For the longest time, I swore I wasn't a morning person. As soon as I ate my routine breakfast of a toasted bagel with butter, I had to pinch myself to stay awake.

Recently, I discovered my heavy lids and endless yawns were not a predisposition, but rather a result of my diet. "Carbohydrates have a relaxing effect," says Judith Wurtman, Ph.D., director of the women's health program at Massachusetts Institute of Technology in Cambridge and coauthor of The Serotonin Solution. "And eating too many will make you sleepy," she says.

Instead of feeling drowsy, I could actually rise and shine in the morning? Absolutely. And you can, too, if you're mindful of what you eat.

"Your diet ultimately has an impact on how you feel," says Mary Beth Augustine, R.D., a dietitian at the Continuum Center for Health & Healing in New York City. Banish three unsavory moods by eating the right foods.

Mood: Stressed Out or Tense

You're running late for an important meeting; you're working on a tight deadline; you're waiting for medical results from a serious test. No matter the scenario, strained situations can produce similar physiological reactions in your body. "Your blood pressure rises, your heart rate in-creases and your body makes glucose to give you the energy you need to get through," says Augustine. There's also a rise in cortisol, a hormone that, when released over time, can lead to heart disease, diabetes and obesity.

Foods to reach for:

Complex carbo-hydrates, such as legumes, whole-grain breads and cereals, and starchy vegetables, such as potatoes and corn.

Why it works:

"Carbohydrates destress you by increasing the production of serotonin," says Dr. Wurtman. This key chemical in your brain improves mood, increases emotional energy and relieves pain.

Keep in mind:

Simple carbohydrates that are refined or processed, such as doughnuts and cookies, up serotonin production faster than complex carbohydrates by quickly releasing glucose, which further increases the brain's ability to produce serotonin. But by choosing a jelly doughnut over a whole-wheat pita pocket you'll pay a hefty price in weight gain and compromised healthy eating goals. In addition, for serotonin to tranquilize, carbs need to be eaten on an empty stomach and, surprisingly, without protein.

By the way...

If you experience irritability brought on by premenstrual syndrome (PMS), then you have all the more reason to consume complex carbohydrates. Dr. Wurtman advises eating a baked potato or drinking PMS Escape, a carbohydrate-based beverage that decreases anxiety.