Associations between micronutrient intake and blood lead level in Uruguayan children
Open Access
- Author:
- Roy, Aditi
- Graduate Program:
- Nutrition
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- September 05, 2011
- Committee Members:
- Katarzyna Kordas, Thesis Advisor/Co-Advisor
Katarzyna Kordas, Thesis Advisor/Co-Advisor - Keywords:
- blood lead level
children
micronutrients
environmental toxicology
international health - Abstract:
- Background: Lead exposure is one of the important pediatric environmental health problems in both developing and developed countries. The primary site for absorption of lead is the gastrointestinal tract. Lead is thought to compete with nutrient metals like iron, calcium and zinc for similar binding sites on intestinal transporter proteins for absorption. On the other hand, vitamin C may chelate and excrete lead in urine. It may also alter iron-lead interaction by increasing iron absorption. In addition, there is some evidence that folate metabolism may be related to lead toxicity. Overall, some evidence exists for an association between micronutrient status and lead exposure, but supplementation with micronutrients has not always been effective. It is important to identify a population at risk for both micronutrient deficiency and lead exposure to carry out successful dietary intervention. This cross-sectional study examined the relation between dietary intakes of micronutrients (calcium, iron, zinc, vitamin C and folate) and blood lead level (BLL) in 6-8 year old children (n=61) from Montevideo, Uruguay. Method: Sixty-one first graders from four primary schools in Montevideo (the capital of Uruguay) participated in the study. The study children came from low-income families, living in areas known for lead exposure. Fasting blood samples were collected during a clinic visit in school to analyze whole blood lead levels by atomic absorption spectrophotometer. Two 24-hour dietary recalls were conducted with mothers or caregivers and daily nutrient intakes calculated from a database of nutrient composition of Uruguayan foods. Parents filled out a brief questionnaire on socio-economic status, parental education and employment and child’s health. In addition, questions were asked to identify sources of lead exposure. Nutrient intakes were adjusted for total calorie intake by residual analysis. The relationship between micronutrient intakes and BLL were modeled in co-variate adjusted multiple linear and logistic models, with each nutrient tested in separate models and entered as tertiles. Results: Mean (SD) BLL of 61 study children was 5.0 (2.6) µg/dL, with 8.2% and 37.7% of the study children having BLL ≥ 10 µg/dL and BLL > 5 µg/dL, respectively. Median (IQR) calorie-adjusted intake of calcium, iron, zinc, vitamin C and folate was 728 (315) mg/day, 10 (5) mg/day, 5 (3) mg/day, 44 (37) mg/day and 325 (240) µg/day, respectively. About 60% children had calcium intake below the Estimated Average Requirement (EAR) (800 mg/day). Intakes of rest of the micronutrients (iron, zinc, vitamin C and folate) were adequate. Nutrient intakes were positively correlated with total daily calorie intake and iron intake was correlated with intakes of vitamin C. Higher dietary calcium intake was associated with lower BLL after adjusting for child’s BMI, environmental exposure, family possessions and school. Children in the highest tertile of calcium intake (871-1474 mg/day) had 1.2 µg/dL lower BLL (p< 0.1) and 83% lower likelihood (p< 0.05) of having BLL > 5 µg/dL than children in the lowest tertile (246 – 728 mg/day). No significant associations were found between BLL and other four micronutrients. There were no significant interactions between iron and calcium or iron and vitamin C. Conclusions: Higher calcium intake was associated with lower blood lead level in 58 Uruguayan school children. However, no association was found between intakes of iron, zinc, vitamin C and folate with children’s BLL. Future studies should confirm the findings by repeating the results with biomarkers of micronutrients. In addition, the effects of calcium supplementation on BLL in young children are also warranted.