Easy With That Salt Shaker: The Effect of Dietary Salt On Sleep

Easy With That Salt Shaker: The Effect of Dietary Salt On Sleep | The Paleo Diet

INTRODUCTION

Got sleep? Fact is many of us have a problem sleeping. You probably fall into one category, either being unable to sleep, or not getting enough sleep. In actuality, “counting sheep” and staring at the clock may be the favorite pastimes of many adults. Poor sleep quality, and associated sleep disorders like insomnia remain at the foremost of global health issues. For many, a common solution to tiredness entails having a daily fix of caffeine. Yet, the negative effects of caffeine on the heart, as well as the importance of sleep in regulating chemical imbalances within the brain, cannot be overstated.1

Sleep disorders have long-term consequences. They increase the risk of chronic diseases such as cardiovascular conditions and diabetes, resulting in a dismal quality of life. In addition, this leads to a big hole in your wallet and great financial burden to the economy.2 Given the increasing prevalence of reduced sleep quality and its costs, finding hidden factors that affect sleep is required to improve public health. Many are aware of risk factors like alcohol and sugar consumption, but a possible risk factor that normally goes unmentioned may lie in the individual’s dietary salt intake.3

While devoted Paleo followers are conscious of reducing dietary salt, after reading Dr. Loren Cordain’s books, it is important to understand the scientific basis behind this premise. Let’s put together results from past research to connect the dots.

DIETARY SALT AND THE BIG WHAMMY CORTISOL

Research studies have shown possible evidence between high dietary salt consumption and increased levels of the stress hormone cortisol.4 Furthermore, there appeared to be indication of metabolic syndrome. This group of conditions are characterized by risk factors including truncal obesity (where fat deposits around the waist line), low HDL cholesterol levels (which helps eliminate bad cholesterol from the body), hypertension and insulin resistance (which leads to hyperglycemia-high blood sugar)5.

This sounds like a lot, but let us put this in perspective. An individual diagnosed with metabolic syndrome doubles the risk of cardiovascular (heart) disease, while also quintupling the risk of diabetes. This should have set some alarms going off.

What exactly is cortisol, and how does it affect the body physiologically and psychologically? That answer will help you really understand where this is headed. Cortisol is a glucocorticoid hormone made in the adrenal cortex, near your kidneys.6 Aldosterone, which regulates sodium, is also made in the same area. Known as the key stress hormone in the body, the highest levels of cortisol are seen in the early part of the morning. A term coined as the “awakening response.” That feeling when you wake up excited and ready to start the day, yes thanks should go to cortisol. Cortisol helps your body in maintaining homeostasis. It keeps everything “A-okay” during and after exposure to stress.7 Regulation of cortisol takes place via the hypothalamic–pituitary–adrenal (HPA axis).

Cortisol acts on many parts of the body. In your immune system, cortisol exhibits weakening effects, while inhibiting the inflammatory process. It leaves you prone to developing infections.8 Cortisol encourages gluconeogenesis, basically it increases glucose/sugar production within the body.9 Makes sense right? In a stressful situation, your body needs energy.

In the brain, the memory zone, known as the hippocampus, has numerous cortisol receptors. Excess cortisol during stress has been shown to affect the hippocampus, through atrophy or wasting, resulting in severe memory loss.10 Evidence shows that cortisol affects the limbic system in the brain, which is responsible for mood and emotion.11

Cortisol prepares the body for a fight or flight response to stress, which explains the link between cortisol and insomnia. High levels of cortisol have been linked with a dysfunctional HPA axis, which helps regulate the sleep-wake circadian cycle. This affects sleep quality, and decreases slow-wave sleep aka deep sleep, and sleep time.12 Well the problem is that we need deep sleep. This is where human growth hormone is released, and where the body undergoes healing and repairs.13

Some evidence has shown the likelihood that cortisol also inhibits the production and release of melatonin, the sleep hormone, from the pineal gland.14 Adequate melatonin hormone is needed to induce good sleep. Melatonin and cortisol work inversely, think of it like a see-saw. Melatonin levels are naturally higher at night, but high cortisol levels at night leave melatonin unable to regulate this process.15

TIME TO CONNECT THE DOTS

Enough said. You may be thinking cortisol is pretty bad, but what does that have to do with dietary salt and sleep again. Well, it is a simple linear relationship. Dietary salt leads to increased cortisol levels, and these excess levels affect sleep. This means you can deduce dietary salt may affect sleep. Sounds simple right? Well in science, a hypothesis can be proposed, but a study must be carried out to provide answers.

A research study using a sample size of 20 individuals validated this hypothesis.16 In the study, significantly affected sleep quality, decreased deep sleep, resulting in frequent awakenings, alongside increased thirst. Given the small sample size of this study, further work is needed. Another study also confirmed the hypothesis that salt affects sleep.17

Yet another study shows that dietary salt increased the severity of the sleep disorder known as obstructive sleep apnea.18 With this condition, your airway narrows, decreasing oxygen availability, and leaving you with the inability to breathe for periods at a time.19

So now you have some science to back up your knowledge, when asked the real reason behind your decreased salt intake. Also remember that increased salt intake will make you wake up frequently to use the bathroom. As the body tries to get rid of the sodium, water goes out with it, leaving you thirsty and feeling dehydrated. As you place the almost empty salt shaker next to the empty wine glass, remember there is indeed a science behind this supposed madness.

Best wishes,

Obianuju Helen Okoye, M.D, M.B.A, M.S.-Epi

 

REFERENCES

[1] Harvard Medical School Division of Sleep Medicine. (2007, December 18). Under The Brain’s Control. Retrieved May 19, 2015, from http://healthysleep.med.harvard.edu/healthy/science/how/neurophysiology

[2]<Grandner, M., Jackson, N., Gerstner, J., & Knutson, K. (2014). Sleep Symptoms Associated with Intake of Specific Dietary Nutrients. J Sleep Res, 23(1), 22–34. Retrieved June 22, 2015, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3866235/

[3] Ibid.

[4] Baudrand, R., Campino, C., Carvajal, C. A., Olivieri, O., Guidi, G., Faccini, G., . . . Cerda, J. (2014). High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome. Clin Endocrinol, 677–684. doi:10.1111/cen.12225

[5] National Health, Lung and Blood Institute. (2011, November 3). What Is Metabolic Syndrome? Retrieved June 23, 2015, from Metabolic Syndrome: http://www.nhlbi.nih.gov/health/health-topics/topics/ms

[6]  Johns Hopkins Medicine. (2015). The Adrenal Glands. Retrieved June 23, 2015, from Health Library: http://www.hopkinsmedicine.org/healthlibrary/conditions/endocrinology/adrenal_glands_85,P00399/

[7] Randall, M. (2011, February 3). The Physiology of Stress: Cortisol and the Hypothalamic-Pituitary-Adrenal Axis. Dartmouth Undergraduate Journal of Science. Retrieved June 24, 2015

[8] Ibid.

[9] Ibid.

[10] Ibid.

[11] Kandhalu, P. (2013, November 4). Berkley Scientific Journal, 18(1), 13-16. Retrieved June 22, 2015, from http://bsj.berkeley.edu/wp-content/uploads/2013/11/04-FeaturesEffects-of-Cortisol_Preethi-KandhaluKim.pdf

[12] Kandhalu, P. (2013, November 4). Berkley Scientific Journal, 18(1), 13-16. Retrieved June 22, 2015, from http://bsj.berkeley.edu/wp-content/uploads/2013/11/04-FeaturesEffects-of-Cortisol_Preethi-KandhaluKim.pdf

[13] National Sleep Foundation. (2006). Sleep-Wake Cycle: Its Physiology and Impact on Health. Washington DC. Retrieved May 15, 2015, from http://sleepfoundation.org/sites/default/files/SleepWakeCycle.pdf

[14] Nikaidoa, Y., Aluru, N., McGuire, A., Park, Y., Vijayan, M., & Takemura, A. (2010, Jan). Effect of cortisol on melatonin production by the pineal organ of tilapia, Oreochromis mossambicus. Comp Biochem Physiol A Mol Integr Physiol, 155(1), 84-90. doi:10.1016/j.cbpa.2009.10.006

[15] Roden, M., Koller, M., Pirich, K., Vierhapper, H., & Waldhauser, F. (1993). The circadian melatonin and cortisol secretion pattern in permanent night shift workers. Am J Physiol, 265(1), R261-7. Retrieved June 24, 2015, from http://ajpregu.physiology.org/content/265/1/R261

[16] Baudrand, R., Campino, C., Carvajal, C. A., Olivieri, O., Guidi, G., Faccini, G., . . . Cerda, J. (2014). High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome. Clin Endocrinol, 677–684. doi:10.1111/cen.12225

[17] Grandner, M., Jackson, N., Gerstner, J., & Knutson, K. (2014). Sleep Symptoms Associated with Intake of Specific Dietary Nutrients. J Sleep Res, 23(1), 22–34. Retrieved June 22, 2015, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3866235/

[18] Pimenta, E., Stowasser, M., Gordon, R., Harding, S., Batlouni, M., Zhang, B., . . . Calhoun, D. (2013). Increased dietary sodium is related to severity of obstructive sleep apnea in patients with resistant hypertension and hyperaldosteronism. Chest, 143(4), 978-83. Retrieved June 21, 2015, from 10.1378/chest.12-0802

[19] Pimenta, E., Stowasser, M., Gordon, R., Harding, S., Batlouni, M., Zhang, B., . . . Calhoun, D. (2013). Increased dietary sodium is related to severity of obstructive sleep apnea in patients with resistant hypertension and hyperaldosteronism. Chest, 143(4), 978-83. Retrieved June 21, 2015, from 10.1378/chest.12-0802

 

About O. H. Okoye, MD, MBA, MSEpi

O. H. Okoye, MD, MBA, MSEpiDr. Obianuju Helen Okoye is a US Health Care Consultant with a Medical Degree (MD), an MBA in Healthcare Management, and a Masters in Epidemiology/Public Health. Her background includes being a National Institutes of Health (NIH) Clinical and Research Fellow, and State of Michigan HIV/AIDS Epidemiologist.

She has a plethora of clinical research experience and has presented at US and International Medical Conferences. Dr. Okoye has authored some publications, such as the impact of the implementation of the Affordable Care Act on medical tourism in the USA, the Market Analysis on US Health Reform (Impact on Supply and Demand for Health Care Services), and on lessons learned from the Ebola epidemic. Dr. Okoye’s interests include disease prevention, empowering under-served communities globally, bridging access (to) and streamlining the delivery of healthcare services.

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