The influence of bariatric (metabolic) surgery on blood polyunsaturated fatty acids: A systematic review

BACKGROUND AND AIMS:Bariatric, also termed metabolic, surgery is an increasingly common treatment for severe and complex obesity. It decreases macronutrient intake, influences nutrient absorption and modifies gastrointestinal physiology with the aim of reducing adiposity, improving metabolism and reducing disease risk. Bariatric surgery has been shown to result in micronutrient deficiencies. Whether it results in deficiencies of essential fatty acids (EFAs) and their bioactive polyunsaturated fatty acid (PUFA) derivatives is not clear. The aim of this systematic review is to identify whether there are effects of bariatric surgery on the blood levels of EFAs and other PUFAs. METHODS:A database search was conducted up to November 2020 using Medline, Embase and Cinahl databases, using relevant search terms identified by a PICO protocol. Only human studies reporting on PUFAs in a blood pool, published in the English language and available in full text were included. The Cochrane tool for assessing risk of bias was used and data were extracted. RESULTS:Fifteen papers from fourteen studies with relevant data were identified for inclusion. Studies differed according to surgical intervention, duration, measured timepoints, sample size and PUFAs reported. Both increases and decreases in selected PUFAs were reported in different studies. For the EFAs linoleic acid and α-linolenic acid and for the longer-chain omega-3 PUFA eicosapentaenoic acid, bariatric surgery is associated with a transient decline in status (to about 6 months post-surgery) with a later return to pre-surgery levels. All studies had some risk of bias and most studies were of small size. CONCLUSION:There is a decrease in blood levels of both EFAs and of eicosapentaenoic acid in the months following bariatric surgery. This may partly counter the desired effects of the surgery on blood lipids, insulin sensitivity and inflammation. Nutritional strategies (e.g. use of modified formulas or of supplements) may be able to correct the decrease in those PUFAs. Nevertheless, the observed decrease in PUFAs is transient.