Organic tomatoes have more antioxidants

Is organic food healthier for you, after all? A 10-year study comparing organic tomatoes with those grown conventionally suggests that it may be. It's the kind of evidence that pro-organic groups have been desperate to dig up, as most studies have suggested otherwise.

According to the new findings, levels of the flavonoids quercetin and kaempferol were found to be on average 79 and 97 per cent higher, respectively, in organic tomatoes. Flavonoids such as these are known antioxidants and have been linked to reduced rates of cardiovascular disease, some forms of cancer and dementia, says Alyson Mitchell, a food chemist who led the research at the University of California, Davis.

Differences in soil quality, irrigation practices and the handling of harvested produce have made direct comparisons difficult in the past, says Mitchell. So in this study, due to be published in the Journal of Agricultural and Food Chemistry, the researchers used data from a long-term project in which standardised farming techniques are used to reveal trends in crop productivity.

Mitchell's team say the finding can be explained by the availability of nitrogen. Flavonoids are produced as a defence mechanism that can be triggered by nutrient deficiency. The inorganic nitrogen in conventional fertiliser is easily available to plants and so, the team suggests, the lower levels of flavonoids are probably caused by overfertilisation.

Nutrition spokesperson for Australia's Biological Farmers Association, Shane Heaton, said the research confirmed other studies showing organic apples, peaches, blackberries, strawberries and corn contained higher levels of antioxidants, minerals and vitamins. “If they don't have an artificial defence mechanism through pesticides and herbicides, they produce more of these compounds. The research adds to the growing body of compelling evidence that there are nutritional differences between organic and non-organic foods that will benefit the consumer,” he added.

Dietitians Association of Australia WA spokeswoman Denise Griffiths agreed the study added to evidence that organic produce was more nutritious but said more studies were needed to prove its health benefits.

New Scientist magazine (issue 2611) July 5, 2007
The West Australian July 10, 2007