Regulative actions of dietary soy isoflavone on biological antioxidative system and lipid metabolism in rats

Male Sprague-Dawley rats, 4 weeks of age, were fed purified diets either with or without 0.2% soy isoflavones rich powder for 5 weeks to elucidate their direct functions such as antioxidative action and regulation of lipid metabolism. Dietary soy isoflavones decreased serum lipid peroxide level in rats. Levels of liver and serum alpha-tocopherol were higher in the rats fed isoflavone than in those fed isoflavones-free diet. Thus, dietary soy isoflavones exhibited mild antioxidative function in this animal experiment. Isoflavone metabolites from diet may act as scavengers of reactive oxygen species. Dietary soy isoflavones lowered hepatic 3-hydroxy-3-methylglutaryl CoA reductase activity, although liver cholesterol level was not modulated. However, the levels of serum cholesterol and triglyceride decreased by consumption of soy isoflavones. Therefore, dietary soy isoflavones may exhibit hypocholesterolemic and hypolipidemic functions. Moreover, dietary soy isoflavones lowered hepatic Delta6 desaturase activity. Reflecting this observation, Delta6 desaturation indices ((18:2(n = 6) + 18:3(n = 6))/20:4(n = 6)) of tissue lipids tended to be lower in rats fed isoflavones than in those fed isoflavones-free diet. This action may contribute to the prevention of inflammatory response by imbalance of eicosanoids. These observations suggest that the positive intake of soy isoflavones may reduce the risk of some cardiovasucular diseases through their radical scavenging function and hypocholesterolemic action.     

Isoflavone-free soy protein prepared by column chromatography reduces plasma cholesterol in rats

To know whether isoflavones are responsible for the hypocholesterolemic effect of soy protein, the effect on plasma cholesterol of isoflavone-free soy protein prepared by column chromatography was examined in rats. Five-week-old male Sprague-Dawley rats were fed cholesterol-enriched AIN-93G diets containing either 20% casein (CAS), 20% soy protein isolate (SPI), 20% isoflavone-free SPI (IF-SPI), 19.7% IF-SPI + 0.3% isoflavone-rich fraction (isoflavone concentrate, IC), or 20% CAS + 0.3% IC for 2 weeks. Plasma total cholesterol concentrations of rats fed SPI and IF-SPI were comparable and were significantly lower than that of rats fed CAS. The addition of IC to the CAS and IF-SPI did not influence plasma cholesterol level. Fecal steroid excretion of the three SPI groups was higher than that of the two CAS groups, whereas the addition of IC showed no effect. Thus, a significant fraction of the cholesterol-lowering effect of SPI in rats can be attributed to the protein content, but the isoflavones and other minor constituents may also play a role.     

Lower weight gain and hepatic lipid content in hamsters fed high fat diets supplemented with white rice protein, brown rice protein, soy protein, and their hydrolysates

The physiological effects of the hydrolysates of white rice protein (WRP), brown rice protein (BRP), and soy protein (SP) hydrolyzed by the food grade enzyme, alcalase2.4 L, were compared to the original protein source. Male Syrian Golden hamsters were fed high-fat diets containing either 20% casein (control) or 20% extracted proteins or their hydrolysates as the protein source for 3 weeks. The brown rice protein hydrolysate (BRPH) diet group reduced weight gain 76% compared with the control. Animals fed the BRPH supplemented diet also had lower final body weight, liver weight, very low density lipoprotein cholesterol (VLDL-C), and liver cholesterol, and higher fecal fat and bile acid excretion than the control. Expression levels of hepatic genes for lipid oxidation, PPARα, ACOX1, and CPT1, were highest for hamsters fed the BRPH supplemented diet. Expression of CYP7A1, the gene regulating bile acid synthesis, was higher in all test groups. Expression of CYP51, a gene coding for an enzyme involved in cholesterol synthesis, was highest in the BRPH diet group. The results suggest that BRPH includes unique peptides that reduce weight gain and hepatic cholesterol synthesis.     

Novel process of fermenting black soybean [Glycine max (L.) Merrill] yogurt with dramatically reduced flatulence-causing oligosaccharides but enriched soy phytoalexins

Black soybeans [Glycine max (L.) Merrill] were germinated under fungal stress with food grade R. oligosporus for 3 days and were homogenized and fermented with lactic acid bacteria (LAB) to produce soy yogurt. Fungal stress led to the generation of oxylipins [oxooctadecadienoic acids (KODES) isomers and their respective glyceryl esters] and glyceollins--a type of phytoalexins unique to soybeans. In soy yogurt, the concentrations of total KODES and total glyceollins were 0.678 mg/g (dry matter) and 0.953 mg/g, respectively. The concentrations of other isoflavones (mainly genistein and daidzein and their derivatives) in soy yogurt remained largely unchanged after the processes compared with the control soy yogurt. Germination of black soybean under fungal stress for 3 days was sufficient to reduce stachyose and raffinose (which cause flatulence) by 92 and 80%, respectively. With a pH value of 4.42, a lactic acid content of 0.262%, and a maximum viable cell count of 2.1 x 10 (8) CFU/mL in the final soy yogurt, soy milk from germinated soybeans under fungal stress was concluded to be a suitable medium for yogurt-making. The resulting soy yogurt had significantly altered micronutrient profiles with significantly reduced oligosaccharides and enriched glyceollins.     

Cholesterol Response and Foam Cell Formation in Hamsters Fed Rice Bran,Oat Bran,and Cellulose + Soy Protein Diets With or Without Added Vitamin E

Four-week-old male golden Syrian hamsters were fed diets containing cellulose (control, CC), cellulose + soy protein (CS), CS + vitamin E, (CSE), rice bran (RB), RB + vitamin E (RBE), oat bran (OB), and OB + vitamin E (OBE) for six weeks (n = 10/treatment). Diets contained (by weight) 10% total dietary fiber, 3% N, 20% fat, 0.5% cholesterol, and some diets had an additional 0.1% vitamin E. After six weeks, RB and OB diets resulted in significantly higher weight gain than the CC diet. Plasma low-density lipoprotein cholesterol (LDL-C) values and the LDL-C/high-density lipoprotein cholesterol ratio in hamsters fed CSE, RBE, OB, and OBE diets were significantly lower than in those fed CC diet. There were no significant differences in total plasma cholesterol values among the hamsters fed any of the diets. Liver cholesterol in animals fed OB and OBE diets was significantly lower than in all other groups. Foam cell areas in the inner bend of the aortic arch in animals fed all treatment diets were significantly reduced when compared with that in animals fed CC diet. The level of additional dietary vitamin E did not result in further significant reductions in foam cell area. The results of this study suggest that diets containing rice bran, oat bran, or soy protein significantly reduced the development of atherosclerosis in hypercholesterolemic hamsters.     

Inulin effects on bioavailability of soy isoflavones and their calcium absorption enhancing ability

The effect of inulin on isoflavone absorption and the effect of isoflavones and synergy with inulin on calcium absorption in rats was investigated. Rats (n = 48) were divided into three groups and fed inulin (50 mg/g), isoflavone (8 mg/g) or inulin + isoflavone (50 mg/g + 8 mg/g) diets for 21 days. After a 2-h fast, rats were given (45)Ca orally or intraperitoneally, together with 25 mg of calcium as calcium acetate. Blood and femurs were collected 4 days later. Sera were analyzed for isoflavones using HPLC-MS, femurs for (45)Ca by beta-scintillation counting, and total femoral calcium by atomic absorption spectroscopy. Both groups fed isoflavones had similar and significantly higher weight-adjusted total femoral calcium content compared to the inulin-fed group (p < 0.0001). (45)Ca absorption was significantly higher (p < 0.01) when isoflavones were added to the diet, and serum equol was significantly lower (p < 0.01) when inulin was added to the diet containing isoflavones. We conclude that isoflavones enhance calcium absorption, without synergy from inulin, and that inulin decreases equol production.     

Comprehensive phytochemical profile of soy protein isolate

Although an FDA health claim for soy protein has been issued, the potential health benefits of soy foods remain controversial among scientists, especially with regard to soy infant formula. The UV detectable isoflavones have been the focus of the majority of studies concerning health-related effects of soy protein isolate (SPI). However, the chemical identities and health effects of other SPI phytochemicals without UV absorption properties are less well-studied. In the current study, we employed liquid chromatography-tandem mass spectrometry methods to reveal a complicated phytochemical profile for SPI consisting of 136 phytochemicals. Also, we have quantitated many of these SPI phytochemicals so that dietary intakes can be estimated for foods containing SPI. On a weight/weight basis, fatty acids are the largest group of phytochemicals in the extract (64.13% total fat), followed by saponins (21.48%), and then isoflavones at 6.82%. Of the 56 lysophospholipids identified in SPI, 0.50% was lysophosphatidylcholines and 0.23% was lysophosphatidylethanolamines.     

Estrogenic activity of glycitein, a soy isoflavone

Glycitein (4',7-dihydroxy-6-methoxyisoflavone) accounts for 5-10% of the total isoflavones in soy food products. The biological activity of this compound has not been reported to date, although numerous studies have been performed with the other soy isoflavones, daidzein and genistein. Glycitein was isolated from soy germ to 99% purity. Weaning female B6D2F1 mice were dosed with glycitein (3 mg/day), genistein (3 mg/day), and diethylstilbestrol (DES) (0.03 microg/day) in 5% Tween 80 by gavage for 4 days. A control group received an equal volume of 5% Tween 80 solution daily. The uterine weight increased 150% with glycitein (p < 0.001), 50% with genistein (p < 0. 001), and 60% with DES (p < 0.001) compared with the control group. DES, 17beta-estradiol, and three isoflavones (daidzein, genistein, and glycitein) were examined for their competitive binding abilities with 17beta-((3)H)estradiol to the estrogen receptor proteins of the B6D2F1 mouse uterine cytosol. The concentrations of each compound required to displace 50% of the ((3)H)estradiol at 5 nM in the competitive binding assay were 1.15 nM DES, 1.09 nM 17beta-estradiol, 0.22 microM genistein, 4.00 microM daidzein, and 3.94 microM glycitein. These data indicated that glycitein has weak estrogenic activity, comparable to that of the other soy isoflavones but much lower than that of DES and 17beta-estradiol.     

Hypocholesterolemic effects of a flavonoid-rich extract of Hypericum perforatum L. in rats fed a cholesterol-rich diet

In a previous study, a flavonoid-rich extract of Hypericum perforatum L. (FEHP) was prepared and its antioxidant activity was determined by a series of models in vitro. In this study, the hypocholesterolemic effects of FEHP in rats fed a cholesterol-rich diet were tested. Forty Wistar rats fed a standard laboratory diet or a cholesterol-rich diet for 16 weeks were used. The serum lipid levels, as well as malondialdehyde (MDA) and activity of superoxide dismutase (SOD) and catalase (CAT) in serum and liver, were examined. Cholesterol-rich diet induced hypercholesterolemia was manifested in the elevation of serum lipid levels such as total cholesterol (TC), total triglycerides (TG), and low density lipoprotein cholesterol (LDL-C). Administration of middle-dose (75 mg/kg of BW/day) and high-dose (150 mg/kg of BW/day) FEHP significantly lowered the serum levels of TC, TG, and LDL-C, while increasing the serum level of high density lipoprotein cholesterol (HDL-C). Also, the content of MDA in serum and liver decreased significantly after oral administration of FEHP compared with those of rats fed a cholesterol-rich diet. In addition, FEHP increased the activity of SOD in serum and liver, but the activity of CAT was significantly elevated only in liver. These results suggested that the hypocholesterolemic effects of FEHP might be due to its abilities to lower serum TC, TG, and LDL-C levels as well as to slow the lipid peroxidation process and to enhance the antioxidant enzyme activity.     

Nutritional aspects of second generation soy foods

Samples of 15 second generation soy-based products (n = 3), commercially available, were analyzed for their protein and isoflavone contents and in vitro antioxidant activity, by means of the Folin-Ciocalteu reducing ability, DPPH radical scavenging capacity, and oxygen radical absorbance capacity. Isoflavone identification and quantification were performed by high-performance liquid chromatography. Products containing soy and/or soy-based ingredients represent important sources of protein in addition to the low fat amounts. However, a large variation in isoflavone content and in vitro antioxidant capacity was observed. The isoflavone content varied from 2.4 to 18.1 mg/100 g (FW), and soy kibe and soy sausage presented the highest amounts. Chocolate had the highest antioxidant capacity, but this fact was probably associated with the addition of cocoa liquor, a well-known source of polyphenolics. This study showed that the soy-based foods do not present a significant content of isoflavones when compared with the grain, and their in vitro antioxidant capacity is not related with these compounds but rather to the presence of other phenolics and synthetic antioxidants, such as sodium erythorbate. However, they may represent alternative sources and provide soy protein, isoflavones, and vegetable fat for those who are not ready to eat traditional soy foods.     

Soy leaf lowers the ratio of non-HDL to HDL cholesterol in hamsters

The present study was to examine effect of soy leaf powder (SLP) and soy leaf ethanol extract (SLEE) on serum lipoproteins in hamsters. The control group was fed a semisynthetic diet containing 0.1% cholesterol, while the tested groups were maintained on the same diet but supplemented with 3% SLP or the equivalent amount of SLEE derived from 3% SLP for 4 weeks. SLP supplementation led to a trend of lowering serum total cholesterol (TC) and nonhigh density lipoprotein cholesterol (non-HDL-C), with HDL-C being unaffected, whereas incorporation of SLEE into the diet led to an elevated level of HDL-C and a lower level of non-HDL-C with TC being unchanged. Both SLP and SLEE supplementation caused favorably a decrease in the ratio of non-HDL-C to HDL-C. The present results demonstrate that not only soybean seeds but also soy leaves are cardioprotective, by favorably modulating serum lipid profile.     

Influence of soy aglycon isoflavones on bone-related traits and lens protein characteristics of ovariectomized rats and bioactivity performance of osteoprogenitor cells

Health benefits of soy isoflavones have attracted the concern of the public and the interest of health-care professionals. In this study, two trials were conducted in characterizing bone-related traits and lens proteins as affected by supplementation of soy aglycon isoflavones (SAI). In trial 1, an in vivo study, 20 Sprague-Dawley rats were ovariectomized (OVX) and randomly distributed into OVX and OVX+SAI (135 mg of SAI/kg of feed; 8.33 mg/kg body weight; 2.5 mg/day) groups. Another group containing 10 rats with a sham operation was control (Sham). The experiment period was 3 months, and the rats were subjected to bone-related traits and lens protein characterization. In trial 2, an in vitro study, osteoprogenitor cells (UMR-106) were divided into SAI-supplemented (0.5 mg of SAI/mL of medium) and unsupplemented groups. Results of the in vivo study indicated that daily BW gains in the OVX and OVX+SAI groups were greater than that of the Sham group (p < 0.05). Bone ash and Ca contents of the Sham and OVX+SAI groups were higher than those of the OVX group (p < 0.05), while bone density, strength, and phosphorus contents among groups varied insignificantly (p > 0.05). When the lens proteins were extracted and analyzed with size-exclusion HPLC, the contents of beta- and gamma-crystallins were lowest in the OVX group and the protein solubility decrease could be recovered by dietary SAI supplementation (shown by OVX+SAI group). Based on Raman spectra of the isolated lens proteins, disulfide bonds were observed more in OVX lens than in the Sham and OVX+SAI lens. Results of in vitro study with osteoprogenitor cells revealed that cell viability, alkaline phosphatase activity, osteocalcin, and Ca contents of the SAI-supplemented group were higher than those of the unsupplemented group (p < 0.05). The likely potency to enhance bone and lens health by SAI supplementation is worth pointing out.     

LC-MS/MS analysis of lysophospholipids associated with soy protein isolate

Approximately 20-25% of babies consuming formula are fed formulas containing soy protein as the sole protein source. Isoflavone phytoestrogens are considered as major bioactive components present in soy protein isolate (SPI) and the most widely studied phytochemicals in human diets and soy infant formulas. In the present study, LC-MS/MS analysis of SPI phytochemical extract resulted in identifications of fifty-six lysophospholipids (lyso-PL), including eighteen lysophosphatidylcholines (lyso-PC), twelve lysophosphatidylethanolamines (lyso-PE), eleven lysophosphatidylinositols (lyso-PI), eleven lysophosphatidic acids (lyso-PA) and four lysophosphatidylglycerols (lyso-PG). The LC-MS/MS conditions were first developed using commercially available standard mixtures. Under these conditions, lyso-PL compounds could be separated by LC and yielded unique fragments and neutral losses in the electrospray ionization mass spectrometry (ESI-MS) with both positive- and negative-ion modes, quite indicative of the polar headgroups for different subclasses. This is the first characterization of lyso-PL in SPI. Lyso-PLs are important cell signaling and growth factor molecules experimentally linked to cardiovascular function and disease, cancer, and neurological disorders. These findings suggest that biological effects of PLs associated with SPI in infants clearly needs to be considered as part of an overall evaluation of potential health benefits.     

Nutritional and health benefits of soy proteins

Soy protein is a major component of the diet of food-producing animals and is increasingly important in the human diet. However, soy protein is not an ideal protein because it is deficient in the essential amino acid methionine. Methionine supplementation benefits soy infant formulas, but apparently not food intended for adults with an adequate nitrogen intake. Soy protein content of another essential amino acid, lysine, although higher than that of wheat proteins, is still lower than that of the milk protein casein. Adverse nutritional and other effects following consumption of raw soybean meal have been attributed to the presence of endogenous inhibitors of digestive enzymes and lectins and to poor digestibility. To improve the nutritional quality of soy foods, inhibitors and lectins are generally inactivated by heat treatment or eliminated by fractionation during food processing. Although lectins are heat-labile, the inhibitors are more heat-stable than the lectins. Most commercially heated meals retain up to 20% of the Bowman-Birk (BBI) inhibitor of chymotrypsin and trypsin and the Kunitz inhibitor of trypsin (KTI). To enhance the value of soybeans in human nutrition and health, a better understanding is needed of the factors that impact the nutrition and health-promoting aspects of soy proteins. This paper discusses the composition in relation to properties of soy proteins. Also described are possible beneficial and adverse effects of soy-containing diets. The former include soy-induced lowering of cholesterol, anticarcinogenic effects of BBI, and protective effects against obesity, diabetes, irritants of the digestive tract, bone, and kidney diseases, whereas the latter include poor digestibility and allergy to soy proteins. Approaches to reduce the concentration of soybean inhibitors by rearrangement of protein disulfide bonds, immunoassays of inhibitors in processed soy foods and soybean germplasm, the roles of phytoestrogenic isoflavones and lectins, and research needs in all of these areas are also discussed. This integrated overview of the widely scattered literature emphasizes general concepts based on our own studies as well as recent studies by others. It is intended to stimulate interest in further research to optimize beneficial effects of soy proteins. The payoff will be healthier humans and improved animal feeds.     

Antioxidant properties of soybean isoflavone extract and tofu in vitro and in vivo

Isoflavones in soybean were extracted in the crude form using 80% food-grade ethanol at 80 degrees C for 6 h and followed by concentration and dehydration. The soy extract contained isoflavones primarily in the forms of glucosides. In vitro antioxidant activities of the soy extract containing 20-500 ppm isoflavones were conducted using a Rancimat method. The results showed that soy isoflavone extract had strong in vitro antioxidant activity. There was a dose-dependent response for the in vitro antioxidant activity at the lower concentrations but not at the higher concentrations. In vivo antioxidant property was determined by measuring the antioxidant enzymes, superoxide dismutase, and catalase in various organs of rats that were fed with diets containing partially oxidized oil and various levels of isoflavones for up to 24 weeks. Neither short-term (8 weeks) feeding nor low isoflavone content (50 ppm) induced changes in superoxide dismutase or catalase activities in rats. Only diets containing high isoflavone contents (150 and 250 ppm) showed obvious elevated enzymatic levels in various organs. In addition, a laboratory-prepared tofu containing approximately 50 ppm isoflavones had better effects than the soy extract with the 250 ppm isoflavone group, which indicated that molecules other than isoflavones may have a synergistic effect on in vivo antioxidant enzyme inductions of tofu.     

Effects of dose and glycosylation on the transfer of genistein into the eggs of the Japanese quail (Coturnix japonica)

Soy isoflavones have been associated with several beneficial effects of soy in human diets. However, most soy is consumed by livestock in the Western countries. It is possible that isoflavones could be transferred and/or accumulated into animal products, which could become additional sources of dietary isoflavones for humans. Our objectives were to determine whether dietary isoflavone genistein could be transferred and/or accumulated into the eggs of Japanese quail (Coturnix japonica) and how the supplementation dosage and glycosylation of the isoflavone would affect this transfer. Adult reproductive female Japanese quail were randomly assigned to treatment groups that received encapsulated 50 or 100 mg genistein or 80 mg genistin per day (four quail per treatment) for 5 days. A control group (two quail) received placebo capsules. Eggs were collected prior to treatment and then daily for 15 days. The egg, separated into yolk and white, and pulverized quail diet were extracted in 80% methanol for 2 h and either centrifuged or filtered before evaporation of the solvent. The extracts were redissolved in 16% acetonitrile for high-performance liquid chromatography (HPLC) analyses. Genistein and genistein metabolites were detected in the egg yolks of treated quail. Trace concentrations of genistein were detected in the control group, due to the presence of genistein derivatives in the diet. Neither genistein nor its metabolites were found in egg white. Levels of genistein in the eggs increased significantly from the 3rd day of supplementation and reached the maximum about 2 days after the supplementation stopped. The higher dose of genistein supplementation resulted in higher genistein concentrations in egg yolks. Glycosylation decreased the transfer and accumulation of genistein into the egg yolks.     

Variations in isoflavone levels in soy foods and soy protein isolates and issues related to isoflavone databases and food labeling

The reliability of databases on the isoflavone composition of foods designed to estimate dietary intakes is contingent on the assumption that soy foods are consistent in their isoflavone content. To validate this, total and individual isoflavone compositions were determined by HPLC for two different soy protein isolates used in the commercial manufacture of soy foods over a 3-year period (n = 30/isolate) and 85 samples of 40 different brands of soy milks. Total isoflavone concentrations differed markedly between the soy protein isolates, varying by 200-300% over 3 years, whereas the protein content varied by only 3%. Total isoflavone content varied by up to 5-fold among different commercial soy milks and was not consistent between repeat purchases. Whole soybean milks had significantly higher isoflavone levels than those made from soy protein isolates (mean +/- SD, 63.6 +/- 21.9 mg/L, n = 43, vs 30.2 +/- 5.8 mg/L, n = 38, respectively, p < 0.0001), although some isolated soy protein-based milks were similar in content to "whole bean" varieties. The ratio of genistein to daidzein isoflavone forms was higher in isolated soy protein-based versus "whole bean" soy milks (2.72 +/- 0.24 vs 1.62 +/- 0.47, respectively, p < 0.0001), and the greatest variability in isoflavone content was observed among brands of whole bean soy milks. These studies illustrate large variability in the isoflavone content of isolated soy proteins used in food manufacture and in commercial soy milks and reinforce the need to accurately determine the isoflavone content of foods used in dietary intervention studies while exposing the limitations of food databases for estimating daily isoflavone intakes.     

Hypotensive and physiological effect of angiotensin converting enzyme inhibitory peptides derived from soy protein on spontaneously hypertensive rats

Angiotensin converting enzyme (ACE) inhibitory peptides prepared from soy protein by the action of alcalase enzyme was tested for its hypotensive effect on spontaneously hypertensive rats (SHR). Captopril, an ACE inhibitor used widely for hypertension treatment, was also applied in comparison. A significant (p < 0.05) decrease in systolic blood pressure of SHR was observed when soy ACE inhibitory peptides were orally administrated at three different dose levels (100, 500, and 1000 mg/kg of body weight/day), whereas little change occurred in the blood pressure of normotensive rats even at the highest dose. After a month-long feeding, blood pressure readings of SHR fell by approximately 38 mmHg from the original level at the lowest dose; a steadily and progressively hypotensive effect existed for these soy ACE inhibitory peptides administration groups. An obvious fluctuation was observed at the third week, although Captopril had a stronger hypotensive effect. The ACE activity of serum, aorta and lung, and lipid content of serum of SHR upon administration of soy ACE inhibitory peptides did not show a significant difference from that of the control group, whereas the serum ACE activity increased and the aorta ACE activity decreased significantly (p < 0.05) for the Captopril group. Serum Na(+) concentration decreased significantly in both the peptides-treated groups and the Captopril-treated group in comparison with the control group, whereas no lowering effect was observed for serum K(+) and serum Ca(2+) concentrations. These results suggested that the hypotensive effect of ACE inhibitory peptides derived from soy protein could be at least partly attributed to the action on salt/water balance.     

Isoflavones in soy-based foods consumed in Brazil: levels,distribution, and estimated intake

The isoflavone content and profile in processed soy-based products consumed in Brazil were determined by high-performance liquid chromatography and photodiode array detection of the intact isoflavones (naturally occurring aglycons, malonyl, acetyl, and beta-glycosides derivatives). Total isoflavone content varied significantly among products, from 2 to 100 mg/100 g (wet basis, expressed as aglycons), with the lowest content being found for soy-based enteral/oral diets and the highest found for textured soy proteins. For soy beverages isoflavone content varied from 12 to 83 mg/L. Soy sauce, miso, and tofu had isoflavone contents of 5.7 mg/L, 20 mg/100 g, and 7 mg/100 g, respectively. The beta-glycosides were the predominant form of the isoflavones in the products analyzed, except for miso, shoyu, and "Diet Shake" in which the aglycons were present in the highest proportions. On the basis of these data, the daily intake of isoflavone from soy products was estimated: the highest values were found for infants fed soy-based formulas, from 1.6 to 6.6 mg/kg of body weight.