What is cortisol?

What is cortisol?

Cortisol is a major hormone produced by our bodies with a big impact on our mental and physical wellbeing, and one of the most common yet little known causes of poor sleep, anxiety and stress. Our expert nutritionists explain cortisol, what cortisol is, how it is created, how cortisol affects us, and how you can lower cortisol. 

What is cortisol?

Cortisol is a stress hormone and also much more than that. Cortisol is a steroid hormone that is released by the adrenal glands. It is a major stress hormone and works with adrenaline in stressful situations.

Your cortisol levels are regulated by glands in the body called 'hypothalamus glands', the pituitary and the adrenal glands. Although cortisol is normally associated with stress, it does play a wider role in the body which includes functions such as regulation of blood sugar levels, metabolism, memory, inflammation, water balance and blood pressure. In pregnancy, cortisol is necessary for the development of the foetus. Discover our acclaimed Pregnancy Multinutrient.

Problems caused by high cortisol

High cortisol levels can cause a number of health issues including weight gain, anxiety, difficulty sleeping, impaired digestion, abdominal obesity, a flushed face, weight gain and mood swings. High cortisol levels can also cause decreased libido and changes in the menstrual cycle.

Some hormones in our body are created in the same way as cortisol, however it is a pre-historic survival mechanism for our body to prioritise the production of cortisol above all other hormones. Our body's prioritisation of cortisol over other hormones can potentially create havoc, in particular with our sleep and mental wellbeing

How does cortisol affect sleep?

One of the most common but little known causes of bad sleep is cortisol. Cortisol disrupts the sleep cycle, with a strong influence on your ability to get to sleep, your quality of sleep and the duration of your sleep. This is because the body uses the same pathways for sleep as it does for stress.

Excess cortisol disrupts the creation of sleep hormones, in particular melatonin, and the sleep cycle. Melatonin is our most important sleep hormone so if our body is unable to produce it due to high levels of cortisol, it is harder to get to sleep and stay asleep

Our bodies follow a pattern of sleeping hours and waking hours, and the synthesis of cortisol follows the same pattern, where cortisol should be at its lowest at midnight, and at its highest around one hour after waking.


The body moves through several phases of sleep each night and a small level of cortisol is produced during some of these phases. If cortisol production is too high before or during sleep, sleep cycles will be disrupted and can lead to broken sleep, insomnia and a shorter duration of sleep. Studies show Ashwagandha KSM-66 lowers cortisol which is why it is commonly taken before bedtime, on its own or alongside other sleep remedies

You may enjoy our research 'The Sleep Problem: More than 1 in 3 people suffer poor sleep'.

How do I lower cortisol?

This is one of the most frequently asked questions of our nutritionists because cortisol has such a big impact on sleep. The good news is you can lower cortisol to improve your sleep through diet, lifestyle and supplements to relieve anxiety and enjoy a better night's sleep.  


A plant-based diet is an excellent place to start for lowering cortisol because animal proteins can increase the level of cortisol in the body. Avoiding refined sugars is another great option. Refined sugar triggers spikes and dips in blood glucose levels which triggers the release of cortisol. Low blood sugar levels create additional stress on the body. 

Understand your diet. Create your free Diet Profile

High salt diets should also be avoided as they can increase cortisol levels. One study found that a meal high in salt increases cortisol metabolites in urine significantly.  The best diet for regulating cortisol is a plant-based diet rich in fruit and vegetables

Best vitamins & supplements for lowering cortisol

Ashwagandha KSM-66

Used for thousands of years in Ayurvedic medicine, Ashwagandha is a herb that helps to induce a state of calm. Ashwagandha works with the adrenal glands, pituitary and hypothalamus glands to help lower cortisol and regulate the stress response, having a beneficial effect on sleep. Research has shown Ashwagandha to help people to fall asleep faster and spend more time asleep, as well as experiencing better sleep quality.

Learn more in our article 8 surprising benefits of Ashwagandha



Magnesium is a 'Mineral Superhero' and essential for the production of a neurotransmitter called GABA. GABA lowers cortisol levels in the body and induces a relaxed state of mind, promoting the onset of sleep. Magnesium is also needed for the conversion of serotonin (your 'happy hormone’) into melatonin (your ‘sleep hormone’). Discover our best-selling Magnesium and learn more in our article 'How do I know if I'm deficient in Magnesium'.

5HTP (5-hydroxy-tryptophan)

5-hydroxy-tryptophan, or 5HTP as it is more commonly known, is a pre-curser to both the hormones serotonin and melatonin. Serotonin is converted into melatonin, and melatonin is the sleep hormone which helps to regulate sleep cycles and is essential for dropping off to sleep quickly.  If you're taking medication for depression it is not advised to take supplements containing 5HTP.


Theanine increases the level of GABA in the brain which promotes relaxation and the start of sleep. Theanine also promotes alpha brain waves which further help with relaxation. In addition, theanine may improve sleep quality.

Shop Vegan Nights | For a better night's sleep


Glycine is an amino acid and can be useful for aiding the transition into sleep. Although the mechanisms are unclear, research shows that glycine induces REM sleep.


Chamomile is a flower with an active compound called apigenin. Apigenin binds to receptors in the brain and studies show it promotes sleep and a reduction in stress.

Other ways to lower cortisol


Meditation changes the pathway in the brain that can stimulate the adrenal glands to release cortisol. When practiced, mindfulness and meditation has been shown to lower the levels of cortisol in the blood.

Be outside with nature

Trees release a substance called phytoncides into the air. This chemical is released to protect the trees from rotting, however it also has a great benefit for humans - when inhaled, it reduces the level of cortisol levels in our blood.

Discover our range of vegan vitamins and supplements

Want to hear more from our nutritionists? Sign up to our newsletters here: