Influence of ultraviolet radiation on the production of 25 hydroxyvitamin D in the elderly population in the city of São Paulo (23 o 34’S), Brazil

Abstract

The lack of vitamin D is a major changeable factor involved in the pathophysiology of osteoporosis. Since the major source for this hormone is its cutaneous synthesis via ultraviolet radiation (UVR), we studied the serum level of 25-hydroxyvitamin D (25OHD) in 250 free-living elderly people (79.1 years old) from a subtropical region according to the UVR incidence and its correlations with parathormone (PTH) and ionized calcium. UVR and 25OHD differed according to the season of the year (P<0.001), with greater radiation in the summer and less in the winter, whereas the 25OHD peak and nadir occurred in autumn and spring, respectively. The highest 25OHD mean was 67.2 nmol/l, and the lowest was 29.1 nmol/l corresponding, respectively, to the measure of the month subsequent to the one of most and least sunlight incidence. Clustered by season, the correlation between UVR and 25OHD for the following seasons was r=0.98 and between the PTH and 25OHD of corresponding seasons, r=-0.95. Vitamin D deficiency occurred in 15.4% of patients, insufficiency in 41.9% and secondary hyperparathyroidism in 55%. In conclusion, we found a seasonal variation in 25OHD levels that strongly correlated with the PTH levels when separated by the seasons of the year. The 25OHD levels correlated with the UVR of the previous quarter, requiring no less than 30 days for serum changes arising from exposure to or deprivation of UVR to be observed. The prevalence of vitamin D deficiency/insufficiency found was greater than expected, even when compared to countries exposed to less solar irradiation. Thus, measures to encourage greater sun exposure and food enrichment policies should also be considered.

Highly prevalence of vitamin D deficiency among Brazilian women of reproductive age

“…In Brazil, a study of 894 adults (mean age: 58.1 ± 12.0 years) in the State of Pernambuco found that the mean 25(OH) D concentration was 26.0 ± 10.3 ng/mL and that the prevalence of vitamin D deficiency was 28.5% (27). Another Brazilian study of elderly individuals (mean age: 79.1 years) in São Paulo during the winter found that the mean 25(OH)D concentration was 11.6 ng/mL (28). However, these discrepancies may be related to differences in the patients' mean age and the season of the analysis.…”

Genetic polymorphisms in vitamin D receptor, vitamin D-binding protein, Toll-like receptor 2, nitric oxide synthase 2, and interferon-γ genes and its association with susceptibility to tuberculosis

“…Research reported at that meeting showed that adults must maintain a much higher blood vitamin D level than children, i.e., approximately 75 nM/L. Low levels of circulating vitamin D were reported for an elderly Brazilian population, which has a deficiency (25 nM/L; 15.4%) or insufficiency (25-50 nM/L; 41.9%) of vitamin D (1). To date, there are no reports regarding the serum level of vitamin D in the Brazilian population comparing age, gender, sun exposure, food intake, and related disease.…”

Insuficiência e deficiência de vitamina D em pacientes portadores de doença renal crônica

“…However, such premise has been refuted by studies that prove the high frequency of vitamin D deficiency in the Brazilian population 13,[20][21][22] . A study that included 250 elderly people living in São Paulo demonstrated a high and unexpected prevalence of vitamin D deficiency (15.4%) and insufficiency (41.9%).…”

“…A study that included 250 elderly people living in São Paulo demonstrated a high and unexpected prevalence of vitamin D deficiency (15.4%) and insufficiency (41.9%). 21 Also in relation to Brazilian data, a study was performed with 16 healthy teenagers from the countryside of São Paulo and showed high prevalence (60%) of vitamin D insufficiency. 22 A study involving 603 normal volunteers, also from São Paulo, found mean value of 25(OH)D of 21.4 ng/mL, and 77.4% of the analyzed patients had vitamin D deficiency.…”