Summary
Davis, Epp and Riordan examined five decades of USDA food composition data for 43 garden crops, reporting apparent declines of between 6% and 38% in median concentrations of six nutrients between 1950 and 1999. The authors attribute a significant portion of these changes to a 'dilution effect', whereby breeding programmes prioritising yield and growth rate have resulted in crops with proportionally lower mineral and vitamin concentrations. The paper is a widely cited contribution to debates about whether modern agricultural practices and crop selection have diminished the nutritional quality of vegetables.
UK applicability
Although based on US data and USDA composition tables, the findings are broadly applicable to UK and European contexts, where similar trends in crop breeding for yield and comparable declines in vegetable mineral content have been reported, including in studies drawing on UK McCance and Widdowson composition data.
Key measures
Nutrient concentrations (protein, calcium, phosphorus, iron, riboflavin, ascorbic acid) in mg or g per fresh weight; percentage change between 1950 and 1999 USDA survey values across 43 vegetable crops
Outcomes reported
The study analysed changes in concentrations of protein, calcium, phosphorus, iron, riboflavin, and ascorbic acid across 43 garden crops using USDA food composition data from 1950 and 1999, finding statistically reliable declines in median concentrations for most nutrients examined.
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