Caffeine is known to keep people awake at night, as are big meals and fatty, sugary or spicy foods.
On the flip side, "There is some information that certain foods help with sleep," says Kathe Henke, laboratory director for the Sleep Disorders Center of Virginia in Henrico, Va.
*Think tryptophan. The brain uses this amino acid to make serotonin and melatonin, substances that promote sleep. Foods high in tryptophan are protein-rich items such as dairy products, seafood, meat, poultry, whole grains, beans, lentils, peanuts, eggs and sesame seeds.
* Combine protein with carbohydrates. Complex carbohydrates allow more tryptophan to enter the brain, while protein-rich foods alone may interfere with sleep because they contain another amino acid that perks up the brain. Some smart combinations: peanut butter or grilled chicken on whole-wheat bread or hummus on whole-grain pita slices.
* Add some calcium. Calcium helps the brain use tryptophan to create melatonin. So have a bowl of low-sugar cereal with milk, a carton of Greek yogurt or some low-fat cheese on whole-grain crackers -- or that old standby, a glass of warm milk.
* ... and magnesium. This mineral plays a role in serotonin production and may also help muscles throughout your body relax. Good sources include almonds, bananas, beans, spinach, soybeans and whole-grain brown rice.
* Keep it light and healthy. Big evening meals, especially those high in fat, keep the digestive system churning longer. Sugary junk foods cause blood sugar to spike and then fall rapidly, which can trigger the release of stress hormones.
* Grab some cherries. Tart cherries naturally boost melatonin levels, according to research from the universities of Pennsylvania and Rochester. Eat them fresh or dried or have a small glass of cherry juice.