Kirsten Brandt, PhD
Potential Conflicts of Interest: Grant (money to institution): Sheepdrove Charitable Trust (£11 250 in 2010); Soil Association (£1000 in 2007); Support for travel to meetings for the study or other purposes: American Society of Agronomy; Other: Other industry-related funding to Dr. Brandt's institution for her research (£145 197 since 2004) is for projects not related to organic food (for example, from Danone and Asda [part of WalMart]). Most of the author's public grant income is also not related to organic food. Dr. Brandt is the corresponding author on one of the cited articles (2).
Brandt K. Are Organic Foods Safer or Healthier?. Ann Intern Med. 2013;158:295. doi: 10.7326/0003-4819-158-4-201302190-00014
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Published: Ann Intern Med. 2013;158(4):295.
TO THE EDITOR:
Smith-Spangler and colleagues' meta-analysis (1) found significant differences for only 1 of 6 groups of secondary metabolites in plant foods (Table 1), which contrasts with the findings of a previously published meta-analysis that showed significant differences for 4 of 6 groups (2). Several aspects of the methodology used by Smith-Spangler and associates seem insufficiently justified or inconsistent, affecting the quality of the meta-analysis.
Five issues require clarification. First, the meta-analysis method used is valid only if appropriate sample sizes are used for the calculations (1). Recognized standards for good practice (3) emphasize that “coding of data from the articles” should be “specified and objective.” However, no procedure for allocation of sample sizes was presented (1), and a comparison with the design descriptions in the papers included in Smith-Spangler and coauthors' review shows no consistent patterns. For example, for reference 217, the “sample size” in Smith-Spangler and colleagues' online Supplement 4 equals the numbers of independently analyzed subsamples (corresponding with the reported averages and SDs, so probably appropriate). However, for reference 260, the “sample size” is the total number of subsamples from all plots and years, even though results were reported separately per year and the “sample size” for references 240 and 151 (1) are the total numbers collected of tomatoes and leaves, respectively, regardless of how many had been analyzed together.
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