Molecular analysis of halorespiration in Desulfitobacterium spp. : catalysis and transcriptional regulation

Elimination of vitamin A deficiency has been high on the agenda of subsequently the Micronutrient Deficiency Meeting held in Montreal Canada 1991 and the International Conference on Nutrition in Rome Italy, 1992. During the last decade, the direction of research and approaches towards controlling vitamin A deficiency have changed enormously and has been shaped and advanced largely by public health professionals, policy makers and different organizations. Although vitamin A deficiency and xerophthalmia</span>is not a public health problem anymore in Vietnam, the prevalence of sub clinical vitamin A deficiency is still high. Main sources of vitamin A in the diet are green leafy vegetables and fruits and only the wealthier part of the population gets a substantial part of their vitamin A from animal sources. To increase the vitamin A intake in the population, several approaches are possible. For many developing countries a food-based approach using foods naturally rich in vitamin A and other micronutrients is preferable because fruits and vegetables provide 70-80% of the total vitamin A intake due to their high content</span>of<span class=SpellE>provitamin</span>A<span class=SpellE>carotenoids</span>.Thus, an increased consumption of plant<span class=SpellE>provitamin</span>A-rich foods should be encouraged. The question is, however, how much can plant foods contribute to vitamin<span class=GramE>A</span>supply. An intervention study in breastfeeding women was carried out, specially designed to provide information about the role of different plant food sources in improving the vitamin A status. The results show that consumption of dark-green leafy vegetable only result in a very small improvement of the vitamin A status, suggesting that the relative bioavailability of β-carotene in dark-green leafy vegetables is lower than previously assumed. Interestingly, the bioavailability of carotenoids</span>differs across different kinds of plant food: β -carotene in yellow/orange fruits is better available than that in dark-green leafy vegetables. The reason of the low bioavailability of carotenoids</span>could be the complex matrix of leaves in addition to absorption inhibitors such as<span class=SpellE>fiber</span>which entraps carotenoids. Parasitic infestation, genetic factors, and dietary factors might play a role as well. The study shows that approaches beyond the promotion of fruits and vegetables are required to eliminate (sub clinical) vitamin A deficiency. It might be necessary to apply combination strategies including public health measures, food fortification, "<span class=SpellE>biofortification and other opportunities for targeted supplementation programs. Promotion of consumption of fruits and vegetables should, however, remain part of the holistic approach, not only because of their<span class=SpellE>provitamin</span>A content but also as protective factor in the prevention of chronic diseases