Researchers at the Stanford University Medical School conducted the most comprehensive independent study to date—“Are Organic Foods Safer or Healthier Than Conventional Alternatives”—in 2012. For their study, the researchers sifted through thousands of papers and identified 237 of the most relevant to analyze. They found nothing to support the notion that organic food, on the whole, is safer or more nutrient dense or vitamin rich. The researchers found organic food had a 30 percent lower risk of pesticide residues but the residue levels on the conventional foods was well within safety limits.

“Some believe that organic food is always healthier and more nutritious. We were a little surprised that we didn’t find that,” said Crystal Smith-Spangler, a Stanford Medicine instructor and one of the paper’s authors.

The only nutrient found to be significantly higher in organic food was phosphorous, but that was considered an inconsequential advantage, since few people have phosphorous deficiency.

The Stanford findings echoed a review of 137 studies drawn from more than 50,000 papers  covering 50 years of research by scientists from the London School of Hygiene and Tropical Medicine published in the American Journal of Clinical Nutrition in 2009. The study was commissioned by the UK Food Standards Agency. The group’s blunt conclusion: “there is no evidence of a difference in nutrient quality between organically and conventionally produced foodstuffs.”

In December 2016, the research arm of the European Parliament released a wide-ranging report examining existing scientific evidence regarding various aspects of organic food and agriculture. The report noted that often, people who eat organic foods are the same people who have healthier diets to begin with, making it difficult to gauge the impact of organic foods on individual health. The report largely acknowledged that there no proven advantages of organic foods:

In conclusion, there is a lack of data from well-designed studies (prospective, long-term duration, accurate data in particular for dietary factors and sources, i.e. conventional or organic) involving a sufficiently large population.

However, the report also offered its support for the idea that organics offer an advantage over conventional foods in terms of exposure to pesticides:

Although the scientific evidence is incomplete, substantial data point to the developing brain being extremely vulnerable to pesticide exposure…As a consequence of reduced pesticide exposure, organic food consequently contributes to the avoidance of health effects and associated costs to society, as well as other hidden and external costs related to pesticide use, as recently reviewed and suggested to be greatly underestimated.

There also have been a few studies claiming that organic foods offer some nutritional benefits.

Two meta-studies, on organic meat and milk, published in the British Journal of Nutrition in February 2016, claimed that organic milk and meat had more omega-3 fatty acids, a debatable benefit; organic meat had lower concentrations of acids linked to cardiovascular disease; and a few other minor differences of questionable benefit. Helpful higher iodine levels were found in conventional foods and organic milk yields were 23% lower.

Newcastle University professor of ecological agriculture Carlo Leifert, who oversaw the meta-studies in cooperation with Charles Benbrook, a US-based economist formerly with Washington State University, claimed the studies were “further evidence

of the health benefits of organic food,” and should prompt people to reconsider their food choices.

The conclusions echoed an almost identical set of claims made by a researcher team led by Leifert and Benbrook in a 2014 British Journal of Nutrition paper. Their review of 340 studies found organic crops had higher antioxidants, lower cadmium concentrations and lower incidence of pesticide residue.

The studies were widely criticized by scientists, who claimed the researchers selectively used data and presented contested claims of health benefits as if they were part of a scientific consensus.

Many of the researchers involved in the Leifert study have connections to the organic industry. Leifert owns an organic farm in Greece and is a vocal public advocate for the claim that organic foods provide substantial health benefits when compared to conventional products.

Benbrook, who lost his adjunct professor job at WSU in 2015, had 100% of his research cited in this meta-review financed by the organic industry. He is now a consultant, most recently for the Environmental Working Group, a critic of conventional farming and crop biotechnology, and has joined the board of the The Organic Center, the research arm of the Organic Consumer Association (OCA), the organic industry’s most prominent trade and lobby group. From 2004-2012, he was “chief scientist” with the Organic Center although he is not a scientist but an economist, and won the organization’s first “Award of Excellence for supporting the science behind the benefits of organic food and farming”–before revelations emerged that his research while at WSU was 100% funded by the organic industry. He is now on the Center’s “science advisory” board.

The study itself was funded significantly by the organic industry: “The European Commission, the executive body of the European Union, and the Sheepdrove Trust, a British charity that supports organic farming research, paid for the analysis, which cost about $600,000,” according to the New York Times.

One other study finding significant benefits for organic foods: a 2008 white paper overseen by Benbrook for OCA’s The Organic Center. The team reviewed 97 published studies, concluding that “organically grown plant-based foods are 25% more nutrient dense, on average, and hence deliver more essential nutrients per serving or calorie consumed.”

There is no independently produced evidence in the scientific literature that organic foods offer any consistent material nutritional or safety advantages over conventional foods. Some claimed advantages, like higher levels of antioxidants or omega-3 fatty acids or phenols, may not be advantages at all, say scientists. Other differences may be the result of whether a cow was grass fed or grain fed and have nothing to do with whether it was raised organically. Claims that organic crops are more “nutrient dense” have not been consistently supported in independent studies.

On the subject of pesticide residue in foods, scientists agree that conventional foods are more likely to contain higher levels of residues.

Stanford’s analysis, for example, found that organic food had 30 percent lower residues than conventional foods. All of the conventional foods had pesticide levels well within global safety standards. In other words, the level of found residues are so small, mainstream scientists say, that there are no meaningful health differences linked to residues.

There is another important caveat. The test for pesticide residue only detects common synthetic pesticides. It does not test for organic pesticides. Many organic pesticides biodegrade quickly and leave almost no residues (as do many synthetics) but some copper based pesticides, commonly used on organics, don’t biodegrade at all and are very carcinogenic. Organic foods also contain significantly higher levels of e. coli and other bacteria, in part because of the use of processed fecal material as fertilizer.