Bioavailability of vitamins A and E from whole and vitamin-fortified milks in control subjects

Abstract

Background: Dairy products fortified with vitamins and minerals represent a growing market that is of interest to those sectors of the population with unbalanced diets and increased needs. However, there is little information on the bioavailability of micronutrients in milk products at dietary intake levels.

Aim of the study: To evaluate the bioavailability of vitamins A and E in whole milk and fortified whole and skimmed milk in control subjects.

Methods: A single-dose bioavailability study was performed using three commercially available milks (unfortified whole milk and whole and skimmed milk fortified with vitamins A and E). Nineteen volunteers (10 women and 9 men) ingested 430 ml of each milk on different days. The contents of retinol and alpha-tocopherol provided in the milks and the retinyl esters and alpha-tocopherol in triglyceride-rich lipoprotein fractions (TRL) from plasma collected for 6.5 h postprandially were assayed using a quality-controlled HPLC method. The relative absorption of vitamins A and E from milks was calculated on the basis of area under the curve (AUC) versus time curve estimations, adjusted for plasma volume and expressed as percentage of the amount of nutrient provided.

Results: The total amounts of retinol and alpha-tocopherol provided ranged between 0.48 and 4.15 micromol and 0.41 and 32.49 micromol, respectively. The AUC value of retinyl palmitate in TRL was higher for fortified whole milk than for the other two milks (unfortified whole and fortified skimmed milk). The percent relative absorption of vitamin A did not differ among the three types of milk. The AUC for alpha-tocopherol was no different after the ingestion of any of these milks.

Conclusion: The mean percentage of retinol absorption was apparently similar for the three types of milk, regardless of the amount of fat ingested with each type of milk and the vitamin A provided.