Soil micronutrients linked to human health in India.

Trace soil minerals are a critical determinant of both crop productivity and the mineral concentration of crops, therefore potentially impacting the nutritional status of human populations relying on those crops. We link health data from nearly 0.3 million children and one million adult women across India with over 27 million soil tests drawn from a nationwide soil health program. We find that soil zinc availability is positively associated with children's linear height growth, and soil iron availability is positively associated with hemoglobin levels. The link between soil zinc and childhood stunting is particularly robust-a one standard deviation increase in satisfactory soil zinc tests is associated with approximately 11 fewer children stunted per 1000. We also find that this zinc-stunting relationship is strongest in wealthier households. Our results suggest that soil mineral availability impacts human nutritional status and health in at least some areas of India, and that agronomic fortification may be a beneficial intervention.

Soil zinc deficiency and child stunting: Evidence from Nepal.

We examine the negative child health impacts of soil zinc (Zn) deficiency in Nepal. Soil Zn deficiency limits both crop yields and the Zn concentration in food crops, leading many to speculate that it underlies human Zn deficiency and child stunting, globally and particularly in South Asia. We find strong evidence that soil Zn deficiency does have a causal impact on child stunting in Nepal's Tarai region, the breadbasket of the country. Using causal bounds, we find that a 1 part per million increase in plant-available soil Zn - achievable with application of Zn-enriched fertilizer - decreases child stunting by between 1 and 7.5 percentage points. Multiple statistical sensitivity tests indicate that this relationship is unlikely to be manufactured by omitted, relevant variables.

Season of Data Collection of Child Dietary Diversity Indicators May Affect Conclusions About Longer-Term Trends in Peru, Senegal, and Nepal.

BACKGROUND: The WHO-UNICEF minimum dietary diversity (MDD) indicator for children aged 6-23 mo is a global monitoring indicator used to track multi-year population-level changes in dietary quality, but the influence of seasonality on MDD estimates remains unclear. OBJECTIVES: To examine how seasonality of data collection may influence population-level MDD estimates and inferences about MDD changes over multiple survey years. METHODS: We selected countries with 3 or more consecutive years of MDD data collection, including continuous national Demographic Health Surveys in Senegal (2012-2017; n = 12,183) and Peru (2005-2016; n = 35,272) and the Policy and Science for Health, Agriculture, and Nutrition sentinel site seasonal surveys (covering 3 seasons/y) in Nepal (2013-2016; n  = 1309). The MDD prevalence (≥5 of 8 food groups) and an 8-item continuous Food Group Score (FGS) and 95% CIs were estimated by month and compared for lean and non-lean seasons using ordinary least squares regression with dummy variables for year. RESULTS: The national prevalence of MDD was higher in Peru (75.4%) than in Nepal (39.1%) or in Senegal (15.7%). Children in Peru were 1.8% (coefficient, -0.0179; 95% CI, -0.033 to -0.002) less likely to achieve MDD during the lean season. Similar seasonal magnitudes were observed in Senegal (coefficient, -0.0347; 95% CI, -0.058 to -0.011) and Nepal (coefficient, -0.0133; 95% CI, -0.107 to 0.081). The FGS was about 0.1 item lower during the lean season in all 3 countries. In comparison, MDD increased by an average rate of only 4.2 and 4.4 percentage points per 5 y in Peru and Senegal, respectively. Intakes of specific food groups were stable across months in all countries, with the provitamin A-rich food group exhibiting the most seasonality. CONCLUSIONS: The magnitude of seasonal variation in MDD prevalence was smaller than expected but large relative to longer-term changes. If large-scale surveys are not conducted in the same season, biased conclusions about trends are possible.

Widespread heterogeneity in staple crop mineral concentration in Uganda partially driven by soil characteristics.

Calcium (Ca), iron (Fe), selenium (Se), and zinc (Zn) deficiencies are widespread in sub-Saharan Africa, with severe implications for human health. In Uganda, where the predominant diet depends heavily on plant-based staples, crop mineral concentration is an important component of dietary mineral intake. Studies assessing the risk of nutrient deficiency or the effectiveness of nutrient-focused interventions often estimate dietary mineral intake using food composition tables that are based on crops grown in developed countries. However, little is known about the actual nutritional content of crops grown in Uganda. Here, we document the Ca, Fe, Se, and Zn concentration of staple crops collected from Ugandan household farms. While median mineral concentrations were similar to those reported previously, variation in crop mineral concentration was high, particularly for Fe and Se. An ordinary least squares regression showed that some soil characteristics were correlated with crop mineral concentrations. Of these, soil pH was often positively associated with crop mineral concentration, while sand and organic carbon concentrations were negatively associated with several crop mineral concentrations. However, much of the variation in crop mineral content was not associated with the soil characteristics measured. Overall, our results suggest that extensive heterogeneity in staple crop mineral concentration in Uganda is likely due to a combination of edaphic characteristics and other variables. Because staple foods constitute a large portion of dietary mineral intake in Uganda and other developing countries, these results have implications for estimates of dietary mineral intake and the development of effective intervention strategies in such regions.

Variation in crop zinc concentration influences estimates of dietary Zn inadequacy.

BACKGROUND: Zinc (Zn) deficiency is one of the most common micronutrient deficiencies worldwide. Accurate estimates of Zn intake would facilitate the design and implementation of effective nutritional interventions. OBJECTIVE: We sought to improve estimates of dietary Zn intake by evaluating staple crop Zn content and dietary Zn consumption by children under the age of 5 in 9 rural districts of Uganda. METHODS: We measured the Zn content of 581 crop samples from household farms and 167 crop samples from nearby markets, and administered food frequency questionnaires to the primary caretakers of 237 children. We estimated Zn consumption using 3 sources of crop Zn content: (i) the HarvestPlus food composition table (FCT) for Uganda, (ii) measurements from household crops, and (iii) measurements from market crops. RESULTS: The Zn content of staple crops varied widely, resulting in significantly different estimates of dietary Zn intake. 41% of children appeared to be at risk when estimates were based on market-sampled crops, 23% appeared at risk when estimates were based on the HarvestPlus FCT, and 16% appeared at risk when estimates were based on samples from household farms. CONCLUSION: The use of FCTs to calculate Zn intake overestimated the risk of dietary inadequacy for children who primarily consumed staple crops that were produced on household farms, but underestimated the risk for children who primarily consumed staple crops that were purchased at market. More information on the Zn content of staple crops in developing countries could lead to more accurate estimates of dietary intake and associated deficiencies.