Donald Davis and his team at the University of Texas lined up USDA nutrient data for 43 garden crops, measured in 1950 and again in 1999. Six nutrients had reliably dropped, including calcium, iron and vitamin C. Riboflavin fell the most, a median of 38%.
Their best explanation: decades of breeding crops to grow bigger and faster. The yield went up. The nutrients didn't keep pace.
Then there's how much of it we actually eat. In 2019, the CDC surveyed nearly 300,000 adults. Only 1 in 10 ate the recommended amount of vegetables, and about 1 in 8 ate enough fruit.