Isomerization of dietary lycopene during assimilation and transport in plasma

Diets of individuals were supplemented with tomatoes, either cooked or as t omato puree in order to compare uptake of lycopene from intact and homogeni zed fruit tissue matrices. Following a diet containing cooked tomatoes over three consecutive 7-day periods, little change in the carotenoid levels in plasma lipoproteins occurred. In contrast, a diet supplemented with concen trated tomato puree, over a 2 week period, caused a significant (p < 0.05) increase in lycopene levels in plasma, showing that the lycopene within int act cells is less bioavailable than that from processed tissue. The isomeri c composition of plasma lycopene was significantly different to that of the ingested puree. A number of ris-isomers (predominantly 5-cis, 13-cis and 9 -cis-) were detected in plasma, that are not present in the lycopene from p uree The significance of the increase in lycopene following dietary supplem entation with respect to bioavailability and the causes of isomerization ar e discussed.