Submitted to: Journal of Renal Nutrition
Publication Type: Review Article
Publication Acceptance Date: 12/13/2002
Publication Date: N/A
Interpretive Summary: We have reviewed the role of dietary soybean and flaxseed in various forms of chronic renal diseases in humans and animals. Soybean and flax contain phytoestrogens. In soybean they are present as isoflavones genistein and daidzein, and in flax as lignans matairesinol and secoisolariciresenol. Since these compounds have structures similar to endogenous estrogen estradiol, they bind to both, estrogen receptor alpha and estrogen receptor beta. It is postulated that many beneficial effects os soy and flax are due phytoestrogens present. However, the nature of protein in soy and flax cannot be ruled out. Further, the interactions between phytoestrogens and type of protein may also be important. In soy isoflavones are present as glycosides and when ingested they are converted to active form aglycone. Phytoestrogens also have biological effects in isolated cells and cells in culture. Some of the mechanisms of action of phytoestrogens include inhibition of cell growth and proliferation, inhibition of tyrosine protein kinases, inhibition of angiogenesis, modulation of growth factors and antioxidative action. Though these phytoestrogens are safe in normal subjects, clinical trials are needed to evaluate the long term safety and effectiveness in renal disease progression in patients with chronic renal failure. These observations will help medical professionals, nutritionists, dietitians, basic scientists and other health professionals to recommend soy and flax meal in the diet of general population and to patients with renal disease.
Technical Abstract: There is growing evidence that consumption of plant-derived proteins rich in phytoestrogens have a beneficial role in chronic renal disease. In several animal models of experimental renal disease, both soy protein and flaxseed have been shown to limit or reduce not only proteinuria but also the renal pathological lesions of glomerular sclerosis, inflammatory cell infiltration, and interstitial fibrosis associated with progressive renal failure. In studies of human subjects with different types of chronic renal disease, soy protein and flaxseed also appear to moderate proteinuria and slow the deterioration of renal function but this effect has not been consistently observed. Furthermore, it is not clear whether the renal protective effects of soy protein and flaxseed are due to the isoflavones and lignans or some other component. How isoflavones and lignans mediate their protective effects on the kidney is poorly understood. Isoflavones and lignans appear to act through various mechanisms that modulate cell growth and proliferation, and oxidative stress. Some of these actions have been shown in vitro; but studies on the mechanisms operative in vivo are lacking. The diversity of cellular actions of isoflavones and lignans supports their protective effects in a variety of experimental and human types of chronic renal disease. Further investigations are needed to evaluate their long-term effects on renal disease progression in patients with chronic renal failure.