Good mood, memory, learning: exposing yourself to the sun for 15 minutes a day does wonders

Fascinating recent research reports that moderate exposure to ultraviolet rays stimulates the production of a neurotransmitter that promotes memory and learning and helps fight depression.

The sun’s ultraviolet rays are one of the best examples of a double-edged sword: on the one hand, exposure to the sun is essential for good health, because UV rays allow the production of vitamin D, a substance that plays very important roles in skeletal development, immune function and the prevention of certain cancers.

On the other hand, several studies have demonstrated beyond any doubt that excessive sun exposure is associated with an increased risk of developing skin cancers such as basal cell carcinoma, squamous cell carcinoma and melanoma. Melanomas are particularly dangerous since they can reach the bloodstream and spread in the form of metastases.

The sun must therefore be considered as an exceptional source of a substance essential to health (vitamin D), but which is so powerful that we must show extreme moderation towards it.

Depression, bipolar disorders: UV rays produce natural antidepressants

Another positive aspect of moderate sun exposure is its beneficial effect on mental health. For example, it has recently been shown that the production of melanin (the brown/black pigment responsible for tanning) in response to UV rays generates in parallel endorphins, endogenous opiates known to create a pleasant sensation and a feeling of well-being. .

Studies have also shown that sun exposure is often associated with a decrease in the severity of certain psychic problems, including bipolar disorders, possibly due to fluctuations in the levels of certain neurotransmitters such as serotonin.

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Conversely, we have known for a long time that a good number of people are particularly sensitive to the reduction in hours of sunshine that accompanies the winter season, developing what is called “winter depression”, characterized by a lack of energy and morale in the heels which can evolve, in more serious cases, into real depression. These symptoms can, however, in many cases be greatly reduced by exposure to bright artificial light (light therapy).

Memory, learning: neurons love the sun

A study recently published in the very prestigious journal Cell suggests that moderate exposure to the sun could also influence certain cognitive functions such as memory and learning. Scientists first observed that skin exposure to UV rays was associated with

a marked increase in blood levels of urocanic acid, a breakdown product of certain proteins present in the epidermis. What is even more interesting is that this urocanic acid generated by radiation crosses the blood-brain barrier and is taken up by the neurons where it is transformed into glutamate, a neurotransmitter which plays very important roles in particular at the level of the motor cortex and hippocampus (the seat of memory). In other words, urocanic acid could represent a kind of “messenger” making it possible to establish a link between exposure to the sun and brain functions.

And it seems that this is the case, because UV exposure greatly improves the ability of the animal models studied to solve certain problems, for example learning to maintain balance or even recognizing certain objects.

This improvement in cognitive abilities can be reproduced simply by injecting animals with urocanic acid, confirming that it is indeed the production of this molecule in response to UV rays and its subsequent transfer into neurons that play a role in the effects. neurobiologicals of the sun.

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No more than 5 to 15 min of exposure per day and avoid sunburn at all costs

These observations confirm that moderate exposure to the sun is beneficial to health, both physical and mental. And that’s easy in the summer: just five to fifteen minutes of occasional exposure of the hands, face and arms to the sun, two or three times a week in the summer, is more than enough.

The most important thing is to avoid sunburn at all costs: occasional and excessive exposure that burns the skin are the main risk factors for melanoma, especially when they occur at a young age and in people with fair complexions.

The vast majority of studies indicate that regular and moderate exposure to the sun does not represent an important risk factor for skin cancer, and could even in some cases reduce the incidence of certain cancers.


Fell GL et al. Skin-endorphin mediates addiction to UV light. Cell 2014; 157: 1527-34. Zhu H et al. Moderate UV exposure enhances learning and memory by promoting a novel glutamate biosynthetic pathway in the brain. Cell 2018; 173: 1716–1727.


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