FOSTER, R.I. January 26, 2005—The Organic Center's second State of Science Review (SSR) 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 compared to conventional food grown under the same conditions. An executive summary and the entire report can be found at:
The report findings are particularly useful for consumers who wish to consume higher levels of antioxidants in fresh fruits and vegetables, without additional caloric intake. The USDA is currently recommending higher daily intake of fruits and vegetables, especially those that are antioxidant rich. The report 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 Benbrook. "This goal was a major factor shaping the new USDA 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 had higher levels in 13 out of 15 cases. On average, the organic crops contained about one-third higher antioxidant and/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.
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 innate defense mechanisms and these mechanisms are driven by and/or entail the synthesis of antioxidants.
Studies reviewed in this SSR provide evidence that several core practices on organic fruit and vegetable farms—use of compost, cover crops, slow release forms of nitrogen—can 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 who choose organic.
"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 Benbrook. "The outer layers of fruits and vegetables generally contain the highest concentrations of antioxidants, but many consumers peal 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."
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 have an impact on antioxidant levels. For example, the synthetic chemical hexane is often used in extraction of oils from crops in conventional oil processing plants, but is prohibited in organic oil processing. Hexane is known to promote removal of certain antioxidants.
High-temperature and high-pressure processing technologies 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.
Though there is much more to learn, the current state of science supports the conclusion that organic farming methods can and often do result in higher antioxidant levels in fruits and vegetables. This health benefit for consumers joins the list of other well-documented reasons to buy organic, including the reduction of farm worker and consumer exposures to pesticides, the impacts of pesticides on the environment, and the prevention of problems associated with hormone and antibiotic use in livestock farming. Many consumers report that they enjoy the richer flavors in organic food and instinctively sense that organic foods are better for them; this SSR confirms that there are good reasons to focus additional scientific resources on gaining a more comprehensive understanding of the taste and health-oriented benefits associated with elevating average antioxidant levels in food.
Research on antioxidant levels in organically grown food is among the Organic Center top research priorities. The Center has initiated and funded three new research projects in 2004 focused on the impact of organic farming methods and food processing technologies on the antioxidant content of food.
Click here to download a pdf version of the SSR's Executive Summary (6 pages)
Click here to download a pdf version of the full Antioxidant SSR (81 pages)
Click here to download the SSR bibliography with full abstracts in pdf format (273 references; 136 pages)
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