Women Nomads Semi-nomads Sedentary Total Livestock Cows Goats Sheep Retinol n 12 20 5 37 25 19 16 3.6 2.8 2.6 3.0 5.7 6.0 6.7 Table 2. Averages of Retinol, b-Carotene and RAEs in Mothers’ and Livestock Milk Avg. (lmol/L) 95% CI 2.7–4.6 1.8–3.8 0–5.4 2.4–3.7 5.0–6.6 4.7–7.4 5.6–7.8 b-Carotene Avg. (lmol/L) 0.07 0.15 0.12 0.12 0.19 0.18 0.16 95% CI 0.04–0.15 0.06–0.23 0.09–0.16 0.08–0.17 0.16–0.22 0.14–0.19 0.12–0.2 Retinol Assessment 117 RAEs Avg. (lmol/L) 3.6 2.8 2.7 3.1 5.8 6.0 6.8 95% CI 2.7–4.5 1.8–3.8 0–5.4 2.4–3.7 5.0–6.6 4.7–7.3 5.7–7.9 RAE = retinol + 0.167 * b-carotene (FAO and WHO 2001). Bold values indicate the retinol activity equivalent. similar, with nomadic women tending towards higher levels of milk retinol (P = 0.07). Retinol and b-carotene levels were signiﬁcantly (two times) higher in livestock milk than in mother’s milk. Sheep milk had the highest retinol levels, followed by goat and cow’s milk. Human blood and mother’s milk retinol values are signiﬁcantly dependent on cow’s milk retinol levels (Figs. 3–4). Spearman’s rank correlations were positive between cows’ milk retinol and mothers’ blood retinol, where R = 0.43 (n = 20, P = 0.05), between mothers’ blood retinol and mother’s milk retinol, where R = 0.24 (n = 38, P = 0.01), between mothers’ milk retinol and infant blood retinol, where R = 0.49 (n = 38, P = 0.001), and a positive trend between cows’ milk and mothers’ milk, where R = 0.48 (n = 11, P = 0.1). The trend in Figs. 3–4 indicates a linear relationship for these variables within the limits of observation. Average human milk retinol values are slightly higher than those of women serum retinol (Tables 1, 2). Risk Factors and Retinol Deﬁciency Multivariate logistic regression of the proportion of retinol deﬁciency in children and women is shown in Table 3. Semi-nomadic and sedentary children have an increased risk compared to nomadic children (OR = 17 and OR = 27; P < 0.01, respectively). Likewise, children older than 36 months had signiﬁcantly higher proportions of retinol deﬁciency compared to infants <12 months of age (OR = 15; P = 0.01). However, there was no signiﬁcant difference in the risk of low retinol concentration between sex, emaciated and non-emaciated, multi-parasitic infected and non-multi-parasitic infected or anaemic and non- anaemic status in children. Among women, retinol deﬁ- ciency was only signiﬁcant in relation to lifestyle. The proportion of retinol deﬁciency is signiﬁcantly higher in semi-nomad (OR = 21; P < 0.01) and higher, but not signiﬁcant, in sedentary (OR = 8; P = 0.06) compared with nomadic communities. Retinol Level and Lifestyle In this study, signiﬁcant retinol deﬁciencies were observed in sedentary and semi-nomadic communities. Similar proportions were found in Ghanaian sedentary commu- nities (Lartey 2008). The proportions in those communities were higher than the post-intervention rate of 15–20% (McLaren and Frigg 2001; World Health Organization 1996). The high proportion of retinol deﬁciency among semi-nomadic communities is likely due to the prevailing livestock management system. During the wet season, semi- nomads remain in a concentrated zone near Lake Chad to sell milk. In contrast, nomadic communities migrate con- siderable distances, increasing self-consumption of milk as it is not easily marketed during this period. Higher milk consumption likely explains the increased retinol values in nomadic women and children. Consumption of half a litre of milk could contribute 15–20% of the dietary reference intake for vitamin A, as the average reference concentration of retinol in milk is 280 lg/L and the recommended daily intake is 700–900 lg/day (Haug et al. 2007; Insel et al. 2004). High levels of vitamin A were also observed among