Life Extension Update
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Soy protein improves kidney function in diabetic men
Fourteen veterans with advanced typed 2 diabetes and kidney disease had their diets supplemented with either isolated soy protein or casein from milk for two eight week treatment periods over a seven month study period. The amount of protein the participants received was measured according to the weight of each patient. Urine and blood samples were collected at the beginning and end of the investigation. The research team found that soy protein lowered urinary albumin by 9.5 percent, while those who received casein experienced an 11 percent increase. (Albumin is a protein that increases in the urine with worsening kidney function.) High density lipoprotein (HDL) levels rose by 4.3 percent in men who received soy, and dropped slightly in the men who received casein. Total cholesterol levels only improved slightly in the soy group.
Study coauthor and professor of nutrition at the University of Illinois College of Medicine, John Erdman, commented that the study "is probably the strongest one done so far from the numbers of subjects and length of time, because it involved an intervention program designed for type 2 diabetes."
Lead author Sandra Teixeira concluded, “The results suggest that a dietary modification as easy to implement as consuming soy-protein-rich foods may help to prevent diabetic kidney disease in addition to improving blood-lipid profile. This is quite important in light of the growing diabetic population, and larger trials are warranted to confirm the findings."
There is evidence that dietary phytoestrogens have a beneficial role in chronic renal disease (Velasquez et al. 2001; Ranich et al. 2001). Nutritional intervention studies demonstrated that consuming soy-based protein and flaxseed reduced proteinuria and attenuated renal functional or structural damage in both animals and humans. To date the studies have been of relatively short durations and involved small numbers of subjects. However, the results are encouraging and further investigations are needed. Three groups of researchers (Tomobe et al. 1998; Aukema et al. 1999; Ogborn et al. 2000) investigated the effects of a soy protein diet on polycystic kidney disease. Although the studies were conducted in rats and mice, the research teams suggested that dietary soy protein-based diets had beneficial effects in polycystic kidney disease: soy diet prevented significant elevation in serum creatinine in diseased vs. normal animals (Ogborn et al. 2000); soy protein is effective in retarding cyst development and this beneficial effect may be unrelated to genistein (an isoflavonoid present in soy protein) content (Tomobe et al. 1998); dietary protein level and source significantly affect polycystic kidney disease, with the effects being most pronounced in female animals fed low protein diets and soy protein-based diets (Aukema et al. 1999).
Yokozawa et al. (1999) studied the effects of green tea tannin to ameliorate cisplatin-induced renal injury in rats. They found that green tea tannin suppressed the cytotoxicity of cisplatin, "the suppressive effect increasing with the dose of green tea tannin." Additional testing showed rats given green tea tannin had decreased blood levels of urea nitrogen and creatinine and decreased urinary levels of protein and glucose, indicating less kidney damage. Yokozawa et al. (1999) concluded that "based on the evidence available, it appeared that green tea tannin eliminated oxidative stress and was beneficial to renal function." Earlier, researchers (Wardle 1999; Yokozawa et al. 1996) reported that green tea tannin was found to be beneficial for the kidney under oxidative stress. In 1991, Mukoyama et al. found that green tea had antiviral activity, inhibiting rotaviruses and enteroviruses in rhesus monkeys.
Taurine is abundant in the brain, heart, gallbladder, and kidneys and plays an important role in health and disease in these organs. Taurine is an amino acid that has been shown to protect against experimentally induced lipid peroxidation of the renal glomerular and tubular cells and may alleviate tubular disorders such as glomerular impairment (Trachtman et al. 1996). It is also thought to lower blood pressure by balancing the ratio of sodium to potassium in the blood. Taurine may also regulate the increased nervous system activity that can contribute to high blood pressure. According to Franconi et al. (1995), some people with Type I diabetes appear to be deficient in the amino acid taurine.
Soy Protein Concentrate provides a very economical concentrated source of soy protein for those who wish to augment their food protein with this important and complete protein.
Taurine is a conditionally essential amino acid produced from cysteine by the body and found abundantly in the body, particularly throughout the excitable tissues of the central nervous system, where it is thought to have a regulating influence. However, taurine is deficient in many diets and may be considered conditionally essential under certain circumstances.
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