Gastric acidity influences the blood response to a beta-carotene dose in humans

The effect of gastric acidity on the blood response to a single dose of 120 mg beta-carotene in humans was investigated in 12 normal subjects (5 women, 7 men) aged 23-68 y. Omeprazole was used for 7 d to obliterate gastric acid secretion and to raise gastric pH to > 4.5. In a crossover design, six subjects were randomly assigned to take beta-carotene with omeprazole either at the beginning (day 9) or at the end (day 26) of the study. The beta-carotene response in blood was not altered by the experimental order. Results from the high-gastric-pH phase (ie, with omeprazole) were analyzed together and compared with the results from the low-gastric-pH phase (ie, without omeprazole). The increases of serum concentrations of both trans beta-carotene and cis beta-carotene 6 and 24 h after the beta-carotene dose were significantly greater at a low gastric pH (pH = 1.3 +/- 0.1, ie, without omeprazole) than those at a high gastric pH (pH = 6.4 +/- 0.3, ie, with omeprazole), P < 0.02. Similarly, 24 h after beta-carotene administration, the area under the blood beta-carotene response curve (trans plus cis beta-carotene) was significantly greater at a low gastric pH (6825 +/- 760 nmol.h/L) than at a high gastric pH (3390 +/- 550 nmol.h/L), P < 0.002. In investigations of bacterial overgrowth, gelatin capsule disintegration and isomeric profiles associated with high and low pH, we could not identify factors to explain the differences observed in the blood response curves between low-gastric-pH and high-gastric-pH conditions. A suppressed blood response of beta-carotene at a high intraluminal pH may have been due to the slower movement of negatively charged micelles through the unstirred water layer and cell membrane.