Raw coffee is, on average, just one percent caffeine, but it contains seven to nine percent chlorogenic acid, a strong antioxidant that prevents retinal degeneration in mice, according to a Cornell study published in the Journal of Agricultural and Food Chemistry.

The retina is a thin tissue layer on the inside, back wall of the eye with millions of light-sensitive cells and other nerve cells that receive and organize visual information. It is also one of the most metabolically active tissues, demanding high levels of oxygen and making it prone to oxidative stress. The lack of oxygen and production of free radicals leads to tissue damage and loss of sight.

The study is "important in understanding functional foods, that is, natural foods that provide beneficial health effects," said Chang Y Lee, professor of food science and the study’s senior author. "Coffee is the most popular drink in the world, and we are understanding what benefit we can get from that."

Previous studies have shown that coffee also cuts the risk of such chronic diseases as Parkinson’s, prostate cancer, diabetes, Alzheimer’s and age-related cognitive declines.