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MEASUREMENT OF MICRONUTRIENT ABSORBTION AND STATUS

Objective

The aim of the present concerted action is to assess critically priorities for the study of micronutrients in the Community and to develop and validate methods which allow more accurate and sensitive measurements of intake, absorption and status of these micronutrients in man.
In order to fully understand the complex relationship between dietary intake, status, morbidity and health, methods for the accurate assessment of dietary intake, micronutrient absorption from mixed diets and biochemical and physiological indices of status are required.
Research has concentrated on intercomparison and optimization of methods for:
measuring micronutrient status;
determining enriched isotopes used for studying mineral metabolism in humans;
studying mineral bioavailability by in vitro methods;
assaying selected vitamins (fat and water soluble) in biological matrices.

2 round robin studies of in vitro methods for measuring iron bioavailability have been completed and a revised method has been devised and is undergoing evaluation.

Measurement of stable isotope ratios in samples from human studies of mineral metabolism have demonstrated very good interlaboratory agreement for samples containing isotopically enriched zinc, iron, magnesium and copper. Further studies are needed on samples containing calcium, selenium and molybdenum.

Intake and status ring tests have also shown good interlaboratory agreement on quantitative measurements of copper, zinc and selenium in plasma. Revised assays for glutathione peroxidase (GPX) and superoxide dismutase (SOD) produced significantly improved data in participating laboratories and the new methods have been recommended for general use. A critical evaluation of the techniques for determining indices of mineral and vitamin body status has been written.

Ring tests on fat soluble vitamins have been completed and have revealed good interlaboratory agreement on determinations of retinol and tocopherol, however problems were experience with carotenoid measurements. These have largely been resolved and a programme has been drawn up for improving results in laboratories which are still having difficulties. Ring tests have also been performed to evaluate folate and vitamin B6 assays and an interlaboratory comp arison of vitamin C determinations has been initiated.
The criteria for determining dietary requirements of micronutrients (vitamins and minerals) are at present largely based on the prevention of deficiency states. There are good reasons to believe, however, that the maintenance of optimal function would be a far better basis for the determination of requirements since marginal status, where none of the classical symptoms of deficiency are observed, may still significantly affect physical and mental wellbeing. However, in order to progress in our understanding of the complex relationship between dietary intake, status, morbidity and health, the development and validation of methods for the accurate assessment of dietary intake, micronutrient absorption from mixed diets and biochemical/physiological indices of status are required.

The objectives of this action are to:

1. improve the precision and sensitivity of isotopic (stable and radioactive) methods for measuring micronutrient absorption and metabolism;

2. develop instrumental and biospecific methods for quantifying micronutrients in foods and mixed diets;

3. develop biospecific, chromatographic and spectrometric methods for the assessment of micronutrient status;

4. identify biochemical and physiological indicators of variation in micronutrient intake and status.

The expertise, in respect of the different micronutrients is distributed throughout Europe. This coordinated programme of work will bring the skills and knowledge of workers in the field into focus, establish firm links between European groups and encourage Community-wide agreement on appropriate dietary recommendations.

Coordinator

Institute of Food Research
Address
Norwich Laboratory Colney Lane
NR4 7UA Norwich
United Kingdom