013;121:333–340.
  5. Hirano Y, Obata T, Takahashi H. et al. Effects of chewing on cognitive processing speed. Brain Cogn. 2013;81:376–381.
  6. Fukushima-Nakayama, Y., Ono, T., Hayashi, M., Inoue, M., Wake, H., Ono, T., & Nakashima, T. (2017). Reduced Mastication Impairs Memory Function. Journal of Dental Research, 96(9), 1058–1066. https://doi.org/10.1177/0022034517708771
  7. Kagaku Azuma, Qian Zhou, Masami Niwa, Kin-ya Kubo. Association between Mastication, the Hippocampus, and the HPA Axis: A Comprehensive Review
    Int J Mol Sci. 2017 Aug; 18(8): 1687. Published online 2017 Aug 3. doi: 10.3390/ijms18081687 PMCID: PMC5578077
  8. Brobeil A, Viard M, Petri MK et al. Memory, and PTPIP51 – A new protein in the hippocampus and cerebellum. Mol Cell Neurosci. 2015;64:61–73.
  9. Koch P, Viard M, Stenzinger A. et al. Expression profile of PTPIP51 in mouse brain. J Comp Neurol. 2009;517:892–905

Image Credits:

  • The Limbic Lobe By OpenStax College – Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148029
  • HPA axis By ShelleyAdams – This file was derived from the HPA Axis Diagram (Brian M Sweis 2012).png, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=53298307
  • Cortical Humonculus By OpenStax College – Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148008
  • Dendritic Spine by By Mrazadazdazz – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10183526

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