Showing papers in "Journal of Nutrition in 1993"

AIN-93 Purified Diets for Laboratory Rodents: Final Report of the American Institute of Nutrition Ad Hoc Writing Committee on the Reformulation of the AIN-76A Rodent Diet

Abstract: For sixteen years, the American Institute of Nutrition Rodent Diets, AIN-76 and AIN-76A, have been used extensively around the world. Because of numerous nutritional and technical problems encountered with the diet during this period, it was revised. Two new formulations were derived: AIN-93G for growth, pregnancy and lactation, and AIN-93M for adult maintenance. Some major differences in the new formulation of AIN-93G compared with AIN-76A are as follows: 7 g soybean oil/100 g diet was substituted for 5 g corn oil/100 g diet to increase the amount of linolenic acid; cornstarch was substituted for sucrose; the amount of phosphorus was reduced to help eliminate the problem of kidney calcification in female rats; L-cystine was substituted for DL-methionine as the amino acid supplement for casein, known to be deficient in the sulfur amino acids; manganese concentration was lowered to one-fifth the amount in the old diet; the amounts of vitamin E, vitamin K and vitamin B-12 were increased; and molybdenum, silicon, fluoride, nickel, boron, lithium and vanadium were added to the mineral mix. For the AIN-93M maintenance diet, the amount of fat was lowered to 40 g/kg diet from 70 g/kg diet, and the amount of casein to 140 g/kg from 200 g/kg in the AIN-93G diet. Because of a better balance of essential nutrients, the AIN-93 diets may prove to be a better choice than AIN-76A for long-term as well as short-term studies with laboratory rodents.

Chromium in Human Nutrition: A Review

Abstract: This review summarizes the results of 15 controlled studies supplementing defined Cr(III) compounds to subjects with impaired glucose tolerance. Three of these (3-4 mumol Cr/d for > 2 mo) produced no beneficial effects: serum glucose, insulin and lipid concentrations remained unchanged. The remaining 12 interventions improved the efficiency of insulin or the blood lipid profile of subjects (ranging from malnourished children and healthy middle-aged individuals to insulin-requiring diabetics). In addition, three cases of impaired glucose tolerance after long-term total parenteral alimentation responding to Cr supplementation have been reported. Chromium potentiates the action of insulin in vitro and in vivo; maximal in vitro activity requires a special chemical form, termed Glucose Tolerance Factor and tentatively identified as a Cr-nicotinic acid complex. Its complete structural identification is a major challenge to chromium research. The development and validation of a procedure to diagnose chromium status is the second challenge. Such a test would allow the assessment of incidence and severity of deficiency in the population and the selection of deficiency in the population and the selection of chromium-responsive individuals. The third challenge is the definition of chromium's mode of action on parameters of lipid metabolism that have been reported from some studies but not others. Future research along these lines might establish whether chromium deficiency is a factor in the much discussed "Syndrome X" of insulin resistance.

Sarcopenia and Age-Related Changes in Body Composition and Functional Capacity

Abstract: Advancing adult age is associated with profound changes in body composition. One of the most prominent of these changes is sarcopenia, defined as the age-related loss in skeletal muscle mass, which results in decreased strength and aerobic capacity and thus functional capacity. Sarcopenia is also closely linked to age-related losses in bone mineral, basal metabolic rate and increased body fat content. Through physical exercise and training, especially resistance training, it may be possible to prevent sarcopenia and the remarkable array of associated abnormalities, such as type II diabetes, coronary artery disease, hypertension, osteoporosis and obesity. Using an exercise program of sufficient frequency, intensity and duration, it is quite possible to increase muscle strength and endurance at any age. There is no pharmacological intervention that holds a greater promise of improving health and promoting independence in the elderly than does exercise.

Low Methionine Ingestion by Rats Extends Life Span

Abstract: Dietary energy restriction has been a widely used means of experimentally extending mammalian life span. We report here that lifelong reduction in the concentration of a single dietary component, the essential amino acid L-methionine, from 0.86 to 0.17% of the diet results in a 30% longer life span of male Fischer 344 rats. Methionine restriction completely abolished growth, although food intake was actually greater on a body weight basis. Studies of energy consumption in early life indicated that the energy intake of 0.17% methionine-fed animals was near normal for animals of their size, although consumption per animal was below that of the much larger 0.86% methionine-fed rats. Increasing the energy intake of rats fed 0.17% methionine failed to increase their rate of growth, whereas restricting 0.85% methionine-fed rats to the food intake of 0.17% methionine-fed animals did not materially reduce growth, indicating that food restriction was not a factor in life span extension in these experiments. The biochemically well-defined pathways of methionine metabolism and utilization offer the potential for uncovering the precise mechanism(s) underlying this specific dietary restriction-related extension of life span.

Short-term dietary calcium fortification increases fecal saturated fat content and reduces serum lipids in men.

Abstract: The effect of dietary calcium on fecal fatty acid excretion and serum lipids was tested in a randomized, single-blind metabolic study in 13 healthy men with moderate hypercholesterolemia. A low calcium base diet containing 34% of energy from fat, 13% from saturated fatty acids, 240 mg cholesterol/d and 410 mg Ca/d was compared with a fortified version in which calcium citrate malate was added to orange juice, (550 mg) muffins (750 mg), and two tablets (500 mg) for a total calcium intake of 2200 mg/d. Fecal collections (72 h, d 8, 9, 10) and blood from fasting subjects for lipids and lipoproteins (d 9, 10, 11) were obtained. The percentage of dietary saturated fat excreted per day increased from 6 to 13% with calcium fortification. There was no change in fecal bile acid excretion. The high Ca diet significantly reduced total cholesterol 6% (5.99 to 5.66 mmol/L), LDL cholesterol 11% (4.13 to 3.67 mmol/L), and apolipoprotein B concentrations 7% when compared with the low Ca diet (P < 0.05). There was no change in HDL cholesterol or apolipoprotein A1 concentrations. Urinary calcium excretion increased from 146 to 230 mg/d when the high Ca diet was consumed. Calcium fortification was effective in lowering total and LDL cholesterol concentrations and may be an effective adjunct to cholesterol-lowering diet therapy.

Physical fitness, growth and appetite of Kenyan school boys with hookworm, Trichuris trichiura and Ascaris lumbricoides infections are improved four months after a single dose of albendazole.

Abstract: We studied physical fitness with the Harvard Step Test, growth, and appetite in primary school boys infected with hookworm (96% baseline prevalence), Trichuris trichiura (98% prevalence) and Ascaris lumbricoides (41% prevalence) who received a single 600-mg dose of albendazole or an identical placebo. Boys were examined, allocated at random within pairs by descending hookworm egg count to placebo (n = 26) or albendazole (n = 27) groups, treated, and re-examined 4 mo later. Four months after treatment, the albendazole group showed highly significant improvements in fitness score, resting heart rate, and heart rates at 1, 2, 3 and 4 min after the Harvard Step Test, whereas the placebo group had not changed significantly. The albendazole group also exhibited significantly more rapid growth judged by weight gain (1.0 kg greater than the placebo group, P < 0.0002), height increment (0.6 cm more, P < 0.003), arm circumference (0.3 cm more, P < 0.0002), and triceps and subscapular skinfolds (1.0 mm more, P < 0.0002), and showed improved appetite with objective and subjective measures. We conclude that single-dose treatment with albendazole can allow improved physical fitness, growth, and appetite in school-age children in areas where these helminths and poor growth are highly prevalent.

A Diet History Questionnaire Ranks Nutrient Intakes in Middle-Aged and Older Men and Women Similarly to Multiple Food Records

Abstract: We evaluated the reproducibility of a modified version of the National Cancer Institute diet history questionnaire and also studied comparability of nutrient estimates from this questionnaire to those from four 2-d food records. Subjects (n = 211) were from a population-based sample of middle-aged and older adults participating in the Beaver Dam Eye Study in south-central Wisconsin. Median age-specific correlation coefficients between the questionnaire, administered twice at a 3-mo interval, were 0.8 in men and 0.7 in women (range = 0.5 to 0.9). Questionnaire estimates of protein, cholesterol, thiamin, niacin, iron and zinc were consistently lower than food record estimates whereas estimates of fat were higher. Correlation coefficients between estimates from the questionnaire and records were generally > 0.5, indicating overall good agreement in ranking. However, the range in correlation coefficients was wide [ranging from 0.06 for iron (without supplements) in middle-aged women to 0.8 for alcohol in middle-aged men and women]. Questionnaire estimates similarly classified persons into the lowest two food record quintiles of intake 50 to 93% of the time depending on nutrient. These results suggest that the questionnaire produces nutrient estimates that rank individuals on the basis of intake of most nutrients similarly to estimates from multiple food records.

Development and testing of the AIN-93 purified diets for rodents: results on growth, kidney calcification and bone mineralization in rats and mice.

Abstract: Because of nutritional and technical problems the AIN-76A rodent diet was revised. One of the new formulations was designated AIN-93G and was suggested for use during growth, pregnancy and lactation studies. Some major differences in this new formulation compared with the AIN-76A diet are as follows: 7 g soybean oil was substituted for 5 g corn oil/100 g diet to increase the amount of linolenic acid; the amounts of vitamins E and K were increased; cornstarch was substituted for most of the sucrose; the amount of phosphorus was reduced to eliminate the problem of nephrocalcinosis in female rats; L-cystine was substituted for DL-methionine; and the manganese concentration was reduced. Various developmental modifications of the AIN-93G diet were fed to weanling rats and mice to determine effects on growth and tissue mineralization. After rats were fed the developmental version of AIN-93G for 16 wk, body weights in both male and female rats were not different from those of rats fed a cereal-based nonpurified diet. After 13 wk, male mice fed this diet weighed 13% more than those fed the nonpurified diet. Body weights of female mice were not affected. The new diet formulation prevented kidney calcification in female rats and mice during 16 wk of feeding.

High Dose Vitamin A Supplementation of Breast-Feeding Indonesian Mothers: Effects on the Vitamin A Status of Mother and Infant

Abstract: For regions where vitamin A deficiency is common, high dose vitamin A supplementation of lactating mothers is currently recommended, but the effects of this intervention have not been carefully evaluated. We conducted a randomized, double-blind trial in which 153 Indonesian mothers 1-3 wk postpartum received either a capsule containing 312 mumol of vitamin A as retinyl palmitate or a placebo. Mothers' serum retinol concentrations in the vitamin A group tended to be lower than in the placebo group at baseline but higher at 3 mo postpartum (1.39 vs. 1.24 mumol/L, P = 0.03) and 6 mo postpartum (1.23 vs. 1.08 mumol/L, P < 0.01). The milk retinol concentrations of the vitamin A group were higher than those of the placebo group by 0.48 to 1.18 mumol/L at 1-8 mo postpartum (P < 0.05). Among the infants at 6 mo of age, the prevalences of low serum retinol concentration (< 0.52 mumol/L) were 36 and 15% in the placebo and vitamin A groups, respectively (P < 0.005), and the prevalences of low vitamin A stores (assessed by relative dose response) were 23 and 10%, respectively (P < 0.03). High dose vitamin A supplementation of lactating mothers is an efficacious way to improve the vitamin A status of both mother and breast-fed infant.

Dietary Lipid Profile Is a Determinant of Tissue Phospholipid Fatty Acid Composition and Rate of Weight Gain in Rats

Abstract: Modifications in membrane fatty acid composition and insulin action are possible through dietary intervention. We examined the metabolic fate of (n-3) fatty acids in male Wistar rats, using three isocaloric, high fat diets. The ET-L, OL-L and SAF-L diets contained edible tallow, olive oil and safflower oil, respectively, with identical amounts of (n-3) fatty acids as linseed oil. Despite isocaloric feeding, weight gain was lower (P < 0.001) in rats fed the more highly saturated ET-L diet (69 +/- 8 g) than in those fed either the high (n-9) fatty acid OL-L diet (93 +/- 2 g) or the high (n-6) fatty acid SAF-L diet (108 +/- 4 g). Analysis of red quadricep fatty acid composition revealed phospholipid (n-3) fatty acid levels in the ET-L-fed group (21.6 +/- 0.8 g/100 g fatty acids) to be significantly higher than in either the OL-L-fed (17.7 +/- 0.6 g/100 g fatty acids, P < 0.05) or SAF-L-fed (15.3 +/- 0.7 g/100 g fatty acids, P < 0.05) group. A similar pattern was observed in other muscles and white adipose tissue. A follow-up study using 14C-labeled (n-3) fatty acids in the diet showed greater (n-3) fatty acid incorporation in the ET-L-fed group relative to the other two groups and conversely lower 14CO2 production than in the SAF-L-fed group. These results demonstrate that metabolic fate of dietary fatty acids is strongly influenced by the overall fatty acid profile of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

The nature and significance of the relationship between urinary sodium and urinary calcium in women.

Abstract: Orally or parenterally administered sodium is known to increase urinary calcium in experimental animals and humans, and there is well-documented correlation between urinary sodium and calcium in 24-h urine collections from normal subjects and renal stone formers. The correlation between urinary sodium and calcium is generally sodium driven, i.e., it is the sodium load that influences urinary calcium rather than vice versa, but the converse may also occur, as after an oral calcium load or in hypercalcemia. When sodium is the determinant, 100 mmol of sodium takes out approximately 1 mmol of calcium in the urine. When calcium load is the determinant, each millimole of calcium appearing in the urine is associated with an extra 10-20 mmol of sodium. Sodium-dependent calcium loss may continue indefinitely, but calcium-dependent natriuresis is self-limiting. There is a significant correlation between calcium and sodium in fasting urine from both pre- and postmenopausal women, but there is more calcium relative to sodium in postmenopausal women than in premenopausal women. In postmenopausal but not premenopausal women, urinary hydroxyproline is also related to obligatory sodium and calcium output, and restriction of salt intake lowers not only urinary sodium but also calcium and hydroxyproline. There is not only an increase in obligatory calcium excretion at the menopause, but also an increase in the fasting urinary sodium, which in turn accounts for some of the increase in calcium output. This rise in fasting urinary sodium represents a delay in sodium excretion that may have a significant effect on calcium homeostasis.

Supplemental Microbial Phytase Improves Bioavailability of Dietary Zinc to Weanling Pigs

Abstract: Two experiments were conducted to determine the effects of supplemental microbial phytase on utilization of dietary zinc by weanling pigs. Experiment 1 was a 2 x 3 factorial arrangement of treatments with 24 pigs for 4 wk. Two levels of phytase activity (0 and 1350 units/g) and three levels of zinc (0, 30 and 60 mg/kg as ZnSO4.7H2O) were added to a corn-soybean meal basal diet. Weekly measures included growth performance, plasma alkaline phosphatase activity and plasma mineral concentrations. In Experiment 2, mineral balances were determined in 12 pigs fed the basal diet or the diet with added zinc (30 mg/kg) or phytase (1350 units/g). The results indicated that either supplemental phytase or supplemental zinc increased plasma alkaline phosphatase activity and plasma zinc concentrations, but these increases were not additive. Supplemental phytase decreased plasma alkaline phosphatase activity in pigs supplemented with zinc. Supplemental phytase also significantly enhanced weight gain, feed intake, gain:feed ratio, plasma concentrations of inorganic phosphorus, and retention of phosphorus and calcium. Neither supplemental phytase nor zinc affected zinc retention. Supplementing corn-soybean meal diets with microbial phytase at 1350 units/g feed improves bioavailability of zinc as well as of phytate phosphorus to weanling pigs.

Dietary 1,25-dihydroxycholecalciferol supplementation increases natural phytate phosphorus utilization in chickens.

Abstract: These studies were conducted to determine if supplementation of a corn-soybean meal diet with 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] would increase the utilization of natural phytate phosphorus by broiler chickens. Two experiments were conducted to evaluate the effect of dietary 1,25-(OH)2D3 in the presence and absence of supplemental phytase and at several dietary levels of inorganic phosphorus supplementation. The criteria measured in these studies were weight gain, gain:feed ratio, bone ash, rickets due to phosphorus deficiency, plasma calcium and phosphorus and retention of calcium, phosphorus and phytate phosphorus. In the first experiment, the types and amounts of fecal inositol phosphates were determined by HPLC, and the total fecal phytate was determined by the classic FeCl3 precipitation technique. In the first experiment, the addition of 1,25-(OH)2D3 to the diet in the presence of dietary phytase resulted in greater 9-d weight and bone ash and lower incidence of rickets; the retention of total fecal phytate and phytate phosphorus was greater than in controls. The second experiment was a complete 2 x 2 x 2 factorial design [phosphorus levels x phytase x 1,25-(OH)2D3]. The addition of 1,25-(OH)2D3 alone to the diet resulted in greater 9-d weight and bone ash, lower incidence of rickets, and greater retention of total calcium and phosphorus and phytate phosphorus. The highest retention of phytate phosphorus (79.4%) was obtained when both phytase and 1,25-(OH)2D3 were present in the diet. The possible mode of action and importance of these results in many areas of nutrition and environmental science are discussed.

Requirements of juvenile milkfish (Chanos chanos Forsskal) for essential amino acids

Abstract: The dietary requirements of juvenile milkfish (Chanos chanos Forsskal) for essential amino acids were determined in a series of experiments. The fish (< or = 8.0 g) were reared in fiber glass tanks provided with flow-through seawater at 28 degrees C and salinity of 32 g/L for 12 wk. In each experiment, a series of amino acid test diets was formulated containing a combination of intact protein sources (casein-gelatin, fish meal-gelatin, fish meal-soybean meal or fish meal-zein) and crystalline amino acids to simulate the levels found in milkfish tissue proteins except for the test amino acid. Each set of isonitrogenous diets contained 40-45% protein and graded levels of the amino acid to be tested. At the end of the feeding experiment, growth, survival and feed efficiency were determined. The requirement level for each essential amino acid was estimated from breakpoint analysis of the growth curve. The dietary essential amino acid requirements (as the percentage of dietary protein) of milkfish juveniles were as follows: arginine, 5.25; histidine, 2.00; isoleucine, 4.00; leucine, 5.11; lysine, 4.00; methionine, 2.50 (cystine, 0.75); phenylalanine, 4.22 (tyrosine, 1.00) or 2.80 (tyrosine, 2.67); threonine, 4.50; tryptophan, 0.60; valine, 3.55. This information is valuable in developing cost-effective practical or commercial feeds and research diets for milkfish juveniles.

Relationship of Colonic Luminal Short-Chain Fatty Acids and pH to In Vivo Cell Proliferation in Rats

Abstract: The mechanism by which fermentable fibers may stimulate colonic cell proliferation was tested using two types of fiber (highly fermentable pectin, and less fermentable wheat bran), measuring in vivo concentrations of short-chain fatty acids (SCFA) in the cecum and the proximal and distal colon of rats and correlating these concentrations with cell proliferation indices at the same locations within the intestine. Pectin supplementation resulted in higher concentrations of propionate in proximal and distal colon as compared with fiber-free controls, whereas wheat bran resulted in a higher concentration of butyrate at every site. In the cecum, pH had the strongest correlation to indices of cell proliferation. The lower the pH the greater the number of cells per crypt column (P < 0.05), cells per crypt circumference (P < 0.01), and total number of cells per crypt (P < 0.001). Butyrate had the strongest correlation between a specific SCFA and indices of cell proliferation. In the distal colon, butyrate concentration was positively correlated with number of cells per crypt column (P < 0.05) and total number of cells per crypt (P < 0.05). This study shows that different fibers are fermented to different SCFA in different amounts and that the in vivo concentration of certain of these SCFA is significantly correlated with cell proliferation indices.

Neural mechanisms in the responses to amino acid deficiency.

Abstract: Food intake is rapidly and reliably reduced when animals are offered diets that result in an essential amino acid deficiency, such as those used in the imbalanced amino acid diet (IMB) paradigm. There seem to be at least three phases in the responses of rats to IMB: 1) In order to respond to a dietary challenge, the animals must first recognize that challenge. The available data suggest that before the behavioral effects occur, a decline in the concentration of an essential amino acid is sensed in a specific brain area, the prepyriform cortex. This recognition phase is associated with localized decreases in the concentrations of the limiting amino acid, norepinephrine and cyclic AMP and with altered protein synthesis. 2) Subsequent to recognition of the deficiency, a conditioned taste aversion develops, mediated in part by serotonin at the level of the vagus. 3) Finally, in the absence of a choice, the animals adapt to an IMB (but not a diet devoid of one or more essential amino acids) in approximately 1 wk. Damage to certain extrahypothalamic brain areas or liver denervation accelerates adaptation to IMB, suggesting both central and peripheral control in the adaptation phase. The resulting behavioral responses provide adaptive advantage to an animal in the selection of a diet with an appropriate balance of amino acids.

Intestinal Calcium Absorption in Rats Is Stimulated by Dietary Lactulose and Other Resistant Sugars

Abstract: Lactulose is a disaccharide analogue of lactose that is resistant to metabolism in the small intestine but not in the large intestine. The effects of lactulose and other sugars on intestinal Ca absorption were determined from the decrease in the 47Ca:47 Sc ratio between diet and feces after feeding male rats diets containing these sugars during a single night. Dietary lactulose was more potent than lactose in stimulating Ca absorption and was effective between 5 and 38 wk of age. The component sugars of lactulose, galactose and fructose, did not influence Ca absorption when provided together at concentrations equimolar to that of lactulose. The stimulation of Ca absorption by dietary lactulose increased as dietary Ca concentration was raised and was not influenced by prior injections of calcitriol. Lactulose must be present in the same meal as Ca to stimulate Ca absorption, but this stimulation was lost if the rats were fed lactulose continuously for 2 or 7 d prior to the test diet. Other sugars thought to be poorly absorbed in the small intestine (xylitol, lactobionate, arabinose, raffinose, pyroglutamate, sorbitol, gluconate and raftilose) stimulated Ca absorption to an identical extent as lactulose. Cecectomy did not influence the enhancement of Ca absorption by lactulose. These results indicate that sugars resistant to metabolism and absorption in the small intestine but not the large intestine stimulate Ca absorption in the small intestine.

Weight Gain of Kenyan School Children Infected with Hookworm, Trichuris trichiura and Ascaris lumbricoides is Improved Following Once- or Twice-Yearly Treatment with Albendazole

Abstract: We studied growth in infected children given one dose (600 mg) or two doses of albendazole per school year. Children were examined and allocated at random within sex by descending hookworm egg count to one of three groups: placebo (n = 93), one dose (1x, n = 96) or two doses (2x, n = 95). Each child was treated and then re-examined and treated 3.6 and 8.2 mo later (Exams 2 and 3). The 1x and 2x groups gained significantly more by Exam 3 than the placebo group in weight (1.1 and 0.9 kg more, respectively), percent weight-for-age (3.3 and 2.7 percentage points more), percent weight-for-height (3.1 and 2.9 percentage points more), percent arm circumference-for-age (2.3 and 2.0 percentage points more) and triceps and subscapular skinfolds but did not differ significantly from each other. The placebo group showed significant decreases between exams (P < 0.0002) in percent weight-for-age and percent arm circumference-for-age and no change in percent weight-for-height, whereas the 1x and 2x groups exhibited significant increases (P < 0.005). At Exam 3, arithmetic mean egg reduction rates for the 1x and 2x groups were 84 and 95% for hookworm, 42 and 32% for Trichuris and 55 and 87% for Ascaris, respectively. We conclude that one or two doses of albendazole per year resulted in similar growth improvements, despite reinfection, in school-age children in an area where these helminths and poor growth are prevalent.

High Dietary Calcium Level Decreases Colonic Phytate Degradation in Pigs Fed a Rapeseed Diet

Abstract: The degradation of phytate (inositol hexaphosphate) in rapeseed meal diet not containing phytase activity was studied in 15 growing ileum-fistulated pigs. Stomach and small intestinal degradation and total gastrointestinal degradation were compared. The effect of addition of calcium carbonate to the rapeseed meal diet at two levels (9.2 and 18.5 g/kg diet) was investigated. A commercial barley-wheat-soybean diet with intrinsic phytase activity was used as reference. Phytate and its hydrolysis products in diets, ileal digesta and feces were determined by HPLC ion-pair chromatography. Hydrolysis of phytate in the stomach and small intestine was 35-45% in pigs fed the rapeseed meal diet independent of calcium addition, and 65% in pigs fed the reference diet. Total gastrointestinal degradation of phytate in pigs fed the rapeseed diet was 97, 77 and 42% (P < 0.001) when calcium intakes were 4.5, 9.9 and 15 g/d, respectively; total gastrointestinal degradation was 72% in pigs fed the reference diet. The intestinal phytate degradation pattern, when rapeseed diet was fed, indicated the activity of an unspecific phosphatase, whereas that of the reference diet indicated intrinsic dietary phytase activity. We conclude that dietary supplementation of calcium carbonate decreases the phytate degradation in the colon of pigs, but not in the stomach and small intestine.

Caffeine, Urinary Calcium, Calcium Metabolism and Bone

Abstract: Oral doses of caffeine increase the urinary excretion of calcium, magnesium, sodium and chloride for at least 3 h after consumption. The hypercalciuric effect can be blocked by adenosine receptor agonists. The effect is proportional to dose per lean body mass and no adaptation to the urinary losses occurs with continuing consumption of caffeine. Uncompensated losses of calcium would be a risk factor for development of osteoporosis. Risks of osteoporosis due to caffeine consumption are reviewed. Comparison of data from epidemiological surveys and animal and human studies suggests that for younger adult women consuming adequate calcium, moderate caffeine intakes may have little or no deleterious effects. Increased urinary and intestinal losses may be compensated for by increased intestinal calcium absorption. However older women do not seem to compensate adequately to maintain their former calcium balance, especially when calcium intakes are below recommendations.

Dietary Phosphorus, Calcium Metabolism and Bone

Abstract: Many American women consume diets high in phosphorus and low in calcium. Concern about this dietary pattern stems from studies that show high phosphorus, low calcium intake causes secondary hyperparathyroidism and bone loss in several animal models. Recent studies in young adults have shown that a high phosphorus, moderately low calcium intake results in mild secondary hyperparathyroidism that persisted over 4 wk. However, plasma concentrations of the active form of vitamin D did not change in these subjects, despite stimulatory changes in parathyroid hormone and serum ionized calcium. Studies in normal adult men have shown that dietary phosphorus at levels within the observed normal range of intake can finely regulate the renal production and serum concentration of 1,25-dihydroxycholecalciferol. Thus, prolonged high phosphorus intake may impair the usual homeostatic mechanisms that are evoked when dietary calcium is limited. The current dietary patterns of high phosphorus, low calcium consumption result in persistent changes in the calcium regulating hormones that are not conductive to optimizing peak bone mass or slowing the rate of bone loss.

Viscosity and Fermentability as Attributes of Dietary Fiber Responsible for the Hypocholesterolemic Effect in Hamsters

Abstract: The attribute(s) of soluble dietary fibers responsible for cholesterol lowering is currently uncertain. A series of experiments were conducted in which viscosity and fermentability was assessed independently for their effect on plasma and liver cholesterol concentration. Hamsters were divided into four dietary groups and fed diets containing 0.12% cholesterol and 5% fiber as high viscosity hydroxypropyl methylcellulose (HV-HPMC group), low viscosity hydroxypropyl methylcellulose (LV-HPMC group), high viscosity guar gum (HV-GG group) or low viscosity guar gum (LV-GG group). Hydroxypropyl methylcellulose is essentially nonfermentable, whereas guar gum is highly fermentable. Plasma cholesterol concentrations at 3, 6 and 11 wk and liver cholesterol concentrations at 6 and 11 wk were significantly lower in the HV-HPMC group relative to the LV-HPMC group (P < 0.05). Intestinal content viscosities of the LV-HPMC and HV-GG groups were similar; consequently, these two groups were compared to examine the independent effect of fermentation. Plasma and liver cholesterol were significantly lower in the HV-GG group compared with the LV-HPMC group at 6 wk (P < 0.05), but not at 3 or 11 wk. Hepatic sterol synthesis rates were not affected by any of the diets. This study shows that greater viscosity of intestinal contents is strongly associated with cholesterol reduction, but that the contribution of fiber fermentation remains uncertain.

Biosynthesis and Metabolism of Retinoic Acid: Roles of CRBP and CRABP in Retinoic Acid: Roles of CRBP and CRABP in Retinoic Acid Homeostasis

Abstract: The enzymes that constitute the pathway of retinoic acid biosynthesis and metabolism may recognize retinoid binding proteins as effectors and substrates. Apocellular retinol-binding protein (CRBP) stimulates a bile-salt independent membrane-bound retinyl ester hydrolase resulting in the hydrolysis of endogenous retinyl esters and the formation of holoCRBP. HoloCRBP delivers retinol to a microsomal nicotin-amide-adenine dinucleotide phosphate-dependent dehydrogenase, protects it from artifactual oxidation and denies enzymes that cannot recognize the binding protein access to retinol. The retinal synthesized may be transferred from the microsomes to the cytosol by CRBP. A cytosolic retinal dehydrogenase has been purified that produces retinoic acid from retinal generated by microsomes in the presence of CRBP and from the complex CRBP-retinal itself. Thus, CRBP(type I) seems to channel retinoids through the reactions of retinoic acid synthesis via a series of protein-protein interactions. Cellular retinoic acid-binding protein (type I) facilitates retinoic acid metabolism by sequestering it and by acting as a low Km substrate, thereby also modulating the steady-state concentrations of retinoic acid.

Dietary native resistant starch but not retrograded resistant starch raises magnesium and calcium absorption in rats.

Abstract: The effects on calcium and magnesium absorption of dietary native and retrograded cornstarch were studied in rats. Uncooked high amylose starch granules (35% of total glucose equivalents as enzyme-resistant starch) and cooked and cooled (-20 degrees C) high amylose starch (24% of total glucose equivalents as retrograded resistant starch) were used as test starches, and cooked normal starch (3% of total glucose equivalents as resistant starch) was used as control starch. Native vs. control starch raised the amount of polymerized glucose in ileum, but not in feces. Retrograded starch produced more polymerized glucose than control starch in both ileum and feces. When compared with control starch, ileal pH was significantly lowered by native starch and tended to be raised by retrograded starch. Cecal pH was lowered by the two preparations rich in resistant starch. Apparent absorption of calcium and magnesium was raised by native starch but not by retrograded resistant starch. Calcium concentrations in the liquid phase of the ileum tended to be elevated by native starch but were significantly lowered by retrograded starch relative to control starch. Magnesium and calcium concentrations in liquid cecal contents tended to be raised with native starch; they were unchanged with retrograded starch. It is suggested that native resistant starch raised calcium and magnesium absorption because it tended to enhance the solubility of these minerals in ileal and cecal digesta.

Development and validation of a total parenteral nutrition model in the neonatal piglet.

Abstract: A model was developed for total parenteral nutrition (TPN) in neonatal piglets, with ingredients typical of those in clinical use. Our goal was to characterize the model and to compare growth and body composition of TPN-fed piglets with a reference sow-fed group. Forty piglets (1 to 3 d of age) received TPN (1040 kJ.-1.d-1, 14.6 g.kg-1.d-1 of amino acids, with nonprotein energy supplied equally by glucose and fat) for 8 d. Weight gain, linear growth, serum biochemistry, hematology and body composition were compared with the reference group of 20 sow-raised piglets. Piglets receiving TPN gained 63 +/- 12 g.kg-1.d-1, less than the mean (79 +/- 21 g.kg-1.d-1, P < 0.01), but within the range (49-118 g.kg-1.d-1), of sow-raised piglets. The TPN-fed piglets used the amino acids in TPN effectively, retaining 80% of infused nitrogen. At postmortem, dry-matter analysis of the bodies yielded similar findings in both groups. Wet-tissue protein concentration was lower in TPN-fed animals (12.5 +/- 0.8 vs 13.8 +/- 1.8 g.100 g body wt) because TPN-fed piglets were more hydrated. Ash concentration was lower in TPN-fed piglets, reflecting limitations in calcium and phosphorous supply.

Soft tissue composition and bone mineral status: evaluation by dual-energy X-ray absorptiometry.

Abstract: Dual-energy X-ray absorptiometry (DXA) is a new method for assessing whole-body and regional bone, fat and fat-free mineral-free soft tissue masses. X-rays at two discrete energy levels are collimated and directed into the body. The attenuation of the X-rays by the various chemical components in the body permits determination of important compositional variables. The precision and accuracy of the DXA measurements of bone mineral content and density are 99% and < 1% error, respectively. The reproducibility of the determinations of soft tissue composition is approximately 99%. Because the radiation dose associated with the X-ray exposure is low, DXA is a safe method for routine use in humans. Various applications are described, including an assessment of bone mineral status and body composition in adults and infants. This method is appealing for nutritional studies because it directly determines the composition of bone and of the body.

Intrauterine Food Restriction is Associated with Obesity in Young Rats

Abstract: The purpose of this study was to examine the effects of malnutrition during the first 2 wk of intrauterine life on the regulation of energy metabolism and the activity of brown adipose tissue in rats at 53 d of age. Intrauterine malnutrition led to an imbalance in the control of energy metabolism that was influenced by gender. In males, the intrauterine malnutrition resulted in impairment of normal weight gain and fat deposition during 1 to 53 d of age, in association with low plasma total triiodothyronine concentration, in spite of normal food intake. In contrast, the intrauterine malnutrition in females led to a marked fat accumulation by 53 d of age with normal food intake, and decreased brown adipose tissue weight, protein content and cytochrome c oxidase activity, indicating a lower sympathetic activity. These data indicate that nutrient availability during the first 2 wk of intrauterine life determines the control of energy utilization during early post-weaning period.

Methionine but not folinic acid or vitamin B-12 alters the frequency of neural tube defects in Axd mutant mice.

Abstract: The Axd (axial defects) mutation, which causes open neural tube defects (NTD) in 25-30% of d 14 mouse embryos of heterozygous (Axd/+) matings and curly tails (CT) in 31%, can be useful in studying neurovertebral morphogenesis. Current interest focuses on the role of methionine in neurulation, because supplementation of dams with this essential amino acid (70 mg/kg body wt) has been shown to reduce by 41% the incidence of NTD among embryos of Axd/+ x Axd/+ crosses when administered on d 8 and 9 of pregnancy. The present experiments were undertaken to determine whether supplementation of dams with a higher dose of methionine could effect a greater level of remediation. At a dose of 180 mg/kg body wt, the amino acid produced a reduction in NTD of 47%, similar to that produced at 70 mg/kg body wt. Supplementation of dams of reciprocal matings of Axd/+ x BALB/cByJ or CF-1 mice allowed assessment of the effects of methionine in heterozygous embryos, which exhibit CT. The amino acid had no effect on Axd/+ embryos from the BALB crosses, but the frequency of CT declined significantly among embryos of the CF-1 outcrosses. Maternal supplements of folinic acid (33 mg/kg) or vitamin B-12 (330 mg/kg) did not alter the incidence of NTD or CT among Axd embryos. No difference in methionine concentration was detected in the serum of Axd/+ and +/+ dams.

The Zinc Nutriture of Preschool Children Living in Two African Countries

Abstract: A study of 57 children aged 44-78 months living in Chilunga village in Zomba District Malawi and of 76 children aged 42-80 months living in the villages of Slepor and Gidantuba in Greater Accra in Ghana aimed to determine intakes of zinc and other dietary components influencing zinc bioavailability. Children from Malawi had higher mean annual intakes of energy (5419 kJ vs. 4698 kJ; p < .05) and phytate (1899 mg vs. 604 mg; p < .05) and higher mean molar rations of [phytate]/[zinc] and [calcium] x [phytate]/[zinc] mmol per megajoule (25 mmol/MJ vs. 12 mmol/MJ and 44 mmol/MJ vs. 20 mmol/MJ respectively; p < .05) than the children from Ghana. A higher proportion of children from Malawi had a molar ratio of [phytate]/[zinc] of at least 15 (72% vs. 0; p < .05). Malawian children were more likely to be severely stunted than the Ghanaian children (57% vs. 28%; p < .05). The median hair zinc concentration of children living in Gidantuba was significantly higher than that of children living in Slepor and in Malawi (1.99 mcmol/g vs. 1.42 mcmol/g respectively; p < .05). Further a higher percentage of children in Slepor and Malawi had lower hair zinc concentrations than those in Gidantuba (83% and 94% respectively vs. 39%; p < .05). The children in GIdantuba with low hair zinc concentrations exhibited low upper-arm-muscle-area-for-age (-0.71) and upper-arm-muscle-are-for-height Z scores (-0.10). The diets in Malawi were cereal-based while those in Ghana consisted of starch staples with relatively low nutrient and phytate densities and fermented cereals with relatively low densities of phytate relative to zinc. The high intakes of phytic acid relative to zinc in Malawian children indicated that they faced a greater risk for insufficient zinc nutrition status than Ghanaian children. The researchers called for a study to determine whether zinc supplementation would improve zinc nutrition status in children in Ghana and Malawi

Relationships between Viscosity of Hydroxypropyl Methylcellulose and Plasma Cholesterol in Hamsters

Abstract: Dietary high viscosity hydroxypropyl methylcellulose (HPMC) lowered plasma and liver cholesterol concentrations in cholesterol-fed hamsters. To determine the level of viscosity needed to effect a significant reduction in total plasma cholesterol, hamsters were fed for 3 wk diets containing 0.12% cholesterol and either 4% cellulose or one of four preparations of HPMC that varied in viscosity between 14 and 1698 centipoise (cP), as estimated in vitro. Blood was collected for plasma cholesterol determination, and intestinal contents were obtained by finger-stripping of the excised small intestine. Contents were centrifuged and the supernatant (ex vivo) viscosity determined. In vitro and ex vivo viscosities were correlated (R2 = 0.96). Plasma cholesterol concentrations declined as in vitro or ex vivo viscosity increased. Maximal plasma cholesterol reduction occurred at an ex vivo viscosity of approximately 150 cP. There was a linear relationship between plasma cholesterol and the logarithm of ex vivo viscosity (R2 = 0.98). Our results suggest that materials that increase the viscosity of intestinal contents can be effective in reducing plasma cholesterol and that only moderate increases in viscosity are necessary to achieve this effect.