Prevalence of Vitamin-D deficiency and respiratory tract infections in adults: A cross-sectional study

To assess the prevalence of Vitamin-D deficiency and respiratory illnesses in Australian adults. In a cross-sectional sample of Australian adults, serum Vitamin-D levels and frequency of cold and flu symptoms were assessed. Those with sub-optimal Vitamin-D levels (<75nmol/L) were supplied with 4000-10,000IU Vitamin-D3 daily for 3-months. Data was analyzed with ANOVA and Pearson-correlation. A total of 199 adults aged 57±15 years participated in the study. A third (34%) had optimal Vitamin-D levels at baseline, 42% were insufficient (<75nmol/L), 19% deficient (<50nmol/L) and 5% severely-deficient (<25nmol/L). About half (56%) had regularly taken Vitamin-D supplements (1000-5000IU/day) prior to the study. The prevalence of respiratory illnesses was slightly higher (70%, mean=3-per-year) in the severely-deficient-group compared to other Vitamin-D-groups (50%, mean=2.5±2). Overall, the frequency of respiratory illnesses tended to be lower with higher Vitamin-D levels (group3: r=-0.285; p=0.009). A total of 66 participants (50%) with sub-optimal Vitamin-D levels (n=131) completed Vitamin-D3 supplementation. After 3-months, no participants were Vitamin-D deficient, only 15% remained insufficient, while 85% reached optimal Vitamin-D levels (mean 97±4nmol/L). Optimal Vitamin-D levels are correlated with the prevention of respiratory illnesses, and can be achieved with Vitamin-D supplementation within 3-months. A large proportion of Australians are Vitamin-D deficient/insufficient. Vitamin-D supplementation is key to alleviate Vitamin-D deficiency and support Vitamin-D’s role in the prevention of acute respiratory infections via the innate and adaptive immune system.