Appendix 7.  Detail on Nutritional Interventions on Blood Lead Levels

Three randomized controlled trials (RCTs)^88-90 and three prospective cohort studies^91-93 did not find a significant correlation between calcium and blood lead levels, although one prospective cohort study⁹⁴ found an inverse association. Fat and caloric intakes were positively associated with blood levels in a prospective cohort study⁹⁵ and a cross-sectional study.⁹⁶  Carbohydrates had an inverse association according to a prospective cohort study.⁹⁵ 

Two prospective cohort studies^91,92 found that ferritin is not significantly related to blood lead levels.  One cross-sectional study¹⁰ found a positive association with folate and a negative association with serum folate. Iron has not been shown to have a effect on blood lead levels in two RCTs^88,90 and one prospective cohort study,⁸¹ although three prospective cohort studies^91-93 and one cross-sectional study⁹⁷ reveal a negative association, while one cross-sectional study shows a positive association.¹⁰ 

Two RCTs^88,90 found no correlation between blood lead levels and phosphorus. One cross-sectional study found a positive association between blood lead levels and pyridoxine.¹⁰  Protein had a paradoxical effect in one prospective cohort study, significantly associating with low lead levels at six months, but then higher lead levels at 12 months.⁹¹ 

Two prospective cohort studies showed no relationship between supplement use and blood lead levels.^91,92  One cross-sectional study found a negative association between blood lead levels and thiamine.¹⁰  Vitamin C is inversely related with blood lead levels according to a prospective cohort study.⁹⁵  Vitamin C has also been inversely associated with blood lead levels in a cross-sectional study,⁹⁸  Dietary vitamin D is also inversely related to blood lead levels according to a prospective cohort study,⁹² whereas serum vitamin D has not been correlated with blood lead levels in two prospective cohort studies.^91,92  Two prospective cohort studies yielded different results concerning zinc, showing no association to blood lead levels,⁹¹ and conflicting results.⁹²

Despite the significant relationships between nutrients and children's blood lead levels in the epidemiological studies described above, it is noticeable that none of the RCTs found significant correlations.^88-90  Similarly, a 2004 retrospective cohort study, using data from the Wisconsin Childhood Lead Poisoning Prevention Program in children aged 0-6 compared children's blood levels enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children from 1996 to 2000 with children not enrolled in the nutrition program did not find any significant differences between the two groups.⁹⁹ 

Other cohort studies reveal significant association with calories, carbohydrates, fat, iron, vitamin C and vitamin D,^81,91-95 whereas the cross-sectional studies demonstrate significant associations with ascorbic acid, calories, fat, folate, serum folate, iron, pyridoxine, and thiamine^10,96-98  Adverse effects were reported in two of the fourteen studies; both are RCTs.  

A calcium study using a 1800 µg/dL⁸⁹ dosage reported abdominal pain in both the treatment and control groups.  A calcium glycerophosphate-supplemented infant formula study reported elevated ratios of urinary calcium to creatinine and low concentrations of serum ferritin, but these effects also occurred in both the treatment and placebo groups.⁹⁰  None of the other studies reported adverse effects.

A recent review, however, concluded that experimental studies in animals and observational studies of humans provide evidence that calcium supplementation during the second half of pregnancy may reduce prenatal lead exposure by reducing mobilization of lead from bone.³

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