I recently pulled a can of spinach out of my cabinet to compare to the USDA food value tables and found the label showed 50% more Potassium, 30% more protein, and 40% more vitamin A than the current USDA food tables for canned spinach. It would be nice to think that Popeye Spinach took pride in beating the USDA averages but really they are just using very old information to make their product look much better than it probably is.
Interestingly, the USDA also shows 20% more calories than the can label and a higher Carbohydrates From Sugar level. This is also a current trend: nearly all fruits and vegetables in the grocery store have higher sugar contents than their 1940 counterpart. The reason for this is that higher sugar levels in produce make the fruits and vegetables more resistant to cold in the fields and help them store better in cold storage. Lower sugar fruits and vegetables tend to be more susceptible to freezing and has a higher spoilage rate in storage.
From World Watch Jan-Feb 2008 Worldwatch Institute
Farmers today can grow two to three times as much grain, fruit, and vegetables on a plot of land as they could 50 years ago, but the nutritional quality of many crops has declined, according to a new report from The Organic Center, a group based in Boulder, Colorado.
In Still No Free Lunch, report author and Worldwatch Institute food expert Brian Halweil notes that today's food contains 10 to 25 percent less iron, zinc, protein, calcium, vitamin C, and other nutrients than it did historically. 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.
"Less nutrient-dense foods, coupled with poor food choices, go a long way toward explaining today's epidemics of obesity and diabetes," says The Organic Center's chief scientist, Charles Benbrook.
Plants cultivated to produce higher yields tend to have less energy for other activities like growing deep roots and generating phytochemicals (health-promoting compounds like antioxidants), the report explains. And conventional farming methods, such as close plant spacing and the application of chemical inputs, can cause crops to absorb fewer nutrients and have unhealthy root systems.
Using organic methods, on the other hand, means plants "develop more robust root systems that more aggressively absorb nutrients from the soil profile, and produce crops with higher concentrations of valuable nutrients and phytochemicals," says Benbrook. Organic food may have up to 20 percent higher nutritional content for some minerals and 30 percent more antioxidants on average than conventional fare, the report concludes.
Update: August 21, 2008 WASHINGTON (Reuters) - Health regulators have approved the use of ionizing radiation for fresh spinach and lettuce, saying the technique already approved for other foods can help control harmful bacteria and other pathogens.(story)