Dietary phytoestrogens: a possible role in renal disease protection.

There is growing evidence that dietary phytoestrogens have a beneficial role in chronic renal disease. This review summarizes the recent findings from dietary intervention studies performed in animals and humans suggesting that consumption of soy-based protein rich in isoflavones and flaxseed rich in lignans retards the development and progression of chronic renal disease. In several animal models of renal disease, both soy protein and flaxseed have been shown to limit or reduce proteinuria and renal pathological lesions 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 preserve renal function. However, most of these clinical trials were of relatively short duration and involved a small number of patients. Furthermore, it is not clear whether the renal protective effects of soy protein and flaxseed are caused by the isoflavones (daidzein and genistein) and lignans (matairesinol and secoisolariciresinol) or some other component. The biochemistry, metabolism, and mechanisms of actions of isoflavones and lignans are discussed. Isoflavones and lignans appear to act through various mechanisms that modulate cell growth and proliferation, extracellular matrix synthesis, inflammation, and oxidative stress. Some of these actions have been shown in vitro, but studies of 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.