March 6, 2003 -- Natural farming fills foods with disease-fighting factors. That's the finding from a study comparing organic foods with foods from sustainable and conventional farms.
Food scientist Alyson E. Mitchell, PhD, and colleagues at the University of California, Davis, study compounds called flavonoids. Recent evidence suggests that these micronutrients play important roles in preventing cancer and heart disease.
Flavonoids protect plants, too. They protect against UV radiation. They fight fungal and bacterial infections. And they taste awful to pests. Plants getting chewed by bugs start making lots of flavonoids. Mitchell reasoned that plants sprayed with insect- and fungus-killing chemicals wouldn't make as many flavonoids as organically grown plants. So her research team compared flavonoid levels in fruits and vegetables farmed in the same place but by different methods.
Sure enough, organic berries and corn had significantly more flavonoids than those grown by conventional methods. And a third method -- called sustainable farming -- yielded even higher flavonoid levels. Sustainable farming is sort of a cross between organic and conventional farming. Like conventional farming, sustainably farmed crops are treated with synthetic fertilizers. But pesticides are used sparingly.
"We were really surprised by the difference between organic and sustainably grown foods," Mitchell tells WebMD. "It could be that the sustainably grown fruits and vegetables had pest pressure, because there were not chemical pesticides used while the plants were in the field. However, they'd had synthetic fertilizer added. What we think is that those plants had a reason to make flavonoids. But the fertilizer gave them more of the building blocks for making them."
This theory sounds good to agronomy professor Charles A. Francis, PhD, University of Nebraska, Lincoln.
"I think Dr. Mitchell's theory makes sense," Francis tells WebMD. "A number of us in the field are intrigued by these ideas. The majority of those folks looking at different ways of farming would be more concerned about pesticides than fertilizers. We worry about residues from pesticides -- these chemicals are much less natural than fertilizers, although we certainly look at cover crops and compost and manure as better long-term approaches."
However, it's not at all clear that organic foods are much better for you than other fruits and vegetables. Carl J. Rosen, PhD, interim head of horticultural science at the University of Minnesota, St. Paul, agrees with Francis that nutritional value isn't the main reason many people find organic foods attractive.
"I think it is to some degree naive to think organic foods are more nutritious," Rosen tells WebMD. "Still, one might buy organic foods for lots of reasons. One is pesticide residue. As for nutritional quality, a lot of the produce that is sold in the supermarket is grown hydroponically -- that means with no organic matter. If you compare the nutritional quality of a tomato grown hydroponically to one grown organically, there likely would be some differences, but you couldn't say one is healthier than the other."
Nevertheless, Mitchell says the findings have changed the way she eats.
"Yes, it changed my habits," she says. "I went into this because we do a lot of work on flavonoids. I am not a farmer. When we got the results we did, I was surprised. I have started buying organic everything. If nothing else, it did convince me."
Mitchell's findings appear in the Feb. 26 issue of the Journal of Agricultural and Food Chemistry. Though the bulk of the research was funded by the University of California, Davis, some funding -- largely in the form of donated fruits and vegetables -- came from Oregon Freeze-Dry Inc. and Stahlbush Island Farms Inc., producers and/or growers of organic and sustainably farmed foods.