But organic options may live up to their billing of lowering exposure to pesticide residue and antibiotic-resistant bacteria, researchers from Stanford University and the Veterans Affairs Palo Alto Health Care System found.

"People choose to buy organic foods for many different reasons. One of them is perceived health benefits," said Dr. Crystal Smith-Spangler, who led the new study.

"Our patients, our families ask about, ‘Well, are there health reasons to choose organic food in terms of nutritional content or human health outcomes?'"

To try to answer that question, she and her colleagues reviewed over 200 studies that compared either the health of people who ate organic or conventional foods or, more commonly, nutrient and contaminant levels in the foods themselves.

Those included organic and non-organic fruits, vegetables, grains, meat, poultry, eggs and milk.

Many of the studies didn't specify their standards for what constituted "organic" food - which can cost as much as twice what conventional food costs - the researchers wrote Monday in the Annals of Internal Medicine.

According to United States Department of Agriculture standards, organic farms have to avoid the use of synthetic pesticides and fertilizers, hormones and antibiotics. Organic livestock must also have access to pastures during grazing season.

Many conventional farms in the U.S., in contrast, use pesticides to ward off bugs and raise animals in crowded indoor conditions with antibiotics in their feed to promote growth and ward off disease. The Food and Drug Administration has been examining that type of antibiotic use and its contribution to drug-resistant disease in humans.

SAME VITAMINS

Smith-Spangler and her colleagues 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 phosphorus in the organic products.

Organic milk and chicken may also contain more omega-3 fatty acids, they found - but that was based on only a few studies.

There were more significant differences by growing practice in the amount of pesticides and antibiotic-resistant bacteria in food.

More than one-third of conventional produce had detectable pesticide residues, compared to seven percent of organic produce samples. And organic chicken and pork was 33 percent less likely to carry bacteria resistant to three or more antibiotics than conventionally-produced meat.

Smith-Spangler told Reuters Health it was uncommon for either organic or conventional foods to exceed the allowable limits for pesticides, so it's unclear whether a difference in residues would have an effect on health.

But Chensheng Lu, who studies environmental health and exposure at the Harvard School of Public Health in Boston, said that while the jury is still out on those effects, people should consider pesticide exposure in their grocery-shopping decisions.

"If I was a smart consumer, I would choose food that has no pesticides," Lu, who wasn't involved in the new study, told Reuters Health. "I think that's the best way to protect your health."

He said more research is necessary to fully explore the potential health and safety differences between organic and conventional foods, and that it's "premature" to conclude organic meat and produce isn't any healthier than non-organic versions.

"Right now I think it's all based on anecdotal evidence," Lu said.

SOURCE: bit.ly/PShmuj Annals of Internal Medicine, online September 3, 2012.

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