James Donadio's August 1999 paper in the "Journal of the American Society of Nephrology" showed that fish oil retards the decline of the health of kidneys in patients with IgA nephropathy. These seminal findings were the first long-term study on the effects of fish oil on the kidneys. They sparked other studies on the effects of fish oil in other kidney diseases.
Mechanism of Disease
Many chronic kidney diseases are immunologically mediated. This means that a defect in the immune system causes some type of immune protein to be deposited in the kidneys, literally "gumming up the works." Inflammation occurs, which further aggravates the problem and causes proteinuria, or elevated urine protein levels. This proteinuria, in turn, damages the glomeruli.
Fish Oil Mechanism
Researchers believe that fish oil relieves the inflammation underlying many chronic kidney diseases. Publishing in the June 2009 issue of "Nutrition Research," Dr. Poudel-Tandukar showed that Japanese men who eat a diet high in alpha-linolenic and linoleic acids have lower levels of C-reactive protein, a marker for inflammation. Fish oil is high in linoleic acids and should produce similar results when taken directly. Comparable reductions in other markers for inflammation were found in rats whose diet was supplemented with fish oil.
Controversy
Only one meta-study examining the response of human kidney patients has been performed. This study showed that kidney patients experienced an improvement in proteinuria but not in how effectively their kidneys filter blood. The authors of this study noted that the mean follow-up period was only nine months and indicated that longer-term studies were necessary.
Hypertension
The 2007 Annual Report of the United States Renal Data System indicates that hypertension caused 25,000 cases of renal failure in the U.S. Moreover, hypertension accompanies almost every other chronic kidney disease. Omega-3 polyunsaturated fatty acids found in fish oil consistently relieve hypertension. This finding suggests that fish may extend the life of kidneys by lowering blood pressure.
References
- "Seminars in Nephrology"; The Role of Fish Oil/Omega-3 Fatty Acids in the Treatment of IgA; James V. Donadio, MD, et al; May 2004
- "American Journal of Kidney Disease"; Omega-3 Polyunsaturated Fatty Acids in the Treatment of Kidney Disease; R.G. Fassett, et al; May 2010
- "American Journal of Clinical Nutrition"; The Effect of n-3 Long-Chain Polyunsaturated Fatty Acid Supplementation on Urine Protein Excretion; E.R. Miller, et al; June 2009
- "Molecular Nutrition Food Research"; The Effects of Dietary Fish Oil on Inflammation, Fibrosis and Oxidative Stress; J.M. Peake; March 2011
- "Nutrition Research;" Dietary Intakes of Alpha-Linolenic and Linoleic Acids are Inversely Associated with Serum C-Reactive Protein; K. Poudel-Tandukar, et al; June 2009
- "Journal of the American Society of Nephrology"; The Long-Term Outcome of Patients with IgA Nephropathy Treated with Fish Oil in a Controlled Trial; James V. Donadio; August 1999
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