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Vitamin A metabolism, in healthy adults and patients with Cystic Fibrosis

Vitamin A metabolism, in healthy adults and patients with Cystic Fibrosis
Vitamin A metabolism, in healthy adults and patients with Cystic Fibrosis

Vitamin A plays a pivotal role in mucus production, non-specific barrier function of the respiratory and gastrointestinal tract and specific immune function. Although low circulating retinol concentrations are frequently observed in patients with CF, the clinical significance of such observations and what constitutes the most appropriate clinical management is unclear. Current guidelines simplistically assume that low retinol concentrations arise from either poor intake and/or poor availability of vitamin A. It is recommended that patients with CF receive prophylactic supplements of vitamin A (3-5 times RNI). However, there is little evidence to support such guidelines and there is concern that high intakes over prolonged periods could cause harm. Safe and effective clinical management requires that we determine whether low circulating retinol concentrations are related to the clinical course and the extent to which they are associated with elevated faecal losses, dietary supply, or impaired mobilisation from the liver.

An audit of clinical notes was used in conjunction with stable isotope tracer methodology to examine the processes that affect plasma concentrations of retinol in patients with CF.

Over 40% of the adult patients with CF had plasma retinol concentrations below the lower limits observed in the reference population, despite supplementation. Patients with the lowest concentrations have the poorest clinical course and raised markers of inflammation. Low concentrations of retinol were not associated with supply of the vitamin, and modest losses of vitamin A in stool could be easily overcome by increased intake, in that patients with CF absorb more retinol than controls. Results suggest that the pool of vitamin A stored in the liver is large due to a constraint in mobilisation. These observations support the view that there is a need to reconsider current guidelines in CF. Current practice should be reviewed in order to prevent potential harm of high intakes.

University of Southampton
Cawood, Abbie Louise
Cawood, Abbie Louise

Cawood, Abbie Louise (2003) Vitamin A metabolism, in healthy adults and patients with Cystic Fibrosis. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Vitamin A plays a pivotal role in mucus production, non-specific barrier function of the respiratory and gastrointestinal tract and specific immune function. Although low circulating retinol concentrations are frequently observed in patients with CF, the clinical significance of such observations and what constitutes the most appropriate clinical management is unclear. Current guidelines simplistically assume that low retinol concentrations arise from either poor intake and/or poor availability of vitamin A. It is recommended that patients with CF receive prophylactic supplements of vitamin A (3-5 times RNI). However, there is little evidence to support such guidelines and there is concern that high intakes over prolonged periods could cause harm. Safe and effective clinical management requires that we determine whether low circulating retinol concentrations are related to the clinical course and the extent to which they are associated with elevated faecal losses, dietary supply, or impaired mobilisation from the liver.

An audit of clinical notes was used in conjunction with stable isotope tracer methodology to examine the processes that affect plasma concentrations of retinol in patients with CF.

Over 40% of the adult patients with CF had plasma retinol concentrations below the lower limits observed in the reference population, despite supplementation. Patients with the lowest concentrations have the poorest clinical course and raised markers of inflammation. Low concentrations of retinol were not associated with supply of the vitamin, and modest losses of vitamin A in stool could be easily overcome by increased intake, in that patients with CF absorb more retinol than controls. Results suggest that the pool of vitamin A stored in the liver is large due to a constraint in mobilisation. These observations support the view that there is a need to reconsider current guidelines in CF. Current practice should be reviewed in order to prevent potential harm of high intakes.

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Published date: 2003

Identifiers

Local EPrints ID: 465066
URI: http://eprints.soton.ac.uk/id/eprint/465066
PURE UUID: 6b86e3c7-fc54-4027-a06f-ff3dae2e3466

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Date deposited: 05 Jul 2022 00:21
Last modified: 05 Jul 2022 04:06

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Author: Abbie Louise Cawood

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