Humans should live longer than any other mammal on Earth because humans can consciously control the amount and quality of food material entering the body. If the intake of this food is decreased to a pleasant frugal minimum (but still includes high-quality raw plant fats, which are antioxidants), then the obstructions and free radicals in the system will be decreased to a minimum. In this way, the system becomes abundant in electrons, is more efficient (well-oiled) and operates with less friction, thus maximizing longevity.
The two raw foods known to have superior longevity properties are royal jelly and wolfberries or goji berries. These should be eaten daily as part of a youthening program.
In reality, eating for detoxification is more about not eating for detoxification. Generally, the less you eat, the longer you live (so the more you get to eat). Eating less has thus far been the only scientifically proven method to extend the lifespan of humans, animals, birds and worms.
If you are doing an extended juice fast (15 days +), you may want to include small portions of cold-pressed olive, hemp or flax oil in with your drinks to provide the body with necessary fat to maintain some equilibrium.
One interesting working theory that I agree with is that (when an individual is ready) one should continue on a juice fast cleansing program until all excessive body fat is eliminated. Body fat is where most of the body's poisons are stored.