The first scientifically controlled trials of soil mineralization suggest that—unless vital elements are returned to the soil—the nutrients in our food supply will significantly deteriorate. Comparing 1940 assessments with those made in 2002, David Thomas, DC, found that iron content of meat had already declined 47 percent and that calcium content of Parmesan cheese had fallen 70 percent. “Food is only as good as the earth it comes from,” explains Moria Thomason, founding director of Scotland’s Sustainable Ecological Earth Regeneration Center.

Over the last half century, widespread use of synthetic and persistent pesticides and other dubious chemicals coupled with decreased use of humus-containing fertilizers have created a “dilution effect” of nutrients in foods.

Studies show that genetic modifications of crops can also decrease their nutrient content. Concentrations of vitamins, minerals, and protein have declined from 5 to 30 percent over the past 50 years, says Donald R. Davis, PhD, of the University of Texas at Austin. Growing high-yield crops can result in bigger produce more quickly, but plants may not be able to take up or make nutrients in sufficient levels, he explains.

Organic growing methods—including avoiding synthetic pesticides and using compost, cover crops, and slow-release nitrogen sources—have been shown to increase antioxidant content by about 30 percent, according to Dr. Davis. It’s no wonder that consumers who want superior nutrient content increasingly choose organic.