Contrary to popular belief, vitamin D synthesis quickly reaches its maximum. Explanations on this astonishing mechanism which reminds us that when it comes to sun, moderation remains the best ally of health.
What many don’t know about vitamin D… and that changes everything
The sun is often presented as the best natural source of vitamin D. Enough to encourage some to increase the hours spent on the terrace, at the beach or in the garden on sunny days. However, our body operates according to a very different logic.
The production of this essential vitamin does not increase indefinitely with time spent in the sun. She quickly reaches a ceiling.
In a recent video published on her Instagram account, dermatologist Dr Audrey Perret-Court, aka @Dermato_Drey, recalls that it is UVB rays which trigger the first step in the production of vitamin D. They transform a cholesterol derivative present in the skin into a precursor, which will then be converted by the liver and kidneys into active vitamin D.
But this mechanism has a natural limit:In 20 minutes of sun exposure on the face and forearms, in summer, when you have fair skin, you have enough peelings to make as many chips as possible that day.explains the dermatologist
A pictorial comparison which illustrates a simple principle: once the maximum quantity of precursor has been produced, the body cannot produce more during the same day.
Beyond 20 minutes, the benefits stop… but the risks continue
This is precisely where the paradox lies. Many people think that an hour or two in the sun will make more vitamin D. In reality, according to the specialist, the opposite can happen.
“If we stay any longer, we destroy the ingredient, so it’s counterproductive and we damage our skin because of UV damage, and therefore we will tan.”he specifies.
In other words, prolonged exposure does not produce more vitamin D. On the other hand, it further exposes the skin to the harmful effects of ultraviolet light.
The consequences are well known to dermatologists: sunburn, accelerated skin aging, appearance of pigment spots, but also increased risk of skin cancer.
Added to this is another lesser known phenomenon: when tanning, the skin produces more melanin. This pigmentation constitutes a natural mechanism of protection against UV rays, but it also reduces the skin’s ability to produce vitamin D during subsequent exposures.
A true paradoxical circle: the more the skin protects itself, the less easily it synthesizes this vitamin.
So why are so many people deficient in vitamin D?
This reality may seem contradictory. If twenty minutes is enough, why do deficiencies remain so common? The answer is multiple.
- First, this duration essentially concerns summer exposure, with fair skin, face and forearms uncovered, and sufficient sunlight. In autumn and especially in winter, in our latitudes, UVB is much less effective in triggering the synthesis of vitamin D;
- Diet also plays a role. Few foods naturally contain it in significant quantities, with the exception of fatty fish, egg yolks or certain enriched products;
- Finally, certain illnesses, age, certain treatments or even individual characteristics can reduce the body’s ability to produce or use this vitamin correctly.
This is why reasonable solar exposure is not always enough to cover everyone’s needs.
Finding the right balance, without putting your skin at risk
The message from dermatologists is ultimately quite simple: seek out the sun, yes, but with moderation. The objective is not to expose yourself for a long time, but enough to allow the body to start producing vitamin D, without crossing the threshold where the deleterious effects of UV rays take over.
If in doubt about a possible deficiency, it is best to speak with a healthcare professional. Depending on the situation, a suitable diet, blood test or supplementation may be offered, particularly for those most at risk.
Because if vitamin D is essential for the proper functioning of bones, muscles and the immune system, it is not worth sacrificing the health of your skin in an attempt to produce more of it. Summer reminds us of an essential lesson: when it comes to sun, it’s not the quantity that counts, but the right balance.