I'm soon to be 57.
I have elder relatives that did not do much in the area of exercise and diet control. These relatives are now battling Alzheimer's, dementia and failing bodies. Although I know exercise and diet are not the only factors, my own mother who has made the effort to exercise and eat well is fairing much better.
In general I have seen people who are active both mentally and physically stay sharper later in life.
Also, peers in my age group (acquaintances, current and old friends) that aren't avid exercisers and don't pay attention to what they eat all seem to have more issues and less desire to push themselves.
So, YES, I feel cycling is my fountain of youth! I will ride, exercise and eat well and hopefully be around for a very long time.