Call it “the blues,” “a funk,” or “waking up on the wrong side of the bed,” we've all felt it at one time or another: For no particular reason, you feel sad or anxious for a day, a week, maybe even several weeks. Muddled thoughts and low energy slow your productivity and wreak havoc on your days. You scour your brain to try to pinpoint what's bothering you, but come up empty.

Americans today fill more than 232 million prescriptions annually for antidepressants — up fourfold from a decade ago. But as rates of both clinical depression and more transient day-to-day mood problems climb, some mental health experts say evaluating diet, lifestyle choices, and your attitude could be key in kicking a persistent bad mood. “Consider your symptoms a wake-up call,” says psychiatrist James Gordon, MD, author of Unstuck: Your Guide to the Seven-Stage Journey Out of Depression (Penguin, 2008). “Something in your life is out of balance.”

It isn't just a hunch that these factors play a role: For decades scientists have believed that depression arises from deficiencies (some of them genetic) in brain chemicals like serotonin. But researchers now realize that blue moods can also be a product of an unhealthy brain structure made up of withering brain cells that, consequently, have trouble communicating. One primary factor that contributes to cell atrophy? A poor diet, says Alan C. Logan, ND, author of The Brain Diet (Cumberland, 2007). Here are five dietary factors and other lifestyle habits that can mess with your mood.

  1. Skipping breakfast. Do you start your day by scarfing down a bagel in the car — or with no breakfast at all? Not fueling your body in the morning will only backfire, Logan says. Blood sugar dips, sending your body into fight-or-flight mode. This drenches your system in stress hormones — such as cortisol and adrenaline — that interfere with mood and thinking. If you have simple carbs, like a white bagel, you get a fleeting lift but then crash even harder than if you'd eaten nothing. A study published in Appetite divided teens into four groups, with two groups eating a high-fiber cereal, one slugging a pure-sugar drink, and another skipping breakfast. When tested later, those who ate no breakfast saw their scores for “contentment and alertness” drop precipitously throughout the morning. Those who had the sugary drink saw their scores spike and then crash 90 minutes later, with mood plunging by morning's end.

    Mood Building Blocks

    Click here for a full list of vitamins and supplements to help banish your bad moods.

    What you can do≫ Always eat an ample breakfast of complex carbohydrates and protein, such as whole-grain toast with poached eggs or low-fat yogurt and granola. Wholesome carbs provide fuel for the brain and have a mood-stabilizing effect. Protein provides the building blocks (amino acids) for feel-good chemical messengers, such as serotonin.

  2. Eating the wrong fats. When it comes to promoting a healthy mood, getting the right ratio of omegas is critical. Omega-3 essential fatty acids, found in cold-water fish, walnuts, flaxseed oil, olive oil, and green leafy veggies, make up the scaffolding of the brain. If you get plenty of omega-3s, you end up with a well-oiled machine, but most of us get too many omega-6 fatty acids (found in corn, sun-flower, safflower, and peanut oils) instead. The result: rigid brain-cell membranes and poor cell communication. Researchers say the omega-6 to omega-3 intake ratio should be no more than 4:1, but the typical American diet puts it closer to 20:1. Experts recommend a 650-mg combo of the omega-3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) per day, but the average American gets about 130 mg. One recent study found 1,000 mg of EPA taken daily for eight weeks as effective in treating depression as fluoxetine (Prozac).

    What you can do≫ Read ingredient labels to avoid overconsuming omega-6 oils. Eat at least two helpings of oily fish per week, and for backup take a fish-oil supplement (up to 1,000 mg per day of EPA-DHA combination). Vegetarians and vegans take note: Fish oil is the best source of omega-3s, says Logan, because it contains DHA, which influences the shape and structure of brain cell membranes, and EPA, which expedites communication between cells. Vegetarian sources of omega-3s, such as flaxseed oil, contain alpha-linolenic acid, only some of which is converted to DHA and EPA by your body. Look for vegetarian DHA supplements derived from marine algae (after all, it's where cold-water fish get their DHA). Loading up on dark green leafy vegetables, walnuts, flaxseed, or omega-3-enriched eggs can't hurt, either.

  3. Low folate and B12 intake. These key B vitamins play a multifaceted role in regulating mood. They serve as building blocks for pleasure-promoting neurotransmitters, such as dopamine; foster nerve health; and flush the body of the mood-compromising amino acid homocysteine. An affinity for refined grains (such as white flour, in which the folate has been stripped out during processing) and a distaste for fresh vegetables (high in folate) has left as many as one-third of Americans low in this nutrient. Adults lacking enough B12 — found in lean red meat, eggs, and milk — are 70 percent more likely to suffer depression. Research shows that people with low B12 or folate levels have a harder time pulling out of the blues — even when they take medication or see a therapist.

    What you can do≫ Eat whole grains and green leafy vegetables, and take 800 mcg folic acid and 1 mg of B12 daily.

  4. An erratic exercise routine. Fewer than half of Americans exercise regularly, according to a new study in the Journal of the American Medical Association, and research shows that regular aerobic exercise — such as running, cycling, or brisk walking — boosts mood. “People who exercise on a regular basis tend to report less depression and anxiety,” says Benson Hoffman, PhD, an assistant clinical professor at Duke. Evidence suggests that exercise may regulate neurotransmitter function (similar to antidepressant medications) or neuroendocrine stress-response systems, and may even result in the growth of new brain cells, says Hoffman. Some animal studies have shown that exercise enhances neuropeptide Y, a brain chemical associated with stress resilience, and dampens the influence of another brain chemical called CCK-4, which is responsible for inciting feelings of panic.

    What you can do≫ After a 10-minute warm-up, get your heart rate up to between 70 percent and 85 percent of your recommended maximum heart rate (220 minus your age). Sustain it for at least 30 minutes, three to four times per week. (For instance, the maximum heart rate for a 40-year-old woman in relatively good health is 180, making her target heart rate between 126 and 153.) Hoffman's research found that a similar 16-week program proved just as effective as a daily dose of the antidepressant sertraline (Zoloft), but he stresses that you have to exercise often to see a difference. “When you get down to two days a week, you may not see a difference at all.”

  5. Succumbing to negativity. Ed Diener, PhD, a psychology professor at the University of Illinois and coauthor of Happiness (Wiley-Blackwell, 2008), says the way you view your world can have a direct impact on mood. You might hold grudges, see the glass as half empty, remember the bad times rather than the good, and forget to pencil in time to do what you love. Seeing happiness as an endpoint — a place you reach when you have the right spouse, right car, right job — can leave you feeling stuck when you get all that, or don't.

    What you can do≫ Forgive an adversary. Look back on good memories. Pencil something joyful — whether it's a warm bath or a short conversation with a friend — into each day. And keep looking forward: “Happiness has to evolve with new goals, fresh projects, and interesting activities,” says Diener. “It's a process, not a destination.”