November 7, 2013 – Women whose diet includes more foods that trigger inflammation—like sugar-sweetened or diet soft drinks, refined grains, red meat, and margarine—and fewer foods that restrain inflammation—like wine, coffee, olive oil, and green leafy and yellow vegetables—have up to a 41% greater risk of being diagnosed with depression than those who eat mostly the less inflammatory diet, according to a new study by researchers at Harvard School of Public Health (HSPH).
The study was published online October 1, 2013 in Brain, Behavior, and Immunity. It is one of the most comprehensive studies to date to link certain foods to inflammation and depression.
“It is important to consider the overall diet relationship with disease risk, and not only isolated nutrients or foods,” said lead author Michel Lucas, visiting scientist in the Department of Nutrition at HSPH. “Foods are consumed in combination and their combined effects cannot be predicted from single food analysis. Our approach allowed us to examine the combined actions of food, better reflecting dietary complexity, and improves our understanding of the relationship between diet and disease risk.”
Previous research suggested a link between inflammation and depression, but the association between inflammatory dietary pattern and depression was unknown. Although some inflammation helps the immune system fight disease and injury, studies have linked excessive inflammation to heart disease, stroke, diabetes, cancer, and other conditions.
For more than 12 years, the researchers conducted a prospective study of 43,685 women, ages 50–77, participating in the Nurses’ Health Study. None had been diagnosed with depression or were taking antidepressant drugs at the start of the study and 10,340 women with severe depressive symptoms were excluded from the study. The researchers tracked the women’s dietary patterns and depression, and they tracked several biomarkers for inflammation through blood tests. They documented 2,594 cases of depression using a strict definition (a diagnosis of depression and antidepressant use) and 6,446 using a broader definition (a diagnosis of depression and/or antidepressant use).
The investigators found women who regularly drank sodas, ate red meat or refined grains, and infrequently consumed wine, coffee, olive oil, and vegetables were 29% to 41% more likely to be depressed than those who ate the less inflammatory diet.
“These results converge with parallel findings on the relation between diet and physical health. From a public health perspective, it is reassuring that what is good for the body is also good for the mind,” said senior author Alberto Ascherio, professor of epidemiology and nutrition.
Other HSPH researchers included Walter Willett, Fredrick John Stare Professor of Epidemiology and Nutrition and chair, Department of Nutrition; Frank Hu, professor of nutrition and epidemiology; and, from the Department of Nutrition, visiting scientist Patricia Chocano-Bedoya, doctoral student Fariba Mirzaei, and research associate Eilis O’Reilly. Support for the study was provided by the National Institutes of Health (grant DK58845) and funding to Ascherio from the National Alliance for Research on Schizophrenia & Depression.
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