Eating at least two portions of oily fish such as mackerel, sardines or herrings a week is linked to a lower risk of chronic kidney disease and a slower decline in the organ’s function, research suggests.
Chronic kidney disease (CKD) affects about 700 million people worldwide. It can lead to kidney failure and death, so there is an urgent need to identify factors that could prevent its onset and progression.
Now a study has found an association between higher levels of omega 3 fatty acids found in oily fish and other seafood, and a reduced risk of kidney problems. The link was not found with higher levels of plant-derived omega 3 fatty acids.
The findings of the international team of researchers, which was led by the George Institute for Global Health and the University of New South Wales, were published in the medical journal the BMJ.
“While we cannot for certain say what specific fishes had the greatest effect on CKD risk, we know that the blood levels of the fatty acids reflect their intake well,” Dr Matti Marklund, a senior research fellow at the George Institute, told the Guardian in an email.
“Among the richest dietary sources of these fatty acids are fatty cold-water fish – for example, salmon, sardines, mackerel, and herrings – and to a less extent shellfish, like oysters, mussels, and crab.”
The findings support guidelines recommending consumption of oily fish and other seafood as part of a healthy diet.
“Current dietary recommendations in most countries suggest at least two servings of fish per week, preferably oily fish, which will provide about 250mg/day of long-chain omega 3s,” said Marklund.
Studies in animals have previously suggested omega 3 fatty acids may help with kidney function, but until now evidence from human research was limited – and relied mostly on dietary questionnaires.
The researchers pooled the results of 19 studies from 12 countries examining links between levels of omega 3 fatty acids and the development of CKD in adults.
About 25,000 people were included in the main analysis, aged between 49 and 77.
After accounting for a range of factors including age, sex, race, body mass index, smoking, alcohol intake, physical activity, heart disease and diabetes, higher levels of seafood omega 3 fatty acids were associated with an 8% lower risk of developing CKD.
When participants were split by levels of seafood omega 3 fatty acids consumed, those in the highest fifth had a 13% lower risk of CKD compared with those in the lowest fifth. Higher levels were also associated with a slower annual decline in kidney function.
The researchers pointed out that their findings were observational and therefore did not prove that including more seafood in your diet definitely lowers the risk of CKD. “We need randomised controlled trials to determine that type of causality,” Marklund said.
Nevertheless, results were similar after further analysis, and appeared consistent across age groups. “Higher levels were consistently associated with lower CKD risk,” he added.