For years, the message has been "the sun ages the skin". There has been talk of spots, wrinkles, loss of elasticity, cellular damage, and an increased risk of skin cancer. But we are increasingly hearing professionals and science communicators talk about the importance of natural light for vitamin D, circadian rhythms, sleep, energy, and overall health.
And so, what is the conclusion?
Should we avoid the sun because it accelerates skin aging? Or do we need more exposure because sunlight is important for the body? Does sunscreen protect us or prevent us from producing vitamin D? Is going out into the sun in the morning healthy, or is it also harmful to the skin?
The answer is not to choose a side. The sun is not an absolute enemy, but it is not a harmless force either. Studies show that sun exposure plays a role in important biological functions, such as the cutaneous synthesis of vitamin D, and that daylight helps regulate our biological rhythms. But that same exposure, when it involves excessive, repeated, or intense ultraviolet radiation, can damage DNA, accelerate photoaging, and increase the risk of skin cancer.
Therefore, the question should not simply be “to sun or not to sun?”, but rather what kind of relationship do we need to have with sunlight to enjoy its benefits without adding unnecessary damage to the skin?
Why the sun seems to be a contradiction for health
The sun seems contradictory because it brings together two truths at the same time.
On one hand, sun exposure has important biological functions. The best known is its role in the production of vitamin D: when UVB radiation reaches the skin, it activates a substance (7-dehydrocholesterol) in the outermost layer of the skin, and from there, the production of vitamin D3 begins. This vitamin then passes through the liver and kidneys until it is transformed into its active form. But the sun doesn't just influence vitamin D. Daylight also helps to set our biological clock, the internal system that organizes many of the body's rhythms, such as sleep, energy, body temperature, or repair processes. Even the skin has its own internal “clocks,” which participate in how it functions and recovers throughout the day and night.
The problem is that not everything that comes from the sun has the same effect. The ultraviolet radiation is also a well-known cause of skin damage. UVB radiation can directly damage the DNA of cells, while UVA promotes oxidative stress and other processes related to skin aging and the development of skin cancer.
That is where the confusion arises. The idea that the sun is bad for the skin is partly true, especially when we talk about sunburns, accumulated radiation, spots, premature wrinkles, and skin cancer. But if it is expressed in absolute terms, it leaves out the other important part: that human beings also need natural light to regulate basic biological processes.
Now, at the opposite extreme, some current narratives present the sun almost as a natural medicine that should be reclaimed without fear. And that approach also falls short. The fact that sunlight has benefits does not mean that all exposure is healthy, nor that more sun is always better. The contradiction is not resolved by choosing between “sun yes” or “sun no,” but by distinguishing between sensible exposure and harmful exposure.
Difference between sunlight and UV radiation
As we have seen, one of the reasons why this topic causes so much confusion is that we use the word “sun” to refer to different things. It is not the same to talk about natural light as it is to talk about ultraviolet radiation. Circadian regulation depends above all on exposure to ambient light, while a large part of the most relevant skin damage comes from UV radiation, especially UVA and UVB.
Going out in the morning, receiving natural light, walking outdoors, or maintaining a life more connected with the day can be positive for biological synchronization. But that does not mean it is advisable to expose yourself to intense sun for hours, to seek to get “a little” sunburned, or to not use protection when radiation is high.
How the sun ages the skin
When we talk about skin aging, we usually think about the passage of time: the years, genetics, hormonal changes, or the progressive loss of collagen. But there is another form of aging that does not depend solely on getting older, which is photoaging.
What is photoaging
Photoaging is the premature aging of the skin caused by cumulative exposure to solar radiation, especially ultraviolet radiation. This is why two people of the same age can have very different skin depending on their history of sun exposure, their sunburns, their protection habits, and the time they have spent outdoors without care.
In this way, when it is said that “the sun ages,” it is not just from an aesthetic point of view. It refers to a set of biological processes that affect the structure and function of the skin. Skin exposed chronically or intensely to the sun usually shows some recognizable signs sooner:
- Spots or hyperpigmentation
- Deeper wrinkles
- Uneven tone
- Rougher texture
- Loss of firmness
- Sagging
- Reduced elasticity
- Dull or less uniform appearance
These signs do not appear overnight. They are the consequence of a prolonged relationship with UV radiation. For this reason, sun care should not be understood as a sporadic summer concern, but as one more part of skin care throughout life.
UVA and UVB: two different ways of damaging the skin
To better understand why the sun ages the skin, it is useful to differentiate between the two most relevant types of ultraviolet radiation: UVA and UVB.
The UVB radiation is more related to sunburns and direct DNA damage. It is also the radiation that participates in the initiation of cutaneous vitamin D synthesis, which explains part of the sun's apparent contradiction: the same radiation that can activate a useful process for the body can also cause damage if the exposure is excessive.
The UVA radiation, on the other hand, penetrates deeper into the skin and is associated with oxidative stress, the degradation of skin structures, and premature aging. Although it does not always produce a burn as obvious as UVB, it also leaves its mark.
This is important because many people interpret the absence of a burn as a sign of safety. But the skin can accumulate damage even without an intense visible burn. A sunburn is a clear sign of excess, but it is not the only form of sun damage.
The danger of sunburns
A sunburn should not be seen as anecdotal; it is a sign that the skin has received more radiation than it could tolerate.
Not all sun exposure patterns carry the same risk. Cumulative exposure over years (for example, many hours outdoors without sun protection throughout your life) is especially related to some types of skin cancer. On the other hand, intense and sporadic exposures, especially when they cause burns, seem to be especially important in the risk of melanoma, one of the most concerning skin cancers.
The sun not only ages, it can also alter skin health
Visible aging is part of the problem, but not the only one. Ultraviolet radiation is also involved in DNA damage and processes related to skin cancer. Excessive sun exposure can accelerate skin aging and increase the risk of developing cancer.
This does not mean that every ray of sunshine is dangerous, nor that we should live avoiding natural light. It means that the skin has a limited capacity for adaptation and repair. When exposure exceeds that capacity, the problem begins. Photoaging does not appear because we get some sun sometimes, but because we accumulate more radiation over the years than our skin can manage well.
Vitamin D and sun protection
So, it is clear that we must be careful about exposing ourselves to the sun without protection, but at the same time, we are told about the importance of vitamin D, which is one of the best-known reasons why the body needs a certain relationship with the sun. We know that UVB radiation participates in the production of vitamin D in the skin. We also know that sunscreens are designed to reduce the impact of ultraviolet radiation on the skin. So, if I need the sun to produce vitamin D, won't using sunscreen be counterproductive?
The reality is more nuanced.
Does sunscreen prevent vitamin D production?
From a theoretical point of view, if sunscreen is applied in sufficient quantity, uniformly, and reapplied correctly, it can reduce the UVB radiation that reaches the skin. And since UVB participates in the production of vitamin D, it could reduce that synthesis under ideal application conditions.
However, in practice, almost no one applies sunscreen perfectly. We tend to use less than the recommended amount, forget areas, do not reapply often enough, or receive light at different times of the day. In fact, daily use of sunscreen has not been associated with significant low vitamin D deficits. And the truth is that, even with high SPF (30-50), a small percentage of UVB (2-7%) always gets through, which is enough for the body to continue producing vitamin D with some time outdoors.
So, to produce vitamin D, sunscreen yes or no?
The confusion about vitamin D and sunscreen has led some people to think that perhaps it is best to expose themselves without cream for a while to better “take advantage” of the sun. But that reasoning can be dangerous if it becomes an excuse to normalize intense exposure, sunburns, or lack of protection during moments of high risk.
For everything we have seen before, it is advisable to use sunscreen daily on the most exposed areas such as the face, neck, décolletage, and backs of the hands, even on cloudy or winter days. In situations of intense or prolonged exposure such as the beach, pool, mountains, or outdoor sports, it is advisable to use photoprotection on the entire body and reapply it frequently.
It is also worth mentioning that to produce adequate amounts of vitamin D, it is not necessary to spend hours in the sun. Exposing just 5% of the body surface (which is equivalent to the backs of the hands and the face) is enough. A light-skinned person reaches their maximum vitamin D production in just 5 minutes, and additional time without protection only generates damage to the skin.
Sunscreens, with chemical or mineral (physical) filters?
Within sun protection, an increasingly common question is whether it is better to choose a cream with chemical filters or with mineral filters, also sometimes called physical filters. Both types have the same goal: to reduce the impact of ultraviolet radiation on the skin. The difference lies in how they do it.
With chemical filters, part of the UV radiation is absorbed into the skin and then transformed into a less harmful form of energy, generally heat. They usually have lighter textures, which is why many people prefer them for daily use. However, some chemical filters have generated scientific debate because they can be absorbed through the skin and detected in the blood. Clinical studies published in JAMA observed systemic absorption of several organic sunscreens (such as avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate). The main concern is not just that they are absorbed, but that some of these compounds have shown in research potential endocrine activity, that is, the ability to interfere with hormonal signals in certain experimental models or observational studies. For this reason, regulatory agencies and the scientific community are calling for more data on their long-term safety.
The mineral filters, such as zinc oxide or titanium dioxide, act mainly by creating a barrier on the surface of the skin that helps to reflect and scatter ultraviolet radiation. That is why they are also known as physical filters. These sunscreens are an interesting option for those who prefer not to expose themselves to the possible risks associated with the cutaneous absorption of some chemical filters, as they act mainly on the skin's surface. In addition, they are especially interesting for sensitive, reactive, mature, or spot-prone skin. Traditionally, they could leave a more visible white layer, although current formulas have improved greatly in texture, finish, and comfort. [see 100% mineral filter sunscreen]
The sun and circadian rhythms
Another of the reasons why the debate about the sun has become more confusing is that there is more and more talk about circadian rhythms. And rightly so, natural light is one of the most important signals the body has to organize its daily cycles.
Our body does not function the same during the day as it does at night. In the morning it needs to activate, at night it needs to prepare to rest and repair. To organize all this, the body has a kind of internal clock that helps regulate sleep, energy, body temperature, some hormones, metabolism, and many recovery processes. This internal clock responds significantly to ambient light. When we receive light during the day, especially in the morning, the body interprets better that it is time to be awake and active. When darkness arrives, it understands that it is time to rest. For this reason, receiving natural light during the day, especially in the early hours, can help the body better differentiate between day and night. This exposure to daylight can promote more orderly sleep, a better sense of energy, and a more stable biological routine.
But, just as with vitamin D, taking care of circadian rhythms does not mean exposing yourself to intense sun without protection. Circadian regulation depends above all on ambient light, while many of the most relevant skin damages come from ultraviolet radiation, especially UVA and UVB. Furthermore, for circadian rhythms sunscreen does not interfere with the light signal that regulates the internal clock.
How to have an intelligent relationship with the sun
The answer to the contradiction of the sun is not in the extremes. It is not about fleeing from natural light as if it were always dangerous (it is very necessary!), nor about romanticizing the sun as if any exposure were healthy. What we must do is learn to have an intelligent relationship with sunlight. This implies accepting both that the body needs natural light to regulate important functions, and that the skin needs protection against excess ultraviolet radiation.
Seek out natural light, especially in the morning
A simple way to take care of circadian rhythms is to expose yourself to natural light during the day, especially in the early hours. We are not necessarily talking about "sunbathing" while lying down or seeking a tan, but rather allowing the body to receive clear daylight signals.
Going for a walk, having breakfast near a window, taking a break outdoors, or maintaining a routine more connected to the outdoors can help the body better differentiate day from night.
If you have decided to spend some time in the sun without sunscreen to promote vitamin D production, this would be the best time to do so.
Avoid the hours of most intense radiation
The intensity of radiation varies according to the time of day, season, location, altitude, cloud cover, and environment. For this reason, receiving soft morning light is not the same as being exposed to intense midday sun for a long time.
When radiation is high, the risk of sunburn and skin damage increases. UV radiation can damage DNA, accelerate photoaging, and increase the risk of skin cancer. To know when it is time to avoid sun exposure, check your weather app, which usually indicates the radiation level.
Protect your skin, especially when exposure is prolonged or intense
As we have seen, the use of sunscreen should be daily, but it is especially important when sun exposure will be prolonged, when the UV index is high, or when the skin is particularly sensitive. Reapply every 2 hours or when you have sweated. And not just sunscreen, but also lightweight clothing, a hat, sunglasses, shade, and common sense.
Sunscreens with mineral filters are an interesting option for those who prefer not to be exposed to the possible risks associated with the skin absorption of some chemical filters, as they act mainly on the surface of the skin and are also generally considered a more environmentally friendly alternative. In any case, no sunscreen should be understood as a license to be exposed without limits. Its function is not to allow us to abuse the sun, but to help us reduce the impact of UV radiation when exposure is inevitable or part of our daily life.
