Healthy soil and sustainable growing

["TradingPostPaul" <tradingpost@riseup.net>]

http://environment.newscientist.com/article/mg19526114.900-organic-tomatoes-

have-more-antioxidants.html


Organic tomatoes have more antioxidants

    * 05 July 2007
    * NewScientist.com news service
    * Duncan Graham-Rowe


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.

Previous research has found no differences between organic and conventional
crops such as wheat or carrots. Meanwhile a study proclaiming that organic
milk had higher levels of omega-3 fatty acids failed to convince the UK's
Food Standards Agency (FSA), which pointed out that these short-chained
fatty acids do not have the health-promoting benefits offered by
long-chained omega-3 oils.

This latest study does not prove that a healthy diet must be organic. The
evidence of health benefits for flavonoids is conflicting, says Peter
Bramley at Royal Holloway, University of London. And even if such benefits
exist, higher flavonoid levels do not necessarily make organic food
healthier, says John Krebs, former chair of the FSA and now at the
University of Oxford. "This depends on the relevance of the differences to
the human body," he says. "Tomato ketchup has higher levels of lycopene
than either organic or conventional tomatoes. So if you wanted lots of
lycopene you should eat ketchup."

>From issue 2611 of New Scientist magazine, 05 July 2007, page 16