Seafood derived omega 3 fatty acids tied to lower risk of chronic kidney disease: BMJ

USA: Higher seafood derived omega-3 fatty acids are associated with a lower risk of chronic kidney disease a slower decline in kidney function; this association, however, was not observed for plant-derived omega-3 fatty acids, says a recent study published in The BMJ. 

"The results support a favorable role for omega-3 fatty acids found in seafood in prevention of cardiovascular disease (CVD)," the researchers wrote.

Although the size of these associations was modest, the findings support current clinical guidelines that recommend adequate consumption of seafood and oily fish as part of healthy dietary patterns, say the researchers.

Chronic kidney disease (CKD) affects about 700 million people worldwide. It can lead to kidney failure and death, so there is a need to identify factors that might prevent its onset and progression.

Animal studies suggest that omega-3 polyunsaturated fatty acids (n-3 PUFAs) may have beneficial effects on kidney function. Still, evidence from human studies is limited and relies mainly on dietary questionnaires, which can be prone to error.

To explore this further, an international team led by researchers at The George Institute for Global Health and the University of New South Wales pooled the results of 19 studies from 12 countries up to May 2020 looking at links between levels of n-3 PUFA biomarkers and development of 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).

CKD was identified by an estimated glomerular filtration rate (eGFR) of less than 60 ml/min/1.73 m2. eGFR measures how well the kidneys are removing waste and excess fluid from the blood. The normal range is 90-120 ml/min/1.73 m2.

Overall, 25,570 participants were included in the main analysis. Their average age ranged from 49 to 77 years and their average baseline eGFR ranged from 76.1 to 99.8 mL/min/1.73 m2.

Sixteen studies recruited men and women, and 15 recruited mainly white participants. In total, 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 a modest (8%) lower risk of developing CKD.

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

Higher levels of total seafood n-3 PUFAs, especially DHA, were also associated with a slower annual decline in eGFR. For instance, the annual decline in eGFR was 0.07 mL/min/1.73 m2 lower for people with total seafood n-3 PUFA level in the highest fifth than those in the lowest fifth.

Plant-derived ALA levels were not associated with CKD.

These are observational findings, and the researchers acknowledge that differences in study design and methods may have affected their results. And they cannot rule out the possibility that some of the observed risks may be due to unmeasured factors.

Nevertheless, the results were similar after further analysis. They appeared consistent across age groups (60 or less v more than 60 years), eGFR (60-89 v 90 or higher mL/min/1.73 m2), high blood pressure, diabetes, and coronary heart disease at baseline, suggesting that they 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 seafood intake 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,” they add.

Reference:

Kwok Leung Ong, Matti Marklund, Liping Huang, Kerry-Anne Rye, Nicholas Hui, Xiong-Fei Pan, Casey M Rebholz, Hyunju Kim, Lyn M Steffen, Anniek C van Westing, Johanna M Geleijnse, Ellen K Hoogeveen, Yun-Yu Chen, Kuo-Liong Chien, Association of omega 3 polyunsaturated fatty acids with incident chronic kidney disease: pooled analysis of 19 cohorts BMJ 2023; 380 doi: https://doi.org/10.1136/bmj-2022-072909