September and the hidden cycle between stress and your magnesium

September has a reputation that almost nobody questions: it's "normal" to arrive more tired, more irritable, sleeping worse, during the first days — or weeks — of getting back into the routine. We accept it as the inevitable toll of leaving summer behind. But there's something that acceptance overlooks: while your mind makes peace with going back to school and work within days, your body may keep paying that bill for a good deal longer.

🍂 Stress & Energy Science · 7 min read · Educational information

What cortisol actually does

Cortisol is the central hormone of the stress response. In short bursts, it's useful and even necessary: it mobilises energy, keeps you alert, helps you perform under pressure. The problem isn't cortisol itself — it's when it stays elevated for a sustained period, which happens easily when the body shifts, almost overnight, from the calm of summer to the pace of September's schedules, obligations and stimuli.

Research on chronic stress is clear on one point: when cortisol stays high for weeks, it isn't a neutral state. A study in older adults found a direct association between cortisol excretion and markers of oxidative damage to DNA and RNA — those who excreted more cortisol showed up to 57-61% more of these markers of cellular wear than those who excreted less. It's one of the pieces linking sustained stress to accelerated ageing.

💡 In simple terms

Your mind might decide it has "got used to" being back in the routine within a couple of weeks. But biology doesn't work by conscious decision: elevated cortisol keeps acting on your cells for as long as the physiological stress level remains, regardless of whether you've mentally already written it off as normal.

The vicious circle almost nobody knows about

Here's the least-known fact of all, the one that gives meaning to the rest of the article. Elevated cortisol doesn't just create that constant sense of alertness: it also makes your body excrete more magnesium through urine. This is a well-documented mechanism — acute and chronic stress increases urinary magnesium excretion, which can lower the amount available in the body.

And here's where the circle closes, and why it's particularly relevant: magnesium isn't a passive bystander in all this. When its levels drop, the hormonal axis that regulates your stress response — the hypothalamic-pituitary-adrenal axis, or HPA axis — becomes more reactive. In other words, with less magnesium, your body tends to release more cortisol in response to the same level of stress. Less magnesium, more cortisol. More cortisol, less magnesium. A self-feeding cycle that continues until something interrupts it.

🔬 Key fact

An analysis of a controlled trial with adults aged 45-70 who took 350 mg of magnesium daily for 24 weeks found an average reduction of 32 nmol in 24-hour urinary cortisol excretion, compared with the placebo group. It's not just a theoretical relationship: replenishing magnesium is associated with a different way the body processes cortisol.

Why September is when it's most noticeable

For many people, summer tends to be a time of lower sustained demands — fewer rigid schedules, more rest, fewer simultaneous stimuli. The return to routine in September represents a relatively sharp jump in daily stress load: schedules, responsibilities, children going back to school, projects starting up again. That jump is precisely the kind of situation that triggers sustained cortisol — and with it, the cycle we've just described.

It's no coincidence, then, that many people notice a fatigue in September that doesn't quite add up with "I've slept the hours I'm supposed to" — because the problem isn't always how much sleep you get, but a stress system that stays switched on in the background.

✨ The key takeaway

Treating September's exhaustion as "normal" doesn't change what's happening inside the body. The biological cost exists, whether or not the conscious feeling of stress builds up. Recognising it is the first step towards not letting it slide.

What role magnesium can play

Given this mechanism, it makes sense to pay attention to magnesium precisely at this time of year. Magnesium contributes to the normal functioning of the nervous system, to normal psychological function, and to the reduction of tiredness and fatigue — three approved claims that are directly relevant to what this cycle describes.

Not all forms of magnesium are absorbed equally. Chelated forms — such as bisglycinate — have notably higher bioavailability than inorganic salts like oxide, and are gentler on the digestive system, making them a suitable choice for sustained use over time, which is exactly what this cycle calls for.

⚠️ An important note

If stress, fatigue or associated symptoms are intense or persistent, consult your healthcare professional — they may require an assessment that goes beyond a nutritional adjustment. Food supplements are not a substitute for a varied and balanced diet, nor for professional stress management when needed.

Conclusion

September fatigue isn't just a matter of "getting used to it". There's a real biological mechanism behind it — sustained cortisol, magnesium loss, an increasingly reactive stress axis — that isn't resolved simply because the mind decides it's now normal. Understanding the cycle is what allows us to stop treating it as cost-free, and start interrupting it where we actually can: by replenishing what this process is depleting.

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High-bioavailability chelated magnesium, which contributes to the normal functioning of the nervous system, to normal psychological function and to the reduction of tiredness and fatigue. Designed to support you through the most demanding times, such as getting back into routine.

Scientific references

Joergensen, A. et al. (2011). Association between Urinary Excretion of Cortisol and Markers of Oxidatively Damaged DNA and RNA in Humans. PLoS ONE, 6(6), e20795.

Pickering, G. et al. (2020). Magnesium Status and Stress: The Vicious Circle Concept Revisited. Nutrients, 12(12), 3672.

Cuciureanu, M.D. & Vink, R. (2011). Magnesium and stress. In: Magnesium in the Central Nervous System. University of Adelaide Press.

Lindberg, J.S. et al. (1990). Magnesium bioavailability from magnesium citrate and magnesium oxide. Journal of the American College of Nutrition, 9(1), 48–55.

Boyle, N.B. et al. (2017). The Effects of Magnesium Supplementation on Subjective Anxiety and Stress. Nutrients, 9(5), 429.

Informational content. This does not constitute an authorised health claim beyond the functions stated in accordance with current regulations, nor medical advice. Food supplements are not a substitute for a varied and balanced diet.