Showing papers in "Journal of The American College of Nutrition in 1991"

Relative contributions of dietary sodium sources.

Abstract: Information on the relative contributions of all dietary sodium (Na) sources is needed to assess the potential efficacy of manipulating the component parts in efforts to implement current recommendations to reduce Na intake in the population. The present study quantified the contributions of inherently food-borne, processing-added, table, cooking, and water sources in 62 adults who were regular users of discretionary salt to allow such an assessment. Seven-day dietary records, potable water collections, and preweighted salt shakers were used to estimate Na intake. Na added during processing contributed 77% of total intake, 11.6% was derived from Na inherent to food, and water was a trivial source. The observed table (6.2%) and cooking (5.1%) values may overestimate the contribution of these sources in the general population due to sample characteristics, yet they were still markedly lower than previously reported values. These findings, coupled with similar observations from other studies, indicate that reduction of discretionary salt will contribute little to moderation of total Na intake in the population.

Nutritional and biochemical aspects of the hypolipidemic action of rice bran oil: a review.

Abstract: In this paper, we review the effects of rice bran oil (RBO), an unconventional oil recently introduced onto the Indian market for human use. RBO contains oleic acid (38.4%), linoleic acid (34.4%), and linolenic acid (2.2%) as unsaturated fatty acids, and palmitic (21.5%) and stearic (2.9%) acids as saturated fatty acids. The unsaponifiable fraction (4.2%) has total tocopherols (81.3 mg%), gamma-oryzanol (1.6%), and squalene (320 mg%). Oryzanol is a mixture of ferulic acid esters of triterpene alcohols such as cycloartenol (CA) (106 mg%) and 24-methylene cycloartanol (494 mg%). Studies on experimental rats demonstrated a hypolipidemic effect of RBO. The unsaponifiable fraction of RBO lowers cholesterol levels. Feeding phytosterols, CA, and 24-methylene cycloartanol in amounts present in RBO to hypercholesterolemic rats for 8 weeks indicates that CA alone reduces cholesterol and triglyceride levels significantly. Endogenous sterol excretion increases in animals given CA. The accumulation of CA in the liver inhibits cholesterol esterase activity, which in turn leads to reduction in circulating cholesterol levels. CA is structurally similar to cholesterol and may compete with the binding sites of cholesterol and sequestrate cholesterol, which is metabolized to its derivatives. RBO, which is rich in tocopherols and tocotrienols, may improve oxidative stability. Tocotrienols inhibit HMG CoA reductase, resulting in hypocholesterolemia. The hypolipidemic effect of RBO has also been established in human subjects. Thus, RBO could be a suitable edible oil for patients with hyperlipidemia.

Alcohol, liver, and nutrition.

Abstract: Until two decades ago, dietary deficiencies were considered to be the major reason why alcoholics developed liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition. Direct hepatotoxic effects of ethanol were also established, some of which were linked to redox changes produced by reduced nicotinamide adenine dinucleotide (NADH) generated via the alcohol dehydrogenase (ADH) pathway. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving cytochrome P-450: the newly discovered ethanol-inducible cytochrome P-450 (P-450IIE1) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. P-450 induction also explains depletion (and enhanced toxicity) of nutritional factors such as vitamin A. Even at the early fatty-liver stage, alcoholics commonly have a very low hepatic concentration of vitamin A. Ethanol administration in animals was found to depress hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A was strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Hepatic retinoid depletion was found to be associated with lysosomal lesions and decreased detoxification of chemical carcinogens. To alleviate these adverse effects, as well as to correct problems of night blindness and sexual inadequacies, the alcoholic patient should be provided with vitamin A supplementation. Such therapy, however, is complicated by the fact that in excessive amounts vitamin A is hepatotoxic, an effect exacerbated by long-term ethanol consumption. This results in striking morphologic and functional alterations of the mitochondria with leakage of mitochondrial enzymes, hepatic necrosis, and fibrosis. Thus, treatment with vitamin A and other nutritional factors (such as proteins) is beneficial but must take into account a narrowed therapeutic window in alcoholics who have increased needs for such nutrients, but also display an enhanced susceptibility to their adverse effects. Massive doses of choline also exerted some toxic effects and failed to prevent the development of alcoholic cirrhosis. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also enhances pyridoxine and perhaps folate degradation and stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of vitamin E on platelet function in humans.

Abstract: alpha-tocopherol, a natural antioxidant, has been found to inhibit platelet aggregation and release when tested in an in vitro system This effect of vitamin E was thought to be due to a slight reduction of platelet cyclooxygenase activity and inhibition of lipid peroxide formation Aggregation of platelets derived from individuals on a dietary supplementation of alpha-tocopherol ranging from 400 to 1200 IU/day showed no significant reduction The discrepancy between the effectiveness of alpha-tocopherol in vitro and ex vivo is probably related to the levels of alpha-tocopherol attainable in platelets and plasma Investigation of the effect of alpha-tocopherol on platelet adhesion showed a major inhibitory activity at doses of vitamin E as low as 200 IU/day Measurements were performed in a laminar flow chamber at both high and low shear rates Reduced platelet adherence to collagen, fibrinogen, and fibronectin could be documented alpha-tocopherol-enriched platelets that adhered to adhesive surfaces failed to show the usual long thin pseudopodia but exhibited short, rounded, blunt projections The reason for this shape change is still unclear, but we speculate that it may be causing the vitamin E-induced reduction of platelet adhesiveness We believe that dietary supplementation with this vitamin could play a role in the treatment of thromboembolic disease, especially when given in conjunction with an inhibitor of platelet aggregation

Total parenteral nutrition in severe acute pancreatitis.

Abstract: The influence of total parenteral nutrition (TPN) was studied in 67 patients with severe acute pancreatitis having three or more criteria according to Ranson (mean +/- SD = 3.8 +/- 0.21). Although TPN has been reported to not be of benefit in the progress and severity of the disease, we have found that the time TPN is started is important in influencing the course of the disease and in the development of local complications, as well as in the mortality rate. Patients whose TPN was started within the first 72 hours of the disease had a 23.6% complication rate and 13% mortality, in comparison with patients whose TPN was started later in the course of the disease, who had a 95.6% complication rate (p less than 0.01) and a mortality rate of 38% (p less than 0.03). The nutritional status of the patients during TPN administration of 28.4 days was maintained either steady or was improved, as assessed by nitrogen balance, serum levels of transferrin (p less than 0.05), and albumin (p less than 0.05). The administration of fat solution, either to prevent essential fatty acid deficiency or to provide part of the caloric requirements, was found to cause neither clinical nor laboratory worsening of the disease. All pancreatic fistulae that developed during the course of the disease spontaneously closed in patients receiving TPN without operation in a mean period of 33.3 days, and all pseudocysts subsided in an average of 18.3 days. Those who died (overall mortality rate 24%) had had uncontrollable sepsis, which resulted in hypercatabolism and multiple system organ failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypocaloric diets and ketogenesis in the management of obese gestational diabetic women.

Abstract: The extent to which given levels of caloric restriction will improve glycemic status but increase plasma ketone bodies in gestational diabetic women has received little attention. After reviewing the underlying physiology, we present data on two feeding studies investigating the question. In the first, a weight-maintaining approximately 2400-kcal/day diet was fed on a metabolic ward to 12 gestational diabetic women for 1 week. In the second week, subjects were randomized to a continuation of the 2400-kcal/day diet or to a 1200-kcal/day diet. Twenty-four-hour mean glucose levels remained unchanged in the control group but declined in the calorie-restricted group (6.7 mM or 121 mg/dl in week 1 vs 5.4 mM or 97.3 mg/dl in week 2) (p less than 0.01). Nine-hour overnight fasting plasma insulin also declined but oral glucose tolerance did not improve with caloric restriction. Fasting plasma beta-hydroxybutyrate rose in the calorie-restricted group, along with an increase in ketonuria, but not in the control group. A second study compared the impact of a 33% calorie-restricted diet or insulin to a full-calorie diet in a similar 2-week experimental design and measured hepatic glucose output and insulin sensitivity with dideuterated glucose before and during an insulin clamp. Diet in three subjects improved fasting and 24-hr mean glucose by 22 and 10%, respectively, whereas prophylactic insulin in three subjects produced 0 and 4% reductions, respectively. On average, ketonuria after a 9-hr fast declined to an equivalent degree with both treatments. Hepatic glucose output and insulin sensitivity were not statistically significantly altered by gestational diabetes or the therapeutic interventions compared to nondiabetic normal weight or obese pregnant controls. In conclusion, 50% caloric restriction improves glycemic status in obese women with gestational diabetes but is associated with an increase in ketonuria, which is of uncertain significance. An intermediate 33% level of caloric restriction (to 1600-1800 kcal daily) may be more appropriate in dietary management of obese woman with gestational diabetes mellitus and more effective than prophylactic insulin. Further studies are required to confirm these findings.

A randomized comparison of routine versus selective iron supplementation during pregnancy.

Abstract: This trial compares routine and selective iron supplementation during pregnancy to determine whether routine supplementation adversely affects fetal growth, increases infections and subjective adverse effects, and/or delays birth. At their first prenatal visit, 2912 pregnant women were randomized into two groups (2694 gave birth). Compliance was satisfactory as measured by self-reports by mothers and hematocrit values in the third trimester. More women in the routinely supplemented group had subjected adverse effects. The groups were similar in regard to most of the other outcomes. In the selectively supplemented group, there was weak evidence for increase in sick-days, referrals to hospital outpatient clinic, cesarean section, blood transfusions, and infants who were diagnosed as having hyperviscosity. In the routine group, there were somewhat more women with gestations greater than or equal to 41 weeks and more dead infants. The subgroup analyses suggest that some of the apparently worse outcomes in the selective group were due to reactions of midwives and physicians to low hematocrit values.

Immediate enteral nutrition following multisystem trauma: a decade perspective.

Abstract: Metabolic support is an integral component of surgical critical care. Although prompt restoration of oxygen availability is clearly essential, the timing, composition, and route of nutritional support may also be decisive factors. The ensuing discussion will focus on: (a) timing of substrate delivery and (b) route of administration based on our clinical investigation over the past decade. The acutely injured patient was selected as a model of ICU hypermetabolism because of relative homogeneity with respect to age, comorbid factors, and stress level. Our first study hypothesis was that early nutritional support would improve outcome in the severely injured, but previously well-nourished patient. During an 18-month period, all patients undergoing laparotomy with a abdominal trauma index (ATI) greater than 15 were randomized to a control or total enteral nutrition (TEN) group. The control patients were given total parenteral nutrition (TPN) after POD 5, whereas the TEN cohort had a needle catheter jejunostomy (NCJ) inserted at laparotomy and received an elemental diet within 12 hours. The control (n = 31) and TEN (n = 32) groups were otherwise comparable with respect to risk stratification. The TEN patients, of course, shared improved nitrogen balance (p less than 0.001), but also had significantly (p less than 0.025) less septic morbidity. Nine (29%) of the controls developed major infections, contrasted to three (9%) of the TEN patients. Acknowledging the benefit of early nutrition, the next issue we addressed was the optimal route of substrate delivery; i.e., TEN vs TPN. The hypothesis was that TEN, compared to TPN, would reduce the injury stress response as reflected by the prioritization of hepatic protein synthesis. TEN given via NCJ and a nutritionally matched TPN solution were administered during the same postoperative period. Indeed, the TEN patients (n = 23) had significantly (p less than 0.05) higher constitutive proteins and lower acute-phase proteins, whereas the TPN patients manifested the opposite protein profile as measured by crossed immunoelectrophoresis. In view of these findings, we continued the study to ascertain clinical impact. Ultimately, 75 patients were randomized, providing groups with equivalent risk factors. Eleven (37%) of the TPN patients developed septic complications compared to five (17%) of the TEN group, and the incidence of major infection was six (20%) following TPN vs one (3%) with TEN. Thus, immediate TEN provided an additional clinical benefit compared to early TPN in these high-risk surgical patients.

Effect of method of administration of psyllium on glycemic response and carbohydrate digestibility.

Abstract: To determine whether there was any advantage to taking a soluble fiber supplement separate from food, as opposed to incorporated into a food, we used psyllium as a model, either taken in water just before a flaked bran cereal test meal, sprinkled on top of the cereal, or actually incorporated into the flake. In normal subjects, psyllium reduced the glycemic response when sprinkled onto or incorporated into the cereal, but not when taken before the cereal. Varying the amount of psyllium incorporated into the cereal from 0 to 20% resulted in a linear dose-dependent reduction of the glycemic index (GI) (GI = 101 -2.2 x % psyllium; r = 0.950; p less than 0.002). In subjects with diabetes, the blood-glucose-lowering effect of the psyllium flake cereal was similar to that in normal subjects. Mixing psyllium with the cereal or incorporating it into the cereal reduced the rate of digestion of bran flakes in vitro but was not associated with increased breath hydrogen levels in vivo as an index of rapid colonic fermentation. The bran flakes with psyllium incorporated was rated as no less palatable than the bran flakes cereal alone, and significantly more palatable (p less than 0.05) than taking psyllium in water before the cereal or sprinkling psyllium onto the cereal. These studies confirm earlier reports that viscous fibers must be intimately mixed with the food to have the effect of reducing blood glucose responses, and that the mechanism of action relates to a reduced rate of digestion rather than carbohydrate malabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of consistency of dietary intake during the first four years of life in a prospective analysis: Bogalusa Heart Study.

Abstract: The consistency of intake levels for several dietary components over a 5-year period (age 6 months to 4 years) in a biracial infant-early childhood cohort has been demonstrated. Young children with high intakes of selected dietary components associated with risk of cardiovascular disease (e.g., total fat, saturated fat, dietary cholesterol) continue to have higher intakes as they mature than do their peers. Spearman rank correlation coefficients at a significant level are noted between ages 2 and 4 for the following nutrients: total protein (r = 0.65), animal protein (r = 0.46), total sugar (r = 0.39), sucrose (r = 0.37), starch (r = 0.33), total fat (r = 0.53), saturated fatty acid (SFA, r = 0.48), polyunsaturated fatty acid (PUFA, r = 0.43), and cholesterol (r = 0.49). At 2 years of age, some 47-65% of those in the upper tertile for total fat, SFA, and cholesterol intake remain in the upper tertile at age 4. Persistence of eating behaviors appears to begin as early as age 2, in part because of parental control over food patterns. These observations have implications for reduction of early cardiovascular risk factors in children and adoption of a more prudent dietary intake through consumer education.

Omega-6 Essential Fatty Acids

Abstract: (1991). Omega-6 Essential Fatty Acids. Journal of the American College of Nutrition: Vol. 10, No. 2, pp. 178-178.

Food use and health effects of soybean and sunflower oils.

Abstract: This review provides a scientific assessment of current knowledge of health effects of soybean oil (SBO) and sunflower oil (SFO). SBO and SFO both contain high levels of polyunsaturated fatty acids (PUFA) (60.8 and 69%, respectively), with a PUFA:saturated fat ratio of 4.0 for SBO and 6.4 for SFO. SFO contains 69% C18:2n-6 and less than 0.1% C18:3n-3, while SBO contains 54% C18:2n-6 and 7.2% C18:3n-3. Thus, SFO and SBO each provide adequate amounts of C18:2n-6, but of the two, SBO provides C18:3n-3 with a C18:2n-6:C18:3n-3 ratio of 7.1. Epidemiological evidence has suggested an inverse relationship between the consumption of diets high in vegetable fat and blood pressure, although clinical findings have been inconclusive. Recent dietary guidelines suggest the desirability of decreasing consumption of total and saturated fat and cholesterol, an objective that can be achieved by substituting such oils as SFO and SBO for animal fats. Such changes have consistently resulted in decreased total and low-density-lipoprotein cholesterol, which is thought to be favorable with respect to decreasing risk of cardiovascular disease. Also, decreases in high-density-lipoprotein cholesterol have raised some concern. Use of vegetable oils such as SFO and SBO increases C18:2n-6, decreases C20:4n-6, and slightly elevated C20:5n-3 and C22:6n-3 in platelets, changes that slightly inhibit platelet generation of thromboxane and ex vivo aggregation. Whether chronic use of these oils will effectively block thrombosis at sites of vascular injury, inhibit pathologic platelet vascular interactions associated with atherosclerosis, or reduce the incidence of acute vascular occlusion in the coronary or cerebral circulation is uncertain. Linoleic acid is needed for normal immune response, and essential fatty acid (EFA) deficiency impairs B and T cell-mediated responses. SBO and SFO can provide adequate linoleic acid for maintenance of the immune response. Excess linoleic acid has supported tumor growth in animals, an effect not verified by data from diverse human studies of risk, incidence, or progression of cancers of the breast and colon. Areas yet to be investigated include the differential effects of n-6- and n-3-containing oil on tumor development in humans and whether shorter-chain n-3 PUFA of plant origin such as found in SBO will modulate these actions of linoleic acid, as has been shown for the longer-chain n-3 PUFA of marine oils.(ABSTRACT TRUNCATED AT 400 WORDS)

Saturated and hydrogenated fats in food in relation to health.

Abstract: The report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults published in 1988 evoked great interest from the medical profession, the public, and food manufacturers. The merits of different dietary interventions to lower plasma cholesterol are debated in advertising, popular publications, and research publications. The present paper is a review of the contributions of saturated and trans fatty acids (FA) to the US diet, their metabolism, and effects upon plasma cholesterol. Saturated (SFA) and trans FA are metabolized to yield energy. They are not dietary essentials; SFA can be biosynthesized, and trans FA are not naturally occurring in plants, with only very small amounts in animals. Trans FA are produced in hydrogenation of liquid vegetable oils and are estimated to contribute 3-7% of the fat consumed. Most of the SFA in the US diet (35% of total fat consumed) is obtained from meat, poultry, fish, and dairy products (approximately 60%). The fats and oils consumed directly or as components of food products, mostly baked goods, contribute approximately 20% of the SFA. More than 30 years of research led the NCEP to conclude that SFA was the most potent dietary component in increasing plasma cholesterol, and that no more than 10% of the energy (en%) of the diet should be SFA. Trans FA are metabolized similarly to SFA, but no recommendation has been made about their consumption. Reduction of consumption of SFA should be practiced in a prudent manner, by reducing consumption of foods high in SFA, and not by eliminating classes of foods. Some changes in formulations of foods or preparation practices (type of frying fat) can be made. These modifications may decrease the palatability of the food, thereby presenting a challenge to the food industry. Substitution of fats hydrogenated to contain trans FA for fats high in SFA may not be beneficial to health. Labeling of foods would improve the ability of the consumer to make appropriate choices.

Inhibition of gastric acid secretion reduces zinc absorption in man.

Abstract: Numerous factors seem to affect zinc absorption. Gastric acid secretion has been demonstrated to facilitate iron absorption. The zinc tolerance test (ZTT with ZnSO4 220 mg p.o.) was performed in 11 healthy volunteers to study the effects of administering the acid secretion inhibitor cimetidine (1 g/day p.o. for 3 days) and to evaluate the influence of HCl gastric secretion on zinc absorption in physiological conditions. Zinc absorption was reduced after cimetidine administration (p less than 0.005), suggesting that gastric pH influences zinc absorption. To rule out any direct effect of the drug on zinc absorption in five other healthy adults we further evaluated zinc absorption by using a different H2 antagonist (ranitidine 300 mg/day for 3 days and 300 mg before the test). Cimetidine was also tested in these subjects at half the dosage administered to the first group of subjects. Gastric acidity was monitored at 60-min intervals throughout the test via a nasogastric tube. The areas under the plasma concentration curves for zinc were significantly reduced after ranitidine (p less than 0.01), but not after cimetidine administration. Gastric acid was also reduced after ranitidine, but not after cimetidine (500 mg) administration, suggesting that gastric acid secretion plays a role in the regulation of zinc absorption in man.

Effects of four doses of n-3 fatty acids given to hyperlipidemic patients for six months.

Abstract: The long-term effects of practical amounts of fish oil on plasma lipids and lipoprotein cholesterol levels, bleeding times, erythrocyte deformabilities, and plasma phospholipid fatty acid (FA) composition were investigated in this trial Twenty-eight hyperlipidemic patients with elevated cholesterol and triglyceride (TG) levels were randomly assigned to take 3, 6, 9, or 12 capsules of fish oil daily for 6 months, providing 125-5 g of n-3 FAs per day Baseline parameters were compared to values after 1 and 6 months of treatment, and after 1 month of washout There were no statistically significant changes in total cholesterol levels at any dose Both low-density-lipoprotein cholesterol (LDL-C) and high-density-lipoprotein cholesterol (HDL-C) levels tended to rise, resulting in an unchanged ratio of LDL-C to HDL-C The TG and very-low-density-lipoprotein cholesterol (VLDL-C) levels decreased significantly with all but the lowest dose Bleeding times were unaffected despite a nonsignificant 34% increase detected at the highest dose Red blood cell deformability tended to increase with the two middle doses only The EPA level in plasma phospholipids was strongly correlated with n-3 FA (FA) consumption We conclude that long-term treatment of hyperlipidemic patients with practical intakes of n-3 FAs produced persistent reductions in TG levels and no change in the LDL-C/HDL-C ratio

Effect of a nutritional supplement on premenstrual symptomatology in women with premenstrual syndrome: a double-blind longitudinal study.

Abstract: To assess the effectiveness of a vitamin/mineral supplement in controlling symptoms of premenstrual syndrome (PMS), we conducted a double-blind randomized study on 44 women with PMS. Subjects were carefully screened and excluded if underlying physical or psychopathological conditions were noted. Follicular and luteal testing with a menstrual symptom questionnaire, subdividing PMS into four subgroups, was completed for 1 month prior to treatment and for three menstrual cycles during treatment. Subjects were randomly assigned to receive either placebo or six or 12 tablets of the supplement a day for three menstrual cycles. All subjects had significant differences in severity of symptoms between the follicular and luteal phase of the control cycle. Comparing pre- vs posttreatment luteal phase scores, significant placebo effects were noted for two PMS subgroups. Significant treatment effects were noted in three subgroups for the six-tablet group and in all four subgroups for the 12-tablet group. These results suggest that this nutritional supplement may play a role in the management of women with PMS.

The prognostic inflammatory and nutritional index in traumatized patients receiving enteral nutrition support.

Abstract: The prognostic inflammatory and nutritional index (PINI) is a clinical assessment tool which aggregates serum C-reactive protein (CRP), alpha 1-acid glycoprotein (AAG), prealbumin (PA), and albumin (ALB) concentrations into a single score. This study was conducted to characterize the index and its determinants over time in 15 critically ill trauma patients receiving enteral nutritional support (ENS). Patients received 1.4 g of protein/kg/day and 32 kcal/kg/day for at least 7 days using a nutritionally complete formula supplemented with whey protein. The PINI was calculated at baseline and on days 4, 7, 10, 14, 21, and 28. The PINI decreased significantly from baseline (186 +/- 202) to day 4 (116 +/- 86) and reached a nadir at day 14 (27 +/- 40). Serum CRP concentrations decreased significantly during the study period, while PA and ALB concentrations increased significantly. There was no change in the AAG concentration. Nitrogen balance increased significantly during the study period. The PINI was positively correlated with CRP concentration (r = 0.72, p = 0.0001) and negatively correlated with PA concentration (r = 0.56, p = 0.0004 and nitrogen balance (r = -0.51, p = 0.0018). The PINI decreased significantly during ENS of critically ill trauma patients, influenced primarily by a decrease in CRP concentration. Further studies are needed to characterize the PINI's performance as a prognostic tool.

Acceptable daily intake vs actual intake: the aspartame example.

Abstract: This article discusses the acceptable daily intake (ADI) and the postmarketing surveillance of consumption levels for a food additive, using the widely used food additive aspartame (APM, L-aspartyl-L-phenylalanine methyl ester) as an example. The safety implications of the ADI and consumption levels are also discussed. Aspartame has been assigned an ADI of 40 mg/kg/day by the World Health Organization and regulatory authorities in Europe and Canada, and of 50 mg/kg/day by the US Food and Drug Administration. A number of different methods have been used to measure consumption levels of food additives. Consumption estimations for aspartame from one such method, the food intake survey, have been done in the United States, Canada, Germany, and Finland. APM consumption in all age groups and selected subpopulations, even at the 90th percentile, is approximately 2-10 mg/kg/day and is thus well below the ADI.

Metabolic fate of chylomicrons obtained from rats maintained on diets varying in fatty acid composition.

Abstract: The importance of the fatty acid component in the metabolism of chylomicrons was demonstrated by feeding diets varying in fatty acid composition which resulted in chylomicrons of different sizes. On a diet rich in polyunsaturated fatty acids (PUFA) from safflower oil, chylomicrons of diameter 1853 +/- 192 A were harvested from the mesenteric lymph, whereas on coconut oil and medium-chain triglyceride diets the chylomicron size was 1403 +/- 83 and 604 +/- 40 A, respectively. When the isolated chylomicrons were injected into recipient rats maintained on a regular diet, their half-life (t1/2) decreased from 5.4 +/- 0.4 to 1.8 +/- 0.3 min with the increase in particle size. No significant difference in the apolipoprotein profile of chylomicrons of various sizes was noted, indicating that alterations of chylomicron removal are not related to apolipoprotein composition. Rats maintained on PUFA diets showed a marked increase in their adipose tissue lipoprotein lipase activity. The fast removal of large chylomicrons and increased tissue lipoprotein lipase activity, together with suppression of hepatic lipogenesis on this diet, apparently explains the low plasma triglyceride level in rats maintained on diets rich in PUFAs.

Mineral requirements of low-birth-weight infants.

Abstract: The minerals calcium (Ca), magnesium (Mg), and phosphorus (P) are essential for tissue structure and function. Recent studies have resulted in a more rational approach to the management of mineral intake in preterm infants receiving parenteral nutrition (PN) and enteral nutrition (EN). For preterm infants requiring PN, the use of PN solutions with a Ca content of 1.25-1.5 mmol/dl (50-60 mg/dl), a P content of 1.29-1.45 mmol/dl (40-45 mg/dl), and an Mg content of 0.2-0.3 mmol/dl (5-7 mg/dl) is supported by studies of mineral homeostasis with serial chemical and calciotropic hormone measurements, standard balance studies, and improved radiographic indices of bone mineralization. For infants requiring EN, an intake of approximately 4 mmol (200 mg) of Ca, 3.2 mmol (100 mg) of P, and 0.33 mmol (8 mg) of Mg/kg/day based on an average retention rate of 64% for Ca, 71% for P, and 50% for Mg should be sufficient to meet the requirements of preterm infants in early infancy. This level of intake is supported by data from balance studies using standard and stable isotope techniques, changes in bone mineral content (BMC) measurements, and calciotropic hormone data. Based on the timing of development of fractures and rickets, changes in BMC, and skeletal growth data, the increased Ca and P intake should continue for at least 3 months after birth or until reaching a body weight of about 3.5 kg. In addition, nonnutritional factors may have the potential to increase mineral loss and disturb mineral homeostasis; chronic diuretic therapy increases mineral loss, and aluminum contamination of nutrients theoretically may compound any skeletal disorder. Thus, attention to the level of mineral intake and factors important in mineral loss and mineral metabolism should optimize mineral retention in small preterm infants.

Polyunsaturated fats enhance peripheral glucose utilization in rats.

Abstract: Carbohydrate intolerance is positively correlated with saturated fat consumption. In contrast, individuals consuming diets comprised of polyunsaturated fatty acids (PUFA) have a lower incidence of diabetes mellitus (DM). To test the hypothesis that dietary fats may influence insulin sensitivity, insulin-stimulated glucose utilization was estimated in vivo in rats consuming diets enriched with saturated fatty acids (SFA) (cocoa butter), monounsaturated fatty acid (MUFA) (olive oil), or PUFA derived from corn or fish sources. Each test meal provided (as percentage of calories) 45% carbohydrate, 39% fat, and 16% protein. The meals were consumed over an 8-week period. Metabolic clearance rate (MCR) for glucose was significantly higher (p less than 0.01; 5.69 +/- 0.46 and 5.18 +/- 0.29 ml/kg/min) for diets containing fish and corn oil sources, respectively, when compared to olive oil (4.34 +/- 0.32 ml/kg/min) and cocoa butter (4.61 +/- 0.11 ml/kg/min). Although the MCR between the fish and corn oil diets were not significantly different, the steady state plasma insulin concentration was lower during the fish oil meal (75 +/- 20 microU/ml) when compared to the corn meal (112 +/- 13 microU/ml). Fasting plasma insulin concentrations were significantly lower (p less than 0.01) following the PUFA diets compared to the other two diets. Fasting plasma glucose levels, despite being lower in the fish meal, were insignificantly different among the four test meals. Lastly, body weights were comparable among the four groups tested. These results suggest that diets enriched with PUFA enhance peripheral glucose utilization significantly more than diets comprised of MUFA or SFA sources.(ABSTRACT TRUNCATED AT 250 WORDS)

The human intestinal response to enteral nutrients : a review

Abstract: This review identifies the factors which influence mucosal integrity during enteral nutrition. These include biliary and pancreatic secretions, trophic influences of endocrine and gastrointestinal polypeptides, intestinal blood flow, and innervation. Fiber, bacterial fermentation products, purines, and glutamines are potential essential nutrients which may not be provided by parenteral nutrition. However, contrary to experience in animal models, the specific advantages of intraluminal delivery of nutrients for the maintenance of mucosal integrity and structure remain unproven in the human. Current evidence in the human suggests that changes in small bowel structure and function when enteral nutrients are excluded are minor and rapidly reversible as long as general nutritional status is maintained.

A comparison of fasting serum amino acid profiles of young and elderly subjects.

Abstract: The fasting serum amino acid profile in 37 healthy young women and men (30-35 years) was compared with the fasting profile in 30 institutionalized elderly women and men (80-89 years), an ambulatory, self-fed senior-residence group. Levels of serum lysine, leucine, methionine, valine, and total essential amino acids were significantly lower in the older group than in the younger group; however, citrulline and hydroxyproline were significantly higher in the older group compared to the younger group. Histidine, threonine, tryptophan, and the ratio of tryptophan to large neutral amino acids (isoleucine, leucine, phenylalanine, tyrosine, and valine) were also generally lower in the older group than in the younger group, while the difference due to age was more pronounced in the females compared to males. The essential/nonessential amino acid ratio was lower in females compared to males.

Effect of diet on bone matrix constituents.

Abstract: Bone formation occurs in an integrated, highly ordered manner, beginning in the embryonic period. Nutrients may affect bone formation by delaying cellular differentiation, altering responses to bone growth factors, affecting supply of needed nutrients, and/or affecting rates of synthesis of the matrix constituents. Several growth factors, both systemic and local, are being identified which affect bone formation. Matrix constituents include collagen and noncollagenous proteins, each of which are thought to have specific roles in bone formation, maintenance, or resorption. Among the nutrients which are known to affect bone formation at a cellular level are vitamins A, D, and K, ascorbic acid, zinc, magnesium, and calcium. Nutrients that are known to affect protein synthesis in general also affect bone formation. It is necessary for nutritionists to consider cellular as well as systemic effects of nutrients on bone formation.

Plasma uptake of manganese as affected by oral loads of manganese, calcium, milk, phosphorus, copper, and zinc.

Abstract: Six adult subjects were administered a series of manganese (Mn) tolerance tests to investigate the influence of various minerals on Mn plasma uptake. Oral loads given to all six subjects included 40 mg manganese alone, or with 800 mg calcium (Ca) as either calcium carbonate (CaCO3) or 545 ml 2% milk. Four of the subjects also received loads of 800 mg phosphorus (P), 2 mg copper (Cu), and 50 mg zinc (Zn) with the 40 mg Mn. Baseline Mn tolerance tests for all subjects produced a rapid increase in plasma Mn, followed by return to baseline. The addition of Ca as either CaCO3 or 2% milk to the oral Mn essentially blocked the plasma uptake of Mn. No significant differences were found between the source of Ca in its inhibitory effect. Plasma Ca uptake was lower when Mn was simultaneously administered, but the results were not significantly different. Ionized levels of plasma Ca did not change significantly. The addition of Cu to the Mn load decreased the area under the curve for plasma Mn by about half, but it was not significantly different in the four subjects. In contrast, the addition of Zn to the Mn produced a significant increase in plasma Mn. Phosphorus has no influence on plasma uptake of Mn. These results indicate that the plasma uptake of Mn is greatly reduced by concomitant ingestion of Ca but may be increased by an oral load of Zn.

Effects of gender on vitamin C pharmacokinetics in man.

Abstract: The pharmacokinetics of vitamin C (VC) were compared in young and elderly male and female subjects following 500 mg oral doses to each subject in two states of VC nutriture: a depleted state achieved by 4-5 weeks on a diet containing less than 10 mg VC/day and a supplemented state which was achieved following 500 mg/day doses of VC for 3 weeks. The males were taller and heavier than their female counterparts and consequently had a greater body surface area (BSA). The body mass index (BMI) and fat mass did not differ between genders within an age group, whereas only the young females exhibited a greater percent body fat. The males exhibited a larger fat-free mass (FFM) than the females. None of the pharmacokinetic parameters differed due to gender in depleted subjects. In the supplemented state the female subjects exhibited a significantly greater peak VC concentration (Cmax), a longer absorption lag time (tlag), apparent volume of distribution (AVd) in L/kg, clearance (CL) in ml/hr/kg, and renal clearance (CLr) in ml/hr/kg. When AVd, CL, and CLr were expressed in absolute terms (i.e., L or ml/min), no gender-related differences were observed. A stepwise multiple linear regression indicated that Cmax was inversely linearly related to body weight, tlag was directly related to BSA and dose, and AVd (L/kg) was inversely linearly related to BSA. CL (ml/hr/kg) and CLr (ml/hr/kg) were not significantly related to any of the body composition parameters examined. Overall, these results indicate that there are few gender-related differences in the pharmacokinetics of VC in humans and that a portion of the observed differences can be explained by body composition differences between the sexes.

Impact of menstrual periodicity on serum lipid levels and estimates of dietary intakes.

Abstract: Nine eumenorrheic women were studied at five separate times each month for a minimum of 2 months. Fasting bloods and 1-day food records were obtained from all women at these times to describe the pattern and magnitude of within-person variation in selected nutrient and lipid indicators attributable to menstrual cyclicity. Serum cholesterol, beta-carotene, 17 beta-estradiol (E2), and dietary selenium intakes exhibited significant periodic regressions against time. For the group as a whole, however, only serum cholesterol and E2 measures exhibited significantly strong consistent periodicities. Future studies with a larger sample of women are warranted to confirm these findings. Unless strict blood sampling protocols are followed, variation attributable to menstrual cyclicity may mitigate the reliability of the serum cholesterol screenings advocated in the past few years.

Zinc and copper status of severely burned children during TPN.

Abstract: Alterations in zinc (Zn) and copper (Cu) homeostasis have been reported during the acute recovery period following thermal injury in both children and adults. Increased urinary losses of Zn and Cu and decreased plasma concentrations of Zn, Cu, and ceruloplasmin (CP), the major copper transport protein, occur despite adequate provision of these elements in enteral feedings. We now report data for moderately to severely burned children receiving total parenteral nutrition (TPN) supplemented to provide Zn and Cu. Hyperzincuria occurred consistently when 50 micrograms/kg Zn was delivered daily to older children. Similarly, when younger children received 100 micrograms/kg Zn daily, profound hyperzincuria ensued despite a reduction in total plasma Zn. Hypozincemia was accompanied by low levels of Zn in the plasma subfraction normally associated with albumin-bound Zn. The delivery of Cu via TPN was 4-12 micrograms/kg daily, and urinary Cu losses were not elevated. Plasma total Cu and plasma CP were invariably re...

Effects of canola oil on serum lipids in humans.

Abstract: Previous work in this laboratory had shown in a pilot study that canola oil could lower blood pressure and serum cholesterol levels. Attempting to extend this work to a larger cohort over a longer period, a 4-month study using a 30 ml/day addendum of canola oil as the replacement of the edible oils in the usual diet was undertaken in 36 hypercholesterolemic and/or hypertriglyceridemic subjects. Serum low-density-lipoprotein cholesterol (LDL-C) decreased from 173 +/- 9.0 to 160 +/- 10.0 mg/dl, p less than 0.025. Blood pressure, total cholesterol, and high-density-lipoprotein cholesterol (HDL-C) did not change significantly even though the HDL subfractions did, HDL2 decreasing and HDL3 increasing.