Summary
Davis, Epp, and Riordan analysed historical USDA food composition data to assess whether the nutrient content of 43 commonly consumed garden crops changed between 1950 and 1999. The study found statistically significant declines in median concentrations of several key nutrients, which the authors attribute in part to the adoption of high-yielding crop varieties that may prioritise biomass over nutrient density — a phenomenon sometimes described as the 'dilution effect'. The paper is widely cited in debates about the relationship between modern agricultural practices and the nutritional quality of the food supply.
UK applicability
Although the data are drawn from US food composition tables, the findings are broadly relevant to UK and European contexts, where similar trends in agricultural intensification and varietal selection have been observed; the paper is frequently referenced in UK nutritional policy and food systems discussions.
Key measures
Nutrient concentrations (protein, calcium, phosphorus, iron, riboflavin, ascorbic acid) in 43 vegetables and fruits; percentage change over time (1950–1999) using USDA food composition tables
Outcomes reported
The study compared USDA food composition data for 43 garden crops between 1950 and 1999, measuring changes in concentrations of key nutrients including protein, calcium, phosphorus, iron, riboflavin, and ascorbic acid. Statistically reliable declines were found for several nutrients across the majority of crops examined.
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