Okubo and Nakayama (2023) analyzed 72,317 mother-child pairs from the Japan Environment and Children’s Study (JECS) to test whether periconceptional diet quality (scored using the Balanced Diet Score, BDS) modifies both blood metal concentrations in early pregnancy and the association between blood lead and low birth weight (LBW). Higher diet quality was associated with modestly lower Pb (β=−0.03 per 10-point BDS increase) and Cd (β=−0.010 per 10-point increase) but higher Hg (β=+0.05 per 10-point increase), the latter reflecting greater fish consumption among women with higher diet quality scores. Critically, in the full cohort, each log2-doubling of blood Pb was associated with LBW (adjusted OR=1.50 per quartile Q4 vs Q1, 95% CI 1.36-1.64), and higher diet quality attenuated this Pb-LBW association (interaction OR=0.991 per log2-Pb doubling, 95% CI 0.983-0.999), suggesting that dietary quality independently modifies fetal vulnerability to lead toxicity.
Key numbers
| Metal | Overall median (ng/g WB) | Q1 median | Q4 median | BDS β per +10pt | Notes |
|---|---|---|---|---|---|
| Pb | 5.85 | 6.05 | 5.71 | −0.03 | Modest BDS association |
| Hg | 3.63 | — | — | +0.05 | Increases with diet quality (fish consumption) |
| Cd | 0.659 | — | — | −0.010 | Modest BDS association |
LBW outcomes:
- LBW prevalence in cohort: 7.6% (n=5,504 / 72,317)
- Pb Q4 vs Q1 LBW adjusted OR: 1.50 (95% CI: 1.36-1.64)
- Diet quality × Pb interaction on LBW: OR=0.991 per log2-Pb doubling (95% CI: 0.983-0.999)
Analyte LODs (ICP-MS Agilent 7700):
- Hg: 0.049 ng/g
- Pb: 0.129 ng/g
- Cd: 0.0234 ng/g
Detection rates: Pb >99%, Cd ~98%, Hg ~96% of samples above LOD. BDS range: 0-24 points (higher = better diet quality). Quartile 4 (highest BDS) had 23% lower odds of Pb-associated LBW compared to Quartile 1 interaction model. JECS recruitment: 2011-2014, 15 regional centers; blood collected at first prenatal visit (median 8 weeks gestation). Hg speciation not performed; reported as total Hg.
Methods (brief)
Whole-blood metals measured by ICP-MS (Agilent 7700) at the JECS central laboratory. Pb, Cd, and tHg reported as wet-weight ng/g whole blood. Diet quality assessed by Balanced Diet Score (BDS) from self-administered food frequency questionnaire at first prenatal visit. LBW defined as birth weight <2,500 g. Logistic regression with adjustment for maternal age, BMI, smoking, alcohol, parity, income, education, gestational age, and child sex. Diet-metal interaction tested by multiplicative interaction term. Missing data handled by multiple imputation.
Implications
Certification: This is one of the largest prospective birth cohort studies (n=72,317) demonstrating Pb-LBW dose-response at blood Pb levels in the range 5-6 ng/g, well below the former CDC “level of concern” of 100 ng/g (10 µg/dL). The finding that diet quality attenuates but does not eliminate the Pb-LBW association supports the relevance of minimizing dietary Pb exposure even when maternal overall nutrition is good. For HMT&C, this study anchors the rationale for strict infant and maternal food Pb limits even at low population-mean Pb exposures.
Courses: Excellent case study for the interaction between dietary quality and metal toxicity. Illustrates the trade-off in dietary guidance: fish consumption improves diet quality and reduces Pb/Cd but increases Hg. Relevant to prenatal nutrition modules and the concept of dietary co-exposure trade-offs.
App: Diet quality → metal exposure interactions are not directly modelable from an ingredient list, but the JECS Pb-LBW association provides supporting context for why minimizing dietary Pb in foods consumed during pregnancy is a priority. Blood Pb values (median 5.85 ng/g) provide a real-world exposure calibration point for Japanese population (low-exposure context).