TABLE 9.

Summary of recommendations to improve retinol isotope dilution techniques¹

Further development of isotope dilution techniques:

• Make the method more field-friendly

• Increase accessibility and further verify usefulness of different tracers and doses to optimize costs

• Further establish guidelines for interpreting retinol isotope dilution techniques

• Further validate the method for different population groups, especially children and pregnant and lactating women

• Design studies with sufficient statistical power for specific conditions

• Determine how vitamin A status and other population characteristics influence vitamin A absorption, distribution, and metabolism

• Consider designs with paired comparisons and both positive and negative controls

Further application of retinol isotope dilution techniques to benefit public health:

• Monitor the safety and effectiveness of high-dose supplementation to young children in developing countries

• Assess alternative vitamin A interventions

• Determine the effectiveness of routinely supplementing with or feeding β-carotene, rather than retinol

• Investigate the usefulness of retinol isotope dilution techniques to assess vitamin A status in populations affected by inflammation

• Improve understanding of the influence of iron or zinc deficiencies on vitamin A metabolism and status evaluation

¹Adapted from reference 314 with permission.