Changes in circulating concentrations of vitamins and trace elements after cessation of nocturnal enteral tube feeding.

BACKGROUND

This study aimed to examine whether circulating concentrations of a range of vitamins and trace elements in patients receiving long-term cyclic enteral tube feeding vary during the day, and whether standardised time points for blood sampling are required for assessment of nutrient status.

METHODS

Circulating concentrations or activities of water-soluble vitamins (thiamine, riboflavin, and vitamins B6, B12, folate and C), fat-soluble vitamins (A, D, E) and trace elements (iron, zinc, copper and selenium (assessed by glutathione peroxidase activity), were measured at 0,3,6 and 9-12h after cessation of nocturnal feeding (fasting), in eight clinically stable patients receiving cyclic nocturnal enteral nutrition.

RESULTS

The circulating concentrations of the nutrients did not change between the fed and fasted state (repeated-measures-ANOVA) except the following: plasma folate increased progressively from 10.9 (SD 4.6)nmol/l in the fed state to 14.0 (SD 4.4)nmol/l at 9-12 h after cessation of feeding (P<0.05); plasma zinc increased progressively throughout the fasting period by 33.5% (8.57, SD 0.68 vs. 11.44, SD 1.85 micromol/l, in fed state vs. 9-12h fast respectively, P<0.05); and total tocopherol/cholesterol ratio decreased by 9.6% during the study period (P<0.02), while gamma-tocopherol increased by 59.2% (P<0.05). For all analytes, the concentrations in blood samples taken at 3 and 6h after cessation of feeding were not significantly different from those at 9-12h.

CONCLUSIONS

Although cessation of nocturnal tube feeding had no significant effect on the circulating concentrations of most micronutrients, it increased plasma folate and zinc concentrations, and decreased the tocopherol/cholesterol ratio. The timing for blood sampling should be standardised when the status of these nutrients is assessed in patients receiving cyclic tube feeding.