Chronic kidney disease (CKD) affects over 700 million people globally and may lead to kidney failure and death, thus there is a need to find elements that may prevent its start and progression.
Omega 3 polyunsaturated fatty acids (n-3 PUFAs) may benefit kidney function, according to animal research, however human studies are few and mostly rely on dietary questionnaires, which are subject to error.
The results of 19 studies from 12 countries up to May 2020 looking at associations between levels of n-3 PUFA biomarkers and development of CKD in adults were pooled by an international team led by researchers at The George Institute for Global Health and the University of New South Wales in order to further investigate this.
Biomarkers included fatty acids such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and alpha linolenic acid (ALA). While ALA is mostly found in plants such as nuts, seeds, and leafy green vegetables, EPA, DHA, and DPA are primarily obtained through seafood.
An eGFR of less than 60 ml/min/1.73 m2 was used as the diagnostic threshold for chronic kidney disease (CKD). eGFR is a test that determines how efficiently the kidneys are filtering the blood of waste and excess fluid. Normal is between 90 and 120 ml/min/1.73 m2.
25 570 people in total were included in the primary analysis. Their baseline eGFR varied from 76.1 to 99.8 mL/min/1.73 m2, and their average age was between 49 and 77 years.
16 research included both males and women, whereas 15 studies mostly included white individuals. In all, 4,944 patients (19%) had CKD throughout the course of an average 11-year monitoring period.
After accounting for a variety of other factors, including age, sex, race, body mass index, smoking, alcohol consumption, physical activity, heart disease, and diabetes, higher levels of total seafood n-3 PUFAs were associated with a small (8%) reduction in the risk of developing chronic kidney disease.
When individuals were divided into five groups according on their n-3 PUFA levels, those with the highest total seafood n-3 PUFA levels had a 13% reduced chance of developing CKD than those in the lowest group.
A slower annual drop in eGFR was also linked to higher levels of total n-3 PUFAs in seafood, especially DHA. For instance, those with total seafood n-3 PUFA levels in the top fifth compared to those in the lowest fifth saw a 0.07 mL/min/1.73 m2 smaller yearly drop in eGFR.
Plant-derived ALA levels were not linked to CKD.
These are observational data, and the researchers recognize that their findings may have been impacted by variations in study design and methodology. Furthermore, they cannot rule out the possibility that part of the reported risk is the result of unmeasured variables.
However, following further analysis, findings were consistent and seemed to hold up across age groups (60 or less vs. more than 60 years), eGFR (60-89 vs. 90 or higher mL/min/1.73 m2), high blood pressure, diabetes, and coronary heart disease at baseline, indicating that they may be trusted.
Although the findings of their study “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 point out.
Further randomised controlled studies are required to examine the possible positive impact of seafood n-3 PUFAs in the prevention and management of CKD, they conclude.
Source: 10.1136/bmj-2022-072909
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