Nanorobots will feed humans through blood and extract waste

Ray Kurzweil : futurist
Nanobots will be capable of entering the bloodstream to "feed" cells and extract waste will exist (though not necessarily be in wide use) by the end of 2020's. They will make the normal mode of human food consumption obsolete.

Kurzweil, Ray. 2005. The singularity is near: when humans transcend biology. New York: Viking.