There are things that supplements cannot provide you that are necessary for your body to fuction and survive, like fat and calories. Without those you would starve to death. I suppose if you drank meal replacement shakes three times a day you would survive although I would think the muscles in your jaw would grow rigid from not chewing food anymore.
If you don’t use your body organs for a long time or ever again or say you don’t have a b.m. because you don’t eat, they may shut down or cause a mass of other health problems, your body is a machine, you cannot live only feeding yourself vitamins and water. You need the whole body working together to have optimum health.