A recent study of 43 garden crops suggests that their nutrient value has declined in recent decades while farmers have been planting crops designed to improve other traits. The study was designed to investigate the effects of modern agricultural methods on the nutrient content of foods. The researchers chose garden crops, mostly vegetables, but also melons and strawberries, for which nutritional data were available from both 1950 and 1999 and compared them both individually and as a group.

Dr Donald Davis of the University of Texas at Austin’s Biochemical Institute led the study.

“Considered as a group, we found that six out of 13 nutrients showed apparently reliable declines between 1950 and 1999.”

These nutrients included protein, calcium, phosphorus, iron, riboflavin (B-2) and ascorbic acid (vitamin C). The declines, which ranged from 6% for protein to 38% for riboflavin, raise significant questions about how modern agriculture practices are affecting food crops.

“We conclude that the most likely explanation was changes in cultivated varieties used today compared to 50 years ago,” Davis said. “During those 50 years, there have been intensive efforts to breed new varieties that have greater yield, or resistance to pests, or adaptability to different climates. But the dominant effort is for higher yields. Emerging evidence suggests that when you select for yield, crops grow bigger and faster, but they don’t necessarily have the ability to make or uptake nutrients at the same, faster rate.”

“Perhaps more worrisome would be declines in nutrients we could not study because they were not reported in 1950 – magnesium, zinc, vitamin B-6, vitamin E and dietary fibre, not to mention phytochemicals,” Davis said.

University of Texas at Austin, Dec 1, 2004