Omega-3 and beyond - Could dietary fat manipulations improve outcomes in chronic kidney disease?
Eating healthily not only provides protein and calories, it also provides many other nutrients whose intake is generally deficient in patients with chronic kidney disease (CKD), and that play important roles in immune function, oxidative stress regulation, anaemia etc. Dietary fat, for example, typically represents 30% or more of total daily energy intake.
At the general population level, replacement of dietary saturated fatty acid (SFA) with polyunsaturated fatty acid (PUFA) has been recommended for the prevention of cardiovascular diseases. However, healthy dietary fat may exert additional beneficial effects of particular interest in the context of renal diseases.
Available evidence suggests poor quality of dietary fat in the CKD population, with insufficient PUFA and excess SFA intake. Less is known about the implications of this poor dietary fat quality in individuals with CKD.
The implications of SFA intake are scarcely investigated, but associations study in the community suggest that increased SFA intake leads to incident albuminuria and more rapid GFR decline 1. In dialysis patients, excess SFA has been linked to systemic inflammation and increased mortality 2. Low fish oil intake, rich in n-3 PUFA has been recently linked to sudden death risk in a large US dialysis population 3.
The most studied dietary fat in terms of intervention studies regards the n-3 PUFA from fish origin, due to its effectiveness in reducing inflammation and cardiovascular risk in general and in disease-specific populations at risk. Increasing evidence supports the concept that n-3 PUFA may be used as a therapeutic option in reducing proteinuria in non-dialyzed individuals 4. In a recent cross-over trial in diabetics with early CKD, the intake of n-3 PUFA improved markers of kidney damage such as NGAL5. Even more exciting, another recent RCT demonstrates a benefit of n-3 PUFA supplementation on graft patency in HD patients 6.
Emerging evidence suggests n-3 PUFA may not be alone in the fight of disease, and linoleic acid, the essential n-6 PUFA from vegetable oils, may also be beneficial for a number of CVD risk factors 7.
What is your opinion about the quality of dietary fat of your CKD patients?
Do you take any action to modify this towards a healthier profile? Do you see feasible that CKD patients would change their dietary patterns?
Is it time to take dietary fat more seriously in the management of CKD patients?
Dietary fat goes beyond omega 3 fatty acids, and despite ensuring good nutritional status we have the possibility to tackle specific risk factors through dietary fat manipulations. The optimal dietary fat quality for patients who have CKD, or are at risk of developing CKD has not been established and has presently received little attention in guideline recommendations. Probably, those recommendations do not deviate much from that of the general population: increased consumption of oily fish as part of plant-based diets with low content of SFA. These recommendations would be, after all, in line with the ‘Mediterranean diet’ concept and are also in line with current dietary guidelines for cardiovascular disease prevention.
1. Lin J, Hu FB, Curhan GC. Associations of diet with albuminuria and kidney function decline. Clin J Am Soc Nephrol. May 2010;5(5):836-843.
2. Huang X, Stenvinkel P, Qureshi AR, et al. Clinical determinants and mortality predictability of stearoyl-CoA desaturase-1 activity indices in dialysis patients. J Intern Med. Mar 2013;273(3):263-272.
3. Friedman AN, Yu Z, Tabbey R, et al. Inverse relationship between long-chain n-3 fatty acids and risk of sudden cardiac death in patients starting hemodialysis. Kidney Int. Jun 2013;83(6):1130-1135.
4. Miller ER, 3rd, Juraschek SP, Appel LJ, et al. The effect of n-3 long-chain polyunsaturated fatty acid supplementation on urine protein excretion and kidney function: meta-analysis of clinical trials. Am J Clin Nutr. Jun 2009;89(6):1937-1945.
5. Miller ER, 3rd, Juraschek SP, Anderson CA, et al. The effects of n-3 long-chain polyunsaturated fatty acid supplementation on biomarkers of kidney injury in adults with diabetes: results of the GO-FISH trial. Diabetes Care. Jun 2013;36(6):1462-1469.
6. Lok CE, Moist L, Hemmelgarn BR, et al. Effect of fish oil supplementation on graft patency and cardiovascular events among patients with new synthetic arteriovenous hemodialysis grafts: a randomized controlled trial. JAMA. May 2 2012;307(17):1809-1816.
7. Huang X, Stenvinkel P, Qureshi AR, et al. Essential polyunsaturated fatty acids, inflammation and mortality in dialysis patients. Nephrol Dial Transplant. Sep 2012;27(9):3615-3620.