Drawing conclusions from divergent data

The review, published in the American Journal of Clinical Nutrition, combined the evidence of 35 controlled trials. There were many differences among the studies, including in the participants’ diagnoses, gender, and age; the amount and types of omega-3 fatty acids taken; and the duration of treatment. Despite these differences, the researchers were able to draw some important conclusions from the data:

• Omega-3 fatty acids had more effect in trials in which the participants had more severe symptoms.
• People with a diagnosis of depression were more likely to benefit from supplementing with omega-3 fatty acids than people without the diagnosis.
• There is little evidence that taking omega-3 fatty acids is helpful in people with mild to moderate depressed mood or in people who are trying to prevent depression.

The study authors summarized their findings: “Trials conducted in individuals with a diagnosis of depressive illness provide some evidence of a beneficial effect of omega-3 polyunsaturated fatty acid supplementation, but no evidence is available suggesting a benefit of omega-3 polyunsaturated fatty acid supplementation in individuals without a diagnosis of depressive disorder.”

The many benefits of fish fats

The omega-3 polyunsaturated fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are found in cold water fish such as salmon, tuna, herring, and mackerel, as well as cod liver oil. Eating these fish regularly and supplementing with cod liver oil or EPA and DHA are healthy and safe practices for most people. In addition to their potential in treating depression, omega-3 fatty acids have been found to reduce high blood pressure, lower triglyceride levels, and improve symptoms in people with certain autoimmune conditions such as rheumatoid arthritis and Crohn’s disease.

Taking on depression from multiple angles

A number of nutritional and lifestyle factors can influence mood in general, and the course of depression in particular. Taking the following steps could lead to a better mood, though it is important to seek medical advice if you feel depressed beyond the normal ups and downs, and especially if these feelings are preventing you from functioning normally:

• Exercise regularly: Studies have found that as little as three hours of aerobic activity every week can reduce depressive symptoms, and exercise therapy may be as effective as antidepressant medication for treating depression.
• Cut down on sugar: There is some evidence that reducing refined sugar intake, along with cutting down on caffeine, can improve mood, and other evidence that an underlying metabolic problem (insulin resistance) may be associated with depression in some people.
• Take the sunshine vitamin: Low levels of vitamin D are more common in people with depression, and supplementing with vitamin D has been found to improve mood in people with and without a diagnosis of depression.
• Try light therapy: For people with seasonal depression, taking in 10,000 lux from a light box for 30 minutes every morning can improve energy level and mood.
• Consider adding a B-complex: Depression is a common symptom in people with vitamin B12 and folic acid deficiencies. Vitamin B6–deficiency, which can occur especially in women using oral birth control, can also contribute to depression.

(Am J Clin Nutr 2010;91:757–70)