On a worldwide scale, more than 1/3rd of all children suffer from protein malnutrition or undernutrition, with the highest prevalence showing in the developing countries of Asia, Africa, Latin America and Oceania. In Asia 80%, in Africa 15% and in Latin America 5% of all children are suffering from consequences caused by protein malnutrition or undernutrition . For more than 230 million children an inadequate vitamin A supply is shown, with 13 million of them being affected by night blindness. The main cause for the loss of their eye sight of currently world wide more than 2.8 million preschool children is dietary vitamin A deficiency . Moreover, insufficient intake of vitamins and minerals is suggested to be a cause for the high prevalence of several sub-clinical diseases and growth retardation. This is especially true for Laos, where UNICEF noticed a growth retardation in all Laotian preschool children, which was classified by the WHO to be the highest in the world. Concerning the widespread night blindness, the national vitamin A study established that the intake of mainly rice as dominant staple food together with recurrent infectious diseases are the main causes of the vitamin A deficiency [3–5].
Vitamin A deficiency is caused by either a deficiency of vitamin A itself or by a reduced availability of precursors of vitamin A, the carotenoids. The reduced availability is either caused by its limited presence in food or by a reduced absorption due to a reduced fat content of the diet or a reduced absorptive capacity of the gut . In addition to their function as precursor of vitamin A , carotenoids together with vitamin E are important micronutrients to maintain health by protecting the body against free radical damage . In this context different epidemiological studies show an association with a variety of degenerative diseases such as cancer, heart disease and age related macula degeneration .
Because carotenoids, tocopherol and retinol plasma levels are biomarkers of their uptake or status [10, 11] these components are frequently investigated in populations with an affluent lifestyle especially with regard to factors affecting plasma levels of these components . Only a few studies have addressed this question in developing countries especially with regard to infants. This is, however, of specific importance to understand firstly how the plasma levels of these components are influenced and secondly how these components might determine longevity and long-term health.
Major reasons for the limited number of studies available on the plasma concentrations in individuals from developing countries are on the one hand logistical problems and on the other hand the limited individual and public acceptance of such kind of investigations. Logistical problems include blood collection, serum preparation by centrifugation, transportation as well as short-term and long-term storage under cool or frozen conditions. Mothers are not very enthusiastic with regard to an invasive sampling of blood especially in their infants. Therefore methods that will avoid the invasive venous blood sampling and a majority of logistical problems as well would be of advantage to encourage more studies on the levels of vitamin A, α-tocopherol and carotenoids in populations of developing countries.
The purpose of this study was thus to answer two questions. Firstly, whether plasma levels of retinol, α-tocopherol and carotenoids determined in capillary blood will validly represent the respective venous blood levels and secondly, whether a method using capillary blood plasma is suitable to asses the possible relation of vitamin A, carotenoid and α-tocopherol status in infants with sex, growth failure and living conditions in children from the high- and lowland region of the Bolikhamxay province Laos.