Eating organic food will not make you healthier, according to researchers at
Stanford University, although it could cut your exposure to pesticides.
They looked at more than 200 studies of the content and associated health gains
of organic and non-organic foods.
Overall, there was no discernable difference between the nutritional content,
although the organic food was 30% less likely to contain pesticides.
Critics say the work is inconclusive and call for more studies.
The research, published in the journal Annals of Internal Medicine, looked at
17 studies comparing people who ate organic with those who did not and 223
studies that compared the levels of nutrients, bacteria, fungus or pesticides
in various foods - including fruits, vegetables, grains, meats, milk and eggs.
Start Quote
There isn't much difference between organic and conventional foods, if you're
an adult and making a decision based solely on your health
Dr Cyrstal Smith-Spangler Lead researcher
None of the human studies ran for longer than two years, making conclusions
about long-term outcomes impossible. And all of the available evidence was
relatively weak and highly variable - which the authors say is unsurprising
because of all the different variables, like weather and soil type, involved.
Fruit and vegetables contained similar amounts of vitamins, and milk the same
amount of protein and fat - although a few studies suggested organic milk
contained more omega-3.
Organic foods did contain more nitrogen, but the researchers say this is
probably due to differences in fertiliser use and ripeness at harvest and is
unlikely to provide any health benefit.
Their findings support those of the UK's Food Standards Agency, which
commissioned a review a few years ago into organic food claims.
Organic
Organic food is produced to standards designed to keep the production more
"natural", using environmentally and animal-friendly farming methods
Fewer, if any, chemicals are used and most pesticides are banned or very
carefully controlled
Various bodies in the UK, including the Soil Association, certify food and
producers as organic
Food certified as organic is not allowed to contain genetically modified
ingredients
Prof Alan Dangour, of the London School of Hygiene and Tropical Medicine, who
carried out that work, said: "Consumers select organic foods for a variety of
reasons, however this latest review identifies that at present there are no
convincing differences between organic and conventional foods in nutrient
content or health benefits.
"Hopefully this evidence will be useful to consumers."
Dr Crystal Smith-Spangler, the lead author of the latest review, said there
were many reasons why people chose to eat organic, including animal welfare or
environmental concerns.
"Some believe that organic food is always healthier and more nutritious. We
were a little surprised that we didn't find that.
"There isn't much difference between organic and conventional foods, if you're
an adult and making a decision based solely on your health."
But the Soil Association said the study was flawed.
"Studies that treat crop trials as if they were clinical trials of medicines,
like this one, exaggerate the variation between studies, and drown out the real
differences.
"A UK review paper, using the correct statistical analysis, has found that most
of the differences in nutrient levels between organic and non-organic fruit and
vegetables seen in this US study are actually highly significant."