The sun is good for your health, in fact, it is the main source of vitamin D, an essential vitamin for life. However, too much sun can damage your skin and increase the risk of cancer. We tell you what the perfect combination would be.
With the arrival of summer and good weather, many people sunbathe in order to get a good tan without thinking about the risks this can pose to their health. Different studies indicate that there is increasing awareness about the importance of using an adequate protection factor and sunbathing during the less “intense” hours of the day, that is, before 12 and after 4 p.m., but it is also true that we continue to see people, especially young people, who do not do it safely.
It can go both ways
Sunbathing causes harm, but not doing it does too. Every year, studies on the benefits of sunbathing in moderate doses are interspersed with those that confirm the risks of doing so excessively. Thus, “although ultraviolet (UV) solar radiation is involved in the development of sunburn, cancer and skin ageing, it also reduces blood pressure, synthesises vitamin D and improves the treatment of various pathologies”, explain experts from the Solar Radiation Research Group at the Polytechnic University of Valencia (UPV). This group analysed the time required for exposure to obtain the recommended doses of vitamin D without harming our health.
Recommended doses
Based on this premise, the expert and her colleagues estimated the time required to obtain the recommended doses – which is equivalent to a daily intake of 1000 IU (international units) of vitamin D – in an area such as the city of Valencia, which receives a large dose of UV radiation throughout the year.
When sunburn occurs
The work analysed ultraviolet solar irradiance (UVER) around midday (between 12:30 and 13:30) for four months of the year (one in each season). These figures were used to calculate the time it takes to produce erythema – reddening of the skin caused by burns.
The data showed that, in July, an individual with skin type III should not be in the sun for more than 29 minutes if they want to avoid sunburn. However, in January, the same individual can remain in the sun for 150 minutes.
They also analysed the minimum exposure time to obtain the recommended daily dose of vitamin D. And, as the author points out, “the problem of vitamin D synthesis appears especially in winter due to the low levels of UV radiation and the fact that people cover most of their body because of the cold.”
In this sense, it was found that, around midday in January, with 10% body exposure, “around 130 minutes are needed to obtain the recommended daily dose of vitamin D.”As this time is less than that which would produce erythema, there would be no risk of sunburn.
Sunbathing
The authors also concluded that in April and July, “with 25% of body exposure, about 10 minutes would be enough to acquire vitamin D, and in October, for example, about 30 minutes would be needed.”
“These calculations were made for skin type III, but if it were lighter or darker, the figures would change,” says Serrano. “It should also be taken into account that a percentage of the body exposed to the sun is considered, which is normal for the season. If this were higher, then the exposure time would be reduced.”
Likewise, the time obtained to produce erythema has been calculated for average days.However, experts point out that sun exposure “should always be taken with caution and that on extreme days, the permissible exposure times would be much shorter,” he stresses.
Vitamin D in winter
This study has also shown that although there is sufficient radiation in countries, it is difficult to reach the recommended doses of vitamin D in winter, that is, in the months from November to February, in a mid-northern latitude, since the necessary exposure time is excessive (130 minutes).
During these months, “with 10% body exposure, during midday sunlight, 2 hours of exposure to the sun would be needed to obtain an optimal dose of vitamin D.” However, during hours of maximum light and sun, because “at 10:00 a.m. approximately 9.7 hours would be required and at 4:00 p.m. approximately 5.7 hours.”
On the contrary, “in the central hours of spring and summer days, with 25% of body exposure, about 10 minutes of sun exposure around 1 pm and about 20 minutes from 3 pm to 5 pm would be enough to meet the daily vitamin D needs,” says the author.
Other things to keep in mind
In addition to the time of year, there are other factors that influence the synthesis of vitamin D. The radiation received also depends on posture, body shape and clothing. Likewise, “it must also be taken into account that all areas of the skin on the body do not synthesize vitamin D with the same efficiency,” reveals Serrano.
The age of individuals also plays an important role in the synthesis of vitamin D from UV radiation, since with age there is a decrease in the capacity to produce vitamin D, with middle-aged adults having 66% of the potential compared to children.
“These results can help in the adoption of appropriate measures to compensate for the possible deficiency, such as informing the medical community about the convenience of increasing vitamin D intake through diet or supplements,” concludes the researcher.
