Organic foods offer little benefit over conventionally farmed foods, a new review of existing research finds.

Crystal Smith-Spangler of Stanford University culled the scientific literature for research into the health benefits and risk of contamination among organic and conventional produce and meats.

An organic garden at Ashland High School in Ashland, Ore. (Julia Moore/AP)

Her review of 17 human studies and 223 evaluations of nutrient and contaminant levels in foods ranging from milk and grains to pork, beef and chicken detected mostly minor differences between organic and conventionally farmed versions.

Overall, her research, published Monday afternoon in the Annals of Internal Medicine, found little scientific evidence to support organic food’s superiority over conventionally farmed food. Among the mixed bag of chief findings:

- Eating organic produce instead of conventional produce may reduce risk of exposure to pesticides by 30 percent. But in general, both organic and conventional produce’s pesticide levels were within limits regarded as safe.

- Organic and conventional produce and animal products were at equal risk of being contaminated with potentially dangerous bacteria. And contamination of animal products, both organic and conventional, with salmonella and campylobacter bacteria was quite common.

- Conventionally farmed chicken and pork were more likely than organic chicken and pork to be contaminated with bacteria that were resistant to three or more antibiotics. It’s not clear how this may affect human health or how it relates to the greater issue of antibiotic resistance, the study notes.

- The only nutrient that organic produce supplied more plentifully than conventional produce was phosphorus. And that doesn’t really matter much, the study notes, as hardly anyone suffers from phosphorus deficiency.

- Weak evidence suggested that organic produce contained higher levels of phenols, which may have antioxidant properties, and that organic milk and chicken supplied more omega-3 fatty acids than conventional varieties.

The study notes a number of limitations, including a surprising lack of scientific research into the differences between these two categories of food. Further, existing studies are designed so differently that it’s hard to draw major conclusions from the current body of research, the study cautions.

Spangler acknowledges that there are other reasons to choose organic foods, including concerns for animal welfare and the environment and preference for the taste of such foods. But her study suggests that when it comes to nutrition and food safety, conventional food is on par with organic.

And it’s usually cheaper, too.