Elevated homocysteine levels with weight loss after Lap-Band surgery: higher folate and vitamin B12 levels required to maintain homocysteine level

OBJECTIVE: To investigate homocysteine levels and their relationship with serum folate and vitamin B12 concentrations with weight loss after the Lap-Band form of gastric restrictive surgery, with the view to minimizing risk. METHODS: We measured levels of fasting plasma homocysteine (tHcy), folate (serum and RBC) and vitamin B12 in two groups. The study group was 293 consecutive patients at 12 (n = 192) or 24 (n = 101) months review after surgery. The controls were 244 consecutive patients presenting for this surgery. RESULTS: The group losing weight had higher geometric mean tHcy levels: 10.4 (95% Cl, 9.8-10.8) micromol/l compared with 9.2 (95% Cl, 8.9-9.7) in controls (P < 0.001). This occurred with higher folate levels and unchanged vitamin B12 levels. Levels of folate and B12 together explained 35% (r2) of the homocysteine variance in the weight loss group compared with only 9% (r2) in controls (P < 0.001). Those taking regular multivitamin supplements had lower tHcy levels: 9.6 (9.1-10.0) micromol/l vs 12.3 (11.4-13.3) in those not taking supplements (P < 0.001). A low normal plateau of tHcy levels occurred at levels of folate > 15 ng/l and B12 > 600 ng/ml. A curvilinear relationship exists between these cofactors and tHcy levels, with the dose-response relationship shifted to the right in the weight loss group. CONCLUSION: This study shows elevated tHcy levels with weight loss, without lower serum folate or vitamin B12 levels. There is an altered dose-response relationship with higher serum B12 and folate levels required to maintain recommended tHcy levels. Patients losing weight have significant health benefits; however, they may be at greater risk of vascular events or fetal abnormality in association with raised tHcy levels. Multivitamin supplementation is effective in lowering tHcy levels.