To some people, just the image of a warm glass of milk comforting one to sleep at night can create drowsiness.The drowsiness caused by that warm glass of milk may be caused by some factors that might surprise some people. The benefit of a good night's sleep from a warm glass of milk may be a tossup between the psychological and the physiological.
Tryptophan is an amino acid found in milk and turkey. Tryptophan in large doses does produce sleepiness, and many people attribute tryptophan to the drowsy feeling after the big Thanksgiving meal. However, according to Dr. Timothy Morgenthaler, a sleep specialist at the Mayo Clinic, there is no food that can produce sleep in an individual. The amount of tryptophan found in a turkey dinner or a glass of milk does not contain enough of the chemical to induce drowsiness.
That sleepiness associated with a warm glass of milk may be more psychological than most would suspect. Most people recall pleasant thoughts about their mothers. Milk is associated with mothers and a mother's love and care. Comforting feelings and remembrances can produce chemicals in the brain that actually form a sensation of well-being and relaxation. This brain chemical, serotonin, is associated with sleep. This feeling of well-being and relaxation may cause the sleepiness.
A glass of warm milk warms the body. People sleep better when they are warm because the muscles relax more. When the body temperature is raised, the body also slows responses. The slowing of bodily responses precedes sleep. The warmth of the milk induces bodily changes that create this slowing of the body's responses and relaxation of muscles.
Warm milk coats and soothes the stomach. When drinking warm milk, a person may actually be a little peptic and milk may ease the feeling and create a sense of relief. Another factor is that most people sleep better when the stomach has something in it. Babies sleep after nursing when their stomachs are full. The same is true of children and adults. A stomach with some milk in it is comforting, which helps to induce sleep.
For some people, particularly those with milk allergies or lactose intolerance, a glass of warm milk may be followed by digestive upsets. Other options that may be tolerated include soy, lactose-reduced, almond and rice milk.