Jen Matlack's husband teases her about buying organic. It's not worth the extra money, he says, but she insists. A new study promises to add fuel to their marital quarrel. Published Monday in the Annals of Internal Medicine, it finds that organic produce has no more vitamins and minerals than conventionally grown produce. Mark one point for the hubby. But the study also confirms that organic produce is less likely to contain pesticides, the real reason Matlack says she buys organic. "We did find that organic produce, so fruits and vegetables, had a 30% lower risk of contamination with pesticide residues compared to conventional produce," said Dr. Crystal Smith-Spangler of Stanford University, the lead study author. The study, which used data from hundreds of previous studies, also looked at pork and chicken. Researchers found a 33% greater risk of antibiotic-resistant bacteria in non-organic pork and chicken, which they say "may be related to the routine use of antibiotics in conventional animal husbandry." They also found higher levels of omega-3 fatty acids in organic milk and chicken. "There are certain things I refuse to buy conventionally, knowing that there are a lot of chemicals in them," said Matlack, who has a 6-year-old daughter. "I feel like a better mom buying these particular foods." And it's not for nothing. <>b>Clarified: What does 'organic' mean? Smith-Spangler and her colleagues note that previous studies have shown lower levels of pesticides in the urine of children who eat organic foods compared with children who eat conventional foods. However, no studies have been conducted to determine specifically whether pesticides at these levels consumed by children actually cause harm, although other research has shown a correlation between higher levels of pesticides in pregnant mothers and reduced IQs and birth weights in their children. This back-and-forth evidence makes a parent's decision less than clear-cut. How common are pesticides? About 7% of organic produce and 38% of conventional produce across the U.S. and Europe contains detectable amounts of pesticides, according to this latest study. The U.S. Department of Agriculture says that in 2010, 59% of conventional produce in the U.S. contained detectable amounts of pesticides. That's after a proper washing, too. Although the USDA doesn't allow organic farmers to spray with pesticides, sometimes chemicals drift over from nearby crops, or produce is handled in the same warehouse as organic produce, says Sonya Lunder, senior analyst at the Environmental Working Group. Assessing the risks Experts say the mere presence of a pesticide doesn't paint a complete picture for consumers trying to determine health risks. The presence of pesticide residue is just one factor that determines risk, said Chuck Benbrook, a professor of agriculture at Washington State University. "The others are the level of the residue, the timing of exposures in terms of a person's life cycle, the tissues that are exposed, the pesticide's innate toxicity, what else the person is exposed to and the presence of any synergistic effects, and whether the individual has normal or constrained ability to metabolize and deal with the toxic insult caused by the residues." The dispute over organics in the home originates, at least in part, from the differing messages put out by institutions charged with protecting consumers. When Matlack got pregnant, she started paying attention to the Environmental Working Group, which says to avoid pesticides and warns that "young children and pregnant women are especially at risk." The American Academy of Pediatrics similarly says to "minimize using foods in which chemical pesticides or herbicides were used by farmers." Matlack's husband, Jefferson Kolle, takes a different approach. "I trust the FDA," he said. "I have to use something as my basis for making a decision. Oftentimes, I'm guided by my pocketbook." The FDA says that "levels of pesticide residues in the U.S. food supply are well below established safety standards." But the FDA limits on pesticides aren't designed to protect consumers from long-term exposure, says Alex Lu, a professor of environmental health at Harvard University. "Because humans are much bigger in terms of body weight, that amount of dose that kills insects will not kill humans right away, but the mechanism is the same," Lu said. The bottom line Smith-Spangler says her patients ask her whether they should buy organic to be healthier, and she tells them it's hard to say. "The decision to purchase organic is complex," she said. "Many factors go into it." She tells them what science is out there, but of course, money is a factor, too. The decision might be different for different people: Since fetuses and small children are growing so rapidly, they may be more vulnerable to harmful effects of pesticides and therefore might need "special consideration." "I buy both organic and conventional," Smith-Spangler said. In the absence of hard scientific data, Matlack and Kolle will continue to disagree about whether it's worth the extra money to buy organic for their daughter and themselves. "For me, it's just kind of obvious that I don't want to put any kind of chemicals in my body that I don't need to," Matlack said.