The Soy Protein Research Committee(Japan)

PROTEIN FRACTION IN SOY PROTEIN ISOLATE BOUND WITH OFF-FLAVOUR COMPOUNDS

Masao FUJIMAKI and Seiichi HOMMA

Department of Food and Nutrition, Ochanomizu University

Nutr. Sci. Soy Protein, Jpn. 3, 5-8, 1982.

n-Hexanal and n-hexanol, which mainly contribute to bean flavour of soy protein, were determined in the soy protein isolate, Fujipro R. These off-flavour compounds consist of both free and bound types: the free type was determined by swirling soy protein isolate (SPI) with an aqueous solution covered with ether phase, and the bound type was measured by digesting SPI with Molsin at pH 2.5 and 30Åé for 21 hr covered with ether phase. Off-flavour compounds were extracted with ether and determined by GLC.
n-Hexanal and n-hexanol of free type were found to be 310-370 and 50-70 É g per 100g SPI respectively. Those of bound type were 600 and 30É g respectively. SPI was fractionated into 7S and 11S proteins. The bound type hexanal in 7S and 11S proteins was found to be 706 and 347É g per 100g protein respectively. Bound hexanol was 70-90É g per 100g protein in both fractions.

INTERACTION OF TRYPTIC MACROPEPTIDES OF SOY PROTEIN ISOLATE WITH MINERALS

Hiroshi NAITO and Tadashi NOGUCHI

Department of Agricultural Chemistry, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 3, 9-12, 1982.

A small amount of macropeptides is formed in the distal small intestine of rat receiving SPI diet.
The present study has been conducted in an attempt to demonstrate whether this peptide fraction concerns any interaction with certain minerals, especially of alkaline-earth ions. Feeding 20% SPI diet together with 45Ca significantly lowered the amount of the radioactivity in total gastro-small intestinal contents, but enhanced those in the large intestinal contents, which was measured 6hr after the beginning of food intake.
No pronounced effect on the distribution in the contents of Ca or Fe, either soluble or insoluble form, was observed.
In in vitro experiments, testing for binding and for inhibition power against phosphate precipitation with alkaline-earth ions, tryptic SPI peptide fraction had not any specific effect compared with casein phosphopeptide or a peptide fraction from egg yolk.

PRODUCTION OF PEPTIDES FROM SOY PROTEIN BY ENZYMATIC MODIFICATION AND EVALUATION OF THEIR NUTRITIONAL PROPERTIES

Soichi ARAI

Department of Agricultural Chemistry, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 3, 13-17, 1982.

A papain-catalyzed process developed by simulating the classical plastein reaction was applied to soy protein isolate for the particular purpose of producing an enzymatically modified protein (EMP) with L-methionine attached covalently at any expected level.
An EMP at a 11% methionine level was formulated with SPI to prepare a series of formulas having different methionine levels. Diets based on these formulas at a 10% protein level were prepared. A feeding test with rats was carried out by using each diet, with the result that PER got maximized at methionine levels of 0.25-0.30% in diet.
On the other hand, an EMP at a 3% methionine level was prepared and then partially hydrolyzed with trypsin. A 66.7%-ethanol treatment on the tryptic hydrolysate afforded an oligopeptide mixture (OPM) with an unchanged methionine level. Chromatography on Bio-gel P-2 showed that the OPM contained only a slight amount of free amino acids, having an average molecular weight of approximately 900 daltons. Effects of feeding the OPM to rats suffering from protein malnutrition on their recovery are discussed.

COMPARATIVE STUDIES ON THE GOITROGENIC ACTIVITIES OF SOYBEAN AND SOY PROTEIN ISOLATE

Shuichi KIMURA, Mieko KAWAMURA and Motoko HIRAMA

Faculty of Agriculture, Tohoku University

Nutr. Sci. Soy Protein, Jpn. 3, 18-23, 1982.

In a previous study, we demonstrated that soybean contains goitrogenic substances which affect thyroid function and that some of these elements are sapogenols and isoflavonoids.
The present study was undertaken to examine the goitrogenic activity of soy protein isolate compared with soybean. It is expected that the goitrogenic substances may be removed by the process of purification from soybean.
Furthermore, this study was undertaken to determine the mechanism of plasma cholesterol-lowering action via thyroid function.
An enlargement of the thyroid was observed in rats fed on soybean but much less enlargement was seen in rats fed on soy protein isolate.
It was observed that a diet containing soy protein isolate produced a lower plasma cholesterol than that of soybean.
Addition of methionine to the diets did not exert a hypocholesterolemic effect, however, the decreases in low-density lipoprotein (LDL) and free cholesterol in plasma were observed.

EFFECT OF DIETARY PROTEIN SOURCE ON METABOLISM OF ANEMIA-RELATED MINERALS

Kazuharu SUZUKI, Yusuke KANKE and Shiro GOTO

Department of Nutrition, Tokyo University of Agriculture

Nutr. Sci. Soy Protein, Jpn. 3, 24-27, 1982.

Present studies were performed to investigate the influence of dietary protein Åmsoy protein isolate (SPI) and caseinÅnand iron level on the iron, copper and zinc utilization and their contents in several organs, using 24 male albino rats of the Wistar strain with initial body weight averaging 50g.
1) On the iron utilization: SPI intake group showed no effect on the iron retention with or without iron supplement in a period of the balance test.
2) On the copper utilization: SPI intake group showed the higher copper retention compared with casein intake group with low dietary iron level.
3) On the zinc utilization: Low iron diet showed a tendency of increasing zinc retention compared with high iron diet.
4) Iron, copper and zinc conceritrations in organs: Low iron diet showed the decrease in iron level and increase in copper level in liver. And this influence reduced in SPI supply compared with casein supply.
SPI supply enhanced the iron level in the femur compared with casein supply with low iron diet.

THE EFFECTS OF SOY PROTEIN ISOLATE AND ITS ENZYMATIC HYDROLYSATE ON CHOLESTEROL METABOLISM

Masao KANAMORI and Hiroshi DOI

Department of Agricultural Chemistry, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 3, 28-32, 1982.

Male Wistar strain rats were fed soy protein isolate (Fujipro R), casein and their pepsin hydrolysate diets for five weeks, respectively, during which terms their serum cholesterol levels were analysed periodically. The soy protein isolate and enzymatic hydrolysate diets decreased the growth rate comparing with casein diets. The soy protein isolate and its hydrolysate diets produced lower levels of serum cholesterol throughout the experiments as compared with those on the corresponding casein diets. These appeared to be no relationship between body weight gains and serum cholesterols in rats fed these four different diets. The pepsin hydrolysate of soy protein isolate decreased the level of serum cholesterol and triglyceride than the level on the corresponding soy protein isolate diets. The soy protein isolate, casein and their enzymatic hydrolysate diets made no significant difference to their effect on the cholesterol contents of high density lipoprotein in serum and also all of these diets consequently decreased the content of free cholesterol in serum.

HYPOCHOLESTEROLEMIC EFFECT OF SOY PROTEIN ISOLATE IN RATS

Michihiro SUGANO, Kazunari TANAKA, Takashi IDE and Katsumi IMAIZUMI

Department of Food Science and Technology, Kyushu University

Nutr. Sci. Soy Protein, Jpn. 3, 33-39, 1982.

Male Wistar rats were fed diets containing proteins or their amino acid mixtures for 24 to 32 days. The livers were isolated and perfused for 4 hours with Krebs-Henseleit buffer containing 0.15% glucose and 25% washed human red blood cells. Feeding soybean protein as compared with casein resulted in a significant reduction of the secretion of cholesterol, triglyceride and apoA-I. The results agreed well with the responses of serum counterparts reported previously. When amino acid mixture diets were fed, however, no such difference could be demonstrated, though the soy-type amino acid mixture had also been shown to decrease serum cholesterol and apoA-I. The production rate of total ketone bodies was the same, but the ratio of É¿-hydroxybutyrate: acetoacetate was significantly higher on soybean protein. The perfusate glucose tended to be higher on soybean protein. These differences were less clear on feeding amino acid mixtures. Neither the rate of bile flow nor the concentration of biliary bile acids and cholesterol were influenced by the type of dietary protein. These observations led us to conclude that soybean protein exerts the cholesterol-lowering action primarily through the regulation of hepatic contribution. The data also suggested that the protein-dependent difference in the concentration of serum cholesterol and apoA-I might not be explained thoroughly by the difference in the amino acid profile alone. In this context, the effect of the difference in the sequence of digestion and absorption of different nitrogen sources should be taken into account.

EFFECT OF SOY PROTEIN ISOLATE ON PLASMA CHOLESTEROL CONCENTRATION IN THE RAT

Shin-ichi HAYASHI, Yasuko MURAKAMI and Yoshiko HARA

Department of Nutrition, Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 3, 40-43, 1982.

1) Rats were fed on high fat-casein, low fat-casein or high fat-soy isolate diet for long term (>24 weeks). The latter two groups of rats were pair-fed to the first group so that all the group showed the same average growth rate. Plasma total cholesterol concentration was markedly lower in the group of rats fed on high fat-soy isolate than in other two groups.
2) When rats fed on low fat-casein diet for 34 weeks were fed on high fat-soy isolate diet, plasma total cholesterol concentration decreased significantly within one week after the shift of diet.
3) When young rats were fed on low fat-gluten diet with or without supplementation of lysine for 2 weeks, their plasma total cholesterol concentrations were significantly lower than those of rats fed on low fat - casein diet.
4) Supplementation of threonine to casein diet did not affect plasma total cholesterol concentration.

EFFECT OF DIETARY PROTEINS ON EXPERIMENTALLY INDUCED HYPERCHOLESTEROLEMIA IN AGED RATS

Yoshikazu SANNO, Tatsuya KIMURA and Takehiko TANAKA

Department of Nutrition and Physiological Chemistry, Osaka University Medical School

Nutr. Sci. Soy Protein, Jpn. 3, 44-45, 1982.

To minimize effects of growth, aged male rats of Sprague-Dawley strain were used for study on the effect of dietary proteins on cholesterol levels in blood. Diets contained 12% (w/w) of protein, supplemented with 1% of cholesterol and 0.25% of sodium cholate.
The result showed that cholesterol levels in the blood tended to be higher in casein-fed rats than those in SPI-fed animals.

LIMITING AMINO ACIDS OF SOY PROTEIN ISOLATE AND THEIR SUPPLEMENTARY EFFECTS (Part 3)

Michio YAMAGUCHI, Masako IWAYA and Motoyoshi MIYAZAKI

National Institute of Nutrition

Nutr. Sci. Soy Protein, Jpn. 3, 46-49, 1982.

The first experiment was undertaken to examine whether or not the supplementary effect of methionine and threonine to soy protein isolate (SPI), which was previously observed in growing rats, is also observed in adult rats. Results were as follows. Although biological value for SPI itself was as low as 41, it was improved up to 60 for that supplemented with methionine, 81 for that additionally supplemented with threonine, and 87 for that similarly supplemented with all the other essential amino acids, thus nearly close to the value, i.e. 88, for whole egg protein. There were no statistically significant differences among the last three values. The methionine and threonine supplement to SPI elevated serum albumin and A/G ratio and lowered urea nitrogen at a significant level as compared to the SPI group. Although this supplement did not change the total cholesterol level remarkably, it elevated the HDL-cholesterol level, suggesting an improvement of cholesterol metabolism. Further supplement of all the other essential amino acids, however, did not give any appreciable changes to the above serum components. From these results, the first limiting amino acid of SPI for adult rats was proved to be the sulfur-containing amino acid and the second one threonine.
The second experiment was conducted to examine the supplementary effects of lactalbumin, fish protein concentrate, egg white and whole egg protein on the improvement of nutritive value of SPI for more practical purpose, where a 15N tracer method was applied at the same time. Biological value of SPI was improved most by the supplement of whole egg protein. This was attributed to the high contents of methionine and threonine.

INDUCIBILITY OF AMINO ACID IMBALANCE BY SUPPLEMENT OF SULFUR - AMINO ACIDS TO A SOY PROTEIN ISOLATE DIET

Akira YOSHIDA and Hidehiko YOKOGOSHI

Department of Agricultural Chemistry, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 3, 50-53, 1982.

When rats are fed a low casein diet, supplementation of a small amount of sulfur containing amino acid to the diet produces fatty liver. This is one type of amino acid imbalances. For an efficient and safe supplementation of sulfur amino acid to soy protein isolate (SPI), it is important to make clear in what conditions fatty livers are produced.
Female young rats of the Wistar strain were used for the experiments. Diets were fed ad lib for 2 weeks. Supplement of 0.3% of Met to a 8.8% SPI diet did not produce significant fatty liver in rats. Whereas the supplement of the same amounts of Met to a 8% casein diet clearly produced fatty livers. Liver fat of rats fed the 8.8% SPI diet increased, however, with each increase in the supplemental amounts of Met from 0.3 to 0.6%. Body weight gain was significantly improved by Met supplement, but the effects were not changed by the increment of supplemented Met from 0.3 to 0.6%. Thus it would be recommended that the supplemental amount of Met to the 8.8% SPI diet should not be increased over 0.3% not to produce fatty liver with efficient improvement for body weight gain. A diet containing an amino acid mixture simulating SPI, however, produced significant fatty liver, therefore, the low inducibility of amino acid imbalance of SPI diet is not due to the only amino acid composition but the characteristic protein quality is also an important factor. Supplement of Met to the SPI diet or the diet containing AA-mix. simulating SPI generally increased the serum cholesterol.
Composition of sulfur-amino acids was variously changed keeping the dietary total S-AA was 0.3%. Replacement of Cys for Met more than 60%, decreased the body weight gain. It can be said, about 60% of Met can be replaceable with Cys without decrease of nutritional quality as sulfur amino acids.
Supplemental effect of Met on fatty liver production was affected by dietary level of SPI. When the level of SPI below 8.8% the supplement of 0.3% Met produced fatty livers.

SUPPLEMENTARY EFFECTS OF LIMITING AMINO ACIDS ON THE UTILIZATION OF SOY PROTEIN ISOLATE IN PREGNANT RATS

Yoshiaki NIIYAMA and Sadaichi SAKAMOTO

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 3, 54-59, 1982.

Pregnant rats of the Sprague-Dawley strain, weighing about 190g, were fed 10% SPI diets added with graded levels of L-methionine (0.3%, 0.4%, 0.5%, 0.7% and 1.0%), 0.4% Lmethionine + 0.25% L-threonine and 0.4% L-methionine + 0.25% L-threonine + 0.2% L-lysine for 21 days. Supplementary effects of these amino acids were examined in terms of food intake and body weight gain during pregnancy, food efficiency, NPU and fetal growth. In addition, free amino acid concentration in plasma from dams at term was determined. Methionine supplementation to the 10% SPI diet resulted in increased food intakes with improvement of food efficiency. Food efficiency was highest in 0.3% methionine added group and efficiency decreased with increasing methionine levels. Pregnant rats receiving diet supplemented with 1.0% methionine ate less and had less reproductive performances as compared those fed less methionine added diets, suggesting that 1.0% methionine addition was excessive. Further addition of threonine or threonine plus lysine to the 10% SPI diet supplemented with 0.3% methionine did not show any favourable effects on body weight gain, food efficiency and reproductive performances. NPU of the 10% SPI diet in pregnant and nonpregnant rats was 47 and 42, respectively. Addition of the limiting amino acids caused a marked improvement of utilization efficiency of the SPI diet, with highest value of NPU being 71 in 0.5% methionine added diet. Further addition of lysine to the SPI diet supplemented with methionine and threonine did not show any effect. Free amino acid concentration in plasma of the pregnant rat did not change by the addition of the limiting amino acids.

UTILIZATION AND REQUIREMANT OF SOY PROTEIN ISOLATE IN ADULT FEMALE

Kayoko KANEKO and Goro KOIKE

Kagawa Nutrition College

Nutr. Sci. Soy Protein, Jpn. 3, 60-64, 1982.

Ten female students aged 19 to 20 were fed protein-free diet for one day and in the following ten days they were given the diets with SPI, 0.3 g protein/kg for four subjects, 0.45 g/kg for two and 0.6 g/kg for four, respectively. Mean energy intake was 36.4 Å} 2.7 kcal/kg/day which corresponds to about 1.7 times as much as their hasal metabolism and was considered as the maintenance level. Twenty-four hour urine was collected completely during experimental period and urinary creatinine and nitrogen contents were measured. Subjects were given three grams of carbon powder as a fecal marker with the breakfast at the beginning of SPI diet and the next morning after experimental period. Feces from marker to marker were collected, dried and their nitrogen contents were determined. Nitrogen balance was calculated from the intake, fecal N excretion and the mean of urinary N excretion of the last four experimental days when urinary N excretion achieved a constant level. Linear regression line of N balance (y) with N intake (x) was calculated as y = 0.411x - 40.8 (n = 10, r = 0.812), and mean N equilibrium value of SPI was 99 mg/kg/day. Digestibility and net protein utilization (NPU) of SPI were calculated from these N halance responses with the figures of urinary and fecal obligatory N losses determined in other fourteen subjects previously, 34.5 mg/kg for urinary loss and 10.0 mg/kg for fecal loss. Digestibility was 98.2 Å} 5.0% (n = 10) and NPU were 47 Å} 24 at protein intake of 0.3 g/kg (n = 4), 49 at 0.45 g/kg (n = 2) and 44 Å} 3 at 0.6 g/kg (n = 4). The results were compared with the data in male subjects reported by other investigators.

THE NUTRITIONAL EVALUATION OF SOY PROTEIN ISOLATE, WHEAT GLUTEN, PURE EGG PROTEIN AND MIXTURE OF THESE THREE MATERIALS

Hideo KOISHI ¹, Toyoko OKUDA ¹, Yoshiko HATTORI ¹, Yoshiko MASE ¹, Naemi KAJIWARA ², Noriko KAWAI ² and Katumi SHIKI ²

¹ Faculty of the Science of Living, Osaka City University
² Department of Home Economics, Kobe Wmen's College

Nutr. Sci. Soy Protein, Jpn. 3, 65-70, 1982.

The nutritional values of soy protein isolate (SPI) were compared with those of gluten, pure egg protein and their mixture on the growing rats. The male Sprague-Dawley rats were fed ad libitum diets containing wheat gluten (A), pure egg protein (B), SPI (C), a mixture of gluten and SPI (D), a mixture of pure egg protein and SPI (E) or a mixture of gluten, pure egg protein and SPI (F) as protein source for 38 days. The level of protein in the diet was 6% (0.99 gN/100g diet) and all these mixtures (D), (E) and (F) contained same amount of nitrogen from each nitrogen source.
Body weight gain, nitrogen efficiency, nitrogen balance and concentration of plasma albumin showed a similar order as follows, BÅÑEÅÑFÅÑC= DÅÑA. Concentration of total cholesterol in plasma showed as follows, BÅÑC=D=E=FÅÑA. The levels of triglyceride and phospholipid in plasma showed also close to the same order.
From above results, the authors concluded that the SPI has lower nutritional value for young rats than pure egg protein but when the half of the protein in pure egg protein diet were substituted with SPI, the nutritional value of this diet is about the same the pure egg protein diet and also cholesterol concentration in plasma of rats fed this diet was maintained at a low level.

EFFECT OF SOY PROTEIN ON CARCASS FAT CONTENT IN GROWING RATS

Goro INOUE, Kyoichi KISHI, Meifu WANG and Hiroko WATANABE

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 3, 71-76, 1982.

Two experiments were conducted to study the effect of soy protein on carcass fat content and plasma and liver lipids of rats given high fat diet. In experiment 1, male Wistar rats weighing 55g were fed 10% proteinÅE 20% lard diet for 16-17 weeks using soy protein isolate (SPI), SPI + 0.3% Met + 0.2% Thr (SMT), lactalbumin (LA) and fish meal (FM) as protein sources. Carcass fat content was similar in all groups being ahout 26%. The concentration of plasma total lipid was greater in SMT diet than in other protein diets. Triglyceride, free fatty acid and HDL-cholesterol in plasma of SPI diet were not different from those of LA diet and FM diet. Plasma total cholesterol was slightly greater in SMT diet than other diets. In experiment 2, male Wistar rats weighing 40g were fed 20% protein. 20% corn oil or butter diet for 5 weeks using SPI, wheat gluten (WG), egg white (EW) and casein (CS) as protein sources. Body weight gain was comparable in all groups except WG diet being lower. No significant difference in carcass fat content was observed between vegetable protein and animal protein and between corn oil and butter. We found no hypocholesterolemic effect of SPI or WG compared with EW or CS. Total lipid and total cholesterol of the liver in SPI diet were comparable with CS diet. It was concluded that soy protein had no effect in lowering carcass fat content on the present experimental conditions.

EFFECT OF SOY PROTEIN ISOLATE ON LIPID METABOLISM

Kiyoshi ASHIDA

Department of Food Science, Sugiyama-Jogakuen University

Nutr. Sci. Soy Protein, Jpn. 3, 77-79, 1982.

Two experiments were conducted to examine which of the protein or ash in SPI has hypocholesterolemic function in male Wistar rats fed 15% protein and 15% hydrogenated oil diets. The protein in SPI was obtained by dissolving in 1N NaOH and precipitating at pH 4.5 with 1N HCl. The ash in SPI was prepared by heating SPI at 550Åé for about 10 hours. Serum cholesterol and triglyceride were measured 5 or 6 weeks after rats were fed diets containing the reprecipitated protein or ash isolated from SPI. Serum cholesterol and triglyceride levels were significantly lower on the reprecipitated protein diet than on the casein diet. However, the ash of SPI did not lead to a reduction in serum cholesterol or triglyceride as compared with AIN - 76TM mineral mixture. These results indicate that the active principle of hypocholesterolemic function in SPI was the protein fraction reprecipitated from SPI. Furthermore, fish meat of cod was found to be more hypercholesterolemic than casein.

EFFECT OF PARTIAL REPLACEMENT OF DIETARY PROTEIN WITH SOY PROTEIN ISOLATE ON THE LIPID CONCENTRATIONS IN PLASMA FROM HYPERLIPIDEMIC PATIENTS WITH CEREBRAL VASCULAR ACCIDENTS

Yutaka MATSUKA ¹ and Yoshiaki NIIYAMA ²

¹ Tokusima National Hospital
² Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 3, 80-84, 1982.

Six hyperlipidemic patients with cerebral vascular accidents were fed a diet containing about 1500 kcal and 65g of proteins including about 10g of SPI for 64 days. On days 16, 44 and 65 after administration of the experimental diet, TG, NEFA, total-, free- and HDL-cholesterols and PL in plasma were determined. Concentrations of TG, total- and free-cholesterol stended to decrease, whereas concentration of HDL-cholesterol increased. From these results a usefulness of SPI as the therapeutic diets for the hyperlipidemia was suggested.

INFLUENCE OF SOY PROTEIN ISOLATE ON CARDIOVASCULAR DISEASE

Seiki NAMBU , Masako INOUE , Motoh TSUSHIMA , Yasuko NISHIOHEDA , Keiji MURAKAMI , Hideki KOH and Toshio KASAMA

Division of Atherosclerosis and Metabolism, Department of Internal Medicine,
National Cardiovascular Center, Osaka.

Nutr. Sci. Soy Protein, Jpn. 3, 85-89, 1982.

Diet has a powerful effect on glucose-intolerance and hyperlipidemia. To decide what the diet is effective on these diseases is difficult in clinical study so that plasma glucose and lipid levels often vary among individual cases on the same diet. The present study was undertaken to investigate an influence of soybean protein isolate (about 10% of total energy) in maintenance of glucose tolerance and catabolism of very low density lipoprotein (VLDL) which had been improved by the therapeutic diet.
The hospitalized patients were kept on the therapeutic diet consisting of 22-24% energy from protein (about 70% of protein from animal protein) before giving the isocaloric soybean protein diet (S-P diet) which was containing of 37.8g of soybean protein isolate. Fasting plasma samples, which were collected before and after 2 or 3 weeks of S-P diet therapy, were subjected to ultracentrifugation for isolation of VLDL and measurement therein of composition of apo-protein by electrofocus-electrophoresis. Also 75g oral glucose tolerance test was done in each period.
The results were obtained as follows: 1) After shifting to the isocaloric S-P diet from the therapeutic diet the normalized glucose tolerance became worse in weight-stable patients. Indirect evidence suggests that glucose intolerance induced by 10% energy of soybean protein isolate might not be due to change in the dietary insulin-releasing amino acid intake. 2) Composition of VLDL which was calculated as apo E/C, apo CII/CIII, apo E3/E2 and cholesterol/triglyceride ratio in VLDL did not show remarkable change by the isocaloric S-P diet. The result suggests that plasma cholesterol and/or triglyceride lowering effect of soybean protein isolate might not be due to influence on VLDL-catabolism.
We conclude that it is necessary to elucidate how much percent energy of soybean protein needs to maintain the normalized glucose tolerance and hyperlipidemia.

EFFECT OF SOY PROTEIN SUBSTITUTING DIET ON HYPERLIPOPROTEINEMIC STATE

Emiko MIYAZIMA, Sizue TAKEYAMA, Kazuo KONDO, Akihiko KAGAMI,
Naoki SUZUKI, Norio TADA, Toshitsugu ISHIKAWA and Haruo NAKAMURA

Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 3, 90-92, 1982

Soy protein substituting diets were given for 3 weeks to 5 hyperlipoproteinemic subjects (IIa 4, IIb 1) in order to assess the effect of the diet on the lowering lipoprotein lipids. The results were compared with those obtained during the administration of control diets.
Total cholesterol fell significantly by 12% on the soy protein diets and LDL-cholesterol decreased significantly by 15%. HDL-cholesterol also reduced significantly on the soy protein diet. Triglyceride level remained almost unchanged. However, phospholipids decreased significantly.
Apoprotein A-I did not show any significant alterations during the administration of soy protein diet, thus resulting in the significant decrease of HDL-C/A-I ratio.
Apparent reduction of LDL- and HDL-cholesterol could be the consequence of the changes of P/S or lysine to arginine ratio, since the diets maintained the same cholesterol contents with those of control diets.

The soy protein protein reserch(Japan)