Eat your vegetables -- and don't worry about whether they're organic. Fruits too.

That's the most important lesson from an extensive new study looking at four decades of research comparing the nutrition and safety of organic food to that of conventional food.

The report, produced by scientists at Stanford University, found that organic foods, including produce and meat, offer little health benefit beyond conventional foods. Organic produce didn't contain more nutrients. Nor was it safer from contamination with E. coli bacteria. The organic stuff did contain less pesticide residue, but pesticide readings on even the nonorganic produce were nearly always below federal safety thresholds. (Some organic produce contains pesticides as well, possibly from ambient sources.)

Organic foods are a big business in this country. Sales grew sevenfold from 1997 to 2011, when they reached $24.4 billion. Once a quirky feature of the counterculture, organic food is now sold at Walmart and other giant chains. To be called organic, foods have to meet a battery of government regulations banning hormones, synthetic pesticides and various other chemicals. These rules help make organic foods quite a bit more expensive than conventional foods.

Stanford physician Dena Bravata decided to launch the study because her patients repeatedly asked her if organic foods were more healthful. She did some reading and was unable to draw a clear conclusion.

To develop one, Bravata and her colleagues winnowed thousands of research papers down to 237, which they analyzed intensively. After four years of effort, the researchers were surprised that they were unable to find much health benefit from organics. There were almost no differences in vitamins, minerals, protein or fat. Nor could they identify specific fruits and vegetables that were clearly more healthful if organic. On the contrary, other variables seemed to matter more. It was more important for a fruit to be ripe than to be organic; ripe fruit is simply more nutrient-rich than unripe fruit, but being organic has no bearing.

Organic produce had more phosphorous, but that probably doesn't matter because most people get plenty from conventional foods. The researchers found limited evidence suggesting organic milk has more omega-3 fatty acids, which could be beneficial. Organic chicken and poultry, meanwhile, had less antibiotic-resistant bacteria, which sounds good except that cooking kills all kinds of bacteria anyway.

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Overall, the findings don't mean people should shun organic foods. It's possible that ingesting less pesticide, however small the reduction, can improve human health. Fewer pesticides in agriculture is probably good for the environment. The study didn't address hormones and antibiotics in non-organic milk and meat. And organic farming practices often go hand in hand with more humane treatment of animals.

But the Stanford study does imply that, in these difficult economic times, people needn't fret if they can't spare the extra expense associated with organic foods. Science has now confirmed common sense; far more important than eating organic is eating healthy. Hardly anyone can afford to do otherwise.