Sight and Life Magazine 1/2011

26 THE IMPORTANCE OF VITAMIN Afigure 8: Retinol and RBP in plasma before and after inhalation of retinyl palmitate (Biesalski et al., 1999) 6422Normal range RBPRetinol [μmol/L]1Normal range RetinolRBP [μmol/L]10Pre-inhalationPost-inhalation0Pre-inh.Post-inhalationWhole population (n =161)Study group (n =25)Placebo group (n =25)Study groupPlacebo groupInhalation of vitamin A improves vitamin A status in Ethiopian children with severe fat malabsorptionmay serve as an alternative method for vitamin A therapy duringchronic or acute episodes of malnutrition, malabsorption or inthe case of insufficient compliance with other therapies, and itmight be useful in treating respiratory diseases associated withvitamin A deficiency.“Delivery of retinyl palmitate byinhalation is effective in improvingvitamin A status”It should be investigated to what extent the “topical” applicationof retinyl esters on the respiratory epithelium, especiallyin those with chronic lung disease of prematurity, can contributeto the replenishment of lung stores and thus lead to an improvedclinical outcome.ConclusionThe results cited show that retinyl esters in respiratory epitheliumand in alveolar cells form a pool of vitamin A, which can beused physiologically by the tissue. The formation of retinol and,subsequently, retinoic acid from retinyl esters is strictly controlled.So far, unphysiological formation of retinoic acid and subsequenttoxicity do not seem possible. Retinyl esters, however, arebiochemically inert with respect to gene expression or vitamin Aactivity as long as they are not hydrolyzed. Consequently, inhalativeapplication, especially in cases of insufficient lung development,could represent a true alternative. Oral administration ishardly successful because of poor RBP synthesis by the liver, anda parenteral solution is currently not available.To ensure sufficient ante- and postnatal lung maturation, acontinuous adequate supply of vitamin A is important beforeand during pregnancy. The vicious cycle of poor vitamin A statusin pregnancy and the consequently poor status of the newbornand the consequences for further development including adulthoodand pregnancy needs to be interrupted. If no fortified foodwith preformed vitamin A is available, -carotene sources eitherfrom green leafy vegetables and fruit or biofortified food (e.g.maize, sweet potatoes) represent an alternative to improve thevitamin A supply. In cases of an “emergency” approach, supplementswith high doses either before pregnancy or in the finalterm may be useful, but data are inconsistent. A future approachwhich might help to overcome poor vitamin A status with impairedlung function is the inhalation of retinyl esters.Despite conflicting results from intervention studies, due todifferent study protocols and dosages, there can be no doubt thatthe adequate vitamin A statuses of mother and newborn have agreat impact on outcome and, in particular, the lung function ofthe newborn and the mortality and morbidity of both mother andchild. It is therefore of great importance to harmonize differentsupplementation protocols to develop useful and effective recommendationsfor vitamin A delivery at the different stages ofpregnancy, as well as the antenatal and postnatal periods.