Anu Ruusunen of the University of Eastern Finland, who presented the results of her doctoral thesis in the field of nutritional epidemiology, said the study's data came from the population-based Kuopio Ischaemic Heart Disease Risk Factor Study. The participants, more than 2,000 middle-age or older Finnish men, were tracked over 13-20 years.
Their diet was measured by food records and food frequency questionnaires, and information on cases of depression was obtained from the National Hospital Discharge Register in Finland.
The effects of the three-year lifestyle intervention on depressive symptoms were investigated in the Finnish Diabetes Prevention Study with 140 middle-age men and women randomized to participate in a lifestyle intervention and a control group.
A healthy diet of vegetables, fruit, berries, whole-grains, poultry, fish and low-fat cheese was associated with a lower prevalence of depressive symptoms and a lower risk of depression during the follow-up period.
Increased intake of folate was also associated with a decreased risk of depression. Vegetables, fruit, berries, whole-grains, meat and liver are the most important dietary sources of folate. In addition, increased coffee consumption was non-linearly associated with a decreased risk of depression.
In addition, participation in a three-year lifestyle intervention improved depression scores. Furthermore, a reduction in body weight was associated with a greater reduction in depressive symptoms, Ruusunen said.
However, those who continued eating an unhealthy diet characterized by a high consumption of sausages, hot dogs, processed meats, sugar-containing desserts and snacks, sugary drinks, manufactured foods and processed potatoes were associated with an increased prevalence of elevated depressive symptoms, the study found.
The study is available online at: http://epublications.uef.fi/pub/urn_isbn_978-952-61-1201-5/urn_isbn_978-952-61-1201-5.pdf.