Are organic foods healthier than non-organic foods?

Foods are described as organic according to the food guidelines of the region where they are produced. Guidelines vary around the world.  However, generally, organic produce is grown without exposure to pesticides, antibiotics, growth hormones, and other chemicals.¹ Organic livestock feed on foods that are organic and are typically allowed access to outdoors, sunlight, fresh air, and freedom of movement. In addition, most organic farming practices require that food not be exposed to radiation and not be grown from genetically modified organisms. Consumers may purchase organic food because they believe it has health benefits including lower exposure to substances or chemicals that they perceive to be harmful to human health.² Producers may claim that the addition of these substances actually enhances the food’s safety, and thus its health value. Scientists have compared organic foods with conventional foods to evaluate these assumptions.

Smith-Spangler et al. conducted a systematic review of the literature on the potential health effects on human populations exposed to organic and conventional diets.¹ The review included 14 unique cohorts (n=13,806), six of which were randomized control trials. Analyses included nutrient levels of the diets and the presence of bacterial or pesticide contamination of the products. The authors found only limited evidence that organic foods were more nutritious. The only statistically significant difference in nutrient composition between the two diets was in the amount of detectable phosphorous in organic produce and in the amount of beneficial fatty acids (phenols) in organic milk and chicken. No statistically significant difference was found for 12 other nutrients analyzed including ascorbic acid, potassium, calcium, iron, protein, and fiber.

Chemicals are sometimes added to conventional produce to lower the risk of bacterial contamination. However, in the same review, the difference in bacterial contamination between organic and conventional produce was statistically insignificant.¹ Prevalence of E. coli contamination was 7% in organic produce (95% confidence interval [CI] [4% – 11%], 826 samples) and 6% in conventional produce (95% CI [2% – 9%], 1454 samples), although only five studies measured bacterial contamination. The authors noted that another study which measured bacterial contamination found a significant difference when organic farmers used cow manure for fertilizer versus organic farmers who used other types of manure-based fertilizers.³  Pesticide levels of produce were significantly higher with the conventional food production methods. In the nine studies that measured pesticide on food, organic produce had a 30% lower risk for contamination with any detectable pesticide residue than conventional produce (risk difference 30% [ 95% CI [37% – 23%], p=0.001).

Five studies in the Smith-Spangler review measured antibiotic resistance of bacteria found on foods.¹ The risk for isolating bacteria resistant to three or more antibiotics was 33% higher among conventional chicken and pork than organic alternatives (95% CI [21% – 45%], p=0.001).

The authors summarized their findings by concluding that there is some evidence that an organic diet might lower exposure to chemicals and that this did not necessarily result in significant exposure to bacterial contamination of food.¹ While antibiotic-resistant bacteria might be more common on organically grown livestock, there is no evidence that this would significantly contribute to antibiotic resistance in humans. In the view of these authors, more study is needed comparing health outcomes among people who are exposed exclusively to conventional versus organic diets to better understand the health consequences of these different eating styles.

A review by Reganold et al. found higher levels of nutrients in organic foods compared to conventional foods.⁴ Of the 15 meta-analyses they summarized,  12 concluded that organic foods were higher in vitamin C, antioxidants, and total omega-3 fatty acids. Brantsaeter et al. point out the difficulty of studying the relevance of organic foods to human health, in part because people choosing to eat organic foods share many other healthy lifestyle choices that may impact health.⁷ Other meta-analyses have come to similar conclusions that some studies try to overcome the difficulty of designing dietary studies with true health outcomes as the endpoint by using certain biomarkers as proxies for health effects. While there is some evidence that sole consumption of organic foods may result in higher levels of some anti-inflammatory markers, the existing studies are small and more research is needed.

Brantsaeter et al. also summarized the results of 14 mostly observational epidemiologic studies that sought to correlate organic food consumption with specific health outcomes including atopy, eczema, respiratory disease, reproductive anomalies, cancer, and risk factors for cardiovascular disease.⁷ Because of the heterogeneity of study designs, it is difficult to draw conclusive evidence from these studies. However, there was some evidence that children fed only organic dairy had a lower incidence of allergy and eczema compared to controls.⁸ Overall, there is consensus that the scientific evidence to date is insufficient to conclude that consumption of organic foods is more beneficial to health than conventional foods.

^References

1. Smith-Spangler C, Brandeau ML, Hunter GE, et al. Are organic foods safer or healthier than conventional alternatives: a systematic review. Ann Intern Med. 2012;157(5):348-366.
2. Lazaroiu G, Andronie M, Uţă C, Hurloiu I. Trust management in organic agriculture: sustainable consumption behavior, environmentally conscious purchase intention, and healthy food choices. Front Public Health. 2019;7:340.
3. Mukherjee A, Speh D, Diez-Gonzalez F. Association of farm management practices with risk of Escherichia coli contamination in pre-harvest produce grown in Minnesota and Wisconsin. Int J Food Microbiol. 2007;120(3):296-302.
4. Reganold JP, Wachter JM. Organic agriculture in the twenty-first century. Nat Plants. 2016;2:15221.
5. Średnicka-Tober D, Barański M, Seal CJ, et al. Higher PUFA and n-3 PUFA, conjugated linoleic acid, α-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses. Br J Nutr. 2016;115(6):1043-1060.
6. Średnicka-Tober D, Barański M, Seal C, et al. Composition differences between organic and conventional meat: a systematic literature review and meta-analysis. Br J Nutr. 2016;115(6):994-1011.
7. Brantsæter AL, Ydersbond TA, Hoppin JA, Haugen M, Meltzer HM. Organic food in the diet: exposure and health implications. Annu Rev Public Health. 2017;38:295-313.
8. Kummeling I, Thijs C, Huber M, et al. Consumption of organic foods and risk of atopic disease during the first 2 years of life in the Netherlands. Br J Nutr. 2008;99(3):598-605.