Short-term effects of soy protein diet in patients with proteinuric glomerulopathies. This study was designed to evaluate the effect of soy protein on proteinuria and dyslipidemia, in patients with proteinuric glomerulopathies. The study period corresponded to eight weeks. During the baseline period and by the end of the study, patients were submitted to laboratorial and anthropometric evaluation. RESULTS: There was no statistically significant difference between baseline and post-diet periods among the three groups in anthropometric parameters or body composition, neither in proteinuria levels Control: 0.
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Short-term effects of soy protein diet in patients with proteinuric glomerulopathies. This study was designed to evaluate the effect of soy protein on proteinuria and dyslipidemia, in patients with proteinuric glomerulopathies. The study period corresponded to eight weeks. During the baseline period and by the end of the study, patients were submitted to laboratorial and anthropometric evaluation.
RESULTS: There was no statistically significant difference between baseline and post-diet periods among the three groups in anthropometric parameters or body composition, neither in proteinuria levels Control: 0. However, a slight decrease in triglycerides Keywords: glomerulonephritis, soy foods, proteinuria, diet. Proteinuric glomerulopathies are chronic kidney diseases, which prognosis is particularly related to the levels of persistent urinary protein excretion.
As the nephrotic condition is an extreme of the manifestations' spectrum of the glomerular diseases, associated with more severe metabolic changes, it illustrates the context in which a nutritional therapeutic approach evaluated in the present study could contribute to the management of proteinuric glomerulopathies. The hallmark of nephrotic syndrome NS is the increased glomerular permeability to proteins, which leads to proteinuria.
Homeostatic mechanisms are unable to cope with such urinary protein losses, and the resulting hypoalbuminemia frequently leads to edema. Another important feature of the NS is hyperlipidemia characterized by increased plasma concentrations of very-low-density VLDL , intermediate-density, low-density lipoproteins LDL and, as the disorder progresses, also by hypertriglyceridemia and decreased concentrations of high-density lipoproteins HDL.
Such lipid abnormalities may predispose to more rapid progression of the renal disease. It is noteworthy that persistent proteinuria is one of the most relevant prognostic factors determining progression of glomerular diseases. Therefore, reduction of proteinuria and maintenance of serum proteins levels are important goals in the treatment of NS, as the protein traffic decrease would protect the kidney from the pro inflammatory consequences of the protein tubular overload determined by protein reabsorption.
Considering all these factors, it has been proven that individuals with NS and proteinuria need a special diet, and protein is the nutrient that deserves a particular emphasis in the nutritional management of these patients. There is abundant evidence that changing the amount of diet protein exerts a profound influence on renal function and course of renal disease.
High protein intake has long been known to aggravate renal injury and accelerate the progression of chronic kidney disease, whereas low protein intake produces the opposite effects. According to Azadbakht et al. In addition, there is evidence that changing the source or type of dietary protein may have a beneficial effect on renal function and renal disease. Meal studies indicate that soy protein does not alter post-prandial renal blood flow or glomerular filtration rates, whereas the animal one significantly increases these indexes.
Long-term intakes of soy-protein diets were associated with lower renal blood flow, glomerular filtration rate, and fractional clearance of albumin than those of animal-protein diets. Of interest in this area, vegan and lactoovovegetarian subjects without renal disease had lower glomerular filtration rates and less urinary albumin excretion than omnivores.
Long-term studies also indicate that soy-protein intake protects kidneys, whereas excessive animal-protein intake may be harmful to kidneys. In animal models of kidney diseases, rats fed with soy protein had much slower progression of renal disease than did rats fed with casein. Human studies have not been optimally controlled, but they suggest that substituting soy protein for animal protein decreases proteinuria in individuals with chronic glomerular disease.
Soy protein is a vegetable protein that sustains adequate growth rate in rats and infants. It has an amino acid profile that meets the requirement for each one in humans and rats to growth and maintenance. Afterwards, soy protein contains isoflavones, which act as weak estrogens, inhibiting tyrosine kinase-dependent signal transduction processes and functioning as cellular antioxidants. Considering recent evidence related to the beneficial effects of soy protein on proteinuria reduction, as well as on hyperlipidemia correction, more detailed studies are necessary to better evaluate such improving effects in patients with the NS.
An additional application of the soy protein prescription may be proteinuric glomerular diseases in which antiproteinuric drugs could not be administered. Therefore, the aim of the present study was to evaluate whether soy protein decreases proteinuria and hyperlipidemia in patients with proteinuric glomerulonephritis in short-term. The selected patients could be in the course of a treatment for proteinuric glomerulonephritis, without response, or they could initiate treatment by this dietitian approach.
In the first condition, immunosuppressive drugs were interrupted when results were considered inadequate; then, two months after total drug withdrawal, the patient became eligible to participate in the present study. Nevertheless, the use of antiproteinuric medication, as angiotensin converting enzyme ACE inhibitors, and angiotensin receptor blockers, could be maintained during the study both by their renoprotective or anti-hypertensive actions.
Failure of such antiproteinuric treatment was defined when, after three different proteinuria determination separated by one month interval, no decrease of proteinuria levels was observed. Besides, during this study, it was not permitted to increase the dosage of such drugs; patients should be under adequate blood pressure control by the time of inclusion in the study, but in case of uncontrolled hypertension during the study period, other drugs were utilized to control blood pressure levels.
Patients were excluded of the study if a secondary glomerulopathy was diagnosed and in the event of noncompliance especially if related to the oriented diet. A prospective, randomized, controlled, clinical study was performed. After meeting the inclusion criteria and providing the informed written consent, all patients were instructed to eat an animal protein diet APD during one month. At the initial period of observation, after admission to the study, patients maintained their previous treatment and were submitted to a clinical evaluation, the laboratory exams were performed hour proteinuria, urinalysis, hour urinary urea, creatinine clearance, hemoglobin, hematocrit, serum iron, transferrin, albumin, calcium, phosphorus, cholesterol, TG, serum and urinary potassium, sodium and phosphorus.
After this period, patients were randomly allocated to three groups. During the period of study, after the initial phase, patients were submitted to a complete physical examination of anthropometric parameters, measures of body composition, and a food diary of three days.
The patients were carefully instructed by a skilled dietitian about the corresponding diet. The APD diet consisted on 0. Energy, macronutrients protein, carbohydrate and lipids and micronutrients calcium, phosphorus, iron and cholesterol intake were estimated from a three-day food diary not at the week end , using a computer software developed at UNIFESP and at the United States of America Department of Agriculture 18 table as the nutrient data base.
Protein intake was also estimated from the normalized protein equivalent of nitrogen appearance nPNA , determined according to the formula of Sargent e Gotch, 19 using a hour urinary urea excretion. The following anthropometric parameters were evaluated: body weight and height. Body mass index BMI was calculated as body weight divided by squared height. The cutoff points used were as recommended by the World Health Organization.
The patients had blood drawn under fasting conditions. Twenty-four urine collection were obtained to measure urinary protein excretion and to evaluate glomerular filtration rate, using standard creatinine clearance corrected for the body surface area 1. These and the following parameters were measured on a monthly basis, and also after two months: urinary urea, phosphorus and sodium, serum creatinine, urea, albumin, cholesterol and TG, sodium and potassium, hemoglobin, hematocrit, and transferrin.
Nonparametric tests were applied. The Wilcoxon test was used to compare the results obtained after animal and soy diet post-diet period versus baseline period pre diet within the same group. It was used the statistical software Sigma-Stat, version 2. Table 1 shows the means of the ingestion of calories, macronutrients protein, lipids and carbohydrates and micronutrients calcium, iron, sodium and potassium in baseline and post-diet periods in the three groups.
It was observed a significant decrease in the energetic intake from the baseline to the post-diet period in the three groups The same behavior was observed in lipids But the carbohydrate ingestion revealed a significant decrease only in the Control Group Nevertheless, in opposition to what was observed through the food diary, when the protein ingestion was evaluated by PNA, no group showed significant decrease.
Considering micronutrients, a significant decrease in calcium ingestion was observed only in the Study Group 2 The cholesterol ingestion presented a significant decrease in the Study Groups 1 and 2 It was not observed any statistical difference related to the anthropometric parameters between baseline and post-diet periods in all the groups.
As concerned to body composition, it was not observed any difference between muscle mass and fat mass between baseline and post-diet periods in all groups. The Study Group 2 presented a significantly lower body water value in post-diet period than in the baseline Table 3 shows the means of laboratory parameters of the three groups' patients.
It was not observed any statistical difference of protein excretion levels between baseline and post-diet periods in all groups. The other laboratory parameters were not statistically different between baseline and post-diet periods, except for hemoglobin and serum urea in the Soy Group, which presented a significant decrease A slight decrease of TG, total and LDL cholesterol was observed at the post-diet period versus baseline in the Study Group 1, although this difference has not been significant.
The Figures 1 , 2 , 3 and 4 show the individual values of the hour proteinuria, total and LDL cholesterol and TG of the patients in the three groups, respectively, where each point represents a patient.
The oligosaccharides present in soy are responsible by part of its peculiar profile, as they are not hydrolyzed in the bowel, being fermented to short chain fatty acids that inhibit the cholesterol synthesis.
Besides, soy is considered one of the main sources of soluble fibers, which decrease significantly serum cholesterol and glucose, and of the insoluble fibers that contribute to the gastrointestinal function. Different studies have shown that the use of soy protein may slow progression of chronic renal disease 8,21 by decreasing hyperfiltration and proteinuria.
In the present study, aiming to evaluate the short-term effect of "soy protein", with the intention of reducing proteinuria and dyslipidemia in patients with proteinuric glomerulopathies, we compared a diet with protein of animal origin 0. When energetic and macronutrients ingestion was evaluated, through the food diary of three days in order to establish whether the patients were following correctly the prescribed diet, a significant decrease in the energetic, lipids and protein intake in the three groups was observed.
Although the food diary evaluation has suggested an expressive decrease in food ingestion, according to the patients' report during the period of study, significant changes were not observed in three groups when weight, BMI and body composition body fat-free mass plus fat mass were evaluated, suggesting that the patients had an adequate diet ingestion during the period of study, and had not reported their true food ingestion by the time of fulfilling the food diary.
When protein ingestion was evaluated by PNA, there was no significant decrease of intake in all groups; besides, the ingested amount was in accordance with the prescribed amount, reinforcing the assumption that the patients have maintained an adequate protein ingestion during this study. We also demonstrated that soy protein diet was safe to maintain the nutritional state weight, BMI and body composition of patients with proteinuric glomerulopathies, as well as APD in short-term.
The ability of soy protein to warrant a good nutritional state can be justified by the fact that it is classified as a protein of high biological value, as it has all essential amino acids in its composition similarly to the animal proteins.
In rats, it seems to be well-established the ability of soy protein to reduce proteinuria and, consequently, to lower the progression of renal disease. Some investigators 14,24,25 have shown lower renal damage and proteinuria in rats fed with soy protein than those with casein. On the other hand, although the effect of soy protein is already well-established in rats, this statement is not true for humans. In humans, this issue was not yet carefully investigated, and there is a lot of controversy about it.
Some studies show positive results 12, and others show negative. Studies performed in healthy subjects have demonstrated that substituting the APD by one of vegetal origin was efficient to prevent the proteinuric and hyperfiltration related effects of meat, which could be very advantageous in the treatment of subjects with chronic renal disease.
Soroka et al. Serum levels of transferrin, albumin, and cholesterol were also similar. Some studies have suggested that the source of protein may affect the excretion of protein in subjects with diabetic nephropathy. The last one has not affected glomerular filtration rate, but it has caused a significant decrease in albumin excretion. Azadbakht et al.
On the contrary, Anderson et al. As previously mentioned, if we take in account that nephrotic patients develop numerous changes in the lipid profile, it would be very interesting to evaluate the effect of soy protein, specifically in subjects with NS, not only due to its possible action on protein loss, but also due to the possibility of lowering cholesterol and TG levels.
Nevertheless, in the present study, when the effect of soy diet on the urinary excretion of protein and on serum total and LDL cholesterol levels and TG was evaluated, we have not observed significant changes in none of the groups between the baseline and post-diet periods. In opposition to the results found in this study, some investigators have observed that the soy protein was efficient to decrease proteinuria and plasma cholesterol in nephrotic syndrome.
Nevertheless, it should be emphasized that, in this study, it was not possible to determine if the favorable effect on proteinuria was due to the change of animal origin protein by soy protein or this effect was due to a significant decrease in the amount of protein ingested by the patients that received vegetal diet. In all these studies, the effect of soy protein on proteinuria in subjects with severe proteinuria was evaluated.
Herein, proteinuria was mainly evaluated in patients with low proteinuria levels. It is possible that the baseline low levels of proteinuria have prevented significant changes in the urinary excretion of proteins, after ingestion of soy protein diet.
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