Confinement and vitamin D: what happens if the sun doesn't give us?

By Marta Beltrá García-Calvo, Miguel Hernández University and Ana Belén Ropero Lara, Miguel Hernández University

The Spanish proverb says it: "Water and sun, snail time". As for this animal, sun rays are also important to us: we need them to make vitamin D.

It is curious that, despite the fact that many hours of sunshine are enjoyed in Spain, a third of the population could be deficient in vitamin D. In addition, more than 90% of Spaniards take less vitamin D than is recommended.

Due to the confinement situation, some people may hardly receive sunlight. This could have consequences for your health, although predicting these effects is as difficult as predicting the duration of the current alarm state.

Sources of vitamin D

The skin produces this micronutrient thanks to the UVB rays of the sun, but we can also obtain it through food. In both cases, in order to function properly in the body, it must first undergo a few touches on the liver and kidney.

Among the few foods that contain vitamin D we find liver, eggs or blue fish. However, the Spanish Agency for Food Safety and Nutrition recommends avoiding or limiting the consumption of large fish with high mercury content, including swordfish, bluefin tuna, shark and pike.

Vitamin D functions

The role of vitamin D in bone health has been known for years. It favors the absorption of calcium in the intestine and is used for many biological processes.

Furthermore, this micronutrient is necessary for the growth and development of bones in children. It also helps, along with calcium, to reduce the loss of bone mineralization in postmenopausal women.

Vitamin D is also involved in other biological functions. Muscles, the immune system, phosphorus metabolism and teeth are some of its targets.

Consequences of vitamin D deficiency

Bones are the main affected when there is vitamin D deficiency. In children it manifests as rickets, which can cause bone fractures and poor tooth development. In adults it causes osteomalacia (weak bones, bone pain and muscle weakness) and osteoporosis in older people.

Studies show that vitamin D deficiencies are associated with an increased risk of various diseases: upper respiratory tract infections, autoimmune diseases or allergies, cardiovascular problems, and even higher mortality. Lower levels of vitamin D have also been linked to obesity, type 2 diabetes, and metabolic syndrome.

The World Cancer Research Foundation is the international benchmark institution for cancer. In its 2018 report it indicates that an adequate intake of vitamin D could be related to a lower incidence of colorectal cancer.

Despite all the information we know, there is great controversy regarding the optimal doses to achieve clear benefits of vitamin D. Furthermore, the clinical efficacy of the supplements does not meet expectations. Even worse: it is difficult to find an appropriate method to detect vitamin D deficiencies.

How much sun do we need?

The ideal is to do outdoor activities in winter and autumn, since the intensity of solar radiation is low and we are more covered. During that time, it takes several hours to obtain the daily dose of vitamin D, so it is necessary to supplement with food.

In summer and spring it is enough to sunbathe on your legs, arms and face for 15 minutes, at least 3 times a week.

Despite the benefits of the sun in the synthesis of vitamin D, UVB rays can cause skin cancer. For this reason, we must take many precautions. In summer, even on cloudy days, you should not be exposed to the sun between 12 and 17 hours. You must use a sun protection factor, minimum of 30, every 2-3 hours and apply it 30 minutes before leaving home.

And during confinement?

One of the effects of confinement is a drastic decrease in outdoor time and less exposure to the sun (the window glass blocks UVB radiation). This is linked to vitamin D deficiency in a good part of the Spanish population. Therefore, it is important to take advantage of the sun on patios and balconies every day, even if it is cloudy. This is especially important for older people and children.

Increasing the consumption of blue fish (avoid those that accumulate mercury) and eggs to the detriment of meat are additional recommendations. If there are usually three servings per week for each of these food groups, increasing the fish and egg to four and lowering the meat can be helpful.

Marta Beltrá García-Calvo, Professor of Nutrition and Food Science., Miguel Hernández University and Ana Belén Ropero Lara, Professor of Nutrition and Food Science – Director of the BADALI project, Nutrition website, University Miguel Hernández

This article was originally published in The Conversation. Read the original.