Introduction
Sun exposure as a therapeutic approach to treat tuberculosis (TB) was used more than 100 y ago, before the identification of Mycobacterium tuberculosis as the causative agent for TB [1]. Exposure of children suffering from rickets and TB to artificial ultraviolet (UV) light resulted in a positive effect on both diseases. The use of sanatoria was also based on the belief that fresh air and sun exposure led to a positive outcome in the treatment of TB [2]. Vitamin D is a known immune modulator [3] that can improve cell-mediated immunity [4] and the phagocytic capacity of macrophages [5]. It also increases the production of antimicrobial peptides such as cathelicidin [5], which is part of the innate immune system that plays a critical role in the fight against TB. Recent research highlighted the production of cathelicidin through toll-like receptor pathway [6].
* Corresponding author Tel.: þ49 152 1132 3555; fax: þ49 711 4592 3822.
E-mail address: tibebe.fscuhoh@gmail.com (T. S. Keflie).
Vitamin D is unique among hormones as it can be made in the skin from sun exposure [7]. Most (90%) vitamin D is synthesized in the skin under the influence of UV sunlight, and only 10% is obtained from food, mainly salmon and cod fish, and dairy products [8]. Although sunshine is abundant, TB is one of the most pernicious infectious diseases in Africa. Sub-Saharan Africa carries the greatest proportion of new cases per population, with