In Antioxidant vitamins and blood carotenoids associated with the incidence of Alzheimer's disease and dementia in American adults, the authors' conclusion is that the higher the level of blood lutein + zeaxanthin and β-cryptoxanthin, the lower the risk of dementia. (Observations followed for 26 years on 7283 people)
Lutein and zeaxanthin are yellow pigments from the carotenoid family found especially in citrus fruits. Various cohorts have already shown their usefulness in the prevention of diseases including cancer, the prevention of obesity, etc.
The peel of Japanese mandarins (satsuma) is especially rich in carotenoids and β-cryptoxanthin. https://journals.sagepub.com/doi/abs/10.1177/1082013210368556
It is the main carotenoid in satsuma essential oil. http://www.chiriottieditori.it/images/stories/IJFS%20archivio/IJFS151.pdf#page=134
But not many people put tangerine peel into their bread dough or rice as its done so well in September in Ehime.
On the other hand, there is another citrus fruit which is rich in carotenoids and β-cryptoxanthin and whose peel we do eat : the kumquat. Researchers from Miyazaki – kumquat country – say that eating a few kumquats every day stimulates our killer cells and alleviates stress.
We distill an essential oil of long kumquats and another of round kumquats are distilled. They are really very good!