Falling asleep and waking up are controlled by a number of chemical changes in the brain and the blood. Both REM and deep sleep are essential parts of the normal sleep cycle. Foods and medicines that alter the balance of these chemicals also can affect how well we sleep.
For example:
- Caffeine, which is found in coffee, tea, colas, and chocolate, can cause insomnia (lack of sleep).
- Antidepressants, alcohol, and smoking can cause a loss of REM (rapid eye movement) sleep.
- Smoking and alcohol also can result in a loss of deep sleep.
