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

Abstract

Objectives

To assess the prevalence of Vitamin-D deficiency and respiratory illnesses in Australian adults.

Methods

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.

Results

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 (group 3: 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).

Conclusion

Optimal Vitamin-D levels are correlated with the prevention of respiratory illnesses, and can be achieved with Vitamin-D supplementation within 3-months.

Implications for public health

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.