In a word: No.
The Evidence
Smith-Spangler, C., Brandeau, M. L., Hunter, G. E., Bavinger, J. C., Pearson, M., Eschbach, P. J., ... & Olkin, I. (2012). Are organic foods safer or healthier than conventional alternatives?: A systematic review. Annals of Internal Medicine, 157, 348-366. doi: 10.7326/0003-4819-157-5-201209040-00007
What did the meta-analysis look into?
This meta-analysis investigated whether organic foods are substantially healthier (more nutritious and safer) than conventional foods. Specifically, the study compared the nutrients, bacteria, fungi, or pesticides found in organic and conventional foods (vegetables, fruits, grains, meat, poultry, eggs, and milk), and in people eating the foods. The meta-analysis synthesized evidence from 17 studies, including a total of 13 806 people (pregnant and non-pregnant women, children, and non-pregnant adults) from Europe and the United States.
How did the type of food affect the health of pregnant women and children?
There was no indication that eating either type of food contributed to the development of ill-health conditions, including wheezing, eczema, asthma, and other allergic reactions.
How did the type of food affect the health of non-pregnant adults?
Vitamin and antioxidant levels were similar in organic and conventional food eaters. Also similar was the function of the immune system, the levels of LDL cholesterol (the so-called "bad cholesterol"), and the quality of the sperm. Interestingly, there was evidence indicating that the consumption of organic meat in the winter increased the risk of campylobacter infection, which is a common food-borne illness.
What did the evidence suggest about the vitamin and nutrient levels in the foods?
Vitamin content was similar in organic and conventional vegetables, fruits, and meats. Protein and fat content was similar in organic and conventional milk. Total fatty acid content was similar in the breast milk of mothers who ate large amounts of organic dairy and meat, and in the milk of mothers who consumed small amounts of organic dairy and milk. However, two nutrients (phosphorus & phenols), were found in substantially higher levels in organic produce. Beneficial omega 3 fatty acids were found in higher levels in organic chicken and organic milk.
What did the evidence suggest about the contaminants in the foods?
Pesticides were detected in both organic and conventional samples (in 7% of the organic samples and 38% of the conventional ones). The risk of finding bacteria resistant to antibiotics was 33% higher in conventional chicken and pork. Total bacteria and heavy metal count (cadmium or lead) was similar in both types of foods. The evidence was unclear for fungal toxins. Only 3 out of the 17 studies detected levels of contamination that exceeded maximum allowed limits.
The take-home message
Compared to conventional foods, organic foods do not appear to provide additional health benefits, even though organic produce may expose consumers to fewer pesticides, and organic chicken/pork may expose consumers to fewer antibiotic-resistant bacteria. Broadly speaking, claims of the superiority of organic foods may be exaggerated.
I was surprised that the conclusion arrived at but for my part the reason for eating organic meat, cheese, veg or drinking organic milk is as much about animal welfare and hopefully the use of less/no harmful pesticides/herbicides generally.