Epidemiology of Vitamin D (EpiVida)—A Study of Vitamin D Status Among Healthy Adults in Brazil

Victoria Zeghbi Cochenski Borba; Marise Lazaretti-Castro; Sandra da Silva Moreira; Maria Conceição Chagas de Almeida; Edson Duarte MoreiraJr


J Endo Soc. 2023;7(1) 

In This Article

Abstract and Introduction


Context: There are few studies of 25-hydroxyvitamin D (25(OH)D) concentrations in healthy adults in Brazil.

Objective: This work aimed to estimate the prevalence of vitamin D status and its association with lifestyle, sociodemographic, and anthropometric data in 3 regions of Brazil.

Methods: A cross-sectional study was conducted among blood donors of both sexes, living in the cities of Salvador, São Paulo, and Curitiba during summer. Blood samples were collected during the procedure. Serum 25(OH)D and parathyroid hormone (PTH) were measured in the same laboratory using chemiluminescence immunoassays. Lifestyle, sociodemographic, and anthropometric data were gathered by an interview with a standardized questionnaire. Vitamin D deficiency and insufficiency was defined as 25(OH)D levels below 20 ng/mL and below 30 ng/mL, respectively.

Results: A total of 1004 healthy adults were evaluated with mean levels of 25(OH)D (28.7 ± 9.27 ng/mL) and PTH (34.4 ± 15.1 pg/mL). The standardized prevalence of vitamin D deficiency and insufficiency was in the study population 15.3% and 50.9%: in Salvador 12.1% and 47.6%, in São Paulo 20.5%, and 52.4% and in Curitiba 12.7% and 52.1%, (P = .0004). PTH levels were negatively correlated with 25(OH)D levels. Greater body mass index (BMI) and higher latitude were significant predictors of vitamin D deficiency, whereas skin color (White), longer duration of sun exposure, and current use of dietary supplement were protective.

Conclusion: This study confirmed the high prevalence of vitamin D deficiency and insufficiency even in the midsummer in a healthy population of Brazil. Vitamin D levels are associated with sun exposure, latitude, BMI, skin color, and use of supplements.


Vitamin D is in fact a "prohormone" given it can be synthesized in the skin from ultraviolet B light on cutaneous sun exposure, and then converted to its active metabolite 1,25-dyhydroxyvitamin D (calcitriol) in the kidney stimulated by parathyroid hormone (PTH). Diet provides low quantities of this "vitamin," and sunlight exposure is its main source. The most abundant circulant form is 25-hydroxyvitamin D (25(OH)D), which is considered the biomarker to evaluate vitamin D status and is classically related to mineral homeostasis and PTH secretion. Low level of 25(OH)D is the most common etiology of secondary hyperparathyroidism.[1]

Vitamin D status depends on the population studied, health status, skin color, age, genetic background, geographic characteristics, among other factors, which makes it a considerable challenge to establish their normal levels. Low concentrations of 25(OH)D have been associated with many detrimental health conditions, both skeletal and extraskeletal. Different end points were used to stablish the 25(OH)D ideal levels, including secondary hyperparathyroidism, osteomalacia or osteoporosis, muscle weakness, increased risk of falls or fractures among others, with no definitive consensus so far.[2]

The Institute of Medicine defines vitamin D deficiency as 25(OH)D levels lower than 20 ng/mL (< 50 nmol/L) regardless of the population studied.[3] Other institutions take into account age, risk factors for vitamin D deficiency, and health status, such as presence of metabolic bone diseases and other chronic diseases to define 30 ng/mL as the preferred level.[2,4,5]

Vitamin D deficiency is highly prevalent worldwide, with levels below 30 ng/mL (75 nmol/L) being described globally. The lowest levels (< 10 ng/mL or 25 nmol/L) are associated with rickets and osteomalacia and, although more frequent in Asia and the Middle East, can be present all over the world.[6] In Brazil, inadequate vitamin D status has been described in all regions. A metanalysis of 72 studies developed throughout the country found an average of 28.16% deficiency (25(OH)D < 20 ng/mL) and 45.26% insufficiency (< 30 ng/mL). The southern and southeastern regions had the highest concentration of vitamin D deficiency, while the insufficiency was concentrated in the southeastern and northeastern regions. This metanalysis included studies that used different vitamin D assays, and the majority of the sample size was from the southernmost regions of the country.[7] Other studies of the Brazilian population also showed a high frequency of vitamin D deficiency and insufficiency in patients with chronic diseases such as osteoporosis, systemic lupus erythematosus, chronic obstructive pulmonary disease, and others.[8–10] Nevertheless, data regarding vitamin D status in a health population of both sexes, with different ages, samples collected at the same time range, measured with the same method, and with sociodemographic information, are lacking for the Brazilian population.

The aim of this study was to evaluate 25(OH)D and parathyroid hormone (PTH) levels in healthy adults from urban areas of Brazil, according to age group, sex, and latitude of residence.