Originally Posted by mary fierce
lycopene in a supplement may be of very little value. It's one of the only nutrients that has very little bioavailability until it's cooked. This is why tomato sauce is considered more nutritious than raw tomato, and why Reagan wasn't far off the mark when he declared ketchup to be a "vegetable" (for the purpose of school lunch program reckoning).
While you say raw "lycopene" has "very little" bioavailablity, from what I've read, raw tomatoes has a lesser concentration of lycopene available than cooked tomatoes -- but I would not characterize it as "very little".
But let's look past that characterization for a while. I am curious as to why
cooked tomatoes has more lycopene available than raw tomatoes. Perhaps you could shed some light on this. In the past, I assumed that that the difference was due to a difference in the type of lycopene isomers in raw tomatoes/food compared to the isomers in cooked fruits/veggies. It seems that this notion was also assumed by many nutrition scientists.
I am sure that you are aware that tomatoes and other food sources contain primarily all-trans isomers of lycopene whereas the human body prefers cis-isomers. However, some of my more recent reading indicates that cooking only converts a small percentage of all-trans to cis-isomers. (OTOH, gastric juices in the stomach can convert quite a bit of the all-trans to cis-isomers). These studies appear to disprove the earlier thinking on the bioavailbility issue.
Since there appears to be a significant difference in the concentration of lycope available from raw foods compared to cooked foods, there must be some other reason. I have not seen any sources that account for the difference and I can only speculate as to the difference occurs. There is possibly something in the raw fruit/veggie, that is diminished with cooking, that limits the available lycopene. Or possibly, the lycopene in raw foods is bound in some manner which limits its utilization. OTOH, perhaps cooking changes the chemical structure in some other manner (other than the isomerization of lycopene) that facilitates the greater availablity of lycopene. Any insights on this?