Immunonutrition does not decrease complications after abdominal surgery

Reference

Probst P, Ohmann S, Klaiber U, et al. Meta-analysis of immunonutrition in major abdominal surgery. Br J Surg 2017;104(12):1594-1608.

Synopsis

These authors searched 3 databases for randomized controlled trials of immunonutrition in patients undergoing abdominal surgery. These are supplements that typically contain various combinations of extra amino acids, polyunsaturated fatty acids, or RNA nucleotides. The thought is that these components suppress immune responses and will improve healing and decrease infections. Two authors independently decided which studies to include and assessed the risk of bias in the those studies. They don't describe searching for unpublished studies, but assessed the potential for publication bias graphically and statistically. Ultimately, they included 83 trials with slightly more than 7000 patients. The studies were fairly mixed as to the potential sources of bias, and only 3 studies were deemed to be at low overall risk of bias. After the authors lumped all the studies together, the patients who received immunonutrition had fewer total complications and infections and had shorter hospitalizations. However, when the authors dumped the crappy studies, these differences disappeared. Additionally, studies funded by industry were more likely to show improvements; the unfunded studies did not. Finally the authors found evidence for publication bias among the studies that evaluated infection rates. Regardless, overall mortality was similar in each group, even when including the biased studies.