Organically Grown Tomatoes Have Higher Antioxidant Content
SANTA FE, N.M., -- 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
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'
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."