"The study reinforces the hypothesis that a healthy diet has potential not only in the warding off of depression, but also in its prevention," says Ms Anu Ruusunen, MSc, who presented the results in her doctoral thesis in the field of nutritional epidemiology.

Depressed individuals often have a poor quality of diet and decreased intake of nutrients. However, it has been unclear whether the diet and the intake of foods and nutrients are associated with the risk of depression in healthy individuals.

Those following a healthy diet are less at risk

A healthy diet characterized by vegetables, fruits, 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, fruits, 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 study improved depression scores with no specific group effect. Furthermore, a reduction in the body weight was associated with a greater reduction in depressive symptoms.

Junk food, sugar and processed meats may increase depressive symptoms

Adherence to an unhealthy diet characterized by a high consumption of sausages, processed meats, sugar-containing desserts and snacks, sugary drinks, manufactured foods, French rolls and baked or processed potatoes was associated with an increased prevalence of elevated depressive symptoms.

Contrary to some earlier observations, vitamin B₁₂ intake, serum concentrations of n-3 PUFAs, serum ratio of n-6 to n-3 PUFAs, tea drinking and total caffeine intake were not related to the risk of depression in this study.

The study was based on the population-based Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study. The participants, over 2,000 middle-aged or older Finnish men were followed-up for an average of 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. The effects of the three-year lifestyle intervention on depressive symptoms were investigated in the Finnish Diabetes Prevention Study (DPS) with 140 middle-aged men and women randomized to intervention and control groups.

Depression is one of the leading health challenges in the world and its effects on public health, economics and quality of life are enormous. Not only treatment of depression, but also prevention of depression needs new approaches. Diet and other lifestyle factors may be one possibility.

The whole 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