COVID-19 Pandemic and Vitamin D Levels in Children

A research team led by Dr. A. Rustecka from the Military Institute of Medicine in Warsaw conducted a comprehensive statistical analysis to evaluate differences in serum 25-hydroxyvitamin D [25(OH)D] concentrations among children residing in Warsaw. The study encompassed a total of 1,472 participants ranging in age from one month to 18 years. Blood samples were systematically collected over a 25-month period—from January 2019 through the end of February 2021. The methodology involved dividing the sample into two distinct temporal cohorts: the **pre-pandemic cohort** (measurements taken between January 2019 and February 2020) and the **pandemic cohort** (measurements conducted from March 2020 to February 2021). Clinical reference standards for vitamin D were applied, with an optimal range defined as 30–50 ng/ml, suboptimal levels categorized as 20–30 ng/ml, and concentrations below 20 ng/ml identified as frank deficiency.

L. Yu et al. conducted an investigation in China among pediatric cohorts aged 3–6 years, comparing serum 25(OH)D measurements from 2017–2019 with data gathered during the COVID-19 confinement period. In 2020, the proportion of young children presenting with clinically significant vitamin D deficiency was markedly higher than in preceding baseline years, demonstrating the detrimental metabolic consequences of indoor confinement and curtailed cutaneous solar synthesis. During periods of favorable sunshine, safe outdoor activity should be prioritized; whenever outdoor access is restricted, systematic vitamin D supplementation is indispensable. A poignant clinical manifestation of unaddressed deficiency is illustrated by the published case of an 18-month-old infant in Sri Lanka diagnosed with advanced nutritional rickets secondary to profound hypovitaminosis D, displaying a serum 25(OH)D concentration of merely 8 ng/mL. The child was exclusively breastfed for the first six months, yet neither the infant nor the mother received postnatal vitamin D supplementation, and the maternal diet completely lacked fatty fish or fortified staples. Extended pandemic-related indoor confinement from March through late 2020 precipitated full-blown symptomatic rickets (Liyanage & de Silva, 2021). Conversely, Swiss research by M. Meoli et al. evaluating late adolescents aged 18–19 years (conscripts evaluated for compulsory military service) detected no statistically significant escalation of vitamin D deficiency during the pandemic relative to pre-pandemic cohorts. This indicates that older demographics with established nutritional patterns and larger endogenous reserves exhibit greater physiological resilience during temporary lockdown measures.

Emerging evidence suggests that reduced serum concentrations of 25-hydroxyvitamin D may serve as a predisposing factor for both heightened susceptibility to SARS-CoV-2 infection and the development of more severe COVID-19 manifestations in pediatric patients. Researchers K. Yimlaz and V. Sen conducted a comparative assessment of vitamin D levels in the blood serum of children and adolescents aged between one and eighteen years who required hospitalization due to confirmed COVID-19 infection, alongside a reference cohort of uninfected children. The findings revealed significantly lower mean vitamin D concentrations in the infected group (13.14 ng/ml) relative to the control group (34.81 ng/ml), thereby underscoring the potential critical role of this micronutrient in supporting the body’s immunological defense mechanisms.

Emerging scientific evidence suggests that maintaining adequate vitamin D levels may offer potential benefits, including a supportive role in immune defense against viral infections such as COVID-19. However, the current body of clinical research remains **insufficient to establish definitive, universally applicable guidelines** for routine vitamin D supplementation in pediatric populations. According to the expert consensus statement on vitamin D supplementation in Polish children and adolescents (led by Prof. Anna Rusińska, 2018), **healthy children aged 1–18 years do not require systematic vitamin D supplementation**—**provided that**, during the summer months (May to September), they receive **regular sun exposure** of at least **10 minutes per day** (between 10:00 AM and 3:00 PM) on **uncovered forearms and legs, without sunscreen application**. Any decision regarding potential supplementation should be **made on an individual basis in consultation with a pediatrician**, particularly if a child’s outdoor activity is restricted (e.g., due to chronic illness, sun allergies, or public health measures). Should supplementation be deemed necessary, **recommended dosages vary**, with **higher amounts prescribed for children with overweight or obesity**, as adipose tissue can impair vitamin D metabolism. It is also important to note that periods of social confinement (e.g., lockdowns) may contribute to **uncontrolled weight gain**, further emphasizing the need for monitoring vitamin D status in at-risk pediatric groups.

The term "covibesity" – coined by researchers M. A. B. Khan and J. E. Moverley Smith – refers to the alarming rise in obesity rates among children and adolescents directly attributable to COVID-19 lockdown measures. The shift to remote education has substantially diminished physical activity levels in this demographic, as evidenced by multiple international studies. For instance, research involving 41 Italian children with obesity revealed a troubling surge in consumption of ultra-processed foods—including salty snacks, fatty meats, and sugar-sweetened beverages—during lockdown periods. Concurrently, average daily screen time increased by nearly five hours, while weekly physical activity decreased by over two hours. Similar patterns emerged in a study by H. Al Hourani, B. Alkhatib, and M. Abdullah among Jordanian pediatric populations, where researchers documented both reduced physical activity and weight gain during pandemic restrictions.