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From Vitamin D to Skin Cancer How much sun is good for health?

From Vitamin D to Skin Cancer How much sun is good for health?

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 intervenes in the development of solar erythema, cancer and aging of the skin, it also reduces blood pressure, synthesizes vitamin D and improves the treatment of various pathologies.

Now, the Solar Radiation Research Group of the Polytechnic University of Valencia (UPV) has analyzed the necessary exposure time to obtain the recommended doses of vitamin D without damaging our health. The results have been published in the journalScience of the Total Environment.

"In Spain, despite being a country with many hours of sunshine, different articles have reported a high percentage of vitamin D deficiency among various strata of the Spanish population", explains María Antonia Serrano, UPV scientist and author to Sinc main job.

Insufficient vitamin D is associated with an increased risk of various diseases in adulthood. Since very few foods contain this vitamin, its synthesis in the skin from sun exposure is the main natural source that exists.

Serrano and his colleagues estimated the time necessary 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 during all year.

How much sun is good for health?

Spanish researchers have estimated the necessary time of exposure to solar radiation to obtain the recommended doses of vitamin D. While in spring and summer 10 to 20 minutes in the sun are sufficient, in the winter months it would take almost two hours, so that it is difficult to achieve optimal values ​​for the vast majority of the population.

Ultraviolet solar radiation reduces blood pressure, synthesizes vitamin D and improves the treatment of various pathologies.

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 intervenes in the development of solar erythema, cancer and aging of the skin, it also reduces blood pressure, synthesizes vitamin D and improves the treatment of various pathologies.

Now, the Solar Radiation Research Group of the Polytechnic University of Valencia (UPV) has analyzed the necessary exposure time to obtain the recommended doses of vitamin D without damaging our health. The results have been published in the journalScience of the Total Environment.

In July, an individual should not spend more than 29 minutes in the sun if he wants to avoid burns

"In Spain, despite being a country with many hours of sunshine, different articles have reported a high percentage of vitamin D deficiency among various strata of the Spanish population", explains María Antonia Serrano, UPV scientist and author to Sinc main job.

Insufficient vitamin D is associated with an increased risk of various diseases in adulthood. Since very few foods contain this vitamin, its synthesis in the skin from sun exposure is the main natural source that exists.

Serrano and his colleagues estimated the time necessary 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 during all year.

Burns in 30 minutes

The work analyzed the ultraviolet solar irradiance (UVER) around noon (between 12:30 pm and 1:30 pm) during four months of the year (one of each season) from 2003 to 2010. With these figures, the time to produce erythema - redness of the skin caused by burns.

Thus, the data underline that, in July, an individual with skin type III (the usual in the Spanish population) should not spend more than 29 minutes in the sun if he wants to avoid it. However, in January, the same individual can stay in the sun for 150 minutes.

In the same way, the minimum exposure time was obtained to obtain the recommended daily dose of vitamin D. "The problem can appear in winter due to low levels of UV radiation and the fact that people cover most of the body" adds the expert.

Mª Antonia Serrano, on the campus of the Polytechnic University of Valencia. / Luis Zurano (UPV)

In this sense, it was found that, around noon in January, with 10% body exposure, it takes around 130 minutes to obtain the recommended daily dose of vitamin D.

As this time is less than the time that would produce erythema, there is no risk of sunburn.

On the other hand, in April and July, with 25% body exposure, about 10 minutes would be enough to acquire the vitamin. And in October, for example, it would take about 30 minutes.

"These calculations were made for skin type III, but if it were lighter or darker the figures would change," says Serrano.

“You also have to take into account that we have considered a normal body percentage for the season. If this were longer, then the exposure time would be reduced ”.

Likewise, the time obtained to produce erythema has been calculated for average days. “It should be taken with caution. For extreme days, the permissible exposure times would be much shorter ”, he emphasizes.

Keeping vitamin D in winter

The results show that, although there is enough radiation in countries like Spain, it is difficult to reach the recommended doses of vitamin D in winter (from November to February) at a mid-north latitude, since the necessary exposure time is excessive (130 minutes) .

In these months, with 10% body exposure, during solar noon, two hours of sun exposure would be needed to obtain an optimal dose of vitamin D - but at 10:00 it would take approximately 9.7 hours and at 16 : 00 about 5.7 hours.

Around noon in January, it takes about 130 minutes to get the RDA of vitamin D

On the contrary, in the central hours of spring and summer days, with 25% body exposure, about 10 minutes of sun exposure around 1:00 p.m. and about 20 minutes from 3:00 p.m. to 5:00 p.m. 00 hours would be enough to meet the daily needs of vitamin D.

“Furthermore, the radiation received depends on posture, body shape and clothing. It should also be taken into account that all areas of the skin of the body do not synthesize vitamin D with the same efficiency ”, reveals Serrano.

The age of the individuals also plays an important role in the synthesis of vitamin D from UV radiation, since over the years 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 the adoption of appropriate measures to compensate for the possible deficiency, such as informing the medical community about the advisability of increasing the intake of vitamin D through diet or supplements", concludes the researcher from the Universitat Politècnica de València .

Bibliographic reference:

María-Antonia Serrano, Javier Cañada, Juan Carlos Moreno, Gonzalo Gurrea. ‘Solar ultraviolet doses and vitamin D in a northern mid-latitude’.Science of the Total Environment574 (2017) 744–750.

SINC


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