There has been substantial research undertaken on the role of a health-promoting diet in depression. Yet, the evidence of the relationship between the Nordic diet and the risk of depression is scarce. This cross-sectional study aimed to assess whether a healthy Nordic diet is associated with depressive symptoms. In total, 2603 men aged 42–60 years from the Kuopio Ischaemic Heart Disease Risk Factor Study were included. Diet quality was evaluated with a healthy Nordic diet score derived from the 4-day food diaries and depressive symptoms with the self-reported Human Population Laboratory (HPL) depression scale. Quade ANCOVA was used to examine the mean values of HPL scores in quartiles of a healthy Nordic diet score. Participants’ mean age was 53 years and BMI 26·8 kg/m2; 31·7 % were current smokers, and 86·9 % were married or living as a couple. The mean healthy Nordic diet score was 12·8 (sd 4·0, range 2–25), and the mean HPL depression score was 1·9 (sd 2·1, range 0–13). The findings suggested that lower adherence to a healthy Nordic diet was associated with higher HPL depression scores after adjusting for age, examination year, daily energy intake, leisure-time physical activity, adulthood socio-economic status, smoking and marital status (extreme quartile difference: 0·33 points, 95 % CI 0·10, 0·56, P for trend across the quartiles = 0·003). The results support the hypothesis that a lower-quality diet increases the odds of having depressive symptoms. However, prospective studies are needed to confirm the association.

Evidence suggests that nutrition interventions produce beneficial effects for people with major depressive disorder. However, limited research is published about their feasibility and acceptability from patient’s perspective. This 8-week randomised controlled pilot study with two parallel groups aimed to assess recruitment capability, intervention acceptability and effect on diet quality and depressive symptoms. In total, fifty-one people aged 20–64 years with moderate or severe depression were randomised either into a group-based nutrition intervention (n 26) or a social support intervention (n 25). Recruitment capability was evaluated from the participant flow data, acceptability with a questionnaire based on Sekhon’s Theoretical Framework of Acceptability, diet with the Index of Diet Quality (IDQ) and depressive symptoms with the Center for Epidemiologic Studies Depression (CES-D) Scale. Mann–Whitney U tests and linear mixed models were used to analyse outcomes. Recruitment proved extremely challenging despite using multiple recruitment channels and collaboration with healthcare organisations. Five groups in each arm completed the intervention. Only 23 % of the participants in the nutrition and 16 % in the social support intervention attended all sessions. The nutrition intervention was considered acceptable, with higher acceptability ratings than the social support intervention (mean 4·41 v. 3·66, P < 0·001). The mean IDQ at baseline was 8·37 (sd 2·0) and CES-D 30·0 (sd 10·9, range 4–50), with no statistically significant changes post-intervention in either intervention arm. Future research should focus on co-designing the interventions and targeted recruitment strategies and considering new approaches for delivering interventions to promote participant engagement and lifestyle changes.