118 M. Bechir et al. Figures 3–4. Regression of blood retinol on cows’ milk retinol and regression of mothers’ milk retinol on cows’ milk retinol. children of cattle breeders in Mauritania (Borel and Etard 1988). Conversely, higher overall levels (40%) of retinol deﬁciency were found among nomadic women in Chad (Zinsstag et al. 2002). This could be due to sampling time, which was at the end of the rainy season and during the dry season. In addition, those retinol measurements were done using high-performance liquid chromatography. In the current study, b-carotene values were ten times higher, which may indicate seasonal differences but could also be due to detection method differences. Mothers’ Blood/Milk Retinol Level and Infant Blood Retinol Level Retinol levels in mother’s milk were all close to normal, with the highest values in nomadic women, as observed by Schmeits et al. (1999). Human milk retinol values were slightly higher, an average 0.7 lmol/L, than serum levels. The b-carotene level in mother’s milk was lower than that observed by Bishara et al. (2008). This study showed the interdependencies of vitamin A in infants, who are nourished mainly through mother’s milk. Infant blood retinol was primarily dependent on the mother’s milk retinol. This was also demonstrated by the high proportion of retinol deﬁ- ciency in children older than 12 months of age, e.g. pre- dominately weaned children, which emphasises the importance of breast feeding and the inﬂuence of the maternal diet. Ecological Link of Human Blood Retinol Level and Livestock Milk Consumption Livestock milk was very rich in retinol at the end of the rainy season, and of all ruminant milk evaluated (cow, camel, sheep and goat), sheep milk was richest, which is consistent with ﬁndings by the Food and Agriculture Organization of the United Nations (1998), but higher than that recorded by Zinsstag et al. (2002) in the same study area. The relationship between serum retinol level and milk consumption has been previously documented (Murphy et al. 2008), and seasonal variation in nomadic communi- ties likely depends on ﬂuctuation in self-consumption resulting from seasonal variation in marketing practices. The mother’s milk retinol levels followed maternal blood retinol values, which were dependent on the livestock milk retinol content, as this was the main source of vitamin A for the women, conﬁrming earlier observations (Zinsstag et al. 2002). The relationship between animal milk and blood retinol level of consumers and, further, mother’s milk and blood retinol level of children is demonstrated in this study. It could be considered as an ecological link along the food chain from livestock to humans. Further infor- mation would be gained through future work examining the link from fodder grass to livestock. Retinol and Nutritional Status In a parallel study, the level of malnutrition in the same study population was investigated, showing a reverse trend with nomadic women experiencing the highest levels of malnutrition compared to semi-nomadic and sedentary women (Bechir et al. 2011). This may indicate that, despite high milk consumption among nomadic women, energy consumption from staple foods, primarily maize and millet is insufﬁcient. According to Wuehler et al. (2011), the nutritional status of young children in the Sahel region would be improved by exclusive breastfeeding for infants,