(RxWiki News) If you pay extra to eat organic food, why do you do it? Is it mostly because you want something more nutritious or mostly because you want to avoid pesticides?
A recent study has found that people who eat organic food are less likely to have pesticide residue on their food.
But organic food doesn't appear to have any more nutrients in it than nonorganic food.
"Wash and cook your food thoroughly."
The study was conducted by Crystal Smith-Spangler, MD, of the Stanford Center for Health Policy and the Center for Primary Care and Outcomes Research at Stanford University, and twelve colleagues, funded by a Stanford grant.
The researchers conducted a survey of the MEDLINE, EMBASE, CAB Direct, Agricola, TOXNET and Cochrane Library databases and retrieved 17 studies involving humans and 223 studies of the nutrient and contamination levels in organic and non-organic foods.
Overall, the researchers found no evidence that organic food contains more nutrients or is otherwise more nutritious than non-organic food.
They did find that people appear less likely to consume pesticide residue and antibiotic-resistant bacteria if they eat organic food, which is grown without pesticides.
The likelihood of consuming food with a disease-causing germ like E. coli is approximately the same, regardless of whether a person is eating organic food or more conventional food.
Since people choose organic food for different reasons — from taste to avoiding chemicals to environmental concerns — this study only provides useful information for a handful of concerns about organic versus inorganic food.
Specifically among the human studies, only three included data on health conditions of the participants. There were no differences in the amount of allergies, such as eczema and wheeze, that people experienced between organic and nonorganic food.
Both organic and nonorganic food were also associated with about equal rates of infection from the bacteria Campylobacter, one of the most common causes of food poisoning in the U.S.
Two of the studies reported lower levels of pesticide in the urine of children who ate organic food instead of nonorganic food.
However, the level of nutrients were about equal in the blood, urine, breast milk and semen of adults tested. The studies focused specifically on vitamin A, vitamin C, vitamin E and beta-carotene.
The 223 studies of food included 153 studies of fruits, vegetables and grains and 71 studies of meats, poultry, milk and eggs. A total of 70 percent of these studies were from Europe, and 21 percent were from the U.S. or Canada.
The researchers found pesticide residue on 7 percent of the organic food and on 38 percent of the nonorganic food. They also found that conventional chicken and pork had a 33 percent higher risk of having bacteria that is resistant to three or more antibiotics.
However, there was little difference between organic and nonorganic food in terms of the reduced risk of consuming pesticide residues above the maximum allowable limits.
One study found the risk at 2 percent for conventional food and 6 percent for organic food. Another found the risk at 1 percent for both types of food.
In other words, people are about as unlikely to eat something with an unsafe level of pesticide on it with nonorganic food as with organic food.
The biggest limitation of the research was how different each of the studies were included in this review. Most of the studies were short-term, few included human health outcomes and they were conducted using very different methods with food grown in very different conditions.
The authors also noted that there may be "publication bias" among these studies. Publication bias means that a journal might be more likely to publish a study that has certain findings instead of a study with opposite findings.
"The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods," the authors wrote. "Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria."
According to a Nielsen report in 2010, 40 percent of the 27,000 people surveyed across the world buy organic fruits and vegetables, and 76 percent of them do so because they believe organic food is "healthier," and 51 percent said they do because it's "more nutritious."
Another 53 percent eat organic in part because they can avoid pesticides and other toxins.
This study found that there is not evidence in the literature to support the nutritious claim, but there is to support the pesticide claim.
Other reasons people buy organic, which were not addressed in this study but are mentioned in the Nielsen report, are believing it is better for the environment and it is better for farm workers and their working conditions.
According to the U.S. Department of Agriculture, organic food generally costs more than conventional food, sometimes up to twice as much.
The study was published September 4 in the Annals of Internal Medicine. The research was funded by a Stanford Undergraduate Research Grant to one of the authors. The authors declared no conflicts of interest.