Thank you for posting this article about carotenoids. I am allergic to Walnuts, so its great to know that there's other alternative natural foods that might help!
Here's the wikipedia page on carotenoids, and an excerpt from it. http://en.wikipedia.org/wiki/Carotenoid
Carotenoids are organic pigments that are found in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms, including some bacteria and some fungi. Carotenoids can be produced from fats and other basic organic metabolic building blocks by all these organisms. Carotenoids generally cannot be manufactured by species in the animal kingdom so animals obtain carotenoids in their diets, and may employ them in various ways in metabolism.
Maybe this is why the Wahls Protocol may work! Terry Wahls who is a MD who has MS suggests we eat a total of 9 cups a day of leafy greens, sulfer containing veggies, and brightly colored fruits and veggies (3 cups of each).
Another excerpt from the wikipedia page I linked to above says:
Since dietary lipids have been hypothesized to be an important factor for carotenoid bioavailability, a 2005 study investigated whether addition of avocado fruit or oil, as lipid sources, would enhance carotenoid absorption in humans. The study found that the addition of both avocado fruit and oil significantly enhanced the subjects' absorption of all carotenoids tested (α-carotene, β-carotene, lycopene, and lutein).
So it sounds like its good to eat some healthy oils with your fruits and veggies, so that the carotenoids can do their thing!
I think there was a recent study showing that the reason the Mediterranean Diet is good for health is the combination of olive oil and veggies eaten at the same time. Maybe for the same reason?