There is little evidence organic foods are more nutritious than conventional products, according to a study from Stanford University in the US.

STANFORD has claimed the “most comprehensive meta-analysis to date” of studies comparing organic and conventional foods concluded there was not “strong evidence that organic foods are more nutritious or carry fewer health risks than conventional alternatives”.

Crystal Smith-Spangler, one of the Stanford team that carried out the study, said yesterday (4 September): “Some believe that organic food is always healthier and more nutritious. We were a little surprised that we didn’t find that.”

The study echoed a 2009 study from the UK’s Food Standards Agency, which claimed organic food gave consumers “no additional health benefits”.

The review, which looked at over 230 papers, concluded consuming organic foods could reduce the risk of pesticide exposure but said such produce was not always free of pesticide and all food fell within “allowable safety limits”.

Stanford said two studies of children consuming organic and conventional diets did find lower levels of pesticide residues in the urine of children on organic diets, though the significance of these findings on child health is unclear. Organic chicken and pork appeared to reduce exposure to antibiotic-resistant bacteria, but the clinical significance of this is also unclear, the university said.

The US organic industry, which has seen sales continue to rise in recent years despite the economic downturn, emphasised the pesticide findings. The Organic Trade Association said the Stanford review confirmed the “health benefits” that over three-quarters of US families choosing organic foods seek.

“Consumers seeking to minimise their exposure to pesticide residues will find that foods bearing the USDA Organic label are the gold standard. This is because organic foods have the least chemicals applied in their production and the least residues in the final products,” said Christine Bushway, executive director and CEO of the Organic Trade Association. “And, because organic livestock practices forbid the use of antibiotics, including the routine use of low-level antibiotics for growth, organic meat contains less antibiotic-resistant bacteria.”

The Ota noted the Stanford researchers did cite higher levels of “total beneficial phenols in organic produce, omega-3 fatty acids in organic milk and chicken, and vaccenic acid in organic chicken.

Bushway said the link between farming practices and the nutritional profile of food was an “emerging research topic”. She added: “We are optimistic that in the future, good applied scientific research on organic food and farming will show that healthy soils produce healthy foods.”

The Stanford researchers noted the “limitations” with their review, including the differences in testing methods, factors affecting food like the weather and “great variation” in farming.

“Our goal was to shed light on what the evidence is,” said Smith-Spangler. “This is information that people can use to make their own decisions based on their level of concern about pesticides, their budget and other considerations.”

Dena Bravata, the senior author behind the review, added: “If you look beyond health effects, there are plenty of other reasons to buy organic instead of conventional.” She listed taste preferences and concerns about the effects of conventional farming practices on the environment and animal welfare as some of the reasons people choose organic products.