Seafood omega 3 ‘lowers risk of chronic kidney problems’

Taking omega 3 fatty acids derived from seafood is associated with a lower risk of chronic kidney disease and a slower decline in kidney function, according to a new Australian study.

The findings published in today’s edition of The BMJ say these associations were not found with high levels of plant-derived omega 3 fatty acids.

Although the associations were only modest, the international team led by researchers at The George Institute for Global Health and the University of New South Wales say their findings support existing clinical guidelines that recommend adequate consumption of seafood and oily fish as part of healthy dietary patterns.

Animal studies suggest that omega 3 polyunsaturated fatty acids (n-3 PUFAs) may be beneficial for kidney function, but evidence from human studies is limited and relies mainly on dietary questionnaires.

For this study, the team pooled the results of 19 studies from 12 countries up to May 2020, which looked at links between levels of n-3 PUFA biomarkers and development of chronic kidney disease (CKD) in adults.

Biomarkers included eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and alpha linolenic acid (ALA). The main dietary sources of EPA, DHA and DPA come from seafood, while ALA is found mainly in plants (nuts, seeds, and leafy green vegetables).

A total of 25,570 participants, aged 49 to 77, were included in the main analysis. CKD was identified by an estimated glomerular filtration rate (eGFR) of less than 60 ml/min/1.73 m2. The normal range is 90-120 ml/min/1.73 m2 and participants’ average baseline eGFR ranged from 76.1 to 99.8 mL/min/1.73 m2.

Out of the total cohort, 4,944 participants (19%) developed CKD during an average monitoring period of 11 years.

After accounting for other a range of factors including age, sex, race, body mass index, smoking, alcohol intake, physical activity, heart disease and diabetes, higher levels of total seafood n-3 PUFAs were associated with an 8% lower risk of developing CKD.

When the researchers split participants by n-3 PUFA levels, those with total seafood n-3 PUFA levels in the highest fifth had a 13% lower risk of CKD compared with those in the lowest fifth.

They also found higher levels of total seafood n-3 PUFAs, especially DHA, were also associated with a slower annual decline in eGFR.

However, these associations were not found in plant-derived ALA levels.

Although these are observational findings, the team says results were similar after further analysis, and appeared consistent across age groups, eGFR, high blood pressure, diabetes, and coronary heart disease at baseline.

This, they say, suggests their findings withstand scrutiny.

“Although our findings do not prove a causal relation between seafood n-3 PUFAs and CKD risk, they are supportive and consistent with current clinical guidelines that recommend adequate intake of seafood as part of healthy dietary patterns, especially when seafood replaces the intake of less healthy foods,” they write.

“Further randomised controlled trials are warranted to assess the potential beneficial role of seafood n-3 PUFAs in preventing and managing CKD.”

Ong KL, Marklund M, Huang L et al. Association of omega 3 polyunsaturated fatty acids with incident chronic kidney disease: pooled analysis of 19 cohorts. BMJ 19 January 2023; doi: 10.1136/ bmj-2022-072909


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