Scientists have recently begun to question whether the levels of ubiquitous natural components of plants, known as phenolic antioxidants, are lower in foods grown using "conventional" rather than in those using organic agricultural practices since conventional agriculture uses levels of pesticides and fertilizers that can result in a disruption of the natural production of plant-defense related metabolites. Differences between the content of phenolic metabolites in organically and conventionally produced fruits and vegetables suggest that organically grown produce may benefit human health more than corresponding conventionally grown produce.

In regard to the consumption of fruits and vegetables in general, studies consistently indicate an inverse correlation between their consumption and the risk of human cancers, cardiovascular disease, diabetes, and age-related declines in cognition. These chronic diseases are linked to the oxidation of critical cellular macromolecules (e.g. proteins, lipids, and DNA) by reactive oxygen species (ROS). Phenolic antioxidants are thought to neutralize ROS before they cause damage and lead to diseases. Additionally, reports by the World Health Organization and the Food and Agriculture Organization of the United Nations emphasize the role of foods and nutrition in the prevention of noncommunicable diseases and describe plant-derived phytochemicals in the prevention of heart disease and cancer. Thus, we can see the vital importance of the actual LEVEL of these phenolic antioxidants in our food.

Differences between the content of phenolic metabolites in organically and conventionally produced fruits and vegetables suggest that organically grown produce may benefit human health more than corresponding conventionally grown produce.

Fertilization is important when comparing organic and conventional agriculture. Organic fertilization does not provide as much nitrogen as conventional fertilizers. Nitrogen has the potential to influence the synthesis of phenolic antioxidants. There is a decrease in the concentration of phenolic antioxidants in plants with increasing nutrient availability. In general, theories state that high nutrient availability leads to an increase in plant growth and development, which commercial growers want, but a decrease in the production of expendable metabolites such as the phenolic antioxidants.

Recent studies have begun to examine how agriculture influences the production of phenolic antioxidants in plants. For example:

• Higher levels of total phenolics were found in organic peaches and pears when compared with their conventional counterparts.
• A study of five vegetables common in the Japanese diet demonstrated that organically grown spinach contained 120 percent higher antioxidant activity while Welsh onion, Chinese cabbage, and qing-gen-cai contained 20-50 percent higher antioxidant activity compared to their conventionally grown counterparts.
• In our own studies, we have found consistently higher levels of total phenolics and ascorbic acid in organic strawberries, marionberries, and sweet corn.

Recent, unpublished studies at the University of California Davis, have found higher levels of total phenolics, soluble solids, and ascorbic acid, as well as the flavonoid aglycone quercetin in two organically produced tomato cultivars.

Interestingly, the same differences were not seen in organic bell peppers grown concurrently with the tomatoes. This demonstrates the important point that differences in agricultural practices will not affect all plants and all secondary metabolites equally. Research is needed to determine whether differences in agricultural practices affect the levels of phenolic antioxidants in soybeans and in many other crops.

Contemporary literature illustrates an apparent trend toward higher levels of phenolic antioxidants, ascorbic acid, and soluble solids in organic foods. Clearly MUCH more research is needed-not only on the nutritional differences between organic and conventional agriculture, but also on the levels of phenolic antioxidants with their apparently vital importance in combating many chronic diseases.

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*Excerpted and edited from an original article "Organic Agriculture: Does It Affect Antioxidants and Nutritional Quality?" by Alyson E. Mitchell, PhD, and Alexander W. Chassy, BS, The Soy Connection, vol. 12, no. 4, Fall 2004.

The article is on the web in a *.pdf Acrobat Reader file at: www.talksoy.com/soyconnection

This article was sent to us by NOHA Honorary Member Beatrice Trum Hunter.

Article from NOHA NEWS, Vol. XXX, No. 2,Spring 2005, page 5.