6 min. read
Journal · Vitality & protection
Extreme heat is not just uncomfortable. It triggers a cascade of physiological imbalances: electrolyte, oxidative, cardiovascular and neurological, which draw on all of the body's resources.
The human body is a thermal machine of remarkable precision. Core temperature must stay within a narrow window: between 36.5 °C and 37.5 °C, so that enzymes work, neurons fire correctly and the heart beats steadily. Above an internal 38 °C, alarm mechanisms kick in. Above 40 °C, cellular proteins begin to denature. A heatwave is a constant battle the body wages against the outside heat, often at the expense of everything else.
Thermoregulation works mainly through sweating: the sweat glands produce sweat which, as it evaporates, cools the skin and the blood. But this mechanism comes at a cost. It requires constant hydration, sufficient electrolyte reserves and a heart able to pump more blood to the periphery. When one of these pillars gives way, the cascade of imbalances begins.
The 2003 heatwave in France caused more than 15,000 deaths in two weeks, mainly among older people living alone in homes without cooling. This figure is a reminder that extreme heat is a collective medical emergency, not simply a summer discomfort. Understanding the physiological mechanisms at play is the first step towards protecting yourself.
Scientific reference
Heat Stroke
This landmark review describes the pathophysiology of heatstroke in detail. It establishes that the response to heat stress involves the simultaneous activation of multiple systems: cardiovascular (redistribution of cardiac output), endocrine (HPA axis, cortisol), immune (pro-inflammatory cytokines) and oxidative (massive production of free radicals).
What this means in practice: this is not an imbalance that can be isolated. It is a systemic physiological storm, in which each system compensates for the failures of the others.
“Heat does more than tire the body. It forces it to reorganise everything, at the cost of the balance of every cell.”
Extreme heat affects the body in a cascade: each system tries to compensate for the imbalances created by the others, until reserves run out. Here are the five most important mechanisms to understand.
Of all the electrolytes lost in sweat, magnesium is the one whose deficiency has the broadest and most underestimated consequences. Already deficient in 70 to 80% of the French population under normal conditions (according to data from the SU.VI.MAX study), this deficiency is greatly worsened by sweating during a heatwave.
Magnesium is a cofactor in more than 300 enzyme systems. It is involved in energy production (stabilisation of ATP-Mg), muscle contraction and relaxation (regulation of calcium channels), nerve transmission (inhibition of NMDA receptors), heart rhythm regulation and the maintenance of deep sleep. Magnesium contributes to a reduction of tiredness and fatigue, to normal functioning of the nervous system and to normal muscle function.
A racing heart on heatwave nights, night-time cramps, brain fog that lingers despite rest: these manifestations are frequently reported during periods of intense heat. The literature links them to a drop in magnesium status, although no single sensation can be attributed to it with certainty. If discomfort persists, seeing a healthcare professional remains the right approach.
Another often overlooked mechanism: the skin vasodilation needed to dissipate heat depends on the production of nitric oxide (NO) by the vascular endothelium. L-Citrulline is described as a precursor of arginine, itself the substrate of NO synthase: this is why the available research is interested in it. In a heatwave, peripheral perfusion is not just a performance parameter: it is part of thermoregulation.
Energy Daily Flow (No. 03) builds on this logic with 1,000 mg of L-citrulline, taurine and Setria® glutathione, in a stick format to take in the morning.
“70% of French people already lack magnesium before summer. A heatwave only worsens a deficiency that is already there.”
BIOLOGYST offers five supplements whose ingredients are documented in relation to the physiological mechanisms described above. They can be used separately depending on priorities, or combined.
Key ingredients: L-citrulline 1,000 mg, taurine 500 mg, Setria® glutathione 250 mg, magnesium, vitamin C, vitamin D3, ginseng. Stick, 1 in the morning.
Role in a heatwave. L-Citrulline is the precursor of arginine, the substrate of NO synthase, the pathway involved in dilating skin blood vessels and dissipating heat. Taurine and glutathione are the subject of research describing their role in the cellular response to heat stress. Vitamin C contributes to the protection of cells from oxidative stress and to the reduction of tiredness and fatigue.
Dosage: 1 stick in the morning in 500 ml of cool water · ideal before and during hot spells.
Key ingredients: 300 mg of magnesium (bisglycinate + citrate + ATA Mg®), with taurine. Stick, 1 in the evening.
Role in a heatwave. Sweating increases magnesium losses; this stick provides 300 mg per serving. Magnesium contributes to normal muscle function, to normal functioning of the nervous system and to a reduction of tiredness and fatigue.
Dosage: 1 stick in the evening · do not exceed 1 stick a day, even with heavy sweating.
Key ingredients: 100 mg of ExceptionHYAL® Star hyaluronic acid and OVODERM® eggshell membrane. Stick, 1 in the morning.
Role in a heatwave. Hyaluronic acid is described in the literature for its ability to hold water in the extracellular matrix. This is the mechanism documented by the available research. It does not replace fluid intake, which remains the foundation.
Dosage: 1 stick in the morning in water · take throughout the summer period.
Key ingredients: quercetin 427 mg, Setria® glutathione 375 mg, vitamin C 150 mg. Capsules, 2 to 3 in the morning.
Role in a heatwave. Vitamin C contributes to the protection of cells from oxidative stress, one of the central mechanisms of the cellular toxicity of heat. The available studies describe an action of quercetin on low-grade inflammation, and of glutathione on maintaining the cellular redox potential, particularly in membranes and mitochondrial DNA.
Dosage: 2 to 3 capsules in the morning or at lunchtime, with a meal · take during and after the heatwave.
Key ingredients: 1.8 mg of melatonin, valerian, passionflower, California poppy (eschscholtzia), marjoram. Spray, 5 sprays in the evening.
Role in a heatwave. Melatonin contributes to the reduction of time taken to fall asleep, while night-time heat disrupts the circadian rhythm and prevents the drop in body temperature needed for deep sleep.
Dosage: 5 sprays 30 minutes before bedtime · under the tongue, hold for a few seconds.
“It is not heat alone that wears you out: it is the cascade of deficiencies it creates. Anticipating means protecting.”
Food supplements are part of an overall approach to protection during a heatwave; they do not replace it. The fundamental habits remain non-negotiable.
Warning signs: medical emergency. Stop all activity and call 15 (SAMU) in France, or your local emergency number, in case of: persistent temperature above 38.5 °C, confusion or disorientation, sweating that stops despite the heat, loss of consciousness or seizures. These signs indicate heatstroke.
Because heat draws on five systems at once: fluid and electrolyte balance, cardiovascular, oxidative, nervous and kidney-digestive. Sweating can reach 1 to 2 litres per hour in intense heat, and the heart must pump more blood to the skin to get rid of the heat.
Magnesium is the electrolyte whose deficiency has the broadest consequences. 70 to 80% of the French population already lack it under normal conditions (SU.VI.MAX study), and it is a cofactor in more than 300 enzyme systems. Magnesium contributes to a reduction of tiredness and fatigue and to normal muscle function.
At least 1.5 to 2 litres of water a day, and 3 litres or more in intense heat or during physical activity. Drink without waiting until you are thirsty: feeling thirsty signals a deficit that has already set in. From −1% of body weight in water, cognitive functions deteriorate.
Sleep requires body temperature to drop by 0.5 to 1 °C. Above 20 to 22 °C in the bedroom, this cooling becomes impossible: deep sleep and REM sleep are fragmented and melatonin secretion is disrupted.
A persistent temperature above 38.5 °C, confusion or disorientation, sweating that stops despite the heat, loss of consciousness or seizures. These signs indicate heatstroke: stop all activity and call 15 (SAMU) in France, or your local emergency number.
More analyses are available in the BIOLOGYST Journal, and details of the ingredients in Active Ingredients.
Precautions. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose. Keep out of the reach of children. If you are taking medication, pregnant or breastfeeding, ask your healthcare professional for advice. This article is general information and does not constitute medical advice.
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