Although organic bodies frequently complain about the amount of research funding which goes
into comparing sustainable farming techniques with conventional ones, they make be thankful
this week given the findings of comparative research published in open source journal PLOS One.
The study, by researchers at the University of Ceara in Brazil, suggests that tomatoes grown on
organic farms accumulate higher concentrations of sugars, vitamin C and ‘plant phenols,’ compounds
associated with combating certain diseases, than conventionally grown tomatoes.
Dr Maria Raquel Alcantara Miranda, who led the research, compared the weights and biochemical
properties of organic and conventional tomatoes grown within 1.5 Km of one another and in similar
natural conditions; working with a team of scientists, she discovered that although organic fruits
were around 40 percent smaller than their conventionally grown equivalents, they accumulated more
healthy material. The team suggested this difference in the fruits’ make-up could be the result of
stressful growth conditions, as the healthy compounds are “linked to stress resistance.”
Concentrations of vitamin C were over 50 percent higher in some organic tomatoes and the fruits
contained up to twice the levels of ‘healthy’ compounds, compared to conventional tomatoes.
According to Dr Alcantara Miranda, organic farming exposes plants to greater stress than conventional
farming, and this increased stress may be behind the increased anti-oxidant and vitamin content. She
suggested that, whereas chemical inputs may reduce stressors, allowing for some benefits, the fact
that organic produce is more exposed means fruits are hardier and can potentially pass on their health
benefits to humans.
In addition to external stressors, the organic fertilisers used on organic crops may contribute to the
development of healthy compounds, as they tend to release nitrogen at a slower rate than do synthetic
fertilisers, slightly stressing the plant.
Based on their observations, Dr Alcantara Miranda and her team suggest that growing strategies for
fruits and vegetables should aim to balance plant stress with efforts to maximize yield and fruit size,
rather than trying to eliminate stress to increase yields.
The recommendations tie in with calls from organic and agroecology aficionados, who have criticised
government and institutional research policy for focusing on ‘organic vs. conventional,’ which they say
is to everyone’s detriment as it prevents knowledge transfer and moves towards developing more resilient
In spite of the Ceara scientists’ findings, expert opinion differs on whether organic food really is healthier
than conventional produce. Although another study published in PLOS One in 2010, and funded by the US
Department of Agriculture, found that “Organic strawberry farms produced higher quality fruit and that their
higher quality soils may have greater microbial functional capability and resilience to stress,” research by
the American Academy of Paediatrics and Stanford University, both released last year, found little evidence
of health benefits from eating organic.
However, both 2012 studies did concede that eating organic would reduce exposure to pesticides in food.