Background: Vitamin D is found in limited selections of food, among other fatty fish and fish liver, as well as fortified food such as margarine and milk. Other vitamin D sources are dietary supplements and sunlight. Low back pain patients have possibly higher prevalence of subjective health complaints, including musculoskeletal pain and depression, than the general population. Seafood consumption and vitamin D status have been proposed to have an impact on these health complaints. The aim of this thesis was to assess whether vitamin D status and seafood consumption can be related to depression and other subjective health complaints in patients with low back pain. Material and Methods: The material in this thesis was a part of the low back pain study Cognitive Interventions and Nutritional Supplements (CINS). The data is collected from baseline and was followed-up after 12 months. A total of 554 participants were included. Seafood consumption, depression and other subjective health complaints were identified from questionnaires. Vitamin D status was determined by measuring plasma levels of 25-hydroxyvitamin D. Seafood consumption and vitamin D status were tested against subjective health complaints and depression by using statistical tests. Results: Depression score higher than cut off was associated with lower vitamin D status (z= -2.614, p=0.009, r=-0.190), but after adjustment for gender, findings were not significant. No correlations were found between seafood consumption and/or vitamin D status and subjective health complaints. Forty-three percent had an average seafood consumption below 300 g/week. The average intake of fatty fish was 30% of the total seafood consumption. The average vitamin D status for the group was 65±24 nmol/l. Participants who used omega-3 supplements had significantly higher vitamin D status (t=-2.317, p=0.022, r=-0.171), but seafood consumption and vitamin D status had no correlation. After 12 months there was no significant difference in seafood consumption, but there were significantly lower scores on depression and other subjective health complaints. Conclusion: Results in this thesis can not confirm the hypothesis that higher consumption of seafood and/or vitamin D status correlate negatively with depression and other subjective health complaints. Intake of fatty fish and seafood in general was lower than Norwegian Recommendations, but the average vitamin D status for the group was sufficient. Use of dietary supplements and sunlight exposure may be more important for adequate vitamin D status than seafood. Further studies are needed to assess possible confounding factors and causality
