BIOAVAILABILITY OF CAROTENOIDS FROM VEGETABLES

Authors: Clevidence, Beverly; Paetau Robinson, Inke; Smith Jr, James

Submitted to: Industrial Crops and Products
Publication Type: Proceedings
Publication Acceptance Date: 6/22/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Carotenoids, the yellow-red pigments in many fruits and vegetables, are among the phytonutrients thought to provide protection from chronic diseases including cardiovascular disease and cancer. Normal cooking and food processing procedures can enhance the availability of carotenoids relative to raw vegetables. These treatments disrupt cell walls and may separate carotenoids from proteins, facilitating the liberation and thus the absorption of carotenoids. Adequate levels of dietary fat are critical for absorption of carotenoids, but this may be less important in Western countries where fat intake is relatively high. Dietary fiber may inhibit absorption of carotenoids. In the practical situation of changing diet to improve health, fat intake is lowered and fiber from fruit and vegetable intake is increased; yet, these changes do not negate an elevation in plasma carotenoid concentration. Various carotenoid supplements are popular, but information relative to interactions among carotenoids is limited. In some cases, carotenoids from supplements are more available to the body than they are from foods. It appears, however, that high levels of certain single carotenoids may alter availability of other carotenoids for absorption. Accumulating evidence strongly indicates that realistic increases in fruit and vegetable consumption can appreciably increase plasma carotenoid levels of Americans: in turn, epidemiological studies suggest that small but habitual increases in consumption of carotenoid-rich vegetables reduce the risk of chronic diseases including cancer and cardiovascular disease. This information will be useful to plant scientists who study carotenoids as well as to nutritionists and other health professionals.

Technical Abstract: For carotenoids to exert their purported benefits, they must be absorbed and transported to sites where they exert their effects. The heat- treatments involved in cooking and food processing generally enhance the bioavailability of carotenoids. Heat treatments associated with food processing can convert the naturally occurring trans isomers of beta- carotene to cis isomers, but heat-induced isomerization of lycopene is minimal. Dietary fat enhances the absorption of carotenoids, but the amount of fat required to optimize carotenoid absorption is unknown. Although plasma carotenoids are elevated in people who consume large amounts of alcohol, the effect appears to result from inhibition of carotenoid metabolism rather than from increased absorption. Dietary fiber reduces plasma response of carotenoids as do certain drugs and dietary agents that interfere with micelle formation or availability. Consuming realistic amounts of carotenoid-rich vegetables has been demonstrated to increase concentrations of carotenoids in human plasma and tissues. Certain carotenoids can enhance or limit the bioavailability of other carotenoids, and in some cases, carotenoid bioavailability is greater from supplements than from foods. Carotenoid supplements, although popular, have not yet been demonstrated to provide major health benefits, but there is substantial evidence that habitual consumption of carotenoid- rich fruits and vegetables is an effective strategy for preserving human health.