Organic meat and produce are not any healthier for consumers than conventional or non-organic foods despite the higher costs, according to new research by Stanford University.
"People choose to buy organic foods for many different reasons. One of them is perceived health benefits," said Crystal Smith-Spangler, who led the research team from Stanford and the Veterans Affairs Palo Alto Health Care.
"Our patients, our families ask about, 'Well, are there health reasons to choose organic food in terms of nutritional content or human health outcomes?'"
The researchers looked at 237 studies that compared either the health of people who ate organic or conventional foods, or, more commonly, nutrient and contaminant levels in the foods such as bacterial, fungal or pesticide contamination.
The foods included organic and non-organic meats, poultry, eggs, milk, fruits, vegetables and grains.
The researchers found there was no difference in the amount of vitamins in plant or animal products produced organically and conventionally - and the only nutrient difference was slightly more phosphorous in the organic products.
The research did find that more than one third of conventional produce had detectable pesticide residues, compared with 7 percent of organic produce. Organic pork and chicken were 33-percent less likely to carry bacteria resistant to three or more antibiotics than conventionally raised meat.
The researchers said it was uncommon for either organic or conventional foods to exceed the allowable limits for pesticides, so it is unclear whether a difference in residues would have an effect on consumers' health.
The Environmental Working Group, an environmental organization that focuses on public health and the environment, has criticized the study and believe the differences are much greater than the study suggests.
Other scientists believe more research is needed to fully explore the potential health and safety differences between organic and conventional foods.