Study looks at Vitamin D levels in Portuguese adolescents


A study by the Epidemiology Research Unit (EPIUnit) of the Instituto de Saúde Pública da Universidade do Porto (ISPUP) and the Faculdade de Medicina da Universidade do Porto (FMUP) analyzed the vitamin D levels of Portuguese adolescents. So far, two articles were published, whose results point to low levels of vitamin D in this population. Specfically, young people with higher levels of this micronutrient in the blood have lower cholesterol values. Further, increasing the intake of foods rich in vitamin D may be a good strategy to increase the levels of this vitamin.


A growing number of studies have suggested a link between lack of vitamin D and the development of cardiovascular diseases, osteoporosis, diabetes, cancer and various autoimmune diseases, which has sparked interest in the study of this vitamin.


"There are two main sources of vitamin D: the one that comes from exposure to sunlight and the dietary vitamin D”, explains Maria Cabral, the first author of the study. The inner production of this micronutrient is complex because it depends on factors such as age, skin pigmentation, exposure to the Sun, the time of year and latitude. Besides, in latitudes above 40ºN, the cutaneous synthesis of this vitamin may not be enough, especially during the winter period, when there is less sunlight. In this context, the contribution of foods rich in this micronutrient may be important to help maintain healthy vitamin D levels.


The study entitled Relationship between dietary vitamin D and serum 25-hydroxyvitamin D levels in Portuguese adolescents, published in the journal Public Health Nutrition, found a weak but positive relationship between vitamin D intake and serum vitamin D (obtained from the diet and cutaneous synthesis), indicating that the more one increases, the other increases as well. "Although the correlation is tenuous, this result shows that there is a relationship between what is ingested and vitamin D levels in the blood, supporting that increasing dietary sources of vitamin D may also be beneficial in raising vitamin D serum levels", says the researcher. Thus, increasing the intake of foods rich in vitamin D, such as fish, may help combat the low serum vitamin D levels of Portuguese adolescents.


Moreover, when vitamin D levels are found to be low, especially in the winter, "the intake of vitamin D through food may be an important way to increase overall levels of this micronutrient”, she says.


Highlighting the importance of the consumption of foods rich in this micronutrient is relevant, because the intake of foods rich in vitamin D, such as fish is low among teenagers.


In the article entitled Vitamin D levels and cardiometabolic risk factors in Portuguese adolescents, and published in the International Journal of Cardiology, the researchers concluded that young people who had more vitamin D in the organism had lower cholesterol levels. However, this same study did not allow to establish an association between low levels of vitamin D and metabolic syndrome - a set of clinical and metabolic factors that, together, confer an increased risk of developing cardiovascular disease, which may be explained by variation in the levels of vitamin D in this population.


"With these two studies, we create a picture of the state of vitamin D in Portuguese adolescents. In adolescence, vitamin D plays a central role in calcium metabolism and bone growth, functions that are essential for adolescents. This phase is also particularly important, because it is a sensitive period to begin a cardiovascular risk profile, whose manifestations are detected later in life", says Maria Cabral.


The investigations mentioned evaluated adolescents belonging to the EPITeen cohort, a longitudinal study that started in 2003 with the objective of understanding how the habits and behaviors acquired in adolescence are reflected in adult health. Adolescents were evaluated at the age of 13, in the public and private schools of the city of Porto, and vitamin D intake (obtained from diet) was analyzed through a food frequency questionnaire and serum vitamin D, quantifying levels of 25-hydroxyvitamin D in blood samples.


These articles are also authored by the researchers Joana Araújo, Carla Lopes, Henrique Barros, João Tiago Guimarães, Milton Severo, Sandra Martins and Elisabete Ramos.



Image: Pixabay/cattalin  



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