The current study found that fish consumption was positively associated with a healthy lifestyle in both men and women in a large study of the adult population in the county of Västerbotten in northern Sweden. This is in agreement with previous studies [8, 10]. We did not find any indication of gender differences, except for alcohol.
There are limitations concerning the dietary measurement method used in this study. FFQs are designed to rank participants according to their dietary intake, not to measure the whole diet. Therefore, we only reported correlations between intake frequencies in this study, not absolute food consumption. The fish consumption questions used in the FFQ have been validated using erythrocyte levels of EPA and DHA, which is a strength of the current study. Spearman correlation coefficients between estimated intake of these fatty acids according to the FFQ and erythrocyte levels were satisfactory (Rs = 0.42-0.51) .
A problem in dietary surveys is that people often report a more healthy behavior than what is actually true . It is well known in the population of northern Sweden that fish is a healthy food. This might increase the positive association between fish consumption and other foods considered healthy and other healthy behaviors. In addition, underreporting is a problem in dietary surveys. In a previous study, no gender difference in the prevalence of underreporting in the northern Swedish population was found , but it is unknown if there is a difference in what men and women underreport, which is a limitation. In the current study, people below the 5th and above the 97.5th percentile of food intake level were excluded, to avoid an effect from the most evident under- and overreporters.
Our finding of higher consumption of alcohol in male high consumers of fish is interesting when considering our previous finding of a higher risk of stroke in male high consumers of fish in northern Sweden . High blood pressure is the dominant risk factor for stroke and high consumption of alcohol is positively associated with hypertension. However, light to moderate alcohol consumption may be protective against ischemic stroke . Hypertension, but not alcohol consumption, was adjusted for in our previous stroke study .
The finding of a positive association between alcohol and fish consumption in men, in this larger study performed in the same population as our previous stroke study , called upon additional analysis in our previous stroke study. Therefore, we requested complementary information on alcohol consumption (frequency of strong beer, wine and spirits consumed) in our previous stroke study. However, addition of alcohol in the statistical model did not change the point estimate for the stroke risk in relation to fish consumption. Therefore, the finding of a higher risk of stroke in men reporting high fish consumption could not be explained by a higher intake of alcohol. The hypothesis that high fish consumption is a marker of unhealthy lifestyle in men in this population must be rejected. As regards the factors measured in this study, there are no gender-specific confounding factors in the association between fish consumption and the risk of stroke in northern Sweden. Additional studies are warranted to clarify the finding of an increased risk of stroke in men reporting high consumption of fish in northern Sweden.