How to obtain the vitamin from the sun from home during confinement?

Vitamin D is necessary to absorb calcium and phosphorus, essential for healthy bones, and the best source to obtain it is exposure to the sun.

Vitamin D, known as the sunshine vitamin, can be considered a true hormone that the body is able to synthesize on its own when sunbathing. Under normal circumstances, sunlight, not so much food, is where the greatest amount of vitamin D comes from. Part of this vitamin is synthesized by the body, at the level of the skin, under the action of ultraviolet light from radiation solar, which converts a substance derived from cholesterol into cholecalciferol (vitamin D3).

It is then stored in the liver and kidney and converted to its active form calcitriol. This is precisely what makes this vitamin special: When the body gets vitamin D, it converts it to a hormone, calcitriol. Our body creates vitamin D from direct sunlight on our skin when we are outdoors (it is estimated that between 80-90% comes from sunlight).

Specifically, we need the action of type B ultraviolet rays because they are the ones that catalyze the production of vitamin D (they are also those that are most associated with greater carcinogenic factors in the skin, hence experts advise using sunscreen). The minimum recommended amount of vitamin D should be, according to the Spanish Academy of Dermatology and Venerology (AEDV):

• From the first year of life and up to age 70: a daily amount of 600 international units (IU) is recommended each day.

• People older than 70 years: 800 IU per day.

• Babies: 400 IU daily.

With these amounts, experts admit that people should reach the optimal blood level of vitamin D above 20 nanograms per milliliter (ng/ml), which are what guarantee good bone health. It is easy to meet these parameters under normal conditions and especially between the months of May to September. A deficiency of this nutrient can compromise people's immune responses and, in the worst cases, can lead to a depressive disorder (serotonin is the brain's neurotransmitter associated with mood and increases with sun exposure).

With the quarantine to which we are obliged to remain until further orders, we have greatly restricted our going out from home and staying outside, and therefore we have greatly reduced our exposure to the sun. How can we get the amount of vitamin D the body needs without leaving home? Can we sunbathe behind the window?

Leaning out on the terrace, balcony or going out to the garden

As we have seen, the skin produces vitamin D with the help of UVB rays. During these days it is advisable to look out the window every day, or if we are lucky and have a terrace, balcony or garden, we must:

• Go out for the sun, at least for 15 minutes about three times a week, without sunscreen. It is also useful to do it on cloudy days since solar radiation can reach the ground (after the recommended time it is necessary to do it with sunscreen).

• If possible, sunbathe not only on the face but on other parts of the body such as hands, arms, and legs. It is not necessary to do it every day, two or three times at noon would be enough.

The radiation that is most effective in achieving optimal vitamin levels occurs in the middle of the day. The best time to do it, therefore, is at noon, when the sun is highest, although doing it at another time of day for a little longer would also produce the necessary amount.

It should also be taken into account that the values depend not only on the time of day or the season of the year but also on the type of skin of each person (the darker, the more amount of solar dose is needed). But the good news is that vitamin D is stored in the body, so good exposure will keep us safe for days.

Another way to make up for the lack of sun during these days without the body suffering in vitamin D levels is to do physical exercise on a regular basis because, by activating ourselves, the blood is mobilized and a greater amount of vitamin D reaches the bone. It is enough to walk around the house a little and take small tours.

What if I sunbathe through the window?

As we have seen, the radiation that helps the body synthesize the vitamin D we need to absorb the calcium that protects our bones is type B ultraviolet (UVB). And this precisely stays outside the crystals because they act as a filter that bounces a significant proportion of the UV rays that pass through them. As the American Cancer Society recalls, typical window panes in cars, homes, and offices block the most UVB rays.

Radiation depends on the intensity and length of its waves. UVA rays, for example, are considered longwave, while UVB rays are a short wave. The only thing we receive behind glass is UVA ultraviolet light, which is longer than UVB and penetrates deeper into the lower layers of the skin, where they produce a tan, but also damages the tissue under the epidermis. , which causes the skin to lose tone (wrinkles and aging).

However, window panes prevent shorter rays from reaching, and only 63% of UVA rays get through. Therefore, it is useless to stand behind the window, because UVB radiation does not penetrate the glass, and therefore exposure to sunlight indoors through a window does not produce vitamin D.

Can diet provide enough vitamin D?

About 20% of the vitamin D the body gets is provided by food, especially animal and fatty products:

• cod liver

• chicken liver

• beef liver

• canned sardines

• cooked salmon

• fresh herring

• raw oysters

• milk

• the cheese

• the butter and

• the eggs

During these days, therefore, we must pay attention to what we eat to achieve the vitamin intake that compensates for the lack of hours of sun.

Does vitamin D protect against coronavirus?

One idea that is circulating these days says that vitamin D could help fight the virus in COVID-19 patients. However, it seems one of the myths regarding the coronavirus, since it is "unlikely that it is an option to enhance the consumption of this nutrient for this purpose", explains the Spanish Academy of Nutrition and Dietetics of the General Council of Official Associations of Dietitians-Nutritionists in the document Food and nutrition recommendations for the Spanish population in the face of the health crisis of COVID-19.