**4. Deficiency of vitamin A and strategies of fortification**

 Some physiological implications about the intake of high doses of vitamin A have been reported; however, it is their deficiency that causes catastrophic damage. Depletion of this nutrient has become a global problem affecting millions of people worldwide, especially those in developing countries [37]. It harms the health of approximately 190 million children and 19 million pregnant women worldwide [37].

In developing countries, it is the leading cause of childhood blindness and further contributes significantly to the morbidity and mortality of common childhood infections such as continuous malnutrition [38]. Additionally, it causes potential changes in the epithelial barrier of vital organs and tissues [39]. It further reduces the synthesis of specific glycoproteins in the intestinal mucosa and liver, as well as the gene expression of glycosyltransferases, fibronectin, and transglutaminases, disrupting macrophage function, blood clotting, and adhesion. Also, it disrupts normal bone growth as it is essential for the activity of cells in the epiphyseal cartilage [29]. Studies with animals also indicate that in the deficiency of this nutrient, the spermatogenesis is blocked causing infertility [29]. Problems in the regulation of vitamin D receptors may also be affected by the lack of vitamin A [40].

Because of all these controversial effects, highlighting the high morbidity and mortality, government agencies have recognized the problem as a public calamity situation and since then have been developing and supporting strategies to combat vitamin A deficiency [41].

Typically, these approaches are based on the fortification of basic foods, food ready for use, condiments, and mostly milk [42]. Among them are microencapsulation techniques and genetic crosses (biofortification) [18, 43, 44].

Microencapsulation has emerged as an alternative to increasing the stability and bioavailability of labile compounds such as vitamin A, and for this reason, it is believed that this process may be a strategy in food fortification to treat vitamin A deficiency [16, 45]. It is based in the encapsulation of the nutrient into microparticles of polymeric material with the variable diameter [46].

 In contrast, the biofortification is an integrated approach of agriculture and nutrition, which uses traditional breeding or genetic engineering techniques [47]. In this case, species of foods containing high β-carotene content are used to obtain hybrid species adapted to places where vitamin deficiency remains a severe problem [48]. For example, genetic crosses made from yellow maize rich in β-carotene gave rise to other tropically adapted maize species [43, 44]. Besides, hybridization of sweet potatoes has also been extensively explored, especially in sub-Saharan Africa [44]. "Golden rice" is another successful example in several vitamin A-deficient countries [49]. According to Tanumihardjo [50], cassava is also included in the basic crops targeted for biofortification.

The chapters presented in this book are intended to help provide a deeper understanding and insight processes of perception and challenges for vitamin A, contributing substantially to the role of future vitamin A effects on human health. *Introductory Chapter: A Global Perspective on Vitamin A DOI: http://dx.doi.org/10.5772/intechopen.84615* 
