All-trans beta-carotene appears to be more bioavailable than 9-cis or 13-cis beta-carotene in gerbils given single oral doses of each isomer.

Male gerbils (28 d old) were used to investigate the beta-carotene (betaC) isomer pattern in the intestine and tissues 6 h after ingestion of three betaC isomers. After a 49- to 52-d period of consuming the AIN93G diet without vitamin A (VA) or betaC, three groups (n = 7) were gavaged with crystalline all-trans (at)betaC, 9-cis (9c)betaC or 13-cis (13c)betaC solubilized in oil and a control group (n = 5) with oil alone. Total betaC per dose for gerbils in the atbetaC, 9cbetaC and 13cbetaC groups was 384 +/- 3, 391 +/- 2 and 386 +/- 2 nmol, respectively. After 6 h, gerbils were killed and serum, stomach contents, small intestinal contents (SIC), small intestinal mucosal scrapings (SIM) and liver were collected. betaC and VA in tissues were quantified using HPLC. Nonspecific isomerization of betaC occurred in the digestive tracts of gerbils administered betaC; the greatest effect was in the SIC of the 13cbetaC (50:50 cis:trans) and 9cbetaC (70:30 cis:trans) groups. Concentrations of total betaC in the SIM of gerbils administered at betaC were greater than those intubated with 9cbetaC and 13cbetaC (P < 0.05). Gerbils that received atbetaC had greater total betaC concentrations in serum (P < 0.05) and total betaC stores in liver (P < 0.01) compared with those administered 9cbetaC and 13cbetaC. Gerbils intubated with 9cbetaC had higher levels of total betaC in serum (P = 0.05) and liver (P < 0.01) compared with those intubated with 13cbetaC. Because of its preferential uptake, transport and tissue accumulation, atbetaC appears to be a more bioavailable isomer than 9cbetaC or 13cbetaC in gerbils.