Just saw this over on r/Soylent, thought the folks here may like the read as well. Also, posting it here somewhat as a placeholder until I can get around to reading up a bit. Until then feel free to chime in on the subject.
[quote] About 20 mg of carotenoids daily are needed to achieve the visual benefits described…
"We can get about 15-20% improved visual function in the healthy eye, which is remarkable really,” says John Nolan, a professor at the Waterford Institute of Technology in Ireland who is running an ongoing study exploring vision enhancement with these supplements. Improvements of about 30% can be achieved in patients with macular degeneration, he says. It takes about six to 12 months for the supplements to take their full effect.
There is also some evidence linking carotenoids with other processes in the body: in motor skills, hearing, immune responses, and cognition.
A 2013 study by Hammond found that higher macular pigment levels are associated with faster processing speed and better balance.
It’s worth pointing out, however, that most of the studies so far have identified only correlations between the pigments and brain function – the mechanism is not yet clear.[/quote]