**Maiken Lindblad, Pernille Tveden-Nyborg and Jens Lykkesfeldt \***

Section of Experimental Animal Models, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Ridebanevej 9, Frederiksberg C 1870, Denmark; E-Mails: mali@sund.ku.dk (M.L.); ptn@sund.ku.dk (P.T.-N.)

**\*** Author to whom correspondence should be addressed; E-Mail: jopl@sund.ku.dk; Tel.: +45-353-33163; Fax: +45-353-53514.

*Received: 3 June 2013; in revised form: 15 July 2013 / Accepted: 18 July 2013 / Published: 25 July 2013* 

**Abstract:** Large cross-sectional population studies confirm that vitamin C deficiency is common in humans, affecting 5%–10% of adults in the industrialized world. Moreover, significant associations between poor vitamin C status and increased morbidity and mortality have consistently been observed. However, the absorption, distribution and elimination kinetics of vitamin C *in vivo* are highly complex, due to dose-dependent non-linearity, and the specific regulatory mechanisms are not fully understood. Particularly, little is known about how adaptive mechanisms during states of deficiency affect the overall regulation of vitamin C transport in the body. This review discusses mechanisms of vitamin C transport and potential means of regulation with special emphasis on capacity and functional properties, such as differences in the *K*m of vitamin C transporters in different target tissues, in some instances demonstrating a tissue-specific distribution.

**Keywords:** vitamin C transport; sodium-dependent vitamin C transporters, SVCT1 and SVCT2; glucose transporters (GLUTs); regulation of transport
