Very sunny, little vitamin D: The paradox of the Portuguese explained

“ Na country where the sun is part of our identity and our daily lives, it would be expected that vitamin insufficiency D was an exception. The reality, however, is quite different. A representative study of the Portuguese population showed that about two out of three adults have serum vitamin levels. D less than 20 ng/mL, despite the many sunny hours that characterize our country. At first glance, it seems a paradox. After all, if the sun is the main source of this vitamin, why do so many Portuguese still have insufficient levels of vitamin D?

The explanation obliges us to look beyond the number of sunny hours. For a long time we have associated this problem only with winter. The days are shorter, we spend less time outdoors and it is natural to think that vitamin levels D decrease then. What many people do not know is that vitamin insufficiency D may persist throughout the year, even in a country such as Portugal.

Vitamin D is produced mainly by exposure of the skin to ultraviolet B (UVB) radiation. However, this production depends on multiple factors, such as age, skin pigmentation, exposed body area, solar radiation intensity and exposure time. Feeding and, when indicated, supplementation also contributes to maintaining adequate levels.

  Bruno Moreno is a family doctor at the Coimbra Sul Family Health Unit © Family Health Unit Coimbra Sul  

But there is another factor that helps explain this paradox: the way we live. Today we spend much of the day in closed environments. We work in offices, we study in classrooms, we travel by car and we occupy more and more free time in indoor spaces. Even during the summer, many people end up having an effective sun exposure much lower than they imagine.

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At the same time, there is now a greater awareness of the importance of sun protection. The use of sunscreen and other photoprotection measures are essential to reduce the risk of skin cancer and should not be devalued. The message is not to expose ourselves to the sun without protection, but to understand that the simple existence of many hours of sun does not in itself guarantee adequate levels of vitamin D.

Another important aspect is that vitamin insufficiency D can remain silent for a long time. In most situations it does not cause specific symptoms, especially when it is mild or moderate. When the deficiency is more marked and prolonged, it can be associated with muscle weakness, bone pain and a higher risk of falls and fractures, especially in older people. The role of vitamin D in bone and muscle health is well established, being essential for calcium absorption and maintenance of skeleton resistance.

Although anyone may have low vitamin D levels, some groups deserve special attention. This is the case of the elderly, the institutionalized or people with reduced mobility, the people with obesity, those with diseases that condition intestinal absorption or those who take medicines that interfere with the metabolism of this vitamin.

It is also important to undo another very common idea: to talk about vitamin deficiency or deficit D does not mean defending analyses for the entire population. Current scientific evidence does not recommend systematic screening of healthy adults. The decision to dose vitamin D should result from clinical evaluation and risk factors, allowing an individualized approach and avoiding unnecessary tests or treatments.

The main message is simple: vitamin D is not an exclusive concern of the winter months. It is a theme that should be part of our health literacy throughout the year. More than counting sunny hours, it is important to understand who has higher risk of presenting insufficient levels, promoting healthy lifestyles and, when necessary, evaluating each situation individually.

Because the true Portuguese paradox is not lack of sunshine. Is to keep finding insufficient vitamin levels D in one of the most sunny countries in Europe."