Higher intakes of omega-3 fats from seafood may modestly lower the risk of chronic kidney disease (CKD) and slow the decline in kidney function, according to new findings.
However, higher intakes of omega-3 fats from plant foods are not linked to the same benefits.
“Although our findings do not prove a causal relation between seafood n-3 PUFA [omega-3 polyunsaturated fatty acids] 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,” the researchers wrote.
The study, “Association of omega 3 polyunsaturated fatty acids with incident chronic kidney disease: pooled analysis of 19 cohorts,” was published in The BMJ.
Omega-3 fats are essential fats found in plants and seafood. Plants contain the shorter chain omega-3 fats called alpha-linolenic acid (ALA), while fish have the longer chained omega-3s – eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA).
Omega-3 fats, especially those from seafood, are protective against heart disease since they increase HDL ‘good’ cholesterol and reduce triglycerides (a blood fat) and blood pressure – two established risk factors for heart disease. High blood pressure and raised blood fats also increase chronic kidney disease risk, but whether omega-3 fats protect the kidneys from damage is unclear. The uncertainty is partly because past studies relied on participants reporting their omega-3 intakes via questionnaires, leading to inaccuracies and inconsistent findings.
Now, researchers combined data from 19 studies evaluating the link between CKD and omega-3 fat intake. CKD was defined as an estimated glomerular filtration rate (eGFR) of less than 60mL/min/1.73m2. Study participants’ eGFR, their annual rate of kidney function decline and blood levels of omega-3 fats, including ALA, EPA, DPA and DHA, were assessed at baseline and after a median follow-up of 11.3 years.
Omega-3 from seafood, not plants, may protect the kidneys
A total of 25,570 individuals (mean age of 44-77) participated in the study, and during the follow-up 4944 developed CKD.
After considering several factors, including body mass index, smoking, alcohol intake and exercise, higher intakes of omega-3 fats from fish were associated with an eight per cent lower risk of CKD and a slower decline in kidney function.
Participants were divided into five groups according to their blood levels of omega-3. Compared to those with the least levels of omega-3s, those with the highest had a 13% lower risk of CKD. Interestingly, there was no link between omega-3 intake from plants and CKD, even though plant omega-3 (ALA) can be converted to the longer-chain omega-3s found in seafood.
“Although ALA could be enzymatically transformed to the longer chain n-3 PUFAs like EPA and DHA, such endogenous [internal] conversion only occurs at a low rate, and our findings suggest the intake of this plant-derived n-3 PUFA alone might not maintain renal health,” the researchers wrote.
Are omega-3 supplements beneficial?
Studies assessing omega-3 supplements to preserve kidney function in people with CKD show that they reduce inflammation and prevent kidney failure. However, the evidence from these studies is strong enough to endorse supplement use in people with CKD. Moreover, since these studies focused on people with existing kidney disease, the findings may not be relevant to people without kidney disease.
The researchers highlighted limitations to the study, including measuring omega-3 levels at only one time point during the study.
Still, “our findings suggest adequate consumption of seafood and oily fish should be part of healthy dietary patterns,” the researchers wrote.
“Further randomised controlled trials are warranted to assess the potential beneficial role of seafood n-3 PUFAs in preventing and managing CKD.”
The Takeaway
CKD affects an estimated 700 million people globally, increasing their heart disease and death risk. Omega-3 fats are essential fats present in plants and seafood. However, most of their health benefits are attributed to those from seafood.
Since omega-3 fats protect the heart, researchers investigated if they protect people from kidney disease. They measured blood levels of omega-3 fats from plants and seafood in over 25,000 people from 12 countries. They found that people with higher blood levels of omega-3 from fish had an 8% lower risk of developing CKD, and kidney function declined slower. Although the reduced risk was modest, the findings support current nutrition guidelines encouraging adults to eat at least two portions of fish weekly.
The study does not imply that low intakes of omega-3 from seafood cause kidney disease. However, it supports nutrition guidelines that recommend eating seafood twice per week. Also, note that at least one portion of the fish should be oily.
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