Showing papers in "Journal of Nutrition in 1996"

Soybean isoflavones improve cardiovascular risk factors without affecting the reproductive system of peripubertal rhesus monkeys.

Abstract: Although the beneficial effects of dietary soybean protein compared with animal proteins on plasma lipids, lipoproteins and atherosclerosis have been known for about 50 years, it has been uncertain whether these effects are due to its amino acid concentrations or other components in soybeans. To assess the effect of soybean protein's alcohol-extractable components (including the isoflavonic phytoestrogens genistein and daidzein) on plasma lipid and lipoprotein concentrations and to establish its lack of effect on the reproductive system, we fed 27 peripubertal male and female rhesus monkeys moderately atherogenic diets in which the source of dietary protein was a soy isolate (20% by weight), either containing phytoestrogens (also termed isoflavones) or with the phytoestrogens removed by alcohol extraction. The study was a crossover design with each period lasting for 6 mo. The phytoestrogen-intact soy protein (compared with the alcohol-extracted soy protein) had favorable effects on plasma lipid and lipoprotein concentrations, specifically by significantly reducing LDL+VLDL cholesterol concentrations in both males and females (approximately 30-40% lower), significantly increasing high density lipoprotein cholesterol (HDLC) concentrations for females (approximately 15% higher) and significantly lowering total plasma cholesterol (TPC):HDLC ratios (approximately 20% lower for males and 50% lower for females). The phytoestrogens had no adverse effects on the reproductive systems of either the males or females, as evaluated by reproductive hormone concentrations and organ weights at necropsy. Thus, the isoflavones in soy protein improve cardiovascular disease risk factors without apparent deleterious effects on the reproductive system of peripubertal rhesus monkeys.

Dietary soybean protein prevents bone loss in an ovariectomized rat model of osteoporosis

Abstract: The purpose of this study was to examine whether soybean protein isolate prevents bone loss induced by ovarian hormone deficiency. Thirty-two 95-d-old Sprague-Dawley rats were randomly assigned to four treatment groups [sham-operated (sham); ovariectomized (ovx); ovx+soybean; ovx + 17 beta-estradiol (E2)] and killed after 30 d. Rats in the sham, ovx and ovx + 17 beta-estradiol groups were fed a casein-based diet, and the soybean group was fed soybean protein isolate instead of casein; the diets were otherwise comparable. Rats in the ovx group had significantly lower densities of the right femur (P < 0.001) and the fourth lumbar vertebra (P < 0.05) than rats in the sham group. These lower bone densities were not observed in animals receiving 17 beta-estradiol or fed soybean. The ovx group also had significantly (P < 0.01) greater serum concentrations of 1,25-dihydroxycholecalciferol than the other three groups. Our findings suggest that dietary soybean protein is effective in preventing bone loss due to ovarian hormone deficiency. Because serum activities of both alkaline phosphatase and tartrate-resistant acid phosphatase were significantly greater in the ovx group and in the ovx + soybean group but not in the group receiving 17 beta-estradiol, compared with sham animals, this confirms that ovariectomy enhances and 17 beta-estradiol suppresses the rate of bone turnover. Despite the higher rate of bone turnover in the soybean-fed animals, the vertebral and femoral bone densities of these rats were significantly greater than those of rats in the ovx group, suggesting that formation exceeded resorption. Further studies are needed to clarify whether this protective effect on bone is due to the protein itself or to the presence of isoflavones in soybean protein.

Stunting is Associated with Overweight in Children of Four Nations That Are Undergoing the Nutrition Transition

Abstract: A higher risk of obesity in stunted children has been described in Hispanic-American, Jamaican and Andean populations, but little systematic exploration has been done concerning this area in nutrition. This paper examines the relationship between stunting and overweight status for children aged 3-6 and 7-9 y in nationally representative surveys in Russia, Brazil, and the Republic of South Africa and a large nationwide survey in China. Using identical cut-offs for body mass index, the prevalence of child overweight in these countries ranges from 10.5 to 25.6% (based on the 85th percentile); recent NHANES III results indicate that this prevalence is around 22% in the U.S. Stunting is also common in the surveyed countries affecting 9.2-30.6% of all children. Our results showed a significant association between stunting and overweight status in children of all countries. The income-adjusted risk ratios of being overweight for a stunted child ranged from 1.7 to 7.8. Clearly, there is an important association between stunting and high weight-for-height in a variety of ethnic environmental and social backgrounds. Although the underlying mechanisms remain unexplored, this association has serious public health implications particularly for lower income countries. As these countries enter the nutrition transition experiencing large changes in dietary and activity patterns, they may face, among other problems, additional difficulties in their fight against obesity.

Vitamin D and Bone Health

Abstract: Vitamin D plays an essential role in maintaining a healthy mineralized skeleton for most land vertebrates including humans. Sunlight causes the photoproduction of vitamin D3 in the skin. Once formed, vitamin D3 is metabolized sequentially in the liver and kidney to 1,25-dihydroxyvitamin D. The major biological function of 1,25-dihydroxyvitamin D is to keep the serum calcium and phosphorus concentrations within the normal range to maintain essential cellular functions and to promote mineralization of the skeleton. Most foods do not contain any vitamin D. Foods fortified with vitamin D have a variable amount present and cannot be depended on as a sole source of vitamin D nutrition. Exposure to sunlight provides most humans with their vitamin D requirement. Aging, sunscreen use and the change in the zenith angle of the sun can dramatically affect the cutaneous production of vitamin D3. Vitamin D insufficiency and vitamin D deficiency is now being recognized as a major cause of metabolic bone disease in the elderly. Vitamin D deficiency not only causes osteomalacia but can exacerbate osteoporosis. It is generally accepted that an increase in calcium intake to 1000-1500 mg/d along with an adequate source of vitamin D of at least 400 IU/d is important for maintaining good bone health.

Dietary glutamine supplementation prevents jejunal atrophy in weaned pigs.

Abstract: The early-weaned pig develops intestinal atrophy and provides a readily accessible animal model for determining the role of dietary supplementation of glutamine (Gln, a major fuel for enterocytes) in preventing intestinal damage. Three experiments were conducted to determine the stability of dietary Gln in the acidic part of the gastrointestinal tract using pigs surgically fitted with a T-cannula in mid-duodenum (Exp. 1), and the effects of dietary Gln supplementation on the villus height and lamina propria depth of duodenum and jejunum (Exp. 2) as well as growth performance (Exp. 3) of pigs weaned at 21 d of age. Postweaning pigs were fed for 14 d corn- and soybean meal-based diets supplemented with 0.0, 0.2, 0.6 or 1.0% free L-Gln. Dietary Gln was not subject to measurable acid hydrolysis in the stomach and upper part of duodenum and was substantially available for the small intestine for metabolic utilization. Glutamine supplementation (1.0%) prevented jejunal atrophy (as indicated by villus height) during the first week postweaning and increased the gain:feed ratio (an indicator of growth performance) by 25% during the second week postweaning. Glutamine supplementation (1.0%) increased plasma concentrations of aspartate, glutamate and alanine and reduced the extent to which plasma taurine concentration fell in postweaning pigs. These results provide an experimental basis for enteral use of Gln in swine production and clinical nutrition to prevent intestinal epithelial damage.

The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans

Abstract: One important aspect of the safety assessment of genetically engineered crops destined for food and feed uses is the characterization of the consumed portion of the crop. One crop currently under development, glyphosate-tolerant soybeans (GTS), was modified by the addition of a glyphosate-tolerance gene to a commercial soybean cultivar. The composition of seeds and selected processing fractions from two GTS lines, designated 40-3-2 and 61-67-1, was compared with that of the parental soybean cultivar, A5403. Nutrients measured in the soybean seeds included macronutrients by proximate analyses (protein, fat, fiber, ash, carbohydrates), amino acids and fatty acids. Antinutrients measured in either the seed or toasted meal were trypsin inhibitor, lectins, isoflavones, stachyose, raffinose and phytate. Proximate analyses were also performed on batches of defatted toasted meal, defatted nontoasted meal, protein isolate, and protein concentrate prepared from GTS and control soybean seeds. In addition, refined, bleached, deodorized oil was made, along with crude soybean lecithin, from GTS and control soybeans. The analytical results demonstrated the GTS lines are equivalent to the parental, conventional soybean cultivar.

Antihypertensive peptides are present in aorta after oral administration of sour milk containing these peptides to spontaneously hypertensive rats.

Abstract: Absorption of inhibitory peptides to angiotensin I-converting enzyme, L-valyl-L-prolyl-L-proline and L-isoleucyl-L-prolyl-L-proline, was studied in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats after an oral administration of Calpis sour milk, which contains these peptides. Six hours after the administration of Calpis sour milk or saline to spontaneously hypertensive rats or normotensive Wistar-Kyoto rats, the blood pressure was measured and rats were killed. Abdominal aorta, lung, kidney, heart and brain were excised, homogenized and solubilized by detergent treatments. Angiotensin I-converting enzyme activity in the solubilized fractions from the abdominal aorta was significantly lower in spontaneously hypertensive rats given the sour milk than in the rats given saline. L-Valyl-L-prolyl-L-proline and L-isoleucyl-L-prolyl-L-proline were detected by HPLC in the heat-treated solubilized fraction from the abdominal aorta of spontaneously hypertensive rats given the sour milk. In contrast, the tripeptides were not detected in rats given saline, or in normotensive Wistar-Kyoto rats given the sour milk or saline. These data suggest that L-valyl-L-prolyl-L-proline and L-isoleucyl-L-prolyl-L-proline in the Calpis sour milk are absorbed directly without being decomposed by digestive enzymes, reach the abdominal aorta, inhibit the angiotensin I-converting enzyme, and show antihypertensive effects in spontaneously hypertensive rats. .

Brain iron and behavior of rats are not normalized by treatment of iron deficiency anemia during early development.

Abstract: Previous studies in rats have shown that iron deficiency anemia (IDA) during brain development results in lower brain iron concentration and behavioral deficits that persist despite iron treatment after weaning. The present study used a developmental IDA model to determine whether earlier iron treatment might normalize brain iron concentration and behavior. One and one-half week periods of IDA were instituted during early or late gestation or lactation by providing low iron diet to adolescent rat dams and oral iron treatment at the end of the anemia period. The iron deficiency anemia of dams during gestation and lactation resulted in significantly lower pup brain iron concentrations at 3 mo of age (15-33% lower than control), despite iron treatment of dams as early as mid-gestation. Dam IDA during lactation lowered pup brain iron concentration significantly more than IDA during gestation (21% lower). All IDA groups had significantly poorer performance and lower activity compared with controls on a screen of home orientation at 8 d of age. Activity on this test was significantly less than controls at 12 d of age. Homing ability on d 12 and 16 and activity on d 16 did not differ from controls. Groups that were anemic around delivery had significant behavioral differences at 3 mo which included less defecation in the open field and greater swim distance in the Morris maze. These results raise the concern that iron sufficiency throughout the course of brain development is crucial to the achievement of normal brain iron concentration and behavior in rats.

Plant wax components: a new approach to estimating intake and diet composition in herbivores.

Abstract: The nutrient status of the herbivore depends on the nutritive value of the plants available, the botanical composition of the consumed diet and the intake of the animal. It has always been difficult to quantify these last two. At present, intake is usually calculated from separate estimates of fecal output and diet digestibility. In this review we discuss the errors inherent in this approach, especially those associated with the determination and application of digestibility in vitro. We then critically evaluate a new approach to the estimation of intake, based on the use of plant cuticular wax alkanes as markers. Plant alkanes are predominantly odd-chain and substantially indigestible. They can be used, in combination with orally dosed even-chain alkanes, to obtain an intake estimate which is essentially independent of marker recovery in feces and which is more truly individual because it accommodates the level of digestibility occurring in individual animals. We present published data which indicate that the method is accurate and can be extended to measure diet composition as well. Previous approaches to estimating diet composition have been based on the laborious microscopic examination of esophageal extrusa, stomach contents or feces. However, most plant species have a characteristic pattern of alkane concentrations in their cuticular wax. This permits the estimation of diet composition from the pattern of alkanes in the feces and in the plants available. We present data to show that this approach can provide accurate estimates of diet composition in terms of either plant species or plant parts. A major advantage of the approach is that, if the animals are also dosed with even-chain alkanes, estimates of total intake and diet composition can be obtained simultaneously. The method is equally applicable to domestic and wild herbivores and to animals receiving supplementary feeds. In future work, the method will be extended to the simultaneous estimation of plant species and plant parts in the diet, and to the use of other wax components as markers.

Human serum carotenoid concentrations are related to physiologic and lifestyle factors.

Abstract: We examined the concentrations of five carotenoids in the serum and diet of a population-based sample of 400 individuals to determine what physiologic and lifestyle factors were related to serum carotenoid concentrations, how these relationships differed among the carotenoids, and if these relationships reflected differences in carotenoid intake. Lower serum concentrations of α-carotene, β-carotene, β-cryptoxanthin, and lutein + zeaxanthin generally were associated with male gender, smoking, younger age, lower non-HDL cholesterol, greater ethanol consumption and higher body mass index. Serum lycopene generally was not related to these factors, but lower lycopene levels were associated with older age and lower non-HDL cholesterol. Only the hydrocarbon carotenoids (α- and β-carotene and lycopene) were directly associated with HDL cholesterol. The associations of some factors (gender, age, smoking, and ethanol intake) with serum carotenoids were similar to the associations of these factors with levels in the diet, indicating that serum carotenoids may reflect the influence of these factors on carotenoid intake. Consistent with this notion, correlations between serum and dietary carotenoids did not differ between smokers and nonsmokers. Other factors (HDL and non-HDL cholesterol and body mass index) associated with carotenoids in the serum were not associated with carotenoid intake, indicating that physiologic conditions that affect the absorption, storage, and utilization of carotenoids may influence these associations. These physiologic and behavioral correlates of carotenoids could explain or modify associations of carotenoids with chronic diseases.

Modulation of inflammation and cytokine production by dietary (n-3) fatty acids

Abstract: The production of pro-inflammatory cytokines, such as interleukin-1 and tumor necrosis factor, is pivotal in the response to infection. However, overproduction of these cytokines might be detrimental. It has been suggested that (n-3) fatty acids suppress inflammation and ameliorate the course of infection by decreasing the production of pro-inflammatory cytokines. We here, review these effects. Use of (n-3) fatty acids induced moderate clinical improvements in rheumatoid arthritis, psoriasis and colitis, but not in systemic lupus erythematosus. Data on critically ill burn or postoperative cancer patients are still inconclusive. The (n-3) fatty acids markedly inhibited sterile inflammation in animal studies and improved survival in some experimental infections. T cell responses decreased in healthy volunteers but remained unchanged or increased in certain patient groups. The production of pro-inflammatory cytokines decreased in most human studies. The (n-3) fatty acids increased cytokine production capacity in mice. Differences in cytokine-producing cell types studied may account for these paradoxical responses in humans and mice. Although the increased cytokine production in mice is partly mediated by effects on prostaglandins, mechanisms of action in other species remain to be elucidated. The (n-3) fatty acids may be of moderate benefit in some chronic inflammatory diseases. Their therapeutic value and possible hazards in critically ill patients remain to be established.

Maternal Protein Restriction Influences the Programming of the Rat Hypothalamic-Pituitary-Adrenal Axis

Abstract: The role of glucocorticoids in the intrauterine programming of hypertension was assessed in the progeny of rats fed either 18 g casein/100 g diet (control diet) or 9 g casein/100 g diet (low protein diet), before conception and throughout pregnancy. Rats exposed to the low protein diet had significantly (P < 0.05) higher systolic blood pressures than control animals, when weaned. These rats had elevated brain and liver activities of specific glucocorticoid-inducible marker enzymes, relative to controls. Glycerol 3-phosphate dehydrogenase activity was also higher (377%) in whole brains of newborn rats exposed to low protein diet in utero, but no similar effect of corticosteroids was noted in brains of d 20 fetuses. Weanling rats of the low protein group exhibited a blunted diurnal pattern of adrenocorticotrophin (ACTH) concentrations in plasma. Plasma corticosterone concentrations were unaltered by prenatal dietary experience and exhibited a normal pattern of diurnal variation. Brain regional 11beta-hydroxysteroid dehydrogenase activities were unaltered by prenatal dietary experience, as was binding of 3H-corticosterone to type I glucocorticoid receptors in hippocampus, hypothalamus and liver. Type II glucocorticoid receptor binding capacity and receptor numbers in male rats were apparently elevated in hippocampus of low protein-exposed rats and were significantly lower in liver (P < 0.05), relative to control rats. Programming of the hypothalamic-pituitary-adrenal axis is inferred, and the observation that binding of steroid to type II receptor sites in vascular tissue is increased in low protein exposed rats may provide a direct mechanism for modulation of blood pressure by glucocorticoids in this model.

Source and Amount of Carbohydrate Affect Postprandial Glucose and Insulin in Normal Subjects

Abstract: To determine if source and amount of carbohydrate affected postprandial glucose and insulin responses, seven nondiabetic subjects consumed 0, 25, 50, 75 or 100 g carbohydrate (total carbohydrate minus total dietary fiber) portions of barley, spaghetti, bread or potato. By ANOVA, both source and amount of carbohydrate had significant effects on incremental response areas for capillary glucose (P = 0.001), plasma glucose (P = 0.01) and plasma insulin (P = 0.03), but there was no source x amount interaction. By regression analysis, source of carbohydrate explained a similar amount of the variability of glucose and insulin responses, 46-64%, as the amount of carbohydrate, 47-57%. Together, carbohydrate source and amount accounted for 85-94% of the variability of mean glucose and insulin responses. We conclude that, for individual foods with different glycemic indices, both source and amount of carbohydrate influence the postprandial glucose and insulin responses of nondiabetic subjects.

Prediction of Glucose and Insulin Responses of Normal Subjects after Consuming Mixed Meals Varying in Energy, Protein, Fat, Carbohydrate and Glycemic Index

Abstract: To see if both the amount and source of carbohydrate consumed determined postprandial glucose and insulin responses of mixed meals, eight nondiabetic subjects took five different mixed meals containing variable energy (1650-2550 kJ), fat (8-24 g), protein (12-25 g) carbohydrate (38-104 g) and glycemic index (43-99). Incremental glucose and insulin responses for the five meals varied over a 2.3-fold range. Amount of carbohydrate alone was not significantly related to the mean glucose and insulin responses. However, using previously derived equations, amount of carbohydrate and glycemic index explained approximately 90% of the variability of the observed mean glucose and insulin responses (P = 0.01). We conclude that both amount and source of carbohydrate determine the glucose and insulin responses of lean, young, nondiabetic subjects after different mixed meals with variable glycemic index. Variation in protein and fat intake, over the range tested here, appears to have a negligible effect on postprandial glucose and insulin.

Effect of rumen protozoa on nitrogen utilization by ruminants.

Abstract: Results obtained during the past decade indicate clearly that protozoa are actively involved in the degradation of dietary and microbial proteins in the rumen. Because of the great ability of protozoa to ingest the particulate matter suspended in the rumen, protozoa are more active in degrading insoluble than soluble proteins. This indicates that studies carried out using lysed and sonicated protozoa are not appropriate for quantifying the actual contribution of protozoa to protein degradation in the rumen. In vivo trials have confirmed that duodenal flow of both undegraded dietary protein plus bacterial protein generally is increased by defaunation. The decrease in ruminal ammonia concentration consistently observed after defaunation accounts for the lower urinary nitrogen (N) excretion found in defaunated animals, whereas the increase in fecal N excretion in the same animals probably results from a shift of plant cell wall digestion from the rumen to the large intestine. Total N excretion is not altered significantly by defaunation. A summary of literature data indicates there are contradictory effects of defaunation on ruminant performance. This implies that animal response to defaunation may depend on the specific nutrient-limiting performance on the one hand and on the modifications of digestion and metabolism resulting from defaunation on the other. Different methods are proposed to either eliminate or decrease the numbers of ruminal protozoa or to alter their makeup. However, none of these approaches has been tested under practical feeding conditions.

Metallothionein I and II protect against zinc deficiency and zinc toxicity in mice.

Abstract: Metallothionein (MT)-bound zinc accumulates when animals are exposed to excess zinc and is depleted under conditions of zinc deficiency, suggesting that MT serves as a means of sequestering excess zinc as well as a zinc reservoir that can be utilized when zinc is deficient. To examine the importance of MT for these processes, mice with null alleles of both MT I and MT II genes were created and the zinc concentration and histological appearance of multiple organs assessed. At birth, the hepatic zinc concentration of these MT-null mice was lower than that of wild-type controls (0.27 +/- 0.02 vs. 0.65 +/- 0.11 micromol zinc/g tissue, P < 0.05). During the next 3 wk of suckling zinc-replete (95 micrograms zinc/g diet) dams, the hepatic zinc concentration of controls fell to 0.42 +/- 0.04 micromol/g but was unchanged in the MT-null mice (0.28 +/- 0.04 micromol/g). The most prominent histological anomaly observed at 3 wk of age was the presence of swollen Bowman's capsules in the kidneys of MT-null mice. When nursing MT-null dams were fed a severely zinc-deficient (1.5 microg/g) diet, kidney development in the MT-null pups was retarded as indicated by the retention of the nephrogenic zone and incomplete tubule development. We suggest that the lack of a hepatic reservoir of zinc jeopardizes the developing kidney in the MT-null mice. In addition to being more sensitive to dietary zinc restriction, MT-null mice are more sensitive to zinc toxicity. When adult mice were challenged with a ramping dose of zinc up to a total of 3700 micromol zinc/kg body weight, MT-null mice had a greater incidence of pancreatic acinar cell degeneration compared with control mice despite accumulating less zinc (2.72 +/- 0.46 vs. 1.23 +/- 0.52 micromol zinc/g pancreas, control and MT-null, respectively, P < 0.05). The results of these experiments suggest that MT I and MT II can protect against both zinc deficiency and zinc toxicity.

Supplementation with an algae source of docosahexaenoic acid increases (n-3) fatty acid status and alters selected risk factors for heart disease in vegetarian subjects

Abstract: The purpose of this double-blind study was to investigate the influence of dietary supplementation with an algae source of docosahexaenoic acid [DHA; 22:6(n-3)], devoid of any eicosapentaenoic acid [EPA; 20:5(n-3)], on serum/platelet DHA status, the estimated retroconversion of DHA to EPA, and risk factors for heart disease in vegetarian subjects. Healthy vegetarians (12 male, 12 female) consumed nine capsules daily of either DHA (1.62 g/d) or corn oil for 6 wk. Consumption of DHA capsules increased DHA levels in serum phospholipid by 246% (from 2.4 to 8.3 g/100 g fatty acids) and in platelet phospholipid by 225% (from 1.2 to 3.9 g/100 g fatty acids). EPA levels increased in serum phospholipid by 117% (from 0.57 to 1.3 g/100 g fatty acids) and in platelet phospholipid by 176% (0.21 to 0.58 g/100 g fatty acids) via metabolic retroconversion; the estimated extent of DHA retroconversion to EPA was 11.3 and 12.0%, based on the serum and platelet analyses, respectively. Arachidonic acid [AA; 20:4(n-6)] levels in serum and platelet phospholipids decreased moderately during the trial period (DHA group) as did both docosapentaenoic acids [22:5(n-6) and 22:5(n-3)]. Although no significant changes were found in the total and LDL-cholesterol levels with DHA supplementation, the total cholesterol:HDL-cholesterol ratio showed a moderate decrease over time as did the LDL-cholesterol:HDL-cholesterol ratio and serum triglyceride concentrations. DHA supplementation did not alter the various thrombogenic factors measured. In conclusion, DHA supplementation markedly enhanced the DHA status (of serum and platelets), provided for the formation of substantial EPA, and lowered the total and LDL-cholesterol:HDL-cholesterol ratios.

The feeding value of soybeans fed to rats, chickens, catfish and dairy cattle is not altered by genetic incorporation of glyphosate tolerance.

Abstract: Animal feeding studies were conducted with rats, broiler chickens, catfish and dairy cows as part of a safety assessment program for a soybean variety genetically modified to tolerate in-season application of glyphosate. These studies were designed to compare the feeding value (wholesomeness) of two lines of glyphosate-tolerant soybeans (GTS) to the feeding value of the parental cultivar from which they were derived. Processed GTS meal was incorporated into the diets at the same concentrations as used commercially; diary cows were fed 10 g/100 g cracked soybeans in the diet, a level that is on the high end of what is normally fed commercially. In a separate study, laboratory rats were fed 5 and 10 g unprocessed soybean meal 100 g diet. The study durations were 4 wk (rats and dairy cows), 6 wk (broilers) and 10 wk (catfish). Growth, feed conversion (rats, catfish, broilers), fillet composition (catfish), and breast muscle and fat pad weights (broilers) were compared for animals fed the parental and GTS lines. Milk production, milk composition, rumen fermentation and nitrogen digestibility were also compared for dairy cows. In all studies, measured variables were similar for animals fed both GTS lines and the parental line, indicating that the feeding value of the two GTS lines is comparable to that of the parental line. These studies support detailed compositional analysis of the GTS seeds, which showed no meaningful differences between the parental and GTS lines in the concentrations of important nutrients and antinutrients. They also confirmed the results of other studies that demonstrated the safety of the introduced protein, a bacterial 5-enolpyruvyl-shikimate-3-phosphate synthase from Agrobacterium sp. strain CP4.

Changing phosphorus content of the U.S. diet: potential for adverse effects on bone.

Abstract: The dietary intake of phosphorus in the United States is high relative to calcium. Intake estimates from the 1989-1991 Continuing Surveys of Food Intakes by Individuals conducted by the U.S. Department of Agriculture show that for both men and women, median calcium intakes do not meet the 1989 Recommended Dietary Allowances (RDAs) for most age groups over 10 y of age, whereas phosphorus intakes exceed the RDAs for most age groups. The use of phosphorus-containing food additives in the processing of foods contributes substantially to the daily phosphorus intake, and their use is increasing. Because much of the phosphorus through food additive use is not reflected in the estimates of phosphorus intakes derived from national food consumption surveys, these estimates underestimate true dietary intakes of phosphorus. High phosphorus intake has been shown to cause secondary hyperparathyroidism and bone loss in several animal models. High phosphorus, low calcium consumption consistent with current observed intake levels resulted in changes in calcium-regulating hormones that were not conducive to optimizing peak bone mass in young women. Evidence that such high phosphorus intakes may impair synthesis of the active metabolite of vitamin D and disrupt calcium homeostasis particularly in older women are discussed.

Dietary intake pattern relates to plasma folate and homocysteine concentrations in the Framingham Heart Study.

Abstract: We examined the relationship between intake of food group (and supplement) sources of folate and plasma folate and homocysteine concentrations among 885 elderly subjects in the Framingham Heart Study. Dietary data were collected by food-frequency questionnaire, and blood samples analyzed for folate and homocysteine concentrations. Top contributors to total folate intake were ranked. Mean folate intake, plasma folate and homocysteine concentrations were estimated for users vs. non-users of supplements, and key foods--those which both contribute to total folate intake and are known to be good sources of folate--and examined statistically with adjustment for age, gender and total energy intake. Plasma folate and homocysteine concentrations were also determined by quintile of intake frequency for breakfast cereals and for fruits and vegetables. Plasma folate was significantly greater and homocysteine lower in women than in men. Despite somewhat greater plasma folate concentrations with age, homocysteine was significantly higher in those over 80 y of age than in younger subjects. Major contributors to folate intake were cold breakfast cereals (13.3%), multivitamins (12.8%) and orange juice (12.4%). Users of supplements, breakfast cereals, or green leafy vegetables had significantly greater plasma folate and lower homocysteine levels than non-users. Plasma folate concentration was also greater in those who drank orange juice. We identified clear dose-response relationships for both plasma folate and homocysteine with increased quintile of breakfast cereal and of fruit and vegetable use. Frequent consumption of these foods is associated with higher folate and lower homocysteine concentrations.

Selenoprotein P Concentration in Plasma is an Index of Selenium Status in Selenium-Deficient and Selenium-Supplemented Chinese Subjects

Abstract: Selenoprotein P, a selenium-rich plasma protein, is an index of selenium status in rats. Antibodies against human selenoprotein P were raised to study the protein and to develop a radioimmunoassay for it. A single collection of plasma from a healthy person in the United States contained 1.84 mumol selenium/L and was defined as containing 1 Unit (U) selenoprotein P/L. Removal of selenoprotein P from the reference plasma by an antibody column indicated that 0.81 mumol selenium/L, or 44% of the plasma selenium, was present as selenoprotein P. Work by others had determined that glutathione peroxidase accounted for 12% of plasma selenium. Stored plasma samples from selenium-deficient (Dechang County) and selenium-supplemented (Mianning County) populations in China were assayed for selenoprotein P. Boys aged 8-12 y had selenoprotein P concentrations of 0.10 +/- 0.04 U/L (n = 22) in Dechang and 0.39 +/- 0.17 U/L (n = 17) in Mianning. Supplementation with 100 micrograms selenium as selenate per day for 14 d raised those levels to 0.51 +/- 0.13 U/L in Dechang and to 0.76 +/- 0.27 U/L in Mianning. Similar results were obtained in men, and plasma selenium concentrations correlated with selenoprotein P concentrations. A study comparing indices of selenium status was conducted in the two counties. Selenoprotein P concentration in Dechang subjects (n = 79) was 36% of that in Mianning subjects (n = 117). For plasma glutathione peroxidase activity the value was 54%; for plasma selenium, 47%; and for whole blood selenium, 64%. We conclude that selenoprotein P is the major selenoprotein in human plasma and that its concentration is an index of selenium nutritional status that appears to be as sensitive as other indices in common use.

Maternal Underweight Status and Inadequate Rate of Weight Gain during the Third Trimester of Pregnancy Increases the Risk of Preterm Delivery

Abstract: This study examines the differences in the pattern of weight gain according to trimesters of pregnancy for women who delivered term vs. preterm and analyzes the independent effect of prepregnancy weight status and rate of weight gain on delivering preterm. The differential effects of these variables on the etiological pathways of prematurity (preterm labor and preterm rupture of the amniotic membranes) were also examined. Data were collected prospectively from 7589 pregnant women receiving care in public health clinics in the West Los Angeles area. Eighty percent of women identified themselves as being of Hispanic origin. Multivariate logistic regression techniques were used to isolate the role of each nutritional variable from other factors that may influence birth outcome. Women who delivered preterm had patterns of weight gain similar to women delivering term infants. Underweight status (body mass index < 19.8 kg/m2) before pregnancy nearly doubled the likelihood of delivering preterm [adjusted odds ratio (AOR) 1.98, 95% confidence interval (CI) = 1.33, 2.98). Inadequate weight gain in the third trimester defined as < 0.34, 0.35, 0.30 and 0.30 kg/wk for underweight, normal weight, overweight and obese women, respectively, increased the risk by a similar magnitude (AOR 1.91, 95% CI = 1.40, 2.61). Slight differentiation of these risk factors occurred when analyzing the etiological pathways of preterm birth. Preconceptional nutrition counseling and promotion of adequate weight gain during the third trimester of pregnancy should be components of public health programs designed to decrease the prevalence of preterm birth.

Absorption and Excretion of the Soy Isoflavone Genistein in Rats

Abstract: Rodent models have been used to study the anticarcinogenic properties of the soy isoflavones, particularly genistein, but there is little information regarding the pharmacokinetics of the absorption and excretion of genistein. In this study, rats were given a single oral dose of genistein (20 mg/kg body weight) or an equivalent dose of its glycone forms, as an isoflavone-rich soy extract. Concentrations of genistein were measured in plasma, urine and feces at intervals up to 48 h after dosing. Plasma genistein concentration at 2 h after dosing was 11.0 ± 2.3 μmol/L in genistein-treated rats compared with 4.93 ± 0.22 μmol/L (P = 0.025) in soy extract-treated rats, but there were no significant differences at 8 h and later times. The mean urinary excretion rate during the first 2 h after dosing was more than 10 times higher in the genistein group compared with the soy extract group (0.27 ± 0.08 μmol/h and 0.020 + 0.011 μmol/h, respectively, P = 0.017) but the percentage of dose recovered in urine over 48 h was not different between groups (19.9 ± 2.4% genistein treated ; 17.5 ± 1.1% soy extract treated). There were no significant differences between groups in the recovery of genistein in feces (21.9 ± 2.8% and 21.1 ± 2.5% of dose, respectively). Only 6.1 ± 0.9% of the daidzein from the soy extract was recovered in the feces. The results suggest that the extent of absorption of genistein is similar for the glycone and aglycone forms. Although higher initial plasma concentrations may be achieved with the aglycone, similar long-term concentrations exist for both forms of isoflavone.

Reduced, oxidized and protein-bound forms of homocysteine and other aminothiols in plasma comprise the redox thiol status--a possible element of the extracellular antioxidant defense system.

Abstract: Reduced, oxidized and protein-bound forms of homocysteine (Hcy), cysteine and cysteinylglycine in plasma interact via redox and disulphide exchange reactions, and these aminothiol species comprise a dynamic system referred to as redox thiol status. Notably, in plasma reduced cysteine is the most abundant low molecular weight sulfhydryl compound. Elevation of plasma Hcy (hyperhomocysteinemia) causes changes in redox thiol status. Protein-bound Hcy increases up to a maximum capacity of about 140 micromol/L, and there is a concurrent displacement of protein-bound cysteine. When the Hcy binding approaches saturation, free oxidized and reduced Hcy show a substantial increase. The resulting increase in reduced/total ratio for Hcy causes a parallel change in this ratio for the other aminothiols. These dynamics were observed during both chronic hyperhomocysteinemia (due to cobalamin deficiency or homocystinuria) and acute hyperhomocysteinemia (induced by methionine or Hcy loading). In addition, changes in redox thiol status have been observed in patients with vascular disease (decreased reduced/total ratio for cysteine), renal failure (low reduced/total ratio for aminothiols) or HIV infection (high level of reduced Hcy), which suggest primary imbalance between prooxidant and antioxidant processes in these patients. In conclusion, redox thiol status is a dynamic system which is probably linked to the extracellular antioxidant defence system. This must be taken into account when designing future experimental or epidemiological studies on Hcy and cardiovascular disease.

Dietary Aspergillus niger Phytase Increases Iron Absorption in Humans

Abstract: Phytate is an inhibitor of iron absorption that can be removed before the intestinal site of absorption by microbial phytase, thereby increasing iron absorption from a meal. The effects of two kinds of dietary phytase, cereal phytase and microbial phytase from Aspergillus niger, on iron absorption were investigated. Iron absorption was measured from single meals containing white wheat rolls supplemented with wheat bran with or without phytase activity (expt. 1) and phytase-deactivated wheat bran with or without addition of microbial phytase from A. niger (expt. 2). Each experiment had 10 subjects and two different radio iron tracers: 55Fe and 59Fe were used for comparison of the absorption from the test meals in each experiment. No differences in iron absorption were found between meals containing wheat brain with or without phytase activity. Addition of microbial phytase to the meal containing phytase-deactivated wheat bran increased iron absorption from 14.3 +/- 2.6% to 26.1 +/- 3.8% (P < 0.0001). Two pH optima, one at pH 2.0 and one at pH 6.0, were found for A. niger phytase at 37 degrees C, but activity occurred at all pH values between 1.0 and 7.5. The results suggest that effective and complete degradation of phytate occurred in the stomach when A. niger phytase was given with the meal. This may be explained by high activity of microbial phytase at physiological pH conditions of the stomach, whereas wheat phytase has a different pH optimum.

Caco-2 Cell Iron Uptake from Meat and Casein Digests Parallels in Vivo Studies: Use of a Novel in Vitro Method for Rapid Estimation of Iron Bioavailability

Abstract: We developed a model for assessing iron bioavailability from foods which combines simulated peptic and intestinal digestion with measurement of iron uptake by Caco-2 cell monolayers Our objective was to further validate this model by determining if meat enhances Caco-2 cell iron uptake relative to casein Caco-2 cell monolayers were covered with Hank's balanced salt solution (HBSS) buffered with HEPES, pH 74 An upper chamber was created over the cells by fitting the bottom of a Costar Transwell® insert with a 12,000-14,000 molecular weight cut-off dialysis membrane This membrane allowed low molecular weight iron complexes to diffuse into the media bathing the cells and prevented damage to the cells from the digestive enzymes Prior to digestion, each sample (homogenate of beef, chicken, fish or casein) was mixed with 59 FeCl 3 to achieve an iron concentration of 10 μmol/L Following pepsin digestion (pH 2), pH was adjusted to 74, pancreatic enzymes and bile extract were added to each digest, and an aliquot was then introduced into the upper chamber of the culture dish During this intestinal digestion period, 59 Fe uptake occurred from iron that dialyzed into the lower chamber The 59 Fe uptake from beef, chicken and fish digests was 300-400% of the 59 Fe uptake from a casein digest Our results parallel human absorption studies indicating that meat enhances iron absorption The results suggest that digestion products of the meat proteins were at least partially responsible for the enhancement of iron uptake Overall, this study supports the usefulness of our model as a means of assessing iron bioavailability

Maximizing microbial protein synthesis in the rumen.

Abstract: Microbial protein supply to the duodenum should be maximized for efficient use of feed protein and energy. High producing ruminants often are fed significant concentrations of cereal grains and fat in their diets. Increasing starch in the diet decreases ruminal pH, which often decreases extent of ruminal fiber digestion and also may decrease efficiency of microbial protein synthesis because of energy-spilling reactions. In contrast, higher grain feeding increased efficiency of microbial protein synthesis in some studies because ruminal passage rate was increased. Ruminal degradation of carbohydrates and protein must be synchronized for optimal microbial efficiency, but the microbes appear to withstand transient periods of asynchronous nutrient supply in many cases. Protozoa extensively prey upon bacteria, and a higher proportion of protozoa than bacteria lyse within the rumen, recycling significant amounts of protein. Feeding moderate amounts of unsaturated fat appears to reduce, especially on relatively low forage diets, protozoal numbers and the extent of intraruminal recycling. Indirect and direct calculations have been derived from models to estimate microbial protein transactions within the rumen; however, models need further definition and more detailed inputs from published literature to further their predictive ability.

Vitamins as Homocysteine-Lowering Agents

Abstract: Moderate hyperhomocysteinemia is, today, considered an established risk factor for cardiovascular disease. A graded dose-response relationship between plasma homocysteine concentration over its full range and cardiovascular risk strongly supports causality. Therefore, intervention studies with homocysteine-lowering vitamins are needed. This mini review shows that supplementation with folic acid not only markedly reduces elevated plasma homocysteine concentrations but also reduces normal homocysteine concentrations. Folic acid doses of < 1 mg/d may be effective. Supplementation with a combination of folic acid and cyanocobalamin will secure full homocysteine-lowering effect and prevent occurrence of vitamin B-12 deficiency during the course of therapy.

Dietary α-Tocopherol Attenuates the Impact of γ-Tocotrienol on Hepatic 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Activity in Chickens

Abstract: The concentration-dependent impact of gamma-tocotrienol on serum cholesterol can be traced to the posttranscriptional down-regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. gamma-Tocotrienol also suppresses tumor growth. Palmvitee, the tocopherol and tocotrienol-rich fraction of palm oil, is the sole commercial source of gamma-tocotrienol. Contrary to the universal findings of the efficacy of gamma-tocotrienol there are conflicting reports of the impact of Palmvitee on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, serum cholesterol concentrations and tumor development. These conflicting reports led us to examine the impact of alpha-tocopherol on the cholesterol-suppressive action of gamma-tocotrienol. Control and experimental diets were fed to groups of White Leghorn chickens (n = 10) for 26 d. The control diet was supplemented with 21 nmol alpha-tocopherol/g. All experimental diets provided 141 nmol of blended tocols/g diet. The alpha-tocopherol and gamma-tocotrienol concentrations of the experimental diets ranged from 21 to 141 and 0 to 120 nmol/g, respectively. We now report that including alpha-tocopherol in tocol blends containing adequate gamma-tocotrienol to suppress 3-hydroxy-3-methylglutaryl coenzyme A reductase activity results in an attenuation of the tocotrienol action (P or = 30% alpha-tocopherol and 45% gamma- (and delta-) tocotrienol.

The Expressed Protein in Glyphosate-Tolerant Soybean, 5-Enolypyruvylshikimate-3-Phosphate Synthase from Agrobacterium sp. Strain CP4, Is Rapidly Digested In Vitro and Is not Toxic to Acutely Gavaged Mice

Abstract: The safety of 5-enolpyruvylshikimate-3-phosphate synthase enzyme derived from Agrobacterium sp. strain CP4 (CP4 EPSPS) was assessed. CP4 EPSPS is the only protein introduced by genetic manipulation that is expressed in glyphosate-tolerant soybeans, which are being developed to provide new weed-control options for farmers. Expression of this protein in plants imparts high levels of glyphosate tolerance. The safety of CP4 EPSPS was ascertained by evaluating both physical and functional characteristics. CP4 EPSPS degrades readily in simulated gastric and intestinal fluids, suggesting that this protein will be degraded in the mammalian digestive tract upon ingestion as a component of food or feed. There were no deleterious effects due to the acute administration of CP4 EPSPS to mice by gavage at a high dosage of 572 mg/kg body wt, which exceeds 1000-fold the anticipated consumption level of food products potentially containing CP4 EPSPS protein. CP4 EPSPS does not pose any important allergen concerns because this protein does not possess characteristics typical of allergenic proteins. These data, in combination with seed compositional analysis and animal feeding studies, support the conclusion that glyphosate-tolerant soybeans are as safe and nutritious as traditional soybeans currently being marketed.