Organic farming can increase antioxidant levels

Nutrition Health Review, Summer, 2004

The Organic Center's second State of Science Review concludes that organic farming methods have the potential to elevate average antioxidant levels, especially in fresh produce.

Charles Benbrook, Ph.D., compiled and analyzed existing scientific information for his report, "Elevating Antioxidant Levels Through Organic Farming and Food Processing." The report reveals that, on average, antioxidant levels were about 30 percent higher in organic food than in conventional food grown under the same conditions.

The report's findings are particularly useful for consumers who wish to consume higher levels of antioxidants in fresh fruits and vegetables without additional caloric intake. The U.S. Department of Agriculture (U.S.D.A.) is currently recommending higher daily intakes of fruits and vegetables, especially those that are antioxidant-rich.

The report's tables include rankings of common foods according to their total antioxidant capacity per calorie and per typical serving. Consumers who seek out foods high in antioxidant content can meet recommended antioxidant intake levels with less than 10 percent of their daily caloric intake.

"Because of the many potential health benefits associated with antioxidant consumption, increasing average daily antioxidant intake through the diet has emerged as an important health goal," says Dr. Benbrook. "This goal was a major factor shaping the new U.S.D.A. Dietary Guidelines for Americans, which increase the average recommended intake of fruits and vegetables to at least nine servings per day from the original five. By generating higher concentrations of antioxidants in fresh produce and other organic foods, organic farming can help people increase their daily consumption of antioxidants without a proportional increase in calories."

This report reviews, among other data, 15 quantitative comparisons of antioxidant levels in organic versus conventional fruit and vegetables. Organically grown produce demonstrated higher levels in 13 of 15 cases. The organic crops contained about one-third higher antioxidant or phenolic content than comparable conventional produce.

Several studies found levels of specific vitamins, flavonoids, or antioxidants in organic foods to be two or three times the level found in matched samples of conventional foods. In studies making direct comparisons of levels of antioxidants in organic versus conventional produce, higher levels are often found in organic produce, but the converse is rarely true.

Organic Farming Techniques Can Increase Antioxidant Content

A wide range of factors can influence the mix of antioxidants that a plant manufactures as well as the levels the plant produces at any given point. In general, factors that impose stress on plants tend to trigger a plant's innate defense mechanisms and these mechanisms are driven by or entail the synthesis of antioxidants.

The studies reviewed provide evidence that several core practices on organic fruit and vegetable farms--the use of compost, cover crops, slow-release forms of nitrogen--van increase antioxidant and polyphenol content compared to conventional practices that depend on commercial fertilizers and pesticides. The prohibition of pesticides in organic farming practices provides additional benefits to consumers.

"Harvesting fruits and vegetables at optimal ripeness and consuming them in less-processed forms, without removing skins or peals, will preserve a greater portion of their antioxidants," says Dr. Benbrook. "The outer layers of fruits and vegetables generally contain the highest concentrations of antioxidants, but many consumers peel their conventionally grown fruits and vegetables to help reduce levels of pesticide residues. Seeking out organic produce can therefore deliver a dual benefit to consumers by maximizing antioxidant intake and minimizing pesticide dietary exposure."

Organic Processing Methods May Preserve Nutrients

There are significant differences between some of the food-processing methods and technologies used in manufacturing conventional foods in contrast to those allowed and used in producing organic processed foods. Some of these differences are known to affect antioxidant levels.

For example, the synthetic chemical hexane is often used in extraction of oils from crops in conventional oil processing plants, and it is prohibited in organic oil processing. Hexane promotes the removal of certain antioxidants.

High-temperature and high-pressure processing techniques also tend to remove significant portions of the antioxidants present in fresh foods. Organic processing plants often use lower pressure, cold-pressing methods to extract juices and oils. The resulting food products are generally richer in flavor and retain more nutrients, including antioxidants.

(Sources: Organic Center for Education and Improvement, January 26, 2005; U.S.D.A.)