British Journal of Nutrition

Full Papers

Fish intake, mercury, long-chain n-3 polyunsaturated fatty acids and risk of stroke in northern Sweden

Maria Wennberga1a2 c1, Ingvar A. Bergdahla2, Birgitta Stegmayra2, Göran Hallmansa2, Thomas Lundha3, Staffan Skerfvinga3, Ulf Strömberga3, Bengt Vessbya4 and Jan-Håkan Janssona1a2

a1 Department of Medicine, Skellefteå Hospital, Skellefteå, Sweden

a2 Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden

a3 Department of Occupational and Environmental Medicine, University Hospital, Lund, Sweden

a4 Department of Public Health and Caring Science, Uppsala University, Uppsala, Sweden


Results of previous studies on fish intake and stroke risk have been inconclusive. Different stroke types have often not been separated. Our aim was to elucidate whether intake of fish, Hg or the sum of proportions of fatty acids EPA (20 : 5n-3) and DHA (22 : 6n-3) influence the risk of haemorrhagic or ischaemic stroke. Within a population-based cohort from a community intervention programme, 369 stroke cases and 738 matched controls were identified and included in the present nested case–control study. Information on fish intake had been recorded at recruitment, i.e. before diagnosis. Hg levels were determined in erythrocyte membranes, also collected at recruitment, and the relative content of fatty acids was measured in erythrocyte membranes or plasma phospholipids. The results showed that in women there was a non-significant decrease in stroke risk with increasing fish intake (OR 0·90 (95 % CI 0·73, 1·11) per meal per week). The risk in women differed significantly (P = 0·03) from that in men, in whom the OR for stroke rose with increasing fish intake (OR 1·24 (95 % CI 1·01, 1·51) per meal per week). The corresponding risk in men for Hg was 0·99 (95 % CI 0·93, 1·06), and for the sum of proportions of EPA and DHA 1·08 (95 % CI 0·92, 1·28). We conclude that the relationship between stroke risk and fish intake seems to be different in men and women. Increased levels of EPA and DHA do not decrease the risk for stroke and there is no association between stroke risk and Hg at these low levels.

(Received October 16 2006)

(Revised February 08 2007)

(Accepted April 03 2007)


c1 Corresponding author: Maria Wennberg, fax +46 910 77 16 57, email


Abbreviations: AMI, acute myocardial infarction; MONICA, Multinational Monitoring of Trends and Determinants in Cardiovascular Disease