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Are organic foods more nutritious? Tomato study adds to the debate

A new study found organically grown tomatoes contain higher concentrations of anti-oxidant compounds than conventionally grown ones.

Organically grown tomatoes were found to be, on average, about 40 percent smaller than those grown by conventional methods, but contained about 55 percent more vitamin C.
USDA/Jess Sanson

Organically grown tomatoes contain higher concentrations of natural sugars, vitamin C and other anti-oxidant compounds than conventionally grown tomatoes, according to a new Brazilian study.

The study’s findings, published Wednesday in the open-access journal PLOS One, add fuel to the ongoing scientific debate over whether organic foods are more nutritious than conventionally grown ones.

Just last September, for example, another team of researchers published a meta-analysis in which they found no difference in the vitamin content of organic and conventional foods. (That study did, however, find higher levels of pesticides and antibiotic-resistant bacteria in conventionally grown foods.)

But other studies have found that organic foods do have greater nutritional content. A 2007 study, for example, found that organic tomatoes contained almost twice as much of the anti-oxidants quercetin and kaempferol than conventionally grown ones.

Smaller size, but more nutrients

For the latest study, researchers compared tomatoes raised on organic and conventional farms located within less than a mile of each other (1.5 kilometers). This factor helped ensure that soil and weather conditions were similar.

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The tomatoes grown organically were found to be, on average, about 40 percent smaller than those grown by conventional methods. Despite their smaller size, however, the organic tomatoes contained about 55 percent more vitamin C and about 140 percent more plant phenols, a class of anti-oxidant compounds that are believed to help protect against heart disease, diabetes, cancer and other chronic illnesses. (One of those compounds, lycopene, gives tomatoes their red color.)

The organic tomatoes also contained more natural sugars, which may explain why organic tomatoes tend to taste better than their conventionally grown counterparts.

A reaction to stress

The authors of the study believe that the higher levels of nutrients in the organic tomatoes may be because plants grown organically are exposed to greater biologic stress from insect predators and disease. The nutrients they produce may help minimize the cell damage caused by that stress.

Historically, conventional farming’s focus has been on yield and size. This study’s findings suggest that such an approach may not be on the best interest of human health.

“[That focus] might be all right for staple food,” write the study’s authors, “but, as far as fruits and vegetables are concerned, it may be argued that gustative and micronutritional quality matter more than energy supply. Our observations suggest that, at least for fruit and vegetable production, growers should not systematically try to reduce stress to maximize yield and fruit size, but should accept a certain level of stress as that imposed by organic farming with the objective of improving certain aspects of product quality.”

You can read the study in full at the PLOS One website.