The nutrient that is not digested but keeps the digestive system healthy is C. Vitamins :)
Explanation: Chemicals
There are four primary chemicals in the brain that effect happiness: dopamine, oxytocin, serotonin, and endorphins. By designing gamified experiences that activate these chemicals, you can increase your users' happiness and loyalty.
A warm soft place to sleep and a quiet environment. Maybe certain music can be a factor too.
