Wellness throughout the seasons: seasonal health advice, what science actually says

Our body is not a machine that runs identically twelve months a year. A major study published in Nature Communications showed that nearly a quarter of our genome, or more than 4,000 genes, changes activity according to the season, especially those governing immunity and inflammation. (1) In other words, your January biology is not your July biology. Understanding these variations means stopping passive endurance of the seasons to start adapting to them intelligently.

This guide reviews each season through the lens of real mechanisms: the effect of light on melatonin and mood, thermoregulation, circadian rhythms, and the famous question of winter immunity. It also aims to dismantle, with supporting evidence, the most persistent beliefs about seasonal well-being, from spring detox cleanses to miracle immunity boosters. The goal: to provide you with reliable reference points rather than recipes.

Why do seasons affect our bodies so much?

The primary conductor of our seasonal rhythms is not temperature, but light. Day length, or photoperiod, modulates the secretion of melatonin, the hormone that signals night to the body. When days shorten, the melatonin secretion window lengthens, shifting our internal clocks and affecting mood, alertness, and sleep.

This internal clock, known as the circadian clock, is located in the brain and resets every day using light captured by the retina. This is why exposure to daylight, especially in the morning, plays a much deeper role than we imagine: it synchronizes sleep, body temperature, and numerous hormonal secretions. (2)

Added to this is a long-ignored reality: our immune system itself fluctuates with the seasons. Researchers observed that in winter, in the Northern Hemisphere, the body adopts a marked pro-inflammatory profile, with an increase in markers such as C-reactive protein. (1) This shift, useful in fighting winter infections, also helps explain why certain cardiovascular and autoimmune diseases peak in winter. Seasons do not just change our mood: they profoundly reconfigure our physiology.

Spring: renewal, between biological reality and the detox myth

What really changes in spring

The return of light in spring produces measurable effects. Lengthening days reduce the duration of nocturnal melatonin secretion and promote a rise in energy and mood as the circadian clock advances. Many people experience a boost in vitality: this is not just an impression, it is the direct consequence of our rhythms being resynchronized by light. (2)

Spring is also the best window to resume regular outdoor physical activity, enjoy natural light, and replenish, through sun exposure, a portion of one's vitamin D stores after winter. These benefits are real and documented. The problem arises when this renewal is grafted onto promises that rest on nothing.

The myth of the spring detox cleanse

Every spring brings back the idea that we need to "detoxify" our body after winter with juices, herbal teas, or restrictive programs. However, a critical review of the scientific evidence is clear: there are no solid clinical data demonstrating that commercial detox cleanses eliminate toxins or improve health. (3) The few available studies suffer from weak methodologies and minuscule sample sizes, and to date, no randomized controlled trial has validated the efficacy of these programs in humans. (3)

The reason is simple: the human body already possesses a remarkably efficient detoxification system, the liver and kidneys, which constantly neutralize and eliminate waste. No herbal tea performs better than these organs. What sometimes "works" in a cleanse is cutting out alcohol, ultra-processed foods, and increasing fruit and vegetable intake—beneficial habits in themselves, but there is nothing magical or seasonal about them. Rather than a one-off cleanse, science advocates for a balanced diet year-round.

Summer: heat, thermoregulation, and the real risks of heatwaves

How does the body manage heat?

In the face of heat, the body deploys sophisticated thermoregulatory machinery to maintain its core temperature around 37 °C (98.6 °F). Two mechanisms dominate: vasodilation, which redirects blood flow to the skin to dissipate heat, and sweating, the evaporation of which cools the body surface. This evaporative cooling is effective, but it comes at a cost: a loss of water and mineral salts which, if not compensated, leads to dehydration.

During a heatwave, this system can become overwhelmed, especially in the elderly, whose perception of thirst and capacity to sweat decrease with age, and in infants. The real danger is not just feeling hot, but the failure of thermoregulation, which leads to heatstroke, a life-threatening emergency. Drinking water is helpful, of course, but that is just the basics: the real challenge is actively helping the body regulate its temperature.

Beyond "drink water": the strategies that matter

Since cooling relies on evaporation and the skin, the most effective strategies act on these levers. Cooling the skin (wet cloth, lukewarm shower, misting) amplifies the evaporative effect. Closing shutters during the day and ventilating at night exploits the thermal inertia of the home. Avoiding physical exertion during hot hours reduces internal heat production.

An often overlooked point: in extreme heat, drinking large amounts of water without replacing the electrolytes lost in sweat can, in extreme cases, dilute blood sodium. A normal diet is generally sufficient to compensate, but in cases of intense, prolonged sweating, salt intake should not be neglected. Finally, acclimatization is real: when gradually exposed to heat over one to two weeks, the body sweats earlier and with a more dilute concentration, which improves thermal tolerance. This is why the first heatwaves of the season are often the most dangerous.

The return to routine: the most underestimated transition of the year

Why the end of summer is a physiological shock

Going back to a routine after summer is not just a social marker: it is a real chronobiological transition. After a summer of late nights and sleeping in that shifted our clocks, returning to strict schedules creates a mismatch between social time and biological time, a phenomenon skin to "social jet lag." This misalignment explains the fatigue, irritability, and concentration difficulties experienced in September, far beyond the simple resumption of work.

This is compounded by the gradual decline in light. Starting in late August, days shorten, melatonin secretion shifts, and waking up becomes more difficult. It is not a lack of willpower: it is your internal clock struggling to keep up with the calendar. The good news is that this clock can be guided precisely by light.

Navigating the transition: acting on light and sleep

The most effective strategy for a smooth transition back to routine is to actively reset your circadian clock. Morning light is the most powerful tool: exposure to natural light upon waking advances the internal clock, facilitates falling asleep at night, and improves daytime alertness. Studies on adolescents show that access to daylight is a major lever, still underutilized, for sleep quality and mood stability. (4)

Concretely, a few principles hold true: gradually advance bedtime one to two weeks before resuming routines rather than doing so abruptly; expose yourself to natural light in the morning (go outside, open curtains wide); limit artificial light and screens in the evening, as they delay melatonin; and maintain consistent wake-up times, including on weekends, to avoid reintroducing jet lag. These are modest adjustments, but they address the root of the problem rather than just the symptoms.

Takeaway: Back-to-routine fatigue is not just a matter of motivation. It is a misalignment between your biological clock and your schedule. Morning light is your best ally to resynchronize them.

Autumn: declining light, immunity, and the seasonal blues

Seasonal depression: a real and documented phenomenon

As days shorten, some people develop true seasonal depression (or seasonal affective disorder), which most often begins in autumn or winter and recedes in spring. Its prevalence varies from 1.5% to 9% depending on latitude: the further from the equator, the more frequent it is, confirming the central role of light deprivation. (5) This is not just a simple temporary slump, but a characterized mood disorder linked to the shifting of circadian rhythms and melatonin caused by falling light levels.

Light therapy, consisting of daily exposure to intense artificial light, is the gold standard treatment for the established form. However, we must remain realistic about the evidence for prevention: some reviews conclude that data remain limited and of low certainty to affirm that light therapy, melatonin, or even psychotherapy effectively prevent the occurrence of a new episode in at-risk individuals. (5) The choice of a preventive treatment must therefore be discussed on a case-by-case basis, ideally with a healthcare professional. If you experience a marked and lasting decline in mood in autumn, it is not insignificant: speak to your physician.

Should we "boost" our immunity in autumn?

Autumn sees a surge of promises for "immunity boosters." Two of them deserve a look at what science actually says. First, vitamin C: a meta-analysis of over 11,000 participants shows that regular supplementation does not reduce the risk of catching a cold in the general population. It slightly shortens cold duration (by about 8% in adults), but taken once cold symptoms have already appeared, it has no reliable effect. (6) The only exception is individuals subjected to short periods of extreme physical stress, such as marathon runners, in whom a protective effect is observed. (6)

Second, vitamin D, the levels of which drop in winter due to lack of sun: a large meta-analysis pooling over 48,000 participants confirms a real but modest protective effect against respiratory infections. (7) The benefit is concentrated in those who receive a moderate daily dose (400 to 1000 IU per day), rather than those taking large periodic bolus doses. (7) The lesson is nuanced: vitamin D is not a miracle shield, but reasoned supplementation in winter, especially in deficient individuals, makes clinical sense. Here too, the advice of a healthcare professional is paramount over high-dose self-medication.

Winter: energy, cold, and the great cold myth

Regaining energy in winter

The winter energy slump has a clear physiological explanation: less light means a less synchronized circadian clock, melatonin secreted longer into the morning, and consequently prolonged drowsiness. The lack of daylight is the central factor, rather than the cold itself. This is why effective strategies target light and rhythm first: maximizing exposure to natural light during the day, going outside even on overcast days, and maintaining regular physical activity.

Exercise deserves a closer look, as it carries a misleading reputation. It is often said that intense exertion "opens a window" of immune vulnerability conducive to infection. This "open window" theory is now widely challenged: the transient drop in immune cells in the blood after exercise does not reflect immunosuppression, but rather a redistribution of these cells to tissues where they enhance immune surveillance. (8) Far from weakening defenses, regular physical activity improves immunological competence and may even delay immunosenescence. (8) Staying active in winter is therefore not a risk; it is an asset.

"The cold causes the common cold": true or false?

This is arguably the most widespread seasonal belief. The truth is more subtle than a simple true or false. Cold weather itself does not "cause" a cold: viruses, notably rhinoviruses, are responsible. However, cold conditions favor them, and a precise mechanism has been identified.

Yale researchers demonstrated that the antiviral response of our cells is less effective at lower temperatures. (9) When cold air cools the nasal mucosa, cells produce less interferon, the molecule that coordinates antiviral defense, allowing rhinoviruses to replicate more easily in the nose, which is cooler than the rest of the body. (9) The cold does not introduce the virus, but it locally weakens our first line of defense. Added to this are behavioral factors (staying indoors, closer to others) and dry winter air, which promotes viral survival and transmission. The good news: bundling up, especially covering the nose and airway, keeps the mucosa warmer and actually supports its defenses. Grandmother was half-right, but for the wrong reason.

Adapting well-being year-round: the role of therapeutic guidance

The common thread across these four seasons is clear: our body is constantly adapting, and the most powerful levers (light, sleep, physical activity, balanced nutrition) are accessible to everyone without miracle recipes. The regularity of physical activity, in particular, spans all seasons as a protective factor for mood, immunity, and energy.

For patients undergoing rehabilitation or accompanied by a therapist, maintaining this regularity throughout the year is precisely one of the major challenges. Tools like Andrew®, used by many physiotherapists and clinicians, allow the prescription of customized exercise programs and clinical monitoring at a distance, including during periods when motivation wanes, such as winter or the transition back to work. This continuity of care, between clinical sessions and through the seasons, helps translate good intentions into lasting habits. If you are a healthcare professional curious about this approach, you can chat with the Andrew® team to see how this tool integrates into evidence-based clinical management.

Conclusion: adapting to the seasons without falling for myths

Living with the seasons is not about following trendy wellness rituals, but about understanding the mechanisms that actually govern our bodies: the light that drives our clocks, the thermoregulation that protects us from heat, and the immunity that fluctuates throughout the year. Once these mechanisms are understood, appropriate reflexes become clear, and false promises are easy to spot.

Science calls for moderation: neither saving biotech detoxes nor miracle immunity boosters, but simple, regular, and evidence-based adjustments. And when well-being relies on movement and physical therapy, structured guidance often makes the difference. To discover how personalized clinical follow-up can support this year-round consistency, you can request a demo of Andrew®. To go further on the role of exercise in structured therapeutic management, consult our article on patient education for chronic pain, or our guide on when to consult a practitioner.