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Stress and the immune system

Stress is accepted as a normal part of our busy lives, yet few of us understand the toll it can take on our health or the associated risk of immune-related diseases.



Stress is accepted as a normal part of our busy lives, yet few of us understand the toll it can take on our health or the associated risk of immune-related diseases.

What is stress?

Most of us think of stress as an emotion – the feeling of inner tension caused by an external trigger such as bereavement, divorce, work deadlines, unpaid bills and being stuck in traffic. The truth is that stress can simply be thought of as any factor, internal or external, that challenges and exceeds the ability of the individual to cope, upsetting the homeostasis and triggering negative health changes and symptoms. Factors that can trigger such stress include shock, fear, emotional worries and upsetting events, unhealthy food, skipping meals, exercising too much, lack of sleep, plus man-made factors that interfere with our circadian rhythm such as bright lights and the blue screens. Added to this, internal imbalances can put the body under stress, such as dysbiosis, nutrient deficiency or food sensitivity.

What happens when we feel stressed?

Regardless of the source of stress, when our bodies detect a stressor, it initiates the stress response – more commonly known as fight or flight. This term represents a complex process involving the autonomic nervous system and stimulation of the hypothalamic-pituitary-adrenal (HPA) axis, which in turn triggers the secretion of adrenal hormones like cortisol and adrenaline. As a result of this, various changes take place.

  • Heart rate, blood pressure and respiration increase to deliver more oxygen to the brain and muscles
  • The immune system is suppressed
  • Blood flow is diverted away from the digestive and reproductive systems, liver, kidneys and skin, and sent to the brain and skeletal muscles
  • Hearing, sight and smell are enhanced.

While this reaction to stress has developed over millions of years to enhance our survival in the face of acute stress, modern stressors tend to be chronic, numerous and unresolved leading to a repeated and prolonged stress response. This constant, inappropriate stimulation of the HPA axis can lead to more long-standing dysregulation in the secretion of cortisol, which has far reaching consequences when it comes to our health, including the immune system and how it behaves.

How stress impacts the immune system and increases risk of autoimmunity

Cortisol, the body’s main stress hormone, is an immunomudulator, meaning it has the ability to interfere with the immune system. Research studies of both humans and animals suggest that exposure to stress can suppress natural killer cell activity by as much as 50%. There may also be alterations in T Helper cell activity, promoting dominance of one branch or the other, a common feature of autoimmunity. Stress may also cause a shift that encourages B cells to increase the manufacture of antibodies, including those against the body’s own tissue. This loss of self tolerance also appears to occur when cortisol is too low, because there isn’t enough to bind to immature T cells produced in lymphoid tissue that have a tendency to attack the body’s own tissue.

While we don’t want cortisol to be elevated indefinitely, when appropriate, it does reduce inflammation to prevent our immune systems over reacting in the face of stress. A chronically lowered cortisol output takes away this safety mechanism allowing inflammation to become elevated, which causes a higher risk of inflammatory conditions such as autoimmune disease. Cortisol resistance may also occur after prolonged periods of elevated cortisol output, meaning that cells reduce the amount of receptors to cortisol or reduce their ability to bind to it. As a result of this, although cortisol is still being produced, the body is less receptive to its inflammation-lowering or immune-calming effects.

Stress also impacts the immune system by undermining the functioning of the digestive system. It does this firstly through the suppression of an immunoglobulin called SIgA, which in turn can reduce the amount of the beneficial flora needed to support a healthy immune response. Stress may also encourage the lining of the intestines to become inappropriately permeable, commonly known leaky gut, because cortisol opens up the enterocyte tight junctions that line the digestive tract. This allows large particles of protein and microbes into the blood stream, where they can interact with and stimulate the immune system causing inflammation. In fact, research suggests that intestinal impermeability is a necessary precursor to autoimmune disease in all cases.

Cortisol can be measured via saliva testing, and much can be done via diet and lifestyle modifications to minimise the symptoms of stress and encourage the body back into better balance – why not call us today for a free chat to see if we might be able to help you.


Written by Emma Rushe

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