Suitability of 3-point versus 7-point postprandial retinyl palmitate AUC in human bioavailability studies

Bioavailability is a critical feature in the assessment of the role of micronutrients in human health. Although postprandial behaviour does not predict long-term responses and acute responses, it is accepted that the study of triglyceride-rich lipoprotein fractions reflects newly absorbed lipids from recent meals.

To assess the predictive value of a 3-point versus 7-point post-prandial response (area under the curve) in nutrient bioavailability studies in humans.

We used results from a human bioavailability study (n = 19) that consisted of a single-dose pharmacokinetic assay involving three types of commercially available vitamin A and E fortified milk.

Correlation coefficients between 3-point AUC (AUCp, predictive) versus 7-point AUC (AUCc, conventional) ranged between r = 0.81 (P < 0.001) for vitamin A-fortified skim milk and r = 0.95 (P < 0.001) for whole milk. Bland-Altman representations showed a good agreement between the two methods with 95% of the differences within the concordance limits. More than 90% of the subjects were correctly classified in the same or adjacent quartiles and he calculated relative absorption of vitamin A from the foods was, on average, <5% lower using the AUCp compared to that estimated using AUCc.

The use of the 3-point approach may be a reliable alternative to assess the relative postprandial lipid response in human bioavailability studies. Nevertheless, since this approach has been studied considering one nutrient (i.e. preformed vitamin A) and one type of food (i.e. milk), its applicability to other nutrients and foods should be tested.