Cortisol, the waking hormone: what the studies say

Cortisol, a rhythm hormone

Cortisol is produced by the adrenal glands under the control of the hypothalamic-pituitary-adrenal axis. It mobilises energy and helps regulate blood sugar, blood pressure and the inflammatory response. Its secretion follows a marked circadian rhythm: low in the early night, it rises towards the end of the night and peaks shortly after waking.

This peak has a name: the cortisol awakening response. It is a normal phenomenon that accompanies the shift from sleep to wakefulness. Talking about cortisol as a hormone to "get rid of" makes little sense. The useful question is its rhythm.

What the video did not have time to say

• A single reading says little: cortisol varies hour by hour. A measurement only makes sense in relation to the time of day.
• Acute and chronic stress differ: a one-off spike is an adaptive response; repetition is what can disrupt the rhythm.
• Sleep matters: bedtime, morning light and regularity all shape the cortisol curve.
• A hormone is not a claim: on a label, the word "cortisol" cannot be tied to a promised effect.

The studies

Stalder et al., 2016, Psychoneuroendocrinology. These expert consensus guidelines describe the cortisol awakening response as a rapid rise in cortisol, peaking about 30 to 45 minutes after waking, and set the rules for measuring it properly, especially the exact timing of samples.

Miller, Chen and Zhou, 2007, Psychological Bulletin. This meta-analysis of 107 studies shows that chronic stress does not raise cortisol uniformly: the effect depends on the type of stress, how long it has lasted and when cortisol is measured, often with a flatter rhythm across the day.

Chandrasekhar, Kapoor and Anishetty, 2012, Indian Journal of Psychological Medicine. 64 adults with a history of chronic stress took 300 mg of ashwagandha root extract twice a day or a placebo for 60 days. Serum cortisol fell significantly in the ashwagandha group compared with placebo.

Lopresti et al., 2019, Medicine. 60 adults took 240 mg of a standardised ashwagandha extract once a day or a placebo for 60 days. Morning cortisol fell more with ashwagandha, with no adverse events reported. These trials remain short and small.

What a supplement can say

Regulation (EU) No 432/2012 contains no claim about cortisol. A "stress" formula therefore relies on the authorised claims of its nutrients, usable when the daily serving provides at least 15% of the nutrient reference value:

• Magnesium contributes to normal psychological function. Magnesium contributes to normal functioning of the nervous system. Magnesium contributes to the reduction of tiredness and fatigue.
• Vitamin B6 contributes to the regulation of hormonal activity. Vitamin B6 contributes to normal psychological function.
• Pantothenic acid contributes to normal synthesis and metabolism of steroid hormones, vitamin D and some neurotransmitters.
• Vitamin C contributes to normal functioning of the nervous system.

Ashwagandha (Withania somnifera) has no authorised claim. The French agency ANSES urges caution with this plant, especially for certain populations: see our article on ashwagandha regulation.

Which format to manufacture

"Stress" formulas raise a dosing question. Magnesium requires several hundred milligrams of salt per day, while B vitamins are dosed in milligrams and a plant extract in hundreds of milligrams.

• Capsules: the reference format to combine a plant extract, magnesium and B vitamins, in sizes 1, 0 or 00.
• Powders: ideal for a high magnesium dose in an evening drink, in stick packs or doypacks.
• Pectin-based gummies and tablets for formulas lighter in magnesium.

To choose a magnesium salt, see our private label magnesium page.