Eating more fish could reel in heart disease risks, new meta-analysis shows

In a recent study published in the journal Nutrients, researchers performed a meta-analysis to determine the association between fish consumption and cardiovascular disease (CVD) risk.

The Importance of Diet in Cardiovascular Health

Studies show that unhealthy dietary habits and sedentary lifestyles contribute to the high mortality rates of cardiovascular disease worldwide. Studies have reported that consuming fish can significantly reduce cardiovascular disease incidence and associated mortality. However, further research, including more meta-analyses, is required to understand the effects of fish type and cooking methods on various CVDs and inform current nutrition guidelines.

Study: Fish Intake in Relation to Fatal and Non-Fatal Cardiovascular Risk: A Systematic Review and Meta-Analysis of Cohort Studies. Image Credit: Created with the assistance of DALL·E 3

Study Design

In the present meta-analysis, researchers evaluated the impact of fish intake on CVD outcomes.

The PubMed (MEDLINE), CINAHL, Cochrane, and Embase databases were searched for observational studies with prospective study designs published in English in peer-reviewed scientific journals between January 1, 2012, and March 31, 2023. Among the included studies, healthy adults comprised the sample population, fish intake was the exposure, risk estimates were ascertained for comparing the effects of high versus low fish consumption, and CVD risk and related mortality was the outcome.

In addition, the references to the included studies were screened to identify additional studies. Systematic reviews, meta-analyses, patents, reports, posters, theses, letters, conference presentations, seminar papers, and opinion papers were excluded. Two researchers independently performed study selection, and discrepancies were resolved by discussion or consultation with a third researcher. Bias risks were evaluated using the Newcastle-Ottawa Scale (NOS).

Using the random effects approach, the researchers synthesized data from multivariate-adjusted relative risk (RR) values of high versus low fish consumption categories concerning cardiovascular disease incidence and associated deaths. Non-linear-type meta-regressions were applied to determine the relationship curve between fish consumption and cardiovascular disease risk.

Further, sensitivity assessments were performed, excluding a study each time and stratifying by the types of cardiovascular outcomes, fish consumed, and cooking methods. Study heterogeneity was assessed based on the I2 values, and publication bias was evaluated using the Egger test.

What the Numbers Say: Results

Of 2,413 records initially identified, 2,348 were eliminated after the title-abstract screening. As a result, 65 studies remained, of which 18 eligible studies were analyzed, conducted in the Netherlands, the United States (US), Denmark, Sweden, Italy, Spain, Germany, Australia, Japan, and China. The median values for participant age, male proportion, sample size, and follow-up durations were 56 years, 45%, and 36,713 individuals and 12 years, respectively.

The median counts of life-threatening and non-life-threatening (combined), non-fatal, and fatal CVD events were 1,865 events, 1,532 events, and 1,135 events, respectively. The most frequently documented cardiovascular diseases were myocardial infarction (median of 1,123 cases), stroke (median of 674 cases), and coronary heart disease (median of 307 cases). A median NOS score of seven was obtained, indicating that the selected studies were high quality. However, a medium-large heterogeneity was observed in the included studies (I2 of 72%).

The meta-analysis analyzed 78,805 cardiovascular disease events in a cumulative population of 1,442,407 individuals over 18,926,486.0 cumulative individual years. High versus low fish intake was linked to an eight percent reduced cardiovascular disease risk (RR of 0.9). The meta-regression analysis indicated that 50 grams of fish consumed daily significantly reduced the risk of life-threatening and non-life-threatening cardiovascular diseases by nine percent (RR, 0.9), denoted by a monotonically decreasing S-shaped curve.

Likewise, consuming two to three 150 gram-portions of fish weekly reduced cardiovascular disease risk by eight percent (RR, 0.9), and consuming a full-sized fish portion daily could lower cardiovascular disease risk by ≤30%. Sensitivity analyses yielded similar findings, indicating the robustness of the primary results, which had no publication bias.

Specifics: Fatty Fish vs. Fried Fish

High fatty fish intake significantly reduced fatal and non-fatal cardiovascular disease risk by 12%, likely due to the high content of omega-3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which reduce platelet aggregation and inflammation. A significant but slightly increased risk of cardiovascular disease was reported for high fried fish intake, likely due to using vegetable oils with a high content of saturated fatty acids, such as palm oil.

Conclusions and Future Directions

Overall, the study findings showed that fish consumption can reduce fatal and non-fatal CVD risks, in line with previous studies. Increased fish consumption could lead to the accumulation of water pollutants such as mercury, heavy metals, and microplastics that may be toxic to the human body. Further research, including more homogeneous studies, is required to disentangle the associations between fish consumption, human well-being, and overall water pollution.