Higher fish intake was significantly associated with lower systemic immune-inflammation index (SII), with mediation analysis suggesting that estimated n-3 PUFA intake substantially contributed to this association, alongside related lifestyle factors such as aerobic exercise and sleep duration.
Key Findings
Results
Higher fish intake was significantly associated with lower systemic immune-inflammation index (SII) levels.
Cross-sectional study of 8675 participants undergoing health check-ups between April 2019 and March 2020
Mean age was 46.7 ± 13.0 years; 59% were men
The average fish intake was 143 ± 88 g/week
The association between higher fish intake and lower SII was statistically significant (p < 0.0001)
Fish intake was assessed using a self-reported questionnaire on weekly consumption frequency
Results
Higher fish intake and aerobic exercise were independently associated with lower SII in multivariable regression analysis.
Multivariable regression analysis identified fish intake and aerobic exercise as independent predictors of lower SII
Shorter sleep duration was independently associated with higher SII
These associations held after accounting for other lifestyle and dietary variables
The proportion of participants engaging in aerobic exercise increased across fish intake categories
Results
Mediation analysis suggested that estimated n-3 PUFA intake substantially contributed to the association between fish intake and lower SII.
Estimated weekly fish and n-3 PUFA intake were calculated by combining intake frequency with age- and sex-specific average intake data derived from the Japanese National Health and Nutrition Survey
N-3 PUFA intake was identified as a mediator rather than merely a correlate in the fish intake–SII relationship
The mediation analysis indicated that n-3 PUFAs explain a substantial portion of the anti-inflammatory association attributed to fish consumption
The SII is described as a composite marker of atherosclerotic cardiovascular disease (ASCVD)
Results
Fish intake categories were associated with differences in lifestyle behaviors, particularly aerobic exercise participation.
The proportion of participants engaging in aerobic exercise increased across fish intake categories
This pattern suggests that fish consumption may cluster with other health-promoting behaviors
The co-occurrence of fish intake and aerobic exercise highlights the importance of considering broader dietary and behavioral patterns when evaluating systemic inflammation
Conclusions
The anti-inflammatory effects associated with fish intake may be partly explained by n-3 PUFA content along with related lifestyle factors.
The study concluded that the relationship between fish intake and lower SII reflects not only the amount of fish consumed but also its nutrient composition
Related lifestyle factors, including aerobic exercise and sleep duration, also independently influenced SII levels
Authors highlight 'the importance of considering fish consumption alongside broader dietary and behavioral patterns that influence systemic inflammation'
What This Means
This research suggests that eating more fish is linked to lower levels of a blood marker called the systemic immune-inflammation index (SII), which is associated with cardiovascular disease risk. The study followed over 8,600 Japanese adults who attended health check-ups, and found that those who ate more fish tended to have lower inflammation scores. Importantly, this association remained even after accounting for other health factors, indicating that fish consumption itself—not just healthier lifestyle habits in general—plays a meaningful role.
The study also found that the omega-3 fatty acids (n-3 PUFAs) found in fish appear to be a key reason why fish eaters have lower inflammation. Using a statistical technique called mediation analysis, the researchers found that a substantial part of the benefit of eating fish could be explained by the omega-3 content of that fish. Additionally, people who ate more fish were also more likely to exercise regularly, and both exercise and fish consumption independently contributed to lower inflammation, while shorter sleep was linked to higher inflammation.
This research suggests that the anti-inflammatory benefits of eating fish are not just about the fish itself, but also reflect the types of nutrients fish provides—particularly omega-3 fatty acids—and the broader healthy lifestyle patterns that tend to accompany regular fish consumption. The findings underline the value of looking at diet and lifestyle together rather than in isolation when studying inflammation and cardiovascular health risk.
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S. Tani, Yasuyuki Suzuki, Tsukasa Yagi, Atsuhiko Takahashi. (2026). Association of fish intake with systemic immune-inflammation index: Potential mediating role of n-3 polyunsaturated fatty acids.. Prostaglandins, Leukotrienes and Essential Fatty Acids. https://doi.org/10.1016/j.plefa.2026.102750