Researchers say, when it comes to nutrition, there’s no difference whether patients consume organic or conventionally produced foods.
A review of more than 50 studies found no difference in nutrient content — including vitamin C, calcium, potassium, and zinc — between the types of food, Alan Dangour, PhD, of the London School of Hygiene & Topical Medicine, and colleagues reported.
The study appears in the September 2009 issue of the American Journal of Clinical Nutrition.
Marion Nestle, PhD, MPH, an expert on nutrition and food studies at New York University, disputed the scope of the findings.
“Plenty of studies have shown organics to have higher levels of nutrients,” she said. “Nutrient levels ought to be higher in plants grown on better soils.”
The “organic” label is reserved for farms that limit pesticide and herbicide use in crops and drug use in livestock.
Organic foods are typically more expensive, but sales have been booming because of the perception that they’re healthier than conventionally produced foods.
So, to determine whether there is a difference in nutritional benefits, the researchers conducted a review of 55 studies published between Jan. 1, 1958 and Feb. 29, 2008.
They evaluated foods’ nutrient content, including vitamin C, phenolic compounds, magnesium, potassium, calcium, zinc, copper, and total soluble solids.
They found no evidence of a difference between organic and conventional crops in terms of eight of those nutrient categories.
Conventional crops contained more nitrogen, while organics had more phosphorus and greater acidity.
The researchers said the differences were likely due to differences in fertilizer use and ripeness of fruits and vegetables at harvest.
But they said it’s “unlikely that consumption of these nutrients at the levels reported in organic foods in this study provide any health benefit.”
Nor did the researchers find nutritional differences with regard to animal-source foods — although they noted that there were far fewer studies on these foods compared with produce. That made analysis was more limited, they said.
Also, the researchers did not include an analysis of contaminants or chemical residues used in the food products.
Chemical fertilizer, herbicides, and pesticides may also affect the chemical content of foods, they said, and the organic foods may have an advantage because of their controlled use of chemicals and medicines. That warrants further study, the researchers said.
Niyati Parekh, PhD, professor of nutrition at New York University who was not involved in the study, said the findings regarding nutritional content are not surprising. The larger concern with organic versus nonorganic foods is chemical content.
“The person who spends the extra $5 to buy organic is not doing it for the nutrients,” Dr. Parekh said. “They’re concerned with the chemicals.”
She said there is not a large body of literature on the chemical content of organic versus nonorganic food because organic labeling is still a “gray area.”
“No one has defined what organic is,” Dr. Parekh said. “Until we do that, it’s hard to study.”
Maria Romano, MS, RD, clinical nutritionist for adult oncology at Montefiore Medical Center in New York, said that even though they’re difficult to design and execute, studies comparing organic and nonorganic products are important.
“We know pesticides pose a risk to human health even in small doses, or those considered safe by industry,” she said. “They can have toxic effects and in the long term can contribute to cancer.”
Meanwhile, Dr. Nestle emphasized that “organics aren’t about nutrients. They are about cleaner and more sustainable production methods,” including “lower levels of pesticides and herbicides, which seems like a good idea.”
The authors noted the possibility of reporting bias, which is a potential limitation of systematic reviews.
The study was supported by the UK Food Standards Agency.
The researchers reported no conflicts of interest.
Primary source: American Journal of Clinical Nutrition
Dangour AD, et al “Nutritional quality of organic foods: A systematic review” Am J Clin Nutr 2009; DOI: 10.3945/ajcn.2009.28041.