Micronutrient deficiencies are common in young children due to the combination of low dietary diversity and high nutrient needs to support rapid growth and development. Provision of infrequently consumed, nutrient-dense animal-source foods may improve diet quality and fill the nutrient gap between children’s nutrient needs and dietary intake. However, few studies have examined the relationships between consumption of these foods on vitamin A and iron status. The studies described in this dissertation stem from the Mazira Project, a randomized controlled trial providing 1 egg/d to young Malawian children. Our objectives were threefold: 1) to evaluate the effect of the intervention providing 1 egg/d on vitamin A deficiency (VAD); 2) to evaluate the effect of the intervention on iron deficiency (ID) and anemia; and 3) to examine the relationship between usual intake of fish and meat on ID and anemia.
The first study examines the impact of supplementing diets of 6-9mo Malawian infants with 1 egg/d for 6mo on the concentration of plasma retinol and retinol binding protein (RBP) as well as the prevalence of VAD (retinol <0.7µmol/L). Venous blood samples were collected at enrollment and 6mo follow-up. Retinol was assessed by HPLC, and RBP, c-reactive protein (CRP), and α-1-acid glycoprotein (AGP) were assessed by ELISA techniques. Prevalence of inflammation (CRP>5mg/L or AGP>1g/L: 62%) and inflammation-adjusted VAD (7%) at enrollment did not differ between groups. At follow-up, the egg intervention group did not differ from the control in inflammation-adjusted retinol [(geometric mean (95%CI); egg: 1.10 µmol/L (1.07, 1.13); control: 1.08 (1.05, 1.12)], RBP [(egg: 0.99µmol/L (0.96, 1.02); control: 0.97 (0.94, 1.00)], or prevalence of VAD [egg: 6%; control: 3%; Prevalence Ratio (PR): 1.87 (0.83, 4.24)].
The second study examines the impact of supplementing diets of 6-9mo Malawian infants with 1 egg/d on 1) plasma ferritin, soluble transferrin receptor (sTfR), body iron index (BII), and hemoglobin (Hb) concentrations and 2) the prevalence of ID (ferritin <12 μg/L, sTfR >8.3 mg/L, or BII <0 mg/kg), anemia (Hb <11 g/dL), and iron deficiency anemia (IDA). Hemoglobin was assessed from venous whole blood at enrollment and 6mo follow-up. Plasma ferritin, sTfR, CRP, and AGP were measured by ELISA techniques at enrollment and 6mo follow-up. At enrollment, the total prevalence of anemia was 61% and did not differ between groups. At 6mo follow-up, groups did not differ in geometric mean concentration of hemoglobin [mean (95% CI); egg: 10.9 (10.7, 11.1) g/dL; control: 11.1 (10.9, 11.2) g/dL] and inflammation-adjusted ferritin [egg: 6.52 (5.98, 7.10) μg/L; control: 6.82 (6.27, 7.42) μg/L], sTfR [egg: 11.34 (10.92, 11.78) mg/L; control: 11.46 (11.04, 11.89) mg/L] or BII [egg: 0.07 (0.06, 0.09) mg/kg; control: 0.07 (0.05, 0.08) mg/kg]. There were also no group differences in anemia [egg: 46%; control 40%; PR: 1.15 (95% CI: 0.96, 1.38)], ID [PR: 0.99 (0.94, 1.05)], or IDA [PR: 1.12 (0.92, 1.36)].
The third study assesses whether usual intake of small fish, large fish, and meat were associated with plasma ferritin, sTfR, Hb, anemia, ID, and IDA in a population of young Malawian children with a high (>50%) prevalence of IDA. Food frequency questionnaires screening for animal source food intake were conducted weekly; 24-hr dietary recalls and venous blood samples were collected at enrollment and 6mo follow-up. Each food category was consumed by <5% of children at enrollment. By the 6mo follow-up, the prevalence of consumption reported in 24-hr dietary recalls increased to 40% for small fish, 12% for large fish, and 9% for meat. Usual portion sizes were small, ranging from 1.2g/d of meat and large fish to 4.9g/d of small fish. Over the 6mo study, children consumed small fish, large fish, and meat on an average of 25%, 8%, and 6% of days, respectively. Frequency of small fish intake was associated with lower sTfR [geometric mean ratio (95%CI): 0.98 mg/L (0.96, 1.00) per 10 percentage point difference] but was not associated with ferritin [1.03 µg/L (0.98, 1.07)] or Hb [1.01 g/dL (1.00, 1.01)]. Frequency of large fish consumption was associated with a higher prevalence of anemia [PR (95%CI): 1.09 (1.00, 1.19)] and lower prevalence of ID [0.96 (0.93, 1.00)]. Neither frequency of meat consumption over the 6mo study nor usual gram weight intake of fish or meat at the 6mo follow-up were associated with any iron or anemia indices.
In summary, providing 1 egg/d for 6mo did not impact VAD, ID, anemia, or plasma indices of retinol, RBP, ferritin, sTfR, and hemoglobin among young children in rural Malawi. In this context, high rates of breastfeeding, vitamin A supplementation programs for children, and mandatory fortification of maize flour, wheat flour, sugar, and oil may have contributed to adequate liver stores of vitamin A. Thus, there may have been limited potential for children to benefit from the added vitamin A provided via the eggs. Further, the egg intervention neither alleviated nor exacerbated the high burden of ID in this population. Other more bioavailable and iron-rich foods, like small fish, have greater potential to improve iron stores. In this population, small fish consumption was only weakly associated with iron status, likely due to the small portion sizes consumed. Consuming a variety of animal-source foods including eggs, fish, and meat in sufficient quantities may improve micronutrient status and complement other interventions to reduce the risk of micronutrient deficiencies in young children.
