FROM:
Am J Clin Nutr 1999 (Aug); 70 (2): 261–268
Van het Hof KH; Brouwer IA; West CE; Haddeman E;
Steegers-Theunissen RP; van Dusseldorp M; Weststrate JA; Eskes
TK; Hautvast J
BACKGROUND: To gain more insight into the relation
between vegetable consumption and the risk of chronic diseases,
it is important to determine the bioavailability of carotenoids
from vegetables and the effect of vegetable consumption on
selected biomarkers of chronic diseases.
OBJECTIVE: To assess the
bioavailability of beta-carotene and lutein from vegetables and
the effect of increased vegetable consumption on the ex vivo
oxidizability of LDL.
DESIGN: Over 4 wk, 22 healthy adult subjects
consumed a high-vegetable diet (490 g/d), 22 consumed a
low-vegetable diet (130 g/d), and 10 consumed a low- vegetable
diet supplemented with pure beta-carotene (6 mg/d) and lutein (9
mg/d).
RESULTS: Plasma concentrations of vitamin C and
carotenoids (ie,
alpha-carotene, beta-carotene, lutein, zeaxanthin, and beta-
cryptoxanthin) were significantly higher after the high-vegetable
diet than after the low-vegetable diet. In addition to an
increase
in plasma beta-carotene and lutein, the pure
carotenoid-supplemented diet induced a significant decrease in
plasma lycopene concentration of -0.11 micromol/L (95% CI: -0.21,
-0.0061). The responses of plasma beta- carotene and lutein to
the high-vegetable diet were 14% and 67%, respectively, of those
to the pure carotenoid- supplemented diet. Conversion of beta-
carotene to retinol may have attenuated its plasma response
compared with that of lutein. There was no significant effect on
the resistance of LDL to oxidation ex vivo.
CONCLUSIONS: Increased vegetable consumption
enhances plasma vitamin C and carotenoid concentrations, but not
resistance of LDL to oxidation. The relative bioavailability of
lutein from vegetables is higher than that of beta- carotene.