Recent reports in much of the media have called into question whether organic food is actually more nutritious than food grown by conventional means. Reporting on a 2009 study in the Journal of Clinical Nutrition the Washington Post stated "the researchers found that organically produced food offered no nutritional advantages over conventionally produced foods." The article finished by stating "organic food might not make so much sense after all." Similarly, the Chicago Sun-Times reported "sorry organic food lovers: A comprehensive review of published research has found no evidence that organic foods are any richer in nutrients than conventionally produced food." In fact, most of news outlets reported basically the same thing.
But is there really no evidence?
In 2001, the French Agency for Food Safety performed an exhaustive and critical evaluation of the nutritional and sanitary quality of organic food. An expert working group of more than 50 people examined papers on well-defined and certified organic procedures. The main characteristics of organic agriculture entails the respect for the environment and animals, promotion of sustainable cropping methods, use of non-chemical fertilizers and control of pests, diseases, and weeds, and no use of genetically modified (GM) crops. After 2 years of work a final consensus report was issued in 2003. A review of this work was recently published in Agronomy for Sustainable Development Journal.
The group found that fruits mineral composition was not noticeably different than conventional growing. However, regarding vegetables there was a trend observed for higher levels of iron and magnesium. "In a recent review, it was estimated that organic crops overall contain 21% more iron and 29% more magnesium that their conventional counterparts."
Fruits and vegetables contain a large variety of micronutrients such as polyphenols, resveratrol, and carotenoids. Their compounds have been shown to be involved in the prevention of certain diseases such as cancers and diseases that involve chronic inflammation. "For phenols and polyphenols, a majority of studies showed higher levels in organic foodstuffs such as apple, peach, pear, potatoes, onion, tomato, pepper, orange, and olive oil." It was also estimated in a recent review that "organic plant food overall contain double the amount of phenolic compounds."
Salicylic acid is an active anti-inflammatory compound that is found in aspirin. "The median content of salicylic acid in organic vegetable soup was higher than in compared non-organic ones. Organically grown tomatoes also have a higher salicylic acid content than conventional ones."
Conventional agriculture makes frequent use of pesticides, fungicides, and herbicides. These chemicals have been shown to have a significant impact on the environment and land workers' health. Studies have also shown that these chemicals can also have an impact on human health. "Because these molecules have a high toxic capacity (including mutagenesis and carcinogenesis) and the long-term effects of chronic low-dose ingestion are not known in humans, the consumer and scientific concern about possible health damage is real."
The authors found convincing evidence that organic grown foods have a "real advantage" over conventional grown crops in the amount of toxic residues. "The vast majority (97.4%) of organic farming products do not contain detectable pesticide residues." In a one study performed on vegetables and strawberries "did not show any contamination of organic ones, while 17-50% of conventional ones contained residues."
Nitrates are a matter of concern for public health because they are easily transformed into nitrites. Nitrites can be converted into nitrosamines which are potent cancer-promoting chemicals. Because of this concern, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) set a maximum daily intake of nitrates to 3.7 mg/kg. The review found that composting compared with chemical fertilizers lead to a lower amount of nitrate accumulation in most vegetables such as lettuce, potato, carrot, turnip, leek, beet, and spinach. "Organic vegetables can overall contain at least 30-50% less nitrates than conventional ones."
This review based on the available scientific literature showed that organic plant products contain an increased amount of iron and magnesium and increased anti-oxidant micronutrients. The vast majority (94-100%) of organic food does not contain any pesticide residue and contains about half the nitrates. The author concludes "this critical literature review indicates that organic agriculture, as developed until now, has the potential to produce high-quality products with some relevant improvements in terms of anti-oxidant phytomicronutrients, nitrate accumulation in vegetables and toxic residue levels."
Source: Denis Lairon, "Nutritional quality and safety of organic food. A review", Agronomy for Sustainable Development Journal, July 2009