“…Journal of the American College of Nutrition. They studied U.S. Department of Agriculture nutritional data from both 1950 and 1999 for 43 different vegetables and fruits, finding “reliable declines” in the amount of protein, calcium, phosphorus, iron, riboflavin (vitamin B2) and vitamin C over the past half century. Davis and his colleagues chalk up this declining nutritional content to the preponderance of agricultural practices designed to improve traits (size, growth rate, pest resistance) other than nutrition.”
“Over the last 50 years, the amounts of protein, calcium, phosphorus, iron, riboflavin and vitamin C in conventionally grown fresh fruits and vegetables have declined significantly. We know this thanks to rigorous analysis of USDA nutrient data by biochemist Donald Davis of the University of Texas. Similar trends have been discovered in the United Kingdom.Wheat grown 100 years ago had twice as much protein as modern varieties.Major declines in protein and several other nutrients have been documented in modern corn varieties (see the chart).
Davis lists the following causes for declines in the nutrient value of food:
Environmental Dilution Effects. Scientists have known for years that high rates of fertilizer and irrigation use can lead to higher yields, but sometimes at the expense of nutrient density of the crops. Nitrogen in particular is difficult to manage in the soil, and when farmers apply too much it causes plants to take up more water, resulting in high yields but giving us foods that have lower nutrient density.
Genetic Dilution Effects. As plant breeders develop “improved” varieties that give farmers ever higher yields, they are inadvertently causing food nutrient values to decline. Consider calcium in broccoli: Widely grown varieties in 1950 had about 13 mg/g of calcium, but today’s varieties provide only about 4.4 mg/g of calcium.”
“A recent study of 43 garden crops led by a University of Texas at Austin biochemist suggests that their nutrient value has declined in recent decades while farmers have been planting crops designed to improve other traits.”
“Today’s food produces 10 to 25 percent less iron, zinc, protein, calcium, vitamin C, and other nutrients, the studies show. Researchers from Washington State University who analyzed 63 spring wheat cultivars grown between 1842 and 2003 found an 11 percent decline in iron content, a 16 percent decline in copper, a 25 percent decline in zinc, and a 50 percent decline in selenium.