Mother Earth News
A study has strengthened evidence that the nutrient content of conventionally grown vegetables and fruits has declined over the past 50 years. The study, published in the Journal of the American College of Nutrition, compared U.S.Department of Agriculture data from 1950 and 1999 for 13 nutrients in 43 crops. After rigorous statistical analysis, the researchers found that, on average, all three minerals evaluated have declined; two of five vitamins have declined; and protein content has dropped by 6 percent.
The researchers hypothesize the declines may be caused by “decades of selecting food crops for high yield, with resulting inadvertent trade-offs of reduced nutrient concentrations.”They note that “for many decades agronomists have cited‚ “the dilution effect” to describe reduced nutrient concentrations caused by intensive agricultural practices. For example, when fertilization is adjusted to maximize yield, the harvest weight and dry matter may increase more rapidly than the accumulation of nutrients.”
So how can such deterioration in our food quality be reversed? This study’s authors (from the University of Texas in Austin and the Bio-Communications Research Institute in Wichita, Kan.) suggest “we would need to consider older, lower-yielding cultivars, or attempt to develop new varieties selected for both high yield and high nutrient density.”
Many gardeners have already discovered that older heirloom varieties often have better flavor than newer high-yielding hybrids. Now this study suggests that in many cases, the older varieties may also be more nutritious. And despite these troubling declines in nutrient content, vegetables and fruits are still far better for us than the white flour and rice, refined sugars and added fats that are so dominant in typical American diets.
– Cheryl Long
“Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999,”
Journal of the American College of Nutrition, Vol. 23, No. 6, 2004