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.
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.
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."
A Department of Health spokeswoman said: "Evidence has not yet emerged that there are nutritional benefits from eating organically produced foods compared to conventionally produced foods. We will continue to review research on this subject."
Article from: bbc.co.uk
Discovery.com reports :
The vast majority of studies that made it into the analysis looked at properties of food itself. And overall, the researchers report today in the journal Annals of Internal Medicine, results showed few differences in the content of vitamins, minerals, antioxidants, proteins or other nutrient measures.
The two groups did show some differences, though.
Organic produce contained more phosphorous than conventional versions, for example, though Brevata pointed out that phosphorous deficiency only occurs in people who are near starvation.
A few very small studies also suggested that organics contained higher levels of a type of antioxidant called phenols. And organic milk and chicken contained more omega-3 fatty acids than conventional varieties did, but Brevata added a caveat there as well: Omega 3s varied equally as much with brand and harvesting season.
Pesticide levels varied between the two groups, with conventional foods carrying a 30 percent higher chemical load than organics. Despite what sounds like a large difference, Brevata said, both groups were well below what are currently considered safe limits.
None of the studies showed that any particular kinds of produce contained more pesticides than others. And none looked systematically at the effects of washing or peeling.
Only 17 studies compared groups of people eating different diets, and most showed no difference on measures like sperm motility, levels of fatty acids in breast milk or antioxidant levels in blood.
Two studies looked at children and both showed higher levels of pesticides in kids who ate a greater proportion of conventional foods. But again, measurements in both groups of kids were well below concerning levels. And some studies showed that people were exposed to more pesticides from household use than from food.
Some research showed that conventional chicken and pork contained 33 percent more antibiotic-resistant bacteria than organic alternatives. It’s hard to translate those numbers into health outcomes, Brevata said, because cooking well kills even drug-resistant microbes.
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