by Carol Anthony, 06/08/2021

Cortisol has a significant role to play in our bodies, however, it can also wreak havoc if left unchecked.

So what is cortisol?

Cortisol is more commonly known as our ‘stress hormone’. Cortisol is produced by the adrenal glands and is released as a ‘fright or flight’ response to physical or psychological stressors. These stressors may include exercise, injury or everyday life stressors. In response to these stressors, there is a physiological reaction too. Glucose is metabolised, inflammation is downgraded and blood pressure is upregulated.

What is the function of Cortisol?

In times of stress, our body and mind need to be adequately supplied with glucose for energy. Our brain needs to be alert in the face of danger in order to make quick, lifesaving decisions. Our bodies need to be adequately fuelled to act in the face of danger, to run away, or fight back. Cortisol stimulates the production of glucose by the liver in order to raise blood sugar levels by increasing blood glucose. Cortisol also suppresses inflammation to conserve energy in times of heightened stress and increases blood pressure for increased blood supply.

In summary, stressors, real or perceived, result in:

  • Increased blood glucose levels
  • Suppression of inflammation
  • Increase in blood pressure.


So let us examine how this affects athletic performance.

Raising blood glucose levels

The release of cortisol results in gluconeogenesis = production of glucose in the liver by breaking down protein and fat.

Cortisol is released à muscle protein is broken down à released amino acids are converted into glucose in the liver à glucose is released in the bloodstream and is available for use by various tissue in the body.

Cortisol also acts on fat cells à triglycerides are broken down into fatty acids and glycerol à glucose is released into the blood stream.

At the same time, cortisol inhibits the pancreas from secreting insulin (which would under normal circumstances lower blood sugar levels). Cortisol ensures that, with insulin inhibited, blood sugar levels remain elevated.

ALARM BELLS – This is not an ideal situation for an athlete, muscle is being broken down to produce glucose and raised blood sugar levels result in weight gain.

Suppressed Inflammation

In the short term, in cases of acute stress, cortisol moderately suppresses the immune system and limits inflammation. The benefit is that the body conserves energy by not exhibiting an excessive inflammatory response.

ALARM BELLS – in the case of a prolonged cortisol response and ensuing lowered inflammatory and immune response, the risk of injury is greater, with an increased chance of getting sick.

Blood Pressure Regulation

Cortisol raises your blood pressure – so that you can run away from the leopard about to chase you!!! It does this by stimulating the reabsorption of sodium by the kidneys which in turn increases blood volume and in turn, blood pressure.

ALARM BELLS – chronically elevated blood pressure is not ideal for long term heart health.

So why does this happen?

Bear in mind that elevated cortisol was designed for short term, acute, stressful (life threatening) situations.

To recap:

Stressful, life threatening situation à raised cortisol à blood sugar is raised by breaking down protein (muscle) and fat to circulate blood glucose à inflammation and immune system are downregulated à blood pressure is increased.

Although this is fine in the short term when indeed there is a life threatening stressor, it is not an ideal state for your body to be in permanently. Yet our stressful lifestyles, poor or insufficient sleep, skipping meals and strenuous exercise, keep us in a heightened state of alert with cortisol in overdrive.

As a performance athlete, this is not an ideal state to be in perpetually.  Muscle breakdown, weight gain, suppressed inflammation and immune system and increased blood pressure are all contraindicated for athletic performance.

Let us further examine the relationship between cortisol and exercise:

Exercise is a short term stressor, not life threatening (usually), but perceived by our bodies as a stressor all the same. Exercise usually results in circulating cortisol. Cortisol releases glucose into the blood and this is good as it supplies energy to working muscles.  The ideal is to then allow cortisol to return to its baseline after exercise. However, this requires rest and adequate recovery time in order to ensure that levels don’t remain elevated, rather dropping to a healthy baseline level. Many athletes find it hard to rest/recover adequately between training sessions and, along with poor sleep and daily stressors, cortisol often remains elevated.

Inadequate rest means that cortisol levels remain elevated, which can result in injury, fatigue and reduced performance. Elevated cortisol levels are also affected by exercise duration, intensity, level of conditioning and time of day.

The longer the duration of a training session, the more cortisol is released. Sessions in excess of 90-120 minutes are more stressful to the body and in turn release more cortisol. Intense sessions reaching a VO2Max of over 60% also result in greater cortisol release. Regarding resistance training, the harder you train, the more cortisol is released. Cortisol levels are generally higher in the morning so if you are very stressed already, evening training sessions may help to regulate cortisol. Strenuous exercise, coupled with fasting can raise cortisol levels. Be mindful of these effects on cortisol and plan your workouts and rest days appropriately. As your body becomes more adapted to training, the effects on cortisol diminish. Training regularly and consistently can allow for this adaptation and reduced cortisol release.

So how do we counteract raised cortisol? By making certain lifestyle changes as follows:

Improved Diet à stress management à exercise with scheduled rest/recovery à better sleep à consider using adaptogens à reduce caffeine.


You diet can play a major role in reducing cortisol levels but can also result in unwanted, elevated cortisol.

Skipping meals, as in the all-fashionable IF (Intermittent Fasting), can be stressful and raise cortisol. The body perceives skipping of meals as starvation à a stressor  à releases cortisol in response. In order to keep blood sugar levels stable and reduce cortisol, meals should be regular. The stress and anxiety about when you will eat your next meal can be regarded as a stressor and raise cortisol. Emotional or stress eating usually results in comfort eating and will often include sugar and will result in raised cortisol.

Sugar and processed foods are known to raise cortisol, these include pastries, pies, cakes, breads, sweets and sugary drinks. Although they raise energy levels in the short term, cortisol levels are also elevated. Aim rather for fiber-rich foods, protein and good fats to maintain stable blood sugar levels and to keep cortisol in the normal range.  Typical cortisol lowering foods include whole grains (like oats and quinoa), fruit, protein (including plant-based proteins) and complex carbs from vegetables like sweet potato.

Breakfast is an important meal, especially to an athlete. By eating in the morning, you lower your cortisol levels and regulate blood sugar levels. This puts your body in an ideal state to train. Fasted training or cardio, on the other hand, has no proven benefits.

Carbs help to modulate endocrine hormones, which includes cortisol.

Sipping on BCAA while training is beneficial. 4g BCAA and 6g Glutamine may assist in lowering cortisol post exercise.

Vitamin C has been known to reduce cortisol and improve cortisol/testosterone ratios.

A drop in cortisol post workout increases connective tissue hypertrophy and enhanced recovery while reducing the chance of colds and flu. It may also aid collagen synthesis.

A healthy, balanced diet consisting mostly of whole foods is recommended, with fruit, dark chocolate and extra virgin olive oil known to reduce cortisol levels.  On the contrary, sugar and an excess of junk food raises cortisol. A bad diet is a double whammy to an athlete, it raises cortisol and results in unwanted weight gain.


Sadly, stress has become an unavoidable part of everyday life. Work, financial, relationship and lifestyle stress are common and living amidst a pandemic doesn’t make it any easier. Find ways to destress. Yoga, meditation, being in nature and scheduled down time are a few ways of effectively managing stress.


Exercise is a wonderful de-stressor, releasing feel-good hormones. Exercise regularly, but not too much. Don’t forget to factor in scheduled rest and recovery days to avoid exercise from becoming an added stressor.


Adopt good sleep hygiene to ensure a good night’s sleep. Not only is it important to get enough sleep, but good quality sleep too. Limit screen time before bed, avoid caffeine and alcohol which are disruptive to sleep. 7 – 9 hours of good sleep is optimal.


Consider using adaptogens like ashwagandha and astragalus. Adaptogens act as anti-oxidants and can help lower cortisol levels. These benefits in turn may help enhance muscle strength and stamina during training sessions and competition.


200mg of caffeine may increase cortisol by 30% within the first hour of drinking it. Cortisol is raised by caffeine even at rest. It is a good idea to decrease caffeine intake later in the day as a late cup of coffee is known to interfere with sleep and raise cortisol levels.



Cortisol in normal amounts is essential for metabolic functioning. Chronically elevated cortisol has adverse effects to health, mood, sleep, relationships, body composition and performance. It results in fat storage and muscle breakdown, suppressed immune function and increased risk of injury. So, while we need a controlled amount of cortisol, elevated levels over a long period of time are detrimental to athletic performance. Make simple lifestyle changes to reduce cortisol and enhance your athletic performance.


If you are looking for a hormone balancing diet to enhance athletic performance, I do 1-on-1 consultations with personalised meal plans. Check out the service options on my website

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