Acute effects of hemp protein consumption on glycemic and satiety control: results of 2 randomized crossover trials.

Research investigating hemp protein consumption on glycemic response is limited. The effects of hemp protein consumption on blood glucose (BG), insulin, and satiety compared with soybean protein and a carbohydrate control were examined. Two acute randomized repeated-measures crossover experiments were conducted. In both, participants consumed the following isocaloric treatments: 40 g of hemp protein (hemp40), 20 g of hemp protein (hemp20), 40 g of soybean protein (soy40), 20 g of soybean protein (soy20), and a carbohydrate control. In experiments 1 (n = 27) and 2 (n = 16), appetite and BG were measured before (0-60 min, pre-pizza) and after a pizza meal (80-200 min, post-pizza). In experiment 1, food intake was measured at 60 min by ad libitum meal; in experiment 2 a fixed meal was provided (based on body weight) and insulin was measured pre-pizza and post-pizza. In both experiments, BG response was affected by treatment (p < 0.01), time (p < 0.001) and time-by-treatment (p < 0.001) from 0-200 min. Protein treatments lowered 0-60-min BG overall mean and area under the curve compared with control (p < 0.05) dose-dependently. In experiment 2, hemp40 and soy40 lowered (p < 0.05) overall mean insulin concentrations compared with hemp20, soy20, and control pre-meal. Results suggest that hemp protein, like soybean, dose-dependently lowers postprandial BG and insulin concentrations compared with a carbohydrate control. Clinical trial registry: NCT02366598 (experiment 1) and NCT02458027 (experiment 2). Novelty: Hemp protein concentrate dose-dependently leads to lower postprandial BG response compared with a carbohydrate control. No differences were seen between hemp and soy protein.

Identification of peptides in blood following oral administration of ß-conglycinin to Wistar rats.

In this study, ß-conglycinin (100 mg/kg) was orally administered to Wistar rats in order to identify peptides that may be derived from the protein in the blood. Plasma samples taken from the tail vein up to 8 h after administration were analyzed by matrix-assisted laser desorption/ionization (MALDI) and liquid chromatography-time-of-flight (LC-TOF) mass spectrometry (MS). In total, 126 signals were detected by MALDI-MS. Among the signals, nine oligopeptides (SEL, KGPL, SILGA, DSEL, GDANI, SYFV, CLQSC, GEQPRPF, and LVINEGDA) were successfully identified as ß-conglycinin-derived peptides by LC-TOF/MS at a plasma concentration of 0.75-756 pmol/mL. The results demonstrated that ß-conglycinin could be the dietary source protein for the oligopeptides produced prior to entering the circulating bloodstream of rats.

Amino Acid Availability of a Dairy and Vegetable Protein Blend Compared to Single Casein, Whey, Soy, and Pea Proteins: A Double-Blind, Cross-Over Trial.

Protein quality is important for patients needing medical nutrition, especially those dependent on tube feeding. A blend of dairy and vegetable proteins (35% whey, 25% casein, 20% soy, 20% pea; P4) developed to obtain a more balanced amino acid profile with higher chemical scores, was compared to its constituent single proteins. Fourteen healthy elderly subjects received P4, whey, casein, soy, and pea (18 g/360 mL bolus) on five separate visits. Blood samples were collected at baseline until 240 min after intake. Amino acid availability was calculated using incremental maximal concentration (iCmax) and area under the curve (iAUC). Availability for P4 as a sum of all amino acids was similar to casein (iCmax and iAUC) and whey (iCmax) and higher vs. soy (iCmax and iAUC) and pea (iCmax). Individual amino acid availability (iCmax and iAUC) showed different profiles reflecting the composition of the protein sources: availability of leucine and methionine was higher for P4 vs. soy and pea; availability of arginine was higher for P4 vs. casein and whey. Conclusions: The P4 amino acid profile was reflected in post-prandial plasma levels and may be regarded as more balanced compared to the constituent single proteins.

An electrochemiluminescence biosensor for the detection of soybean agglutinin based on carboxylated graphitic carbon nitride as luminophore.

As an important glycoprotein of the lectin family, soybean agglutinin (SBA) is an anti-nutritional factor with considerable toxic and side effects and plays a significant role in tumor analysis. In order to achieve the sensitive detection of SBA, a sandwich-structured electrochemiluminescence (ECL) biosensor was constructed using carboxylated carbon nitride (C-g-C3N4) as luminophore and D-galactosamine (galM) as a recognition element. A glassy carbon electrode (GCE) was modified with Au nanoparticles (Au NPs) for capturing the galM via Au-N bond, and further capturing the target SBA by specific recognition between galM and SBA. In the presence of SBA, the composite C-g-C3N4-galM was immobilized onto the electrode. With the increase in the concentration of SBA, the ECL signal from C-g-C3N4 increased, thus achieving a signal-on detection of SBA. The linear range of the biosensor was 1.0 ng/mL~10 µg/mL and detection limit for SBA was as low as 0.33 ng/mL. In this construction strategy, C-g-C3N4 not only acted as an excellent signal probe, but also as an immobilization matrix to easily achieve a high loading of the small molecule recognition element galM. This strategy provides a simple alternative SBA detection platform. Graphical abstract.

Ingestion of Insect Protein Isolate Enhances Blood Amino Acid Concentrations Similar to Soy Protein in A Human Trial.

BACKGROUND: Increased amino acid availability stimulates muscle protein synthesis (MPS), which is critical for maintaining or increasing muscle mass when combined with training. Previous research suggests that whey protein is superior to soy protein in regard to stimulating MPS and muscle mass. Nevertheless, with respect to a future lack of dietary protein and an increasing need for using eco-friendly protein sources it is of great interest to investigate the quality of alternative protein sources, like insect protein. OBJECTIVE: Our aim was to compare the postprandial amino acid (AA) availability and AA profile in the blood after ingestion of protein isolate from the lesser mealworm, whey isolate, and soy isolate. DESIGN: Six healthy young men participated in a randomized cross-over study and received three different protein supplementations (25 g of crude protein from whey, soy, insect or placebo (water)) on four separate days. Blood samples were collected at pre, 0 min, 20 min, 40 min, 60 min, 90 min, and 120 min. Physical activity and dietary intake were standardized before each trial, and participants were instructed to be fasting from the night before. AA concentrations in blood samples were determined using ¹H NMR spectroscopy. RESULTS: A significant rise in blood concentration of essential amino acids (EAA), branched-chain amino acids (BCAA) and leucine was detected over the 120 min period for all protein supplements. Nevertheless, the change in AA profile was significantly greater after ingestion of whey than soy and insect protein (p < 0.05). Area under the curve (AUC) analysis and AA profile revealed comparable AA concentrations for soy and insect protein, whereas whey promoted a ~97% and ~140% greater AUC value than soy and insect protein, respectively. A tendency towards higher AA concentrations beyond the 120 min period was observed for insect protein. CONCLUSION: We report that ingestion of whey, soy, and insect protein isolate increases blood concentrations of EAA, BCAA, and leucine over a 120 min period (whey > insect = soy). Insect protein induced blood AA concentrations similar to soy protein. However, a tendency towards higher blood AA concentrations at the end of the 120 min period post ingestion was observed for insect protein, which indicates that it can be considered a "slow" digestible protein source.

Combining 2-DE immunoblots and mass spectrometry to identify putative soybean (Glycine max) allergens.

Soybean is recognized as a commonly allergenic food, but the identity of important allergens is not well studied. Recently, some global regulatory agencies started requiring quantitative analysis of individual allergens, including unproven allergens, as part of the risk assessment for genetically engineered (GE) soybeans. We sought to identify soybean proteins that bind IgE from any of 10 individual soybean-sensitized subjects. Soybean IgE binding proteins were identified by 2-DE immunoblots using sera from four soy-allergic and plasma from six soy-sensitized human subjects. Corresponding spots were excised from stained gels, digested, and analyzed using a quadrupole TOF Synapt G2-S tandem mass spectrometer. Results showed the major IgE binding proteins were subunits of either ß-conglycinin (Gly m 5) or glycinin (Gly m 6). Soybean Kunitz trypsin inhibitor (SKTI) was a significant IgE binding protein for four subjects. Soybean agglutinin, seed biotinylated protein (SBP) of 65 kDa, late embryogenesis protein (LEP), and sucrose-binding protein were identified as IgE binding only for soy-sensitized subjects. We conclude that the major soybean allergens are isoforms of Gly m 5, Gly m 6, and possibly SKTI and that requirements for quantitative measurement of proteins that are not clear allergens is not relevant to safety.

Magnetic beads modified with an electron-transfer carbohydrate-mimetic peptide for sensing of a galactose-dependent protein.

For use in the voltammetric sensing of galactose-dependent proteins, we modified magnetic beads with a peptide that had both electroactive- and molecular recognition properties. The peptide consisted of a YXY sequence and behaved as an electron-transfer carbohydrate-mimetic peptide that would combine with proteins. With this tool, the protein could be detected via a label-free system. We synthesized several penta- and hexa-peptides with a cysteine residue on the C-terminals to examine the properties of peptides. These peptides contained amino acid residues (X) of alanine, serine, or tyrosine. The peptides were immobilized on magnetic beads via N-(8-maleimidocapryloxy) succinimide. Soybean agglutinin(SBA), the in vivo function of which has been well established in animals, was selected as a model protein. The protein was detected via the changes in electrode response due to the oxidation of tyrosine residues from the phenol group to quinone. As a result, SBA was selectively accumulated on the beads modified with YYYYC. The calibration curve of SBA was linear and ranged from 2.5 × 10-12 to 1.0 × 10-10 M. With this system, SBA was recovered in human serum at values that ranged from 98 to 103%. Furthermore, the beads with peptides were regenerated five times using a protein denaturant. Accordingly, this electrochemical system was simple and could be rapidly applied to the detection of galactose-recognition proteins.

Limited hydrolysis combined with controlled Maillard-induced glycation does not reduce immunoreactivity of soy protein for all sera tested.

Combining proteolysis and Maillard-induced glycation was investigated to reduce the immunoreactivity of soy protein. Soy protein was hydrolyzed by Alcalase following response surface methodology utilizing three variables, temperature, time, and enzyme:substrate ratio, with the degree of hydrolysis (DH) and percent reduction in immunoreactivity as response variables. Western blots and ELISA were used to evaluate immunoreactivity using human sera. Data were fitted to appropriate models and prediction equations were generated to determine optimal hydrolysis conditions. The hydrolysate produced under optimized conditions was subjected to glycation with dextran. Hydrolysate produced under optimal conditions had 7.8% DH and a percent reduction in immunoreactivity ranging from 20% to 52%, depending on the sera used. Upon glycation, immunoreactivity was further reduced only when using serum that had the highest soy-specific IgE. This work revealed limitations and provided premises for future studies intended to prove the potency of the combined modification approach to produce a hypoallergenic protein ingredient.

Effect of soy protein isolate preload on postprandial glycemic control in healthy humans.

OBJECTIVE: Premeal consumption of whey protein improves the postmeal glycemic profile, but little information exists on soy protein. The study aim was to examine the effect of consuming different amounts of a soy protein isolate (SPI) before a 75-g oral glucose tolerance test (OGTT) on subsequent glycemic control. METHODS: After overnight fasting, eight healthy young subjects consumed a 400-mL liquid meal containing 0 g (SP0), 20 g (SP20) or 40 g (SP40) SPI. Thirty minutes after SPI consumption, an OGTT was performed to evaluate the individual glycemic response. Blood glucose and plasma insulin concentrations were measured immediately before the SPI preload (i.e., 30 min before the start of the OGTT) and before (-10 min) and during the OGTT (15, 30, 45, 60, 90, and 120 min). RESULTS: The incremental area under the curve and peak blood glucose response were significantly less for SP40 than those for SP0 and SP20. Insulin secretion was significantly higher for SP20 and SP40 than that for SP0 before and at 15 min after oral glucose consumption. The incremental area under the curve of plasma insulin was significantly higher for SP20 and SP40 than that for SP0. CONCLUSIONS: An SPI preload of 40 g, but not 20 g, improved glycemic control in young healthy subjects. Glycemic control appears to be attributed not only to the exaggerated insulin response to SPI preload, but also to non-insulin dependent mechanism(s), such as delayed gastric emptying.

Cognitive Effects of Soy Isoflavones in Patients with Alzheimer's Disease.

BACKGROUND: In a previous trial, treatment with soy isoflavones was associated with improved nonverbal memory, construction abilities, verbal fluency, and speeded dexterity compared to treatment with placebo in cognitively healthy older adults. OBJECTIVE: The current trial aimed to examine the potential cognitive benefits of soy isoflavones in patients with Alzheimer's disease. METHODS: Sixty-five men and women over the age of 60 were treated with 100 mg/day soy isoflavones, or matching placebo capsules for six months. APOE genotype was determined for all participants. Cognitive outcomes and plasma isoflavone levels were measured at baseline, and at two additional time points: three and six months after baseline. RESULTS: Of the sixty-five participants enrolled, thirty-four (52.3% ) were women, and 31 (47.7% ) were APOEɛ4 positive. Average age was 76.3 (SD = 7.2) years. Fifty-nine (90.8% ) subjects completed all study visits. Plasma isoflavone levels increased in subjects treated with soy isoflavones compared to baseline and to placebo, although intersubject variability in plasma levels was large. No significant differences in treatment effects for cognition emerged between treatment groups or genders. Exploratory analyses of associations between changes in cognition and plasma isoflavone levels revealed an association between equol levels, and speeded dexterity and verbal fluency. CONCLUSIONS: Six months of 100 mg/day treatment with soy isoflavones did not benefit cognition in older men and women with Alzheimer's disease. However, our results suggest the need to examine the role of isoflavone metabolism, i.e., the ability to effectively metabolize soy isoflavones by converting daidzen to equol when attempting to fully clarify the cognitive effects of isoflavones.

Effects of dietary traditional fermented soybean on reproductive hormones, lipids, and glucose among postmenopausal women in northern Thailand.

Isoflavone in soybean and its products have numerous beneficial health effects. A number of clinical studies have demonstrated that dietary soy isoflavone can relieve menopausal symptoms, lower risks of breast cancer, and lower cholesterol and glucose. Among the various effects of isoflavone, the role of cholesterol and glucose reduction seems to be well documented; however, other effects such as reproductive hormones were inconclusive and inconsistent. The main objective of the present study was to investigate the effects of six-month dietary traditional fermented soybean intake on BMI, reproductive hormones, lipids, and glucose among postmenopausal women. Subjects were women with their last menstrual period occurring at least 12 months prior to selection by interview and health screening from Baan Tham Village, Phayao Province, Thailand. A total of 60 women were divided into 2 groups: experimental group (n=31) and reference group (n=29). The experimental group was permitted to continue their usual diet, and supplemented with fermented soybean for 6 months. The fermented soybean provided approximately 60 mg of isoflavone per day. The remarkable findings were that dietary fermented soybean had favorable effects on progesterone and cholesterol, but had no effects on estradiol, glucose, and triglycerides. Although estradiol and glucose in the experimental group did not change, a decrease of estradiol and an increase of glucose were found in the reference group. Our results, therefore, suggest that fermented soybean may have beneficial effects on reproductive hormones and cholesterol, and they would be warrant further detail investigations.

Structural property of soybean lunasin and development of a method to quantify lunasin in plasma using an optimized immunoassay protocol.

Lunasin is a 43-amino acid naturally occurring chemopreventive peptide with demonstrated anti-cancer and anti-inflammatory properties. The objectives of this study were to determine the effect of temperature on the secondary structure of lunasin, to develop a method of isolating lunasin from human plasma using an ion-exchange microspin column and to quantify the amount of lunasin using an optimized enzyme-linked immunosorbent assay. Lunasin was purified using a combination of ion-exchange chromatography, ultrafiltration and gel filtration chromatography. Circular dichroism showed that increased in temperature from 25 to 100 °C resulted in changes on the secondary structure of lunasin and its capability to interact with rabbit polyclonal antibody. Enzyme linked immunosorbent assay showed that lunasin rabbit polyclonal antibody has a titer of 250 and a specific activity of 0.05 mL/µg. A linear response was detected between 16 to 48 ng lunasin per mL (y=0.03x-0.38, R(2)=0.96). The use of diethylaminoethyl microspin column to isolate spiked lunasin in human plasma showed that most lunasin (37.8-46.5%) bound to the column eluted with Tris-HCl buffer, pH 7.5 with a yield up to 76.6%. In conclusion, lunasin can be isolated from human plasma by a simple DEAE microspin column technique and can be quantified using a validated and optimized immunoassay procedure. This method can be used directly to quantify lunasin from plasma in different human and animal studies aiming to determine its bioavailability.

A pilot study on the effects of S-equol compared to soy isoflavones on menopausal hot flash frequency.

BACKGROUND: S-equol, a metabolite of the soy isoflavone daidzein, has been proposed as having potential for relief of menopausal symptoms. This study compared the efficacy of the natural S-equol supplement, SE5-OH, with isoflavones for relieving hot flashes and other menopausal symptoms. METHODS: An 8-week randomized, double-blind, active comparator trial with SE5-OH was conducted in postmenopausal women (aged 45-65 years), who experienced ≥5 hot flashes/day. Participants (n=102) were assigned to one of four treatment groups: 10 (n=24), 20 (n=27), or 40 (n=25) mg S-equol/day or soy isoflavones (n=26). Participants recorded their hot flash frequency and rated their menopause symptom severity. RESULTS: Reductions in hot flash frequency at week 8 were similar for all treatment groups. However, based on analyses of the cumulative effect for the 8-week period, 40 mg/day S-equol had a greater reduction of hot flash frequency compared to isoflavones (p=0.021). A subgroup analysis further indicated that for subjects with >8 hot flashes/day at baseline, 20 and 40 mg/day S-equol were superior to isoflavones in reducing hot flash frequency (p=0.045 and p=0.001, respectively). In addition, 10 and 20 mg/day S-equol improved muscle and joint pain score compared with isoflavones (p=0.003 and p=0.005, respectively). CONCLUSIONS: S-equol, 10 mg/day, appears to be as effective as soy isoflavones at reducing hot flash frequency and more effective for relieving muscle and joint pain in postmenopausal women. S-equol, ≥20 mg/day, alleviates hot flashes to a greater extent than soy isoflavones in those women who experience >8 hot flashes/day.

Absolute bioavailability of isoflavones from soy protein isolate-containing food in female BALB/c mice.

Soy isoflavones, genistein and daidzein, are widely consumed in soy-based foods and dietary supplements for their putative health benefits; however, evidence for potential adverse effects has been obtained from experimental animal studies. An important prerequisite for understanding the pharmacodynamics of isoflavones is better information about pharmacokinetics and bioavailability. This study determined the bioavailability of genistein and daidzein in a mouse model by comparing plasma pharmacokinetics of their aglycone and conjugated forms following administration of identical doses (1.2 mg/kg genistein and 0.55 mg/kg daidzein) by either an intravenous injection (IV) or gavage of the aglycones in 90% aqueous solution vs a bolus administration of equimolar doses delivered in a food pellet prepared using commercial soy protein isolate (SPI) as the isoflavone source. The bioavailability of genistein and daidzein was equivalent for the gavage and dietary routes of administration despite the use of isoflavone aglycones in the former and SPI-derived glucosides in the latter. While absorption of total isoflavones was nearly quantitative from both oral routes [>84% of areas under the curve (AUCs) for IV], presystemic and systemic phase II conjugation greatly attenuated internal exposures to the receptor-active aglycone isoflavones (9-14% for genistein and 29-34% for daidzein based on AUCs for IV). These results show that SPI is an efficient isoflavone delivery vehicle capable of providing significant proportions of the total dose into the circulation in the active aglycone form for distribution to receptor-bearing tissues and subsequent pharmacological effects that determine possible health benefits and/or risks.

Absorption kinetics are a key factor regulating postprandial protein metabolism in response to qualitative and quantitative variations in protein intake.

We have previously demonstrated that increasing the habitual protein intake widened the gap in nutritional quality between proteins through mechanisms that are not yet fully understood. We hypothesized that the differences in gastrointestinal kinetics between dietary proteins were an important factor affecting their differential response to an increased protein intake. To test this hypothesis, we built a 13-compartment model providing integrative insight into the sequential dynamics of meal nitrogen (Nm) absorption, splanchnic uptake, and metabolism, and subsequent peripheral transfer and deposition. The model was developed from data on postprandial Nm kinetics in certain accessible pools, obtained from subjects having ingested a (15)N-labeled milk or soy protein meal, after adaptation to normal (NP) or high (HP) protein diets. The faster absorption of Nm after soy vs. milk caused its earlier and stronger splanchnic delivery, which favored its local catabolic utilization (up to +30%) and limited its peripheral accretion (down to -20%). Nm absorption was also accelerated after HP vs. NP adaptation, and this kinetic effect accounted for most of the HP-induced increase (up to +20%) in splanchnic Nm catabolic use, and the decrease (down to -25%) in peripheral Nm anabolic utilization. The HP-induced acceleration in Nm absorption was more pronounced with soy than with milk, as were the HP effects on Nm regional metabolism. Our integrative approach identified Nm absorption kinetics, which exert a direct and lasting impact on Nm splanchnic catabolic use and peripheral delivery, as being critical in adaptation to both qualitative and quantitative changes in protein intake.

Presence of lunasin in plasma of men after soy protein consumption.

Lunasin is a 43-amino acid bioactive peptide from soybean and other plant sources which is reported to possess anti-inflammatory and anticancer properties. The objective of this study was to assess the presence and concentration of lunasin in blood of men fed soy protein products. Five healthy male subjects who were 18-25 years old consumed 50 g of soy protein for 5 days, and blood was taken 30 min and 1 h after soy protein ingestion on day 5. Lunasin was isolated from plasma using strong anion exchange beads in a magnetic particle concentrator and eluted with 20 mM triethanolamine at pH 8.0 with 0.20 M NaCl. The concentration of lunasin in plasma as determined by an enzyme-linked immunosorbent assay ranged in the various subjects from 50.2 to 110.6 ng/mL of plasma (average +/- standard deviation, 66.0 +/- 25.4 ng/mL) for blood taken at 30 min and from 33.5 to 122.7 ng/mL of plasma (71.0 +/- 32.8 ng/mL) for blood withdrawn 1 h after ingestion on day 5. We estimated an average of 4.5% absorption (range of 2.2-7.8%) of lunasin from the total lunasin ingested from 50 g of soy protein. Matrix-assisted laser desorption ionization time-of-flight peptide mass mapping showed that a 5 kDa peptide similar to synthetic lunasin was present in plasma samples of people who consumed soy protein while absent at the baseline plasma samples from the same individuals. Liquid chromatography-tandem mass spectrometry analysis showed the presence of amino acid sequences from lunasin in plasma samples after soy intake for 30 min and 1 h. No peptides from lunasin were present in plasma samples without soy intake. The results of this study suggest that lunasin is bioavailable in humans, an important requirement for its anticancer potential.

A breakfast with alpha-lactalbumin, gelatin, or gelatin + TRP lowers energy intake at lunch compared with a breakfast with casein, soy, whey, or whey-GMP.

BACKGROUND & AIMS: Dietary protein plays a role in body weight regulation, partly due to its effects on satiety. The objective was to compare the effects of casein-, soy-, whey-, whey without glycomacropeptide (GMP)-, alpha-lactalbumin-, gelatin-, or gelatin with tryptophan (TRP)-protein breakfasts at two concentrations on subsequent satiety and energy intake (EI). METHODS: Twenty-four healthy subjects (mean+/-SEM BMI: 24.8+/-0.5 kg/m(2); age: 25+/-2 years) received a breakfast; a custard with casein, soy, whey, whey-GMP, alpha-lactalbumin, gelatin, or gelatin+TRP as protein source with either 10/55/35 (normal) or 25/55/20 (high) En% protein/carbohydrate/fat in a randomized, single-blind design. At the precedingly determined time point for lunch, 180 min, subjects were offered an ad lib lunch. Appetite profile (Visual Analogue Scales, VAS) and EI were determined. RESULTS: Both at the level of 10 and 25 En% from protein, EI at lunch was approximately 20% lower after an alpha-lactalbumin or gelatin (+TRP) breakfast (2.5+/-0.2 MJ) compared with after a casein, soy, or whey-GMP breakfast (3.2+/-0.3 MJ, p<0.05). Appetite ratings at 180 min differed 15-25 mm (approximately 40%, p<0.05) between types of protein. Differences in EI were a function of differences in appetite ratings (R(2)=0.4, p<0.001). CONCLUSIONS: Different proteins (alpha-lactalbumin, gelatin, gelatin+TRP) that are approximately 40% more satiating than other proteins (casein, soy, whey, whey-GMP) induce a related approximately 20% reduction of subsequent energy intake.

A comparison of the effects of soya isoflavonoids and fish oil on cell proliferation, apoptosis and the expression of oestrogen receptors alpha and beta in the mammary gland and colon of the rat.

Isoflavonoids and fish oil may be protective against colorectal cancer, but the evidence in relation to breast cancer risk is ambiguous. In the present study, we have investigated the impact of soya-derived isoflavonoids and n-3 fatty acids from fish oil, both individually and in combination, on apoptosis, cell proliferation and oestrogen receptor (ER) expression in the colon and mammary gland of the rat. Female rats were fed diets high in n-3 fatty acids (80 g/kg diet) or soya protein (765 mg/kg diet isoflavones) for 2 weeks, and then killed before the removal of the colon and mammary glands. Cell proliferation and apoptosis were quantified morphologically in whole crypts and terminal end buds. The expressions of ERalpha and ERbeta were measured in colon tissue scrapes and the mammary gland. Fish oil significantly increased apoptosis and decreased mitosis in both tissues, an effect associated with a decrease in the expressions of ERalpha and ERbeta. Soya had no effect on apoptosis in either tissue, but reduced mitosis in the colon (P < 0.001) while increasing it in the mammary gland (P = 0.001). The changes in proliferation were associated with contrasting changes in the ER expression such that fish oil significantly decreased both ERbeta and ERalpha, while soya increased ERalpha and decreased ERbeta. The results may provide a novel mechanism by which n-3 fatty acids could reduce cancer risk, but the interpretation of the results in relation to soya consumption and breast cancer risk requires further investigation.

Effects of oral ingestion of amino acids and proteins on the somatotropic axis.

CONTEXT: GH is an important regulator of growth and body composition. It has been shown that GH release can be promoted by iv as well as oral administration of various amino acids (AAs), especially arginine (ARG) and lysine (LYS), which are amply present in soy protein. However, the effects of dietary protein on GH secretion are less well described. OBJECTIVE AND DESIGN: In an experiment, we compared the effects of oral ingestion of a mixture reflecting the AA composition of soy protein (AA), with oral ingestion of ARG + LYS, on GH secretion in eight healthy women (body mass index 19-25 kg/m(2); age, 18-24 yr). In a second experiment, we compared oral ingestion of hydrolyzed soy protein and complete soy protein with the AA mixture on GH secretion in eight healthy women (body mass index 19-26 kg/m(2); age, 19-36 yr). Both experiments were performed in a randomized, single-blind crossover design. GH, insulin, glucose, and plasma AA were determined every 20 min, during 3 h in the first experiment and during 5 h in the second experiment. RESULTS: Peak values of GH were higher after ingestion of the AA mixture compared with ingestion of ARG + LYS (P < 0.05). GH responses, as determined by area under the curve, did not significantly differ after ingestion of the complete soy protein, hydrolyzed soy protein, or AA mixture but were all higher than after placebo (P < 0.05). Insulin responses (area under the curve) were higher after ingestion of hydrolyzed soy protein, complete soy protein, and AA mixture, compared with placebo (P < 0.05). Glucose concentrations were unaffected. CONCLUSION: Ingestion of soy protein, either hydrolyzed or intact, as well as AAs reflecting soy protein, stimulates GH release to a similar extent.