RESUMO
Twenty-four pregnant women, in their second trimester, participated in two seven-day metabolic experiments to evaluate zinc and copper utilization from self-selected diets, with or without supplementation. Recommended dietary allowances for zinc or suggested intakes for copper were not met unless supplements of these nutrients were consumed. Zinc retentions in the unsupplemented group were 1.9 and 0.3 mg/day during the first and second metabolic periods, respectively. Zinc retentions in the supplemented group were 2.3 and 4.7 mg/day during the same two periods. Intakes above 8 mg/day resulted in positive retentions. Based on individual variation, however, intakes of 20 mg/day, the current RDA, would not be excessive although possibly some level between these two extremes would be adequate. Copper retentions in the unsupplemented and supplemented groups combined over the two balance periods were -0.02 and 0.89 mg/day, respectively. Adequate copper retention does not appear possible without the use of a supplement.
Assuntos
Cobre/metabolismo , Dieta , Gravidez , Zinco/metabolismo , Peso ao Nascer , Peso Corporal , Cobre/administração & dosagem , Cobre/sangue , Feminino , Cabelo/análise , Humanos , Recém-Nascido , Necessidades Nutricionais , Cuidado Pré-Natal , Zinco/administração & dosagem , Zinco/sangueRESUMO
Balance studies were conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat in preadolescent boys and girls. During the studies, the losses of calcium, iron, magnesium, manganese, potassium, sodium, and zinc were determined in the arm sweat of the subjects. Sweat from the forearm was collected in a polyethylene bag for 1 hr on three different occasions. Using the concentrations of nitrogen in the arm bag and in the whole body collection and the concentration of minerals in the arm bag, the total body loss of minerals were estimated. Losses of minerals through sweat, expressed as a percentage of intake, ranged from 0.12 to 1.10%. Under conditions of these studies, sweat losses of the essential minerals were not a significant factor in estimating total losses.
Assuntos
Cálcio/metabolismo , Potássio , Sódio , Suor/metabolismo , Oligoelementos , Cálcio da Dieta , Criança , Dieta , Feminino , Antebraço/fisiologia , Humanos , Masculino , Nitrogênio/metabolismo , Potássio/metabolismo , Fatores Sexuais , Sódio/metabolismo , Oligoelementos/metabolismoRESUMO
Adult women were fed dietary regimens that provided 2.0 mg of copper and either 8, 16, 24, mg of zinc daily in a 18-day controlled metabolic study. Zinc retentions were positive at all levels of intake, but the lowest level was probably not sufficient to maintain equilibrium. An intake of 16 mg of zinc was sufficient to maintain subjects in positive balance or at equilibrium, although this level may be marginal for individuals living in warm climates with potentially large sweat losses. None of the dietary groups was in positive balance on a copper intake of 2 mg/day, although the dietary level of zinc had no effect on copper retentions. Serum levels of copper decreased and zinc increased during the study.
Assuntos
Cobre/metabolismo , Zinco/farmacologia , Adulto , Cobre/sangue , Relação Dose-Resposta a Droga , Fezes/análise , Feminino , Humanos , Necessidades Nutricionais , Zinco/metabolismoRESUMO
Young adult women were selected from a group of volunteers on the basis of present and past use of oral contraceptive agents. Subjects were either those who had never used oral contraceptives or those who had used an agent for a minimum of two menstrual cycles. All subjects were fed diets that provided 2.02 to 2.11 mg of copper and 9.15 to 9.10 mg of zinc daily in an 18-day controlled metabolic study. Both oral contraceptive users and nonusers were in negative zinc balance and zinc excretion as not different (P > 0.05) for the groups. Oral contraceptives did not alter (P > 0.05) the metabolic balance of copper; the mean copper retention values were -0.16 mg/day for the nonusers and -0.13 mg/day for the users of oral contraceptives. As anticipated from reports in the literature, the plasma copper levels were higher (P < 0.01) in the oral contraceptive group, but the levels of zinc were not different. Although blood levels of zinc and copper are usually changed with the use of oral contraceptives, the retention of the two nutrients appears not to be affected.
PIP: Young adult women were selected from a group of volunteers on the basis of present and past use of (OCs) oral contraceptives. Subjects were either those who had never used OCs or those who had used an agent for a minimum of 2 menstrual cycles. All subjects were fed diets which provided 2.02-2.11 mg of copper and 9.15-9.10 mg of zinc daily in an 18-day controlled metabolic study. Both OC users and nonusers were in negative zinc balance and zinc excretion was not different (P 0.05) for the groups. OCs did not alter the metabolic balance of copper (P 0.05); the mean copper retention values were -0.16 mg/day for the nonusers and -0.13 mg/day for OC users. As anticipated from reports in the literature, the plasma copper levels were higher (P 0.01) in the OC group, but the levels of zinc were not different. Although blood levels of zinc and copper are usually changed with the use of OCs, the retention of the 2 nutrients appears not to be affected.
Assuntos
Anticoncepcionais Orais/farmacologia , Cobre/metabolismo , Zinco/metabolismo , Adulto , Anticoncepcionais Orais Combinados/farmacologia , Anticoncepcionais Orais Sintéticos/farmacologia , Cobre/sangue , Combinação de Medicamentos , Etinilestradiol/farmacologia , Combinação Etinil Estradiol e Norgestrel , Diacetato de Etinodiol/farmacologia , Feminino , Humanos , Noretindrona/farmacologia , Norgestrel/farmacologia , Zinco/sangueRESUMO
Erythrocyte zinc has been suggested as an index of zinc status. This study was undertaken to investigate the possible relationships of erythrocyte zinc concentration to age, physical maturity, and zinc intake of teenage girls of two races. Dietary zinc was calculated from two 1-day food recalls, and erythrocyte zinc was determined for over three hundred 12-, 14- and 16-yr-old girls in Oklahoma and Virginia. Erythrocyte zinc concentration increased and the intake of zinc from the diet decreased after attainment of menarche. Among girls of the same menarcheal state, age was not related to zinc intake, but concentration of zinc in erythrocytes increased with each 2-yr age increment in those that were past menarche. Results did not show a direct relationship of erythrocyte zinc values to calculated intakes of zinc by adolescent females. Black and white races did not differ in either zinc intake or red cell zinc content.
Assuntos
Dieta , Eritrócitos/metabolismo , Zinco/sangue , Adolescente , Envelhecimento , Feminino , Humanos , Fatores Sexuais , Zinco/administração & dosagemRESUMO
A nitrogen balance study was undertaken to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess the impact of sweat nitrogen on the protein needs of preadolescent girls. Values were determined through the collection of 24-hour, total body sweat samples from 15 healthy girls with a mean age of 8 years, 7 months. Mean height and weight of the subjects were 132 cm and 28.9 kg, respectively. Mean sweat nitrogen losses, collected under uncontrolled environmental conditions, were 201 mg, 263 mg and 319 mg/day on 34 g, 57 g and 88 g of protein intake. The environmental conditions throughout the study remained fairly constant. Mean nitrogen balances per day were 0.04 g, 0.55 g and 1.42 g on the respective levels of nitrogen intake, with the inclusion of sweat nitrogen loss, however, a negative nitrogen balance per day was found in 8 and 2 subjects on 34 g and 57 g protein intake. After considering nitrogen retention of 0.3 g which has been recommended by NRC for the minimum nitrogen allowance for growth of preadolescent children, protein intakes higher than that recommended by the NRC-RDA for preadolescent girls may be required for support of normal growth.
Assuntos
Proteínas Alimentares , Nitrogênio/metabolismo , Suor/metabolismo , Superfície Corporal , Criança , Fenômenos Fisiológicos da Nutrição Infantil , Proteínas Alimentares/administração & dosagem , Fezes/análise , Feminino , Crescimento , Humanos , Nitrogênio/urina , Necessidades Nutricionais , Deficiência de Proteína/metabolismoRESUMO
Preadolescent girls, ages 7 to 9 years, were fed levels of zinc ranging from 5.61 to 14.61 mg/day during an 18-day metabolic study. All other nutrients were provided at or above Recommended Dietary Allowance levels. The sweat loss of zinc was measured using an arm-bag method and whole body zinc loss was calculated from whole body nitrogen and arm loss of nitrogen and zinc. Fecal zinc reflected dietary zinc, but urinary zinc remained relatively stable. The mean daily loss of zinc through sweat was calculated to be 1.43 mg. Zinc retentions were not significantly different (P greater than 0.05) though the retention increased generally with intake of zinc. A comparison of these data with previously reported studies indicated that the absorption of zinc was usually in the range of 20 to 30%. Based on sweat losses reported by others and found in this study and on usual absorption of zinc, it appears that diets should provide a minimum of 7 mg of zinc daily for growing children.
Assuntos
Suor/metabolismo , Zinco/metabolismo , Criança , Relação Dose-Resposta a Droga , Fezes/análise , Feminino , Humanos , Necessidades Nutricionais , Zinco/administração & dosagem , Zinco/urinaRESUMO
The effects of zinc intake on nitrogen utilization was investigated during a 20-day balance study with 23 preadolescent girls. The children were fed a diet which provided 4.17 g of nitrogen and 5.5 mg of zinc daily; the diet was supplemented with a combination of 5 mg of zinc and/or nitrogen supplied from either amino acids or nonspecific nitrogen. Complete collections of excreta were made throughout the study. Neither the supplementation of amino acids nor zinc improved the retention of nitrogen. Urinary excretion of urea nitrogen, uric acid, and creatinine were not different as a result of zinc supplementation. Subjects consuming the lower level of zinc were in negative zinc balance, but the subjects consuming 10.5 mg of zinc were in positive balance. The supplementation of this low protein diet with amino acids did not improve nitrogen retention.
Assuntos
Nitrogênio/metabolismo , Proteínas/metabolismo , Zinco , Aminoácidos , Criança , Relação Dose-Resposta a Droga , Fezes/análise , Feminino , Humanos , Compostos de Amônio Quaternário , Zinco/metabolismoRESUMO
Twenty-three young adult males were fed diets containing either 400 or 1400 mg of cholesterol per day under controlled conditions for 4 wk. There were minimal differences between the two diets in total protein, carbohydrate, fat, and the P/S fatty acid ratio. In both diets 400 mg of cholesterol was supplied from nonegg food sources; the additional 1000 mg of cholesterol was from four whole eggs. Blood samples were collected after a 12- to 14-h fast at the beginning of the study, weekly throughout the experimental period, and 1 wk after completion of the study. Plasma total cholesterol and triglycerides and high-density, low-density, and very low-density lipoprotein cholesterol levels were measured. No significant differences in plasma total cholesterol, triglycerides, and lipoprotein cholesterol levels were observed between groups at any time. However, plasma cholesterol and cholesterol content of individual lipoproteins varied considerably among the individual subjects fed the high cholesterol diet. The importance of changes in the properties and metabolic activity of individual lipoproteins induced by dietary cholesterol with or without gross changes in the cholesterol levels remains to be determined.
Assuntos
Colesterol na Dieta/farmacologia , Colesterol/sangue , Lipoproteínas/sangue , Triglicerídeos/sangue , Adulto , HDL-Colesterol , LDL-Colesterol , VLDL-Colesterol , Relação Dose-Resposta a Droga , Ovos , Humanos , Lipoproteínas HDL/sangue , Lipoproteínas LDL/sangue , Lipoproteínas VLDL/sangue , MasculinoRESUMO
A nitrogen balance study was conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess further the impact of sweat nitrogen on protein needs of preadolescent children. Values were determined through the collection of 24-hr, total body sweat samples from twelve healthy boys having a mean age of 8 years, 8 months. Mean height and weight of the subjects were 131.4 cm and 31.0 kg, respectively. Environmental conditions were relatively constant during the study. Mean sweat nitrogen losses were 208, 287, and 368 mg/day on daily protein intakes of 29, 54, and 84 g, respectively. Mean nitrogen balances per day were 0.39, 0.09, and 1.95 g when sweat nitrogen losses were included in the calculations. At the lower and moderate levels of protein intake, nine and six subjects were in negative nitrogen balance when sweat losses were considered. Sweat nitrogen losses in the boys were similar to a previous study with preadolescent girls. Based upon published basal metabolic rates and mean sweat nitrogen losses of 261 and 288 mg/day for girls and boys, the nitrogen lost through sweat was 0.25 mg/basal kcal for both sexes. An estimation of 0.5 mg/basal kcal for integumental nitrogen loss appears realistic for this age group.
Assuntos
Proteínas Alimentares , Nitrogênio/metabolismo , Suor/metabolismo , Superfície Corporal , Criança , Proteínas Alimentares/administração & dosagem , Proteínas Alimentares/metabolismo , Fezes/análise , Feminino , Humanos , MasculinoRESUMO
The effects of the American Association of Cereal Chemists coarse wheat bran fiber and exercise were evaluated in 20 males, aged 24 to 35 yr, and at least 10% above ideal weight. Thirteen of the subjects participated in a 4 mile walk-jog run program 3 times weekly. In a cross-over design with diets switched midway through the experiment, both the exercising and sedentary groups consumed isocaloric amounts of either white bread or white bread containing wheat bran (0.5 g/kg body weight). Plasma total and lipoprotein cholesterol and triglycerides, body weights, and percentage body fats were determined at 0, 6, and 12 wk. No consistent effects were observed as a result of the wheat bran feeding on any of the parameters measured. Exercise training tended to decrease body weights and percentage body fats, and was associated with significantly increased (p less than 0.05) plasma high-density lipoprotein cholesterol levels and high-density lipoprotein cholesterol to low-density lipoprotein cholesterol ratios. After a rise in triglycerides at wk 6, a significant decline (p less than 0.05) back to base-line values was observed at wk 12 for the exercised subjects.
Assuntos
Fibras na Dieta/farmacologia , Lipídeos/sangue , Lipoproteínas/sangue , Obesidade/sangue , Esforço Físico , Adulto , Pão , Colesterol/sangue , HDL-Colesterol , LDL-Colesterol , Ingestão de Energia , Humanos , Lipoproteínas HDL/sangue , Lipoproteínas LDL/sangue , Masculino , Triglicerídeos/sangue , TriticumRESUMO
The plasma total cholesterol (TC) and lipoprotein cholesterol concentrations of sedentary young men (n = 23) were determined during 4 wk of controlled feeding and 6 wk of supervised aerobic conditioning. Subjects were assigned to dietary treatments of 400 mg cholesterol per day (M) or 1400 mg cholesterol per day (H); both diets had a P/S ratio of about 0.6. Dietary groups M and H were subdivided into exercise (MX and HX) and sedentary (MS and HS) groups. Compared to the sedentary groups, MX and HX exhibited significant (p less than 0.01) improvements in cardiorespiratory fitness. After 2 and 4 wk of high cholesterol feeding, group HS exhibited significant (p less than 0.05) elevations in TC (+30 +/- 7 and +32 +/- 9 mg/dl) with nonsignificant increases in very low-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Group HX exhibited consistent weekly increases in high-density lipoprotein cholesterol (HDL-C) (from 46 +/- 3 mg/dl, the base level, to 53 +/- 4 mg/dl at wk 4) with aerobic conditioning. By combining exercise and sedentary group data at each level of dietary cholesterol it was shown that TC and HDL-C levels significantly (p less than 0.05) increased by the 4th wk of high cholesterol feeding. The TC/HDL-C ratio significantly (p less than 0.05) increased for the sedentary subjects as compared to all the exercising subjects by wk 4 of controlled feeding.
Assuntos
Colesterol na Dieta , Colesterol/sangue , Adulto , Peso Corporal , Humanos , Lipoproteínas HDL/sangue , Lipoproteínas LDL/sangue , Lipoproteínas VLDL/sangue , Masculino , Esforço FísicoRESUMO
Body weight, lean body mass (total weight less body fat), carcass protein, and serum protein were examined as potential parameters by which to assess the effect of age on protein requirements for maintenance in male rats, aged 11 months and 18 months, fed diets containing 1.53, 3.41, 4.98, 6.52, or 8.05% dietary protein, casein plus methionine, for a 5-week period. Body weight change was maintained in older animals at 6.52% dietary protein and in younger animals at 4.98% dietary protein. Older animals consuming the two diets highest in protein had a greater percent body fat and less percent body protein than younger animals. Significant effects of diet and the interaction of diet and age on serum protein were also observed. As dietary protein level increased, serum protein increased gradually in younger rats, but only between 3.41 and 4.98% dietary protein in older rats. Lean body mass and total carcass protein increased as dietary protein level increased, but there were no significant differences due to age or the interaction of diet and age. Changes in body weight indicate a greater protein requirement for 18-month-old rats compared with 11-month-old rats, although complicated by greater food intake and fat deposits in older animals. Measures of body protein indicate that age has some influence on protein needs for maintenance purposes.
Assuntos
Envelhecimento/fisiologia , Proteínas Alimentares/administração & dosagem , Animais , Proteínas Sanguíneas/análise , Composição Corporal , Peso Corporal , Masculino , Necessidades Nutricionais , Proteínas/análise , Ratos , Ratos Sprague-DawleyRESUMO
Jelliffe's standards for evaluating measurements of mid-upper arm circumference, triceps skinfold thickness, and mid-upper arm muscle circumference of American adults were compared with percentile distributions developed from the first Health and Nutrition Examination Survey (NHANES I). These comparisons show that the standards poorly represent the adult U.S. population. Replacement of the standards with updated sex-specific values is not recommended, as (a) no single value for each arm parameter can be considered as "normal" for men or women of all ages and (b) the expression of arm measurements as percentages of standards is an inappropriate method of evaluation. Instead, measurements should be evaluated by comparison with age- and sex-specific percentile distributions developed from the NHANES I.
Assuntos
Antropometria/métodos , Antebraço/anatomia & histologia , Adolescente , Adulto , Fatores Etários , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Músculos , Fatores Sexuais , Dobras Cutâneas , Estados UnidosRESUMO
Proximate composition, edible yields, and selected nutrients were measured in cantaloupe, cherries, grapes, nectarines, plums, and watermelon sampled in six major U.S. markets. Yields were lowest (about 55%) for the melons, but were much higher (about 90% or above) for other fruits. Fruits were high in moisture, low in protein, fat, and energy. The estimated carbohydrate content ranged from about 8% for the melons to 17% for cherries. Vitamins A and C were present in moderate concentrations, but fruits were found to be low in vitamin B-6, folic acid, and pantothenic acid, as well as in the mineral elements.
Assuntos
Frutas/análise , Carboidratos da Dieta/análise , Proteínas Alimentares/análise , Oligoelementos/análise , Vitaminas/análiseRESUMO
The Recommended Dietary Allowances (RDA) by the National Academy of Sciences are revised approximately every five years. The RDA are compromise opinions of highly qualified nutritional scientists based on interpretations of available data. As with any interpretations of available data. As with any, interpretations and opinions not found on definitive information, they are subject to challenges. The RDA for protein for 7-to 9-uear-old children have been adjusted downward from 60 g in 1958 to 36 g in 1974, a 40% reduction. Data from our laboratories have shown positive apparent nitrogen balances on intakes as low as 18 g daily when no allowances were made for integumental and other nitrogen losses, however, based on accumulative data over several years we calculate the protein requirement to be 45 g daily from a typical American diet. If a safety factor of 30% is added the allowance would become 58.5 g. Currently the RDA for protein for the 7- to 10-year-old child supplies 6% of the RDA for Calories which contrasts to 8.30 and 9.20% for adult males and females, respectively. For comparison, energy from protein as a percentage of total energy for some common foods are: white bread, 12%; corn meal 10%; white rice 7%; and wheat flour 13%.
Assuntos
Proteínas Alimentares , Fenômenos Fisiológicos da Nutrição , Adulto , Fatores Etários , Criança , Ingestão de Energia , Metabolismo Energético , Feminino , Humanos , Masculino , Necessidades Nutricionais , Fatores Sexuais , Fenômenos Fisiológicos da Pele , Suor/fisiologiaRESUMO
This study investigated whether boron would enhance the ability of 17beta-estradiol (E2) or parathyroid hormone (PTH) to improve bone quality in ovariectomized OVX rats. Adult OVX rats were treated for 5 wk with vehicle, boron (5 ppm as boric acid), E2 (30 microg/kg/d, sc), PTH (60 microg/kg/d, sc), or a combination of boron and E2 or PTH, respectively. The E2 treatment corrected many adverse effects of OVX on bone quality, increased bone Ca, P, and Mg contents, and decreased trabecular plate separation. Dietary boron supplementation had no effects on these bone parameters in OVX rats. When OVX rats were treated with boron and E2 together, trabecular bone volume (Tb.BS/TV) and plate density were increased significantly more than that caused by E2 alone. The boron and E2 combination also increased trabecular bone surface (Tb.BV/TV) and decreased trabecular plate separation in OVX rats. In contrast, whereas daily PTH injection also increased bone Ca, Mg, and P contents, Tb.BV/TV, Tb.BS/TV, trabecular plate density and thickness, and decreased trabecular plate separation in OVX rats, the combination of boron and PTH had no additional improvement in bone quality over that achieved by PTH alone. In summary, this study shows for the first time that boron enhanced the action of E2, but not that of PTH, to improve trabecular bone quality in OVX rats.
Assuntos
Osso e Ossos/efeitos dos fármacos , Boro/administração & dosagem , Estradiol/administração & dosagem , Hormônio Paratireóideo/administração & dosagem , Animais , Peso Corporal/efeitos dos fármacos , Densidade Óssea/efeitos dos fármacos , Osso e Ossos/anatomia & histologia , Cálcio/metabolismo , Suplementos Nutricionais , Sinergismo Farmacológico , Feminino , Magnésio/metabolismo , Tamanho do Órgão/efeitos dos fármacos , Ovariectomia , Fósforo/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
The present study investigated whether boron would enhance the action of 17beta-estradiol (E2) or parathyroid hormone (PTH) on bone mineral balance in ovariectomized (OVX) rats. Forty-three days after OVX, the rats were treated for 5 wk with vehicle, boron (5 ppm as boric acid), E2 (30 microg/kg/d, sc), PTH (60 microg/kg/d, sc), or a combination of boron and E2 or PTH. Bone mineral balance was assessed by measuring apparent absorption, excretion, and retention of calcium (Ca), phosphorus (P), and magnesium (Mg). Serum Ca, P, Mg, and osteocalcin were also measured in this experiment. Boron alone had no effects on food consumption, weight gain, bone mineral balance, and serum levels of Ca, P, Mg, and osteocalcin. E2 alone increased serum P and Mg and decreased serum osteocalcin, but it had no effect on bone mineral balance. The combination of boron and E2 markedly improved apparent absorption of Ca, P, and Mg. In addition, the combination treatment increased the apparent retention of Ca and Mg (but not P) and also increased serum Ca and Mg but not serum P. On the other hand, boron cotreatment did not prevent the E2-induced reduction in serum osteocalcin in OVX rats. PTH alone significantly increased serum Ca, P, Mg, and osteocalcin concentrations, although it had no effect on bone mineral balance. Contrary to the boron-E2 combination treatment, the combination of boron and PTH did not enhance bone mineral balance. However, inasmuch as boron-PTH cotreatment did not enhance the stimulatory action of PTH on serum Ca, P, and osteocalcin, boron completely abolished the stimulatory effect of PTH on serum Mg. In conclusion, we have demonstrated for the first time that although boron by itself has no effect on bone mineral homeostasis, it appears to have synergistic enhancing effects on the action of E2 on Ca and Mg homeostasis in OVX rats.
Assuntos
Densidade Óssea/efeitos dos fármacos , Boro/administração & dosagem , Dieta , Estradiol/fisiologia , Ovariectomia , Animais , Boro/farmacologia , Cálcio/metabolismo , Cálcio/urina , Estradiol/sangue , Comportamento Alimentar , Feminino , Magnésio/metabolismo , Magnésio/urina , Osteocalcina/sangue , Hormônio Paratireóideo/farmacologia , Fósforo/metabolismo , Fósforo/urina , Ratos , Ratos Sprague-Dawley , Aumento de PesoRESUMO
Seven adolescent female runners with secondary amenorrhea and six adolescent eumenorrheic female runners received dietary supplements of 1200 mg calcium carbonate and 400 IU vitamin D/d for 12 months. Bone mineral density (BMD) of the axial skeleton was measured by dual photon densitometry at the beginning and end of the 12 month period. Plasma estradiol and ionized calcium concentration were also determined. Bone mineral density decreased in two of the amenorrheic subjects, with the lowest estradiol values concurrent with the severest training regimen and highest calcium intake. There was a significant decrease in plasma estradiol concentration in the amenorrheic runners (p less than 0.05). Plasma ionized calcium and estradiol explained 99% of the variation in BMD (r2 = 0.999). A significant inverse relationship between plasma estradiol and miles run/week was observed (r2 = -0.748). Adolescent female runners who train extensively and have low plasma estradiol levels may be adversely affecting BMD despite supplemental calcium and vitamin D intake.