Serum carotene, vitamin A, retinol-binding protein and lipoproteins before and after jejunoileal bypass surgery.

The plasma vitamin A and carotene transport in 45 obese patients was examined before and at various times after bypass surgery. The serum levels of lipoproteins, carotene, vitamin A and retinol-binding protein (RBP) were monitored and compared to those of healthy controls. LDL-cholesterol levels were decreased by 40 per cent (P less than 0.001) within the first year after surgery and remained low thereafter. The reduction of serum carotene (from a mean of 64 to 17 micrograms/dl) was rapid and constant. This change was observed already within 1-2 weeks post-surgery. The serum concentrations of carotene and LDL-cholesterol were highly correlated (r = 0.74). The concentrations of vitamin A and RBP were normal before the operation and remained so until 30 months after surgery, when slight reductions were observed compared to the control values [46 +/- 28 vs 66 +/- 11 micrograms/dl for vitamin A (P less than 0.01) and 32 +/- 8 vs 41 +/- 6 mg/l for RBP (P less than 0.01)]. No overt signs of vitamin A deficiency were observed. The mechanisms by which carotene (but not vitamin A) decreases so rapidly after bypass surgery cannot be explained by the decreased LDL levels.