Winter brings short days and chilly temperatures, and you might find your mood mirroring these bleak winter days. Of course, many of us feel a little more sluggish during winter but for some people the winter blahs can develop into a more serious type of depression.
In some cases, the winter blues develop into Seasonal Affective Disorder (aka SAD), a form of depression that begins in late fall, peaks in January and February and usually fades by early spring. Common symptoms of SAD include extreme tiredness--the kind that makes you just want to curl up under the covers and sleep until spring--an intense craving for carbs (especially sweets), irritability, weight gain and the desire to avoid social situations. About 6 percent of the U.S. population falls into its grips annually, and about 15 percent more suffer from a milder version of the winter blues.
What Causes SAD?
One theory holds that the increased hours of darkness disrupt the brain chemicals that affect mood, such as serotonin and melatonin. Some experts believe reduced sunlight causes vitamin D deficiencies--but whether that translates into depression is not entirely clear. There have been conflicting studies on whether there's a causal connection between low vitamin D levels and depression. So when it comes to a clear cause for SAD, the jury's still out. While light therapy appears to be one of the most effective treatments for SAD, what you eat can also play a role in alleviating its symptoms. Of course, as with any medical issue, talk with your doctor about treatments if you're dealing with any kind of depression.
Can Vitamin D Help?
Studies of vitamin D's ability to curb SAD have been mixed--some show a benefit, while others don't. Proponents of vitamin D supplementation as a therapy for SAD note that many of the contradictory studies used doses that were too low or used D2, a form of vitamin D that is weaker than the recommended D3. A 2010 comprehensive review of existing studies that looked at the effects of vitamin D on different kinds of depression and anxiety concluded that treating vitamin D deficiencies in people with depression might be an easy and cost-effective way to improve mental health.
In another study, researchers from the University of Toronto noticed that people who were suffering from depression, particularly those with SAD, tended to improve as their levels of vitamin D in the body increased over the course of a year. Researchers, though, are unsure how much vitamin D is ideal. Still, it doesn't hurt to make sure you're getting what you can from your diet. Some studies suggest that as many as 7 out of 10 Americans don't get enough of this "sunshine vitamin"--particularly during winter. The Institute of Medicine's daily-recommended amount (for ages 1 to 70) is 600 International Units (IUs). Check with your doctor to see if you might need a supplement.
Food Sources of Vitamin D: Certain fatty fish (salmon, tuna, sardines, rainbow trout), fish oils (like cod liver oil), fortified milk and egg yolks are some of the richest sources of vitamin D.
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Are Omega-3 Fatty Acids a Factor?
Studies have long linked deficiencies of beneficial omega-3 fatty acids to depression, as well as to SAD specifically. A 2011 study in Nature Neuroscience has even demonstrated--albeit in mice--how lower omega-3 levels change brain activity. The omega-3 deficient mice had decreased function of specific brain receptors involved in pain and appetite regulation, which are found in regions of the brain associated with mood disorders. The behavioral changes seen in the mice were all typical of depression. Other studies have shown that omega-3s appear to help maintain healthy levels of the brain chemicals dopamine and serotonin. Researchers note that cell membranes are partly made up of omega-3 fats. Higher omega-3 levels may make it easier for serotonin--a chemical that enables brain cells to communicate--to pass through cell membranes. Low levels of serotonin are linked with depression, aggression and suicidal tendencies, while dopamine is a "reward" chemical that the brain releases in response to pleasurable experiences, such as eating or having sex.
Some results suggest that SAD is less common in those who consume more omega-3 fatty acids, such as Icelandic people, who eat plenty of coldwater fish. One of the largest studies ever conducted assessing omega-3s' effectiveness in treating major depression (published in 2010 in the Journal of Clinical Psychiatry) looked at 432 people with major depression. Half the participants took a high-concentration fish oil supplement (1,050 mg of EPA and 150 mg of DHA); the other half took a similar-looking placebo. The researchers found the omega-3 supplements effective, comparable to results with conventional antidepressants. Although this study looked at depression in general and not specifically at patients whose depression is caused by SAD, its strong results are encouraging.
Food Sources of Omega-3 Fats: Because our bodies cannot make these essential omega-3 fatty acids, we've got to eat them. Oily, fatty fish (mackerel, herring, salmon, sardines, anchovies) are the best sources of omega-3s because they contain the "more potent" forms of omega-3s: eicosapentaenoic (EPA) and docosahexaenoic acid (DHA). Flaxseed, hemp, canola and walnut oils are all rich sources of another omega-3, alpha-linolenic acid (ALA). Our livers metabolize ALA into EPA and DHA. But our livers are limited in their abilities to convert ALA. It is estimated that only 5 to 15 percent of ALA is ultimately converted to EPA and DHA.
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Careful Carb Snacking
Part of the reason people with SAD crave carbohydrates may be due to decreased serotonin activity. Carbohydrates promote the production of serotonin, a feel-good brain chemical. (Drugs such as Paxil, Prozac and Zoloft, are often used to treat depression, as well as SAD, because of their ability to increase serotonin.)
Snacking on the right kinds of carbohydrates can relieve some of the symptoms of SAD, according to Judith Wurtman, Ph.D., co-author of The Serotonin Power Diet. (Wurtman has long researched carbohydrates and their link to depression, publishing a landmark article about it in Scientific American in 1989.) A recent study she led looking at the SAD-carb connection indicated that about 30 grams of carbs--or about 120 calories--per day were enough to make the serotonin you need. But not all carbs are created equal. Eating sweets and simple carbohydrates, like doughnuts, white rice and white bread, quickly raise blood sugar levels, triggering a spike in insulin. The flood of insulin in turn causes all that blood sugar to be rapidly metabolized. That sudden drop in blood sugar--aka "sugar crash"--can cause fatigue, headache and irritability--not good when you're already struggling with the fatigue that comes with SAD! Wurtman recommends eating carbohydrates that have little fat and low protein to ensure serotonin is made (protein can dampen the effects of serotonin production in the body).
Food Sources of SAD-Friendly Carbohydrates: Good snacking choices include popcorn, pretzels, shredded wheat squares or low-fat biscotti. When it comes to meals, Wurtman recommends making dinner your main carbohydrate-containing meal. That's because evening is usually the time when the symptoms of SAD are at their strongest--and so is the urge gorge on cookies. Eating healthier carbs, like lentils, brown rice and potatoes, may help fight that urge.
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What helps you beat the winter blues?
By Gretel H. Schueller
Gretel H. Schueller is an award-winning journalist and book author. A graduate of New York University's Science, Health and Environmental Reporting Program, she's put her masters in journalism to good use. While on assignment, she has eaten backyard weeds, harvested cactus buds in an Arizona desert and made goat cheese in Greece.
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