British Journal of Nutrition

Human and Clinical Nutrition

Effect of bariatric surgery on sulphur amino acids and glutamate

Erlend T. Aasheima1a2a3a4 c1, Amany K. Elshorbagya5, Lien My Diepa6, Torgeir T. Søvika7, Tom Malaa7, Maria Valdivia-Garciaa5, Torsten Olbersa8, Thomas Bøhmera1, Kåre I. Birkelanda1a3 and Helga Refsuma5a9

a1 Department of Endocrinology, Oslo University Hospital Aker, Trondheimsv 235, 0514 Oslo, Norway

a2 Hormone Laboratory, Oslo University Hospital Aker, Trondheimsv 235, 0514 Oslo, Norway

a3 Faculty of Medicine, University of Oslo, Sognsvannsv 9, 0315 Oslo, Norway

a4 Imperial Weight Centre, Imperial College London, London, UK

a5 Department of Pharmacology, Oxford University, Mansfield Road, Oxford OX1 3QT, UK

a6 Research Centre, Oslo University Hospital Aker, Trondheimsv 235, 0514 Oslo, Norway

a7 Department of Gastrointestinal Surgery, Oslo University Hospital Aker, Trondheimsv 235, 0514 Oslo, Norway

a8 Department of Surgery and Gastrosurgical Research, Sahlgrenska University Hospital, Box 100, 40530 Göteborg, Sweden

a9 Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Sognsvannsv 9, 0316 Oslo, Norway


Plasma total cysteine (tCys) concentrations are associated with BMI. To study the relationship between tCys and BMI, we monitored the changes in serum concentrations of tCys and metabolically related compounds in sixty obese patients (BMI 50–60 kg/m2) from before to 1 year after either gastric bypass surgery (mean 30 % weight loss) or duodenal switch surgery (mean 41 % weight loss). A total of fifty-eight healthy persons (BMI 17–31 kg/m2) served as controls. Before surgery, obese patients had modestly (approximately 17 %) higher mean serum tCys, and markedly (>2-fold) higher glutamate concentrations, than controls (P ≤ 0·001 for both). Serial examinations after surgery revealed that gastric bypass patients had no change in tCys concentrations (P = 0·22), while duodenal switch patients showed a modest (approximately 12 %) but significant decrease in tCys (P < 0·001). Total homocysteine concentrations increased in duodenal switch patients but not in gastric bypass patients. Independent of surgery type, serum concentrations of methionine and cystathionine decreased (P < 0·05 for both), while serum glutathione and taurine remained stable. Glutamate concentrations declined, as did γ-glutamyltransferase activity (P < 0·001 for both). These results show that despite 30 % weight loss, and decreases in methionine, cystathionine and glutamate, there was no significant change in serum tCys in patients after gastric bypass surgery. The decrease in tCys in patients undergoing duodenal switch could be related to malabsorption. The present findings do not suggest that BMI is a causal determinant of plasma tCys.

(Received August 16 2010)

(Revised December 01 2010)

(Accepted December 21 2010)

(Online publication May 04 2011)


c1 Corresponding author: Dr E. T. Aasheim, fax +44 2033130673, email


Abbreviations: BCAA, branched-chain amino acids; GGT, γ-glutamyltransferase; GSH, glutathione; SAA, sulphur amino acids; tCys, total cysteine; tGSH, total glutathione; tHcy, total homocysteine