Donald Doyle, M.D., often sends patients to a local sleep lab for tests and analyzes the results on his computer.

Desperate for those 40 winks? Tossing and turning through the night? Maybe that insomnia has something to do with what you had to eat or drink before going to bed.

Foods with carbohydrates and tryptophan can actually promote a good night’s sleep.

Sleep will be elusive if you snack or sip on certain foods and beverages before bedtime, according to Donald Doyle, M.D., a sleep specialist with NorthBay Center for Specialty Care in Fairfield.

Caffeine tops the list.

Four out of five adults in America consume at least one serving of coffee, tea, soda or other caffeinated beverage each day, according to National Sleep Foundation, but having that last cup just before bed can be a bad idea. “You should really avoid having any caffeine at least six hours before going to bed. And remember that it can be hidden in many foods. Colas, chocolates, and some teas contain caffeine, and if you are sensitive to even small amounts of it, that could be just enough to keep you awake.”

Alcohol is another beverage that can really affect your sleep.

“Sure, having a drink or two may help you fall asleep, but it will affect your ability to stay asleep,” Dr. Doyle notes. “After the alcohol wears off, you can have increasingly restless and fragmented sleep.”

Alcohol keeps you from entering the deeper stages of sleep, which may cause you to wake up still feeling tired even though you have spent an adequate amount of time in bed. Avoid having any alcohol several hours before bedtime.

On the other hand, some foods can actually promote a good night’s sleep. Foods with carbohydrates and tryptophan are best.

Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals can make you drowsy. Proteins from the food we eat are the building blocks of tryptophan.

This is why the best bedtime snack is one that contains both a carbohydrate and protein, Dr. Doyle notes, such as cereal with milk, peanut butter on toast, cheese and crackers, a banana with some peanut butter, or even a glass of milk with an oatmeal cookie. “It also helps keep hunger pangs away, which could prevent you from sleeping.”

But, don’t overdo it. Avoid munching on heavy foods, such as a slice of pizza, leftover pasta and meat sauce, or anything that is high in fat or enriched proteins, Dr. Doyle recommends. “That could be hard to digest and cause indigestion.”

Finally, don’t drink too many fluids before bedtime. Drinking lots of fluids before bed can cause you to wake up repeatedly to use the bathroom.