HEALTH: Produce has been losing vitamins and minerals over the past half-century By Deborah K. Rich, Special to The Chronicle Saturday, March 25, 2006
The fruits and vegetables that our parents ate when they were growing up were more nutritious than the ones we'll serve our children tonight. On average, the produce we grow in the United States has lower levels of several vitamins and minerals today than it did 50 to 60 years ago. By growing or buying and eating organic produce, however, we can make up much of the difference. Organically grown fruits and vegetables are proving to have higher levels of anti-oxidants, vitamins and minerals than their conventionally grown counterparts.
Donald R. Davis, a research associate with the Biochemical Institute at the University of Texas, Austin, recently analyzed data gathered by the USDA in 1950 and 1999 on the nutrient content of 43 fruit and vegetable crops. He found that six out of 13 nutrients had declined in these crops over the 50-year period (the seven other nutrients showed no significant, reliable changes). Three minerals, phosphorous, iron and calcium, declined between 9 percent and 16 percent. Protein declined 6 percent. Riboflavin declined 38 percent and ascorbic acid (a precursor of vitamin C) declined 15 percent. A study of the mineral content of fruits and vegetables grown in Britain between 1930 and 1980 shows similar decreases in nutrient density. The decline in our produce's nutritional value corresponds to the period of increasing industrialization of our farming systems. As we have substituted chemical fertilizers, pesticides and monoculture farming for the natural cycling of nutrients and on-farm biodiversity, we have lessened the nutritional value of our produce. Integrated well-established organic farming systems can counter the decline. Good science comparing the nutritional value of organic and conventional foods is accumulating rapidly. It isn't uncommon for researchers to find that the higher nutrient levels in organic produce completely offset the declines Davis found in conventional produce. "What all our data shows," says Charles Benbrook, chief scientist at the Organic Center and a former executive director of the Board on Agriculture of the National Academy of Sciences, "is that whenever there's been a valid comparison between conventional and organic, organic is virtually never lower than conventional and, in a significant number of cases, it's higher. Sometimes it's significantly higher in several important nutrients." For example, Virginia Worthington, a clinical nutritionist who earned her doctorate in nutrition at Johns Hopkins, published a review in 2001 of 41 studies comparing the nutritional value of organic and conventional produce. After tallying the data across all the studies, Worthington concluded that organic produce had on average 27 percent more vitamin C, 21.1 percent more iron, 29.3 percent more magnesium and 13.6 percent more phosphorous than conventional produce. Benbrook released a review in 2005 of the research comparing antioxidant levels in conventional and organic foods. In humans, anti oxidants reduce damage to cells and DNA from free radicals (molecules generated by metabolic processes within the body), and thereby promote cardiovascular health, inhibit the reproduction of cancerous cells, slow the aging process in the brain and nervous systems, and lessen the risk and/or severity of Alzheimers, Parkinson's and Huntington's diseases. Benbrook found that in 85 percent of the comparable data points, produce from organic farms had higher levels of anti oxidants than did produce from conventional farms. On average, antioxidant levels in organic produce were 30 percent higher. Earlier this year, a Swedish team of scientists demonstrated that extracts from organically grown strawberries slowed the proliferation of colon and breast cancer cells to a significantly greater degree than extracts from conventional strawberries did. The levels of all the antioxidants analyzed by the team were higher in the organic strawberries than in the conventional. "As someone that has been involved with science and science policy for my whole life," says Benbrook, "I think the scientific case has been made for organic produce. The case has been made firmly enough so that it is appropriate and, indeed, irresponsible at this point not to tell consumers straight up that choosing organic fruits and vegetables probably delivers nutritional benefits because of the higher levels of antioxidants and vitamins and minerals." To read the full and extensive article go to http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/03/25/HOG3BHSDPG1.DTL
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