Cortisol

Cortisol is made in the adrenal glands, small organs that sit atop your kidneys. It’s released in response to signals from the pituitary gland in your brain whenever a stressor — physical, mental, or emotional — is detected. Cortisol works hand-in-hand with DHEA-S, another adrenal hormone, to help the body cope with and recover from stress. Together, they help maintain blood pressure, regulate energy and metabolism, and support immune and inflammatory balance.

Cortisol operates under the control of your autonomic nervous system, which has two branches:

• The sympathetic nervous system, often called the “fight-or-flight” system — activated when you’re under pressure, rushing, or anxious.
  

• The parasympathetic nervous system, known as “rest and digest” — responsible for recovery, digestion, and calm.
  

For optimal health, these systems must stay in balance. When cortisol remains high for too long, the sympathetic system dominates, leading to tension, anxiety, sleep disruption, digestive issues, and eventually, exhaustion. Conversely, if cortisol becomes depleted, your ability to adapt to stress declines, resulting in fatigue and burnout.

Reference Ranges for cortisol in nmol/L:

Morning (AM): 145 - 619

Afternoon (PM): 95 - 462

Cortisol’s effects reach virtually every cell in the body. It acts as both a first responder and a long-term regulator during stress. When your brain detects a threat, it triggers the release of adrenaline (epinephrine) and noradrenaline (norepinephrine), increasing heart rate, muscle tension, and alertness — preparing you for action. Cortisol then follows, providing sustained energy and maintaining vigilance.

This system is vital in short bursts — but chronic activation can backfire. Persistently high cortisol can suppress the parasympathetic nervous system, keeping the body in a constant “on” state. Over time, this may lead to:

• Sleep disturbances, anxiety, and irritability

• Weakened immune function and increased inflammation

• Blood sugar imbalance, insulin resistance, and risk of type 2 diabetes

• Slower metabolism and weight gain, especially around the abdomen

• Reduced DHEA production, contributing to hormonal imbalances and fatigue

• Mineral depletion, particularly potassium and magnesium

• Menstrual irregularities or increased facial hair in women due to altered hormone conversion
  

In essence, cortisol helps you cope, but when chronically elevated or depleted, it can disrupt nearly every major body system — from metabolism and mood to immune health and hormonal balance.

Cortisol levels naturally peak in the morning (8–10 AM) and decline by evening (4–6 PM) as part of your circadian rhythm. This rhythm can be disrupted by stress, diet, or lifestyle habits.

Dietary Factors:

• Increase cortisol: High intake of caffeine, refined sugars, alcohol, and processed foods.

• Support balance: Anti-inflammatory, nutrient-dense foods such as leafy greens, cruciferous vegetables, healthy fats (olive oil, avocado, nuts), and omega-3-rich fish help nourish adrenal function.

• Helpful nutrients: Magnesium, B vitamins, and vitamin C play key roles in cortisol metabolism.
  

Lifestyle Factors:

• Raise cortisol: Chronic stress, overworking, poor sleep, and excessive exercise.

• Lower cortisol: Restorative sleep (7–9 hours), mindfulness, breathwork, and relaxation practices help recalibrate your nervous system.
  

Related Biomarkers:

• ACTH (adrenocorticotropic hormone): Directly stimulates cortisol release.

• DHEA-S: Works in balance with cortisol; low DHEA can amplify the effects of high cortisol.
  

Environmental Influences:

• Chronic emotional stress, blue light exposure at night, and endocrine-disrupting chemicals (like BPA) can disrupt circadian cortisol rhythms.

If Cortisol is High

When cortisol is elevated, the body is stuck in “fight-or-flight” mode. The goal is to calm the nervous system and restore balance between the sympathetic and parasympathetic systems.

Diet

• Reduce sugar, refined carbohydrates, and caffeine — all of which overstimulate cortisol release.

• Focus on anti-inflammatory foods like olive oil, avocados, berries, and green leafy vegetables.

• Include omega-3 fatty acids (salmon, chia, flaxseed) 2–3 times weekly.

• Stay hydrated and avoid skipping meals to stabilise blood sugar.
  

Lifestyle

• Practice deep breathing, yoga, or meditation daily to activate the parasympathetic system.

• Set boundaries to reduce mental load; incorporate “rest breaks” during work.

• Prioritise consistent sleep (7–9 hours) and limit screen exposure before bed.

• Engage in light to moderate exercise such as walking, swimming, or Pilates — avoid overtraining.
  

Supplements

• Magnesium (200–400 mg/day): Calms the nervous system and supports adrenal function.

• Vitamin C (500–1,000 mg/day): Aids in cortisol metabolism and reduces oxidative stress

• Herbal support: Calming herbs such as lemon balm, chamomile, or ashwagandha (avoid if sensitive to nightshades) can help modulate stress.

Other

• Consider mindfulness-based stress reduction or acupuncture for nervous system balance.
  

If Cortisol is Low

Low cortisol indicates reduced adrenal responsiveness, often from chronic over-activation or long-term stress depletion.

Diet

• Eat regular, balanced meals to support energy and stable blood sugar.

• Incorporate healthy fats, lean proteins, and complex carbs at each meal.

• Include sea salt, bone broth, and electrolyte-rich foods to support adrenal hydration.

• Avoid skipping meals or extreme fasting.
  

Lifestyle

• Prioritise rest and recovery — nap if needed and schedule downtime.

• Reduce caffeine intake, which can exhaust adrenal output.

• Focus on gentle exercise (walking, stretching) rather than intensity.

• Practice grounding routines such as morning sunlight exposure or journaling.
  

Supplements

• B-complex vitamins: Support energy production and adrenal resilience.

• Vitamin C and magnesium: Rebuild adrenal hormone synthesis.

• Adaptogens: Herbs like rhodiola or licorice root (under supervision) may support stress adaptation.

Testing

• Low cortisol should be evaluated alongside ACTH and DHEA-S to identify adrenal or pituitary involvement.

• Seek medical review for potential secondary adrenal insufficiency if fatigue and low blood pressure persist.

1. Russell G, Lightman S. The Human Stress Response. Nature Reviews. Endocrinology. 2019;15(9):525-534. doi:10.1038/s41574-019-0228-0.

2. Lightman SL, Birnie MT, Conway-Campbell BL. Dynamics of ACTH and Cortisol Secretion and Implications for Disease. Endocrine Reviews. 2020;41(3):bnaa002. doi:10.1210/endrev/bnaa002.

3. Knezevic E, Nenic K, Milanovic V, Knezevic NN. The Role of Cortisol in Chronic Stress, Neurodegenerative Diseases, and Psychological Disorders. Cells. 2023;12(23):2726. doi:10.3390/cells12232726.

4. Juliana N, Maluin SM, Effendy NM, Abu IF, Azmani S. Cortisol Detection Methods and the Hormone's Role in Evaluating Circadian Rhythm Disruption. International Journal of Molecular Sciences. 2025;26(18):9141. doi:10.3390/ijms26189141.

5. Stalder T, Oster H, Abelson JL, et al. The Cortisol Awakening Response: Regulation and Functional Significance. Endocrine Reviews. 2025;46(1):43-59. doi:10.1210/endrev/bnae024.

6. Boonen E, Bornstein SR, Van den Berghe G. New Insights Into the Controversy of Adrenal Function During Critical Illness. The Lancet. Diabetes & Endocrinology. 2015;3(10):805-15. doi:10.1016/S2213-8587(15)00224-7.

7. Herman JP, McKlveen JM, Ghosal S, et al. Regulation of the Hypothalamic-Pituitary-Adrenocortical Stress Response. Comprehensive Physiology. 2016;6(2):603-21. doi:10.1002/cphy.c150015.

8. Papadimitriou A, Priftis KN. Regulation of the Hypothalamic-Pituitary-Adrenal Axis. Neuroimmunomodulation. 2009;16(5):265-71. doi:10.1159/000216184.

9. Uchoa ET, Aguilera G, Herman JP, et al. Novel Aspects of Glucocorticoid Actions. Journal of Neuroendocrinology. 2014;26(9):557-72. doi:10.1111/jne.12157.

10. James KA, Stromin JI, Steenkamp N, Combrinck MI. Understanding the Relationships Between Physiological and Psychosocial Stress, Cortisol and Cognition. Frontiers in Endocrinology. 2023;14:1085950. doi:10.3389/fendo.2023.1085950.

11. Oster H, Challet E, Ott V, et al. The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids. Endocrine Reviews. 2017;38(1):3-45. doi:10.1210/er.2015-1080.

12. Nicolaides NC, Kyratzi E, Lamprokostopoulou A, Chrousos GP, Charmandari E. Stress, the Stress System and the Role of Glucocorticoids. Neuroimmunomodulation. 2015;22(1-2):6-19. doi:10.1159/000362736.

13. Kamin HS, Kertes DA. Cortisol and DHEA in Development and Psychopathology. Hormones and Behavior. 2017;89:69-85. doi:10.1016/j.yhbeh.2016.11.018.

14. Lennartsson AK, Theorell T, Kushnir MM, Bergquist J, Jonsdottir IH. Perceived Stress at Work Is Associated With Attenuated DHEA-S Response During Acute Psychosocial Stress. Psychoneuroendocrinology. 2013;38(9):1650-7. doi:10.1016/j.psyneuen.2013.01.010.

15. Mueller B, Figueroa A, Robinson-Papp J. Structural and Functional Connections Between the Autonomic Nervous System, Hypothalamic-Pituitary-Adrenal Axis, and the Immune System: A Context and Time Dependent Stress Response Network. Neurological Sciences. 2022;43(2):951-960. doi:10.1007/s10072-021-05810-1.

16. Lowrance SA, Ionadi A, McKay E, Douglas X, Johnson JD. Sympathetic Nervous System Contributes to Enhanced Corticosterone Levels Following Chronic Stress. Psychoneuroendocrinology. 2016;68:163-70. doi:10.1016/j.psyneuen.2016.02.027.

17. Nunez SG, Rabelo SP, Subotic N, Caruso JW, Knezevic NN. Chronic Stress and Autoimmunity: The Role of HPA Axis and Cortisol Dysregulation. International Journal of Molecular Sciences. 2025;26(20):9994. doi:10.3390/ijms26209994.