Stress -- both good and bad -- can affect our health and eating habits. At the best of times, our relationship with food is complex, and when we're under stress our food routines can change: for some people, stress may mean eating more, for others less; some of us will crave particular foods, while others will want to eat at particular times. There's no diet to make stress go away, but the good news is some foods can modify your mood.

1. Certain elements in food can lift your mood by releasing neurotransmitters, brain chemicals that help brain cells communicate with one another.
Serotonin is a neurotransmitter that regulates well-being, calmness, patience and energy. When your serotonin levels are low, you are more likely to feel worried, anxious, angry, stressed and tired.

"Carbohydrates, including bread or pasta, are the one class of foods that can indirectly impact serotonin levels," says Dr. Judith Wurtman, director of the Adara Weight Loss Center in Boston and coauthor of The Serotonin Power Diet (Rodale, 2007), who has studied food and mood for more than 25 years. When you eat carbohydrates, says Wurtman, your body produces insulin, which allows a substance called tryptophan to get into your brain, and it's the tryptophan that is used to manufacture serotonin.

2. Some of the foods that are best at releasing serotonin include bread, cereal, pasta, potatoes, popcorn, rice and even vegetable sushi.
But not all carbohydrates do the job. For instance, fruit doesn't work, says Wurtman, because its sugar -- fructose -- causes insulin to be released too slowly to trigger a serotonin boost.

3. When you eat can also affect your mood.
Your serotonin levels get lower as the day goes on, so it makes sense to eat some carbohydrates late in the afternoon or at night to increase the levels -- and your mood. It's also helpful to eat them on an empty stomach, probably as a snack, so the process can happen more easily.

4. Despite what most of us believe, turkey does not make you sleepy.
On the contrary, says Wurtman, protein foods such as turkey release an amino acid called tyrosine, which, once in the brain, is used to make two chemicals, dopamine and norepinephrine, that have been found to improve alertness and mental sharpness. But, she says, the improvement is most effective if you are engaged in arduous mental activity -- and less profound for most of us.

The sleepy, calm feeling you get after eating a turkey dinner is more likely related to the quantity of food you eat as well as the fat (in the stuffing, gravy and other dishes). Large volumes of food and lots of fat digest more slowly and tend to make you more tired.

5. Omega-3 fats may help with mood and depression.
Some research studies are examining the role that omega-3 fats may play in helping with mood and depression.

Found in fatty fish such as salmon, mackerel, herring and sardines, as well as in omega-3-enriched eggs and dairy products, these fats are an important part of nerve and brain cell membranes, make up part of the communication network in the brain and are a key component in brain development. It is possible that people who do not have enough omega-3 fat in their diet may be at increased risk for depression.

Quick facts
• Eating a fatty food along with your carbohydrates slows down digestion and blunts the feel-good response of carbs. That means pasta with tomato sauce is a better mood-improver than pasta with cream sauce.

• Skipping meals can have negative effect on mood and energy. Eat small amounts of food throughout the day to keep your energy levels and mood more constant.

• When you're tired, you're more likely to be in a poor mood. So limit alcohol and caffeine, both of which can affect sleep.

• There may be even more to the food-mood connection. It's possible that the feelings you have when you eat certain foods can also determine your mood. For instance, eating the foods you associate with happy family times may make you feel good. (Of course, the reverse may be true, as well.)

Want mood-boosting meals without the calories? Check out these 7 slimming comfort foods.