I just Googled around some, gnu, and though there don't seem to be side effects at the suggested dosages, there also doesn't seem to be any legitimate study on whether lutein (a carotenoid) supplements are useful.

Apparently eggs are the best dietary source (most easily absorbed by the body), folloed by dark leafy greens like spinach and kale. Or you could just eat marigold flowers, as that seems to be a main source for the extract.