(17-09-11) Higher Fish and Long-Chain Omega-3 Intakes Linked to Lower Risk of Chronic Kidney Disease

Chronic kidney disease is one of several major health conditions of increasing frequency in older adults. The condition is defined as a glomerular filtration rate of less than 60 ml/min per 1.73 m2 or urinary albumin-to-creatinine ratio greater than 30 mg/g. The disease affects approximately 13% of the adult population 20 years of age or older in the U.S. or about 26 million people. It is associated with diabetes, obesity, cardiovascular disease and hypertension. It is estimated that about 40% of individuals with diabetes and 42% of those with undiagnosed diabetes have the condition. The high prevalence of health conditions that increase the risk of developing chronic kidney disease and its progressive morbid nature add to the urgency of identifying factors that might reduce the likelihood of developing the condition.The anti-inflammatory properties of some omega-6 (n-6) PUFAs and especially of the long-chainomega-3 PUFAs (n-3 LC-PUFAs) suggest that they may reduce renal inflammation and improveorgan function in chronic kidney disease. A 3-year prospective study of adults aged 65 years or older reported that higher plasma levels of total, n-6 and n-3 PUFAs were associated with a slower decline in creatinine clearance and a lower risk of renal insufficiency compared with participants having low PUFA levels. In a controlled trial of fish oil supplementation in patients with severe IgA nephropathy, patients treated with low- or high-dose n-3 LC-PUFAs had significantly lower rates of renal function loss compared with the placebo-treated patients. The addition of marine n-3 LC-PUFAs to the diets of a small number of hemodialysis patients was associated with reduced C-reactive protein, a marker of systemic inflammation.Taking the anti-inflammatory model further, animal studies with resolvin D1 and protectin D1, derivatives of n-3 LC-PUFAs, reported that these mediators of inflammation resolution were produced in animals with kidney ischemia/reperfusion injury. Administration of either of these substances prior to ischemia reduced the functional and morphological injury associated with the injury. In a study comparing n-3 and n-6 PUFAs in ischemic renal injury, animals fed the n-6 PUFA (corn oil) diet did not survive extended ischemia, while all those fed the n-3 LC-PUFA diet (menhaden oil) survived. Protection against ischemic injury correlated with decreased polymorphonuclear leukocyte recruitment and increased levels of protectin D1.A meta-analysis of 17 trials of n-3 LC-PUFA supplementation in chronic kidney disease patients reported a reduction in urinary protein excretion, but no effect on the decline in glomerular filtration rate. Inconsistency among methods and data reporting, as well as small numbers of participants in many trials, speak to the need for larger, adequately powered, randomized trials to determine the efficacy of n-3 PUFAs in kidney disease.The study described here, while not a large randomized controlled trial, is an observational study in a large community-based cohort of adults 50 years of age or older. It was designed to determine whether dietary PUFAs are associated with chronic kidney disease and if a diet high in fish affects the likelihood of developing the disease.Study participants were part of the Blue Mountains Eye Study living west of Sydney, Australia. Data were available from 2,600 participants who provided information about their diet and fish intake via food frequency questionnaire. Kidney disease was assessed from serum creatinine concentrations measured in fasting venous blood. Glomerular filtration was estimated indirectly from the creatinine values, accounting for age and sex. Other health and demographic information was collected from in-person interviews at entry to the study.There were 504 (19%) participants with chronic kidney disease of stage 3 or higher. These individuals were more likely to be older, inactive, and have hypertension, diabetes or stroke as well as higher hemoglobin and hematocrit, total cholesterol and triglycerides than participants with mild or no chronic kidney disease. Those with the disease were less likely to be male, smokers or heavy drinkers.As shown in the Table, intake of energy-adjusted n-3 LC-PUFAs was associated with a significant 13% lower risk of chronic kidney disease, but intakes of total n-3 PUFAs or total n-6 PUFAs were unrelated to disease risk. Interestingly, increased consumption of alpha-linolenic acid was associated with a significant 18% greater risk of chronic kidney disease. Fish consumption was not related to risk.When the data were analyzed by quartiles of n-3 PUFA consumption, those in the highest quartile of n-3 LC-PUFA consumption were 31% less likely to develop chronic kidney disease compared with those in the lowest quartile (P = 0.05) after adjusting for age, sex, body mass index, smoking, alcohol consumption, physical activity, serum homocysteine, serum total cholesterol and triglycerides, hypertension and history of diagnosed diabetes. Similarly, those in the highest quartile of fish consumption were 32% less likely to develop chronic kidney disease compared with those in the lowest quartile of fish intake (P = 0.02). In contrast, the odds of chronic kidney disease were 73% greater for those in the highest quartile of alpha-linolenic acid intake (P = 0.004). This study reported a significant association between higher intakes of n-3 LC-PUFAs or fish and a lower risk of developing chronic kidney disease in a general population of adults 50 years of age or more. It also observed a significantly higher risk of the disease with greater intakes of the plant-based n-3 PUFA, alpha-linolenic acid. There was no association with the consumption of total n-6 PUFAs. The study provided no data on the potential involvement of immune function, reduced inflammation or changes in blood pressure or protein excretion in contributing to these associations. It is left to intervention studies to clarify the mechanisms underlying these encouraging observations.
Gopinath B, Harris DC, Flood VM, Burlutsky G, Mitchell P. Consumption of long-chain n-3 PUFA, ?-linolenic acid and fish is associated with the prevalence of chronic kidney disease.

Source: Br J Nutr 2011;105:1361-1368. [Pubmed]

News

---

In evidenza

"L'informazione presente nel sito serve a migliorare, e non a sostituire, il rapporto medico-paziente."

Per coloro che hanno problemi di salute si consiglia di consultare sempre il proprio medico curante.