It makes intuitive sense that organic food could be healthier than conventionally raised foods. After all, conventional farming grows food primarily by delivering the right ratio of a handful of nutrients -- nitrogen, phosphorus and potassium -- directly to plants in the form of fertilizer, while organic farming is all about creating healthy living soil, which you might imagine is more complex and nutritious. Some studies, and advocates, have found hints that organic food is more healthy... but a new report, which its authors bill as the most comprehensive to date, says otherwise.
The study, published in The American Journal of Clinical Nutrition, is the first "systematic review of the available published literature," according to the authors from the London School of Hygiene & Tropical Medicine.
The authors found no statistical difference in nutritional content in 10 of the 13 nutrient categories studied, and chalked up any differences that were noted to use of fertilizer and ripeness at harvest. Conventionally produced crops had a significantly higher content of nitrogen, and organically produced crops had a significantly higher content of phosphorus and higher titratable acidity. But the margin of difference in these nutrient categories was deemed "unlikely to be of any public health relevance," according to one of the authors, Alan Dangour.
The nutrient categories found to be no different between organic or conventional food include:
"Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority," Dangour said.
The authors themselves, however, point out two big limitations that prevented a "formal meta-analysis":
Two-thirds of the 162 potentially relevant studies were excluded from the analysis, either because the studies did not identify the organic certification method (87), did not state the plant cultivar or livestock breed (33), did not state statistical or laboratory methods (24), or could not be obtained (11). The authors noted a "generally poor quality of research" in the published literature on this subject.
The analysis grouped nutrients into categories, resulting in "the loss of more nuanced findings from individual studies on specific foods."
The authors also note that there are many factors that determine nutritional quality of foods -- production method being just one: "All natural products vary in their composition of nutrients and other nutritionally relevant substances. Different cultivars of the same crop may differ in nutrient composition, which can also vary depending on fertilizer and pesticide regimen, growing conditions, season, and other factors. The nutrient composition of livestock products can similarly be affected by factors such as the age and breed of the animal, feeding regimen and season. This inherent variability in nutrient content may be further affected during the storage, transportation and preparation of the foodstuffs before they reach the plate of the consumer."
It's good to remember here that people buy organic food for more reasons than just a perception that they are more nutritious. Organic food is grown without pesticides, so they won't have pesticide residue when you eat them (the study explicitly did not include an analysis of pesticide residue). Further, farm workers and nearby wildlife are protected from the chemicals. Organic foods are grown in such a way as to support the health of the soil, so the farms are more sustainable. They are grown without huge inputs of fertilizers derived from fossil fuels or mined minerals, further lessening their environmental impact. Livestock raised organically cannot be fed grain dosed with antibiotics and growth hormones, which generally means animals aren't confined in unhealthy and inhumane pens that can breed disease.
So when you plunk down a few extra pennies for that organic veggie, you're buying more than a "health aura."
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