A cross-sectional study of urinary cadmium concentrations in relation to dietary intakes in Uruguayan school children

Abstract

Background: Cadmium (Cd) exposure has adverse health effects in children. Diet contributes to Cd exposure, but dietary components could affect body Cd levels.

Objective: To examine associations between diet and urinary Cd (U-Cd) in children.

Methods: In this cross-sectional study conducted in Montevideo, Uruguay, Cd exposure of 5-8 year old children (n = 279 with complete data) was assessed in first morning urine (U-Cd), a marker of long-term exposure, measured by ICP-MS and adjusted for specific gravity. Distribution of U-Cd was (median [5%, 95%]: 0.06 [0.02, 0.17] μg/L); data were natural-log-transformed (ln) for statistical analyses. Serum ferritin (SF), an indicator of iron stores, was measured in fasting samples. Trained nutritionists completed two non-consecutive 24-h dietary recalls with both child and caregiver present. Measures of iron, zinc, calcium and fiber intake, and the consumption of grains, root vegetables, milk, and foods rich in heme iron (white and read meats) and non-heme iron (legumes, spinach, broccoli, tomatoes, dried fruit) were derived. Multivariable ordinary least squares (OLS) and ordinal regressions were used to examine associations among tertiles of water Cd, SF, diet, and U-Cd. OLS models were further stratified by sex.

Results: In covariate-adjusted models, SF was not related to ln-U-Cd. Children in highest tertile of iron and zinc intake had lower ln-U-Cd: (-0.23 [-0.42, -0.03]) and (-0.25 [-0.44, -0.05]), respectively, compared to the reference group. Children consuming higher amounts of foods rich in heme iron had slightly lower ln-U-Cd (-0.17 [-0.36, 0.03]). High grain consumption was related to higher ln-U-Cd (0.25 [0.06, 0.45]).

Conclusions: Diets rich in grains were related to higher urinary Cd levels among children living in the context of low Cd pollution. Higher intake of iron and zinc was related to lower Cd levels. Given that urinary Cd is mainly a marker of long-term exposure, these findings should be further corroborated.

Keywords: Child; Diet; Grains; Iron; Urinary cadmium; Zinc.

Figure 1:. Covariate-adjusted¹ associations between dietary intakes and ln-transformed U-Cd² concentrations in Uruguayan children.

¹Model adjusted for age, crowding in the home, maternal education (years), and household possessions; ²Concentration (μg/L) was adjusted for specific gravity of urine; natural-log-transformed for OLS modeling; ³Quantile of dietary intake, T=tertile, M=median; the lowest quantile serves as the reference group and is not shown. ⁴Foods rich in heme iron include red and white meats; ⁵Fods rich in non-heme iron include beans, peas, lentils, soy/bean burgers, spinach, broccoli, tomatoes, dried fruit; ⁶Grains include white and whole wheat flour, corn flour and starch, cereals, rice, granola bars and cereal bars, muesli, polenta, prepared dishes containing rice or grains; ⁷Root vegetables include carrots, beets, potatoes (including French fries), sweet potatoes, turnips; *p<0.10; **p<0.05; ***p<0.01.

Figure 2:. Covariate-adjusted¹ associations between dietary intakes and the proportional odds of elevated U-Cd² among Uruguayan children.

¹Model adjusted for age, crowding in the home, maternal education (years), and household possessions; ²Concentration (μg/L) was adjusted for specific gravity of urine; ³Quantile of dietary intake, T=tertile, M=median, the lowest quantile serves as the reference group and is not shown; ⁴Foods rich in heme iron include red and white meats; ⁵Fods rich in non-heme iron include beans, peas, lentils, soy/bean burgers, spinach, broccoli, tomatoes, dried fruit; ⁶Grains include white and whole wheat flour, corn flour and starch, cereals, rice, granola bars and cereal bars, muesli, polenta, prepared dishes containing rice or grains; ⁷Root vegetables include carrots, beets, potatoes (including French fries), sweet potatoes, turnips; *p<0.10; **p<0.05; ***p<0.01.