Isomerization of dietary lycopene during assimilation and transport in plasma

Diets of individuals were supplemented with tomatoes, either cooked or as tomato puree in order to compare uptake of lycopene from intact and homogenized 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 concentrated tomato puree, over a 2 week period, caused a significant (p < 0.05) increase in lycopene levels in plasma, showing that the lycopene within intact cells is less bioavailable than that from processed tissue. The isomeric 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 puree The significance of the increase in lycopene following dietary supplementation with respect to bioavailability and the causes of isomerization are discussed.