However, we do know that with age human adipose becomes very yellow. From balance analysis, we know that you absorb more carotenoid from your diet than can be found by analyzing the carotenoid content of all your tissues. That means that some of it must be degrading, but we don't know to what. The identification and fate of the ultimate metabolites of carotenoids is an important research question. As I said, I am going to focus on absorption and on the macula.
Human tissue shows substantial levels of most dietary carotenoids.
We absorb most of the carotenoids in our diet, although there is an unusual carotenoid in chloroplasts that we do not absorb. We are unlike most other animals, which show very low carotenoid levels in the tissues despite abundant dietary intake. For example, pigs probably have a substantial amount of carotenoid in their diet because they eat a lot of corn. But lard is white, because pigs do not absorb much carotenoid. There are important and distinctive differences between the metabolism of carotenoids in humans, other primates, and other laboratory animals.