Organically Grown Tomatoes Have Higher Antioxidant Content

SANTA FE, N.M., July 18 /PRNewswire/ -- The first-ever, decade-long study evaluating organic versus conventionally grown tomatoes revealed antioxidant differences between the two agricultural systems. University of California-Davis researchers found that organically grown tomatoes were significantly higher in flavonoids, a type of antioxidant, and that the differences between the two agricultural systems increased over time.

The existing body of research on the nutritional differences between organic and conventionally grown foods has found inconsistent results, due, in part, to the difficulty in studying agriculture systems that are dynamic and hard to control. In order to study the long-term impact of agricultural practices, University of California-Davis researchers started the Long-Term Research on Agricultural Systems (LTRAS) project in 1993. In the current study, researchers analyzed tomato samples collected from 1994-2004. The conventionally grown tomatoes used fertilizers and other standard irrigation and farming practices while the organic plots used crop rotation, manure, and other sustainable farming practices.

The results found, over time, that the organic tomatoes had increasingly higher amounts of the three flavonoids studied: quercetin, naringenin and kaempferol, whereas the levels of flavonoids did not vary significantly in conventional tomatoes. Mean values for quercetin and kaempferol in organic tomatoes were 79% and 97% higher than those in conventional tomatoes, respectively. Conventional farming uses mineralized nitrogen fertilizers, while organic crops receive nitrogen through manure application. The researchers suggest that the organic crops contained higher flavonoids due to the type of nitrogen available to the tomato plants. There was no significant difference in the crop yields between the two agricultural systems, but the organic plot had less year-to-year variation in crop yield than the conventional plots.

"The results of our study are intriguing, and warrant a closer look at the agricultural systems used across the United States," noted lead researcher, Alyson Mitchell, Ph.D., professor and food chemist in the Department of Food Science and Technology at the University of California-Davis. "Additional well-controlled studies like LTRAS will provide a much deeper understanding of the differences between organic and conventional crops."

Flavonoids are a class of bioactive plant compounds that help protect plants from UV-radiation, chemicals and other environmental stressors. In humans, flavonoids help protect cells against environmental insults that may contribute to chronic disease. Several population-based studies suggest that diets rich in flavonoids may help protect against cardiovascular disease, certain cancers and other age-related conditions, such as dementia. Maximizing the flavonoid content of fruits and vegetables could provide a public health benefit.

Tomatoes are one of the most common vegetables consumed in the U.S. diet. In 2003, Americans ate nearly 86 pounds of tomatoes and tomato products per person, making tomatoes one of the major contributors of several nutrients, such as vitamin C, lycopene and flavonoids in the U.S. diet. The major flavonoids in tomatoes include quercitin, narangenin and kampferol. Finding ways to boost the nutritional attributes of tomatoes could have a positive impact on the nutritional quality of Americans' diets.

These findings are good news for the organic food industry, which has long believed in and promoted the benefits of organic agriculture. For companies like Seeds of Change, a certified organic seed company and producer of organic pasta sauces and other foods, news around higher antioxidant contents in organic tomatoes supports its mission of preserving biodiversity and promoting sustainable agriculture.

"Based on the length and detail of the LTRAS project, these results are significant," said Mark Koide, president, Seeds of Change. "It shows great promise that over time, organic crops could provide superior nutritional benefits over conventional crops. We fully support continued research in agricultural systems as part of our long term commitment to producing nutritionally superior food products with scientific integrity."

Reference:

Mitchell AE, Hong YJ, Koh E, et al. Ten-Year Comparison of the Influence of Organic and Conventional Crop Management Practices on the Content of Flavonoids in Tomatoes. J Ag Food Chem 2007; doi: 10.1021/jf070344+ S0021-8561(07)00344-5. Accessed from internet on July 5, 2007.