Studies on the absorption of beta-carotene and the distribution of total carotenoid in human serum lipoproteins after oral administration

Abstract

The carotenoid increment in human serum was measured after the oral administration of aqueous dispersions and lipid dispersions of β-carotene with different test meal regimens. β-carotene was readily absorbed in both forms. Absorption of the aqueous dispersion was similar when administered with either high lipid or protein-carbohydrate test meals. Aqueous dispersions were poorly absorbed by fasting subjects. The lipoprotein distribution of the serum carotenoid increment was determined in normal, hypercholesterolemic, and hyperlipemic subjects to investigate the absorption and transport pattern for β-carotene. Peak carotenoid increments occurred first in the chylomicron and Sf 10–400 lipoprotein fractions, and considerably later in the Sf 0–10 fraction. A major part of the serum Carotenoid increment was found in the Sf 0–10 lipoprotein fraction. This is reflected in the delayed peak found in serum carotenoid tolerance curves. Very little newly absorbed carotenoid was found in the high density lipoprotein fraction. Carotenoid-to-cholesterol and carotenoid-to-fatty acid ester ratios were determined after carotenoid administration and after a lipid test meal containing no carotenoid. These ratios indicated that the peak carotenoid increments represented newly absorbed carotenoid associated with specific lipoprotein fractions rather than rapid carotenoid exchange between lipoprotein fractions that varied in their total concentration. The absorption and transport of carotenoid was compared with the absorption and transport of other lipids. Portal absorption of at least a part of the ingested carotenoid is proposed as a possible explanation for the observed carotenoid transport pattern.