The functional assessment of nutritional status: principles, practice and potential

Handgrip strength: Best practice for a rapid nutrition screening and risk stratification in male patients with alcoholic liver cirrhosis, a classification and regression tree analysis study

BACKGROUND

Rapid nutrition screening (NS) is vital for apt management in patients with alcoholic liver cirrhosis (ALC).

AIM

To identify a quick method of NS having high reliability and prognostic significance.

METHODS

NS of patients with ALC was assessed using mid-upper arm circumference (MUAC), handgrip strength (HGS), fat-free mass index (FFMI), and the Royal Free Hospital-Global Assessment (RFH-GA). Baseline clinical and biochemical information were recorded along with 90-day survival data. The classification and regression tree method was used to classify HGS, MUAC, and FFMI values as well nourished (WN), moderately malnourished (MM), and severely malnourished (SM), and their concordance with RFH-GA categories was assessed using Kendall tau-b coefficient. The prognostic proficiency of each method was tested by Cox regression analysis.

RESULTS

According to the RFH-GA, of 140 male patients with ALC, 13 of 140 (9.3%) were WN, 93 of 140 (66.4%) were MM, and 34 of 140 (26.8%) were SM. HGS has the strongest association with the RFH-GA (Kendall tau-b = 0.772; diagnostic accuracy -81.4%). HGS was found to be the independent predictor of 90-day mortality (26 of 140 [18.6%]; hazard ratio, 0.93; 95% CI, 0.88-0.98; P = 0.002) after adjusting for age, body mass index, and disease severity. The hazard of mortality was 8.5-times higher in patients with ALC with HGS < 22 kg as compared with those with HGS > 29.

CONCLUSION

HGS is a reliable tool for rapid NS. HGS < 22 kg suggests a high risk for severe malnutrition and is strongly associated with short-term mortality in male patients with ALC.

Personalized nutrition diagnostics at the point-of-need

Micronutrient deficiency is widespread and negatively impacts morbidity, mortality, and quality of life globally. On-going advancements in nutritional biomarker discovery are enabling objective and accurate assessment of an individual's micronutrient and broader nutritional status. The vast majority of such assessment however still needs to be conducted in traditional centralized laboratory facilities which are not readily accessible in terms of cost and time in both the developed and developing countries. Lab-on-a-chip (LOC) technologies are enabling an increasing number of biochemical reactions at the point-of-need (PON) settings, and can significantly improve the current predicament in nutrition diagnostics by allowing rapid evaluation of one's nutritional status and providing an easy feedback mechanism for tracking changes in diet or supplementation. We believe that nutrition diagnostics represents a particularly appealing opportunity over other PON applications for two reasons: (1) healthy ranges for many micronutrients are well defined which allows for an unbiased diagnosis, and (2) many deficiencies can be reversed through changes in diet or supplementation before they become severe. In this paper, we provide background on nutritional biomarkers used in nutrition diagnostics and review the emerging technologies that exploit them at the point-of-need.

Functional assessment of nutrition status

Functional status assessment has been recommended as a part of a complete nutrition assessment for decades, but the specific components of this assessment have eluded a consensus definition. The recent Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition consensus criteria for identification of malnutrition include functional assessment determined by handgrip dynamometry, with the understanding that this technique is not practical for use in some patient populations. Other techniques for functional assessment include physical performance measures such as timed gait and chair stands, as well as activities of daily living tools such as the Katz Index, Lawton Scale, and Karnofsky Scale Index. Manual muscle testing and computed tomography scan assessment of lean tissue are other tools that show promise in correlating functional and nutrition assessments. Functional assessment parameters may be least well correlated with nutrition status in older individuals. Despite a number of scientific studies of a variety of tools for functional assessment, there is to date no definitive tool for use in all individuals in all settings. Nutrition scientists and clinicians must continue to collaborate with colleagues in physical and occupational therapy, geriatrics, and nursing to refine current functional assessment tools to more effectively correlate with nutrition and malnutrition assessment parameters.

Alimentación y estado nutricional de los niños en zonas palúdicas de Antioquia (Colombia)

Introducción: Malaria, parasitosis intestinales y desnutrición interactúan en los habitantes de zonas palúdicas, en particular en niños. Objetivo: Medir el estado nutricional de niños (4-10 años) con malaria y algunos aspectos del consumo alimentario familiar en dos zonas maláricas del departamento de Antioquia. Metodología: Estudio transversal en niños que consultaron por paludismo. Diseño muestral aleatorio. Resultados: A) Consumo alimentario familiar: 74% obtenían regularmente alimentos de criar animales menores, huerta casera o ambos; 17% recibían regularmente alimentos, dinero o ambos; consumo de alimentos fuentes de vitamina A (veces/semana): carnes-vísceras animales 1, leche y huevos 2-3 cada uno, frutas con provitamina A. Satisfacción alimentaria de requerimientos nutricionales familiares de fuentes de vitamina A: 55% (grado bajo-medio). B) Estado nutricional infantil: Riesgo de desnutrición: 52% crónica, 15% aguda; parásitos intestinales patógenos 80%; promedio de hemoglobina pretratamiento 10.3 gr/dL (6.39 mmol/L) y al día 30 en 11.8 gr/dL (7.32 mmol/L); promedio de retinol pretratamiento de 19.1 µg/dL (0.67 µmol/L) y al día 30 31.2 µg/dL (1.09 µmol/L). Conclusiones: La desnutrición crónica amenaza a ≥50% de los niños; esa frecuencia es 3-4 veces la encontrada en Colombia.  No hubo asociación estadísticamente significativa entre estado nutricional y las variables asociadas a obtención-consumo alimentario. Quizás esta ausencia de relación se deba a que las variables usadas para medir estas condiciones no sean adecuadas o se hayan medido de manera inapropiada. 

Multiple micronutrient deficiencies: future research needs

There has been a rising current of calls for a moratorium on international nutritional research in favor of an investment in intervention programs, per se. The topic of multiple-micronutrient supplementation reviewed at the International Workshop on Multi-Micronutrient Deficiency Control in the Life Cycle (May 30-June 1, 2001) has confirmed once again, however, the intimate interaction between program development and a supporting agenda of applied research. The areas of research required to produce successful intervention programs include biologic availability, safety and efficacy, communications and behavior, effectiveness, cost-effectiveness (efficiency), and food and pharmaceutical technology. Attention to safety and surveillance for unintended adverse effects has acquired new relevance as we analyze the multi-center International Research on Infant Supplementation (IRIS) I studies. All professionals involved in research projects in this area must assure both the quality and reliability of investigations and adhere to the highest principles of ethical conduct of research in human studies. The fundamental principles of research design and hypothesis development, quality assurance, reliability of measurements, and sound and unbiased interpretation of findings apply to all experimental science, and must be guaranteed for this mission. Agencies, academic institutions, and industry alike must work to create a system in which researchers can uphold these standards, and realize at the same time that the area of multi-micronutrient supplementation in developing countries can be a fertile area for training future researchers.

Laboratory issues: use of nutritional biomarkers

Biomarkers of nutritional status provide alternative measures of dietary intake. Like the error and variation associated with dietary intake measures, the magnitude and impact of both biological (preanalytical) and laboratory (analytical) variability need to be considered when one is using biomarkers. When choosing a biomarker, it is important to understand how it relates to nutritional intake and the specific time frame of exposure it reflects as well as how it is affected by sampling and laboratory procedures. Biological sources of variation that arise from genetic and disease states of an individual affect biomarkers, but they are also affected by nonbiological sources of variation arising from specimen collection and storage, seasonality, time of day, contamination, stability and laboratory quality assurance. When choosing a laboratory for biomarker assessment, researchers should try to make sure random and systematic error is minimized by inclusion of certain techniques such as blinding of laboratory staff to disease status and including external pooled standards to which laboratory staff are blinded. In addition analytic quality control should be ensured by use of internal standards or certified materials over the entire range of possible values to control method accuracy. One must consider the effect of random laboratory error on measurement precision and also understand the method's limit of detection and the laboratory cutpoints. Choosing appropriate cutpoints and reducing error is extremely important in nutritional epidemiology where weak associations are frequent. As part of this review, serum lipids are included as an example of a biomarker whereby collaborative efforts have been put forth to both understand biological sources of variation and standardize laboratory results.

Micronutrients: interaction between physical activity, intakes and requirements

The present literature review examines the following questions: (a) What is the evidence that micronutrient requirements are increased in physically active people? (b) Is there an association between physical activity and micronutrient intake? (c) Are there any significant differences between indices of micronutrient status between physically active and inactive people? The available data suggest that micronutrient requirements are increased in physically active people because of increased losses through sweat, urine and faeces, and an increased need for defence against free radicals. However the evidence is controversial, and it is not possible to make any quantitative estimations. Micronutrient requirements in moderately active people are not likely to be very much above the levels recommended for the general population. The intake of micronutrients increases with increasing energy intake. Therefore, physically highly active people (athletes) have higher micronutrient intakes than untrained subjects. However, moderate physical activity does not necessarily affect daily micronutrient intake. The available indices of micronutrient status do not support the belief that micronutrient status is compromised in highly trained athletes, even without use of dietary supplements. Hence, there are no reasons to believe that the situation would be different in people who are only moderately active. The results suggest that micronutrient status is adequate for health and functional performance in physically active people who follow a normal, mixed Western diet.

The reliability of muscle function analysis using different methods of stimulation

BACKGROUND

The purpose of our study was to determine the reliability of nonvolitional muscle function analysis (MFA) by determining the day-to-day and within-day reliability of conventional electrical stimulation and a newer, magneto-electrical stimulation method, using standard laboratory methodology.

METHODS

Ten healthy, human immunodeficiency virus-negative adult men volunteered as subjects. MFA consisted of measuring the maximal relaxation rate, for magneto-electrical stimulation at 1 Hz and conventional electrical stimulation at 20 Hz, and force-frequency ratios using conventional electrical stimulation at 10 Hz:20 Hz and 10 Hz:50 Hz. Within-day and day-to-day reliability were determined by calculating the coefficient of variation (CV) for all subjects.

RESULTS

Maximal relaxation rate using magneto-electrical stimulation had a significantly lower CV compared with the other nonvolitional MFA methods (p = .002).

CONCLUSIONS

Maximal relaxation rate using magneto-electrical stimulation was more reliable and technically easier than the other muscle function parameters examined. However, the day-to-day CV of muscle function parameters is larger than traditional nutrition assessment techniques. Development within the field should strive to improve testing techniques so that the reliability of MFA will allow definition of a range of normal values against which an individual's value can be compared. Until this is available, the precision and reliability of MFA restrict its use to research and population studies.

Use of dietetic-specific nutritional diagnostic codes in clinical reasoning relevant to the nutritional management of core clinical outcome indicators in hemodialysis patients

The Health Care Financing Agency (HCFA) has recommended conscientious monitoring of four core outcome indicators (anemia, albumin, treatment adequacy, and hypertension) by the end stage renal disease (ESRD) health care team. Dietetic-specific nutritional diagnostic categories (D-S NDCs) can be a powerful tool in guiding renal nutrition specialists through the clinical reasoning required to diagnose and clinically correct nutrition-related problems in hemodialysis (HD) patients. The purpose of this article is to portray one clinician's dual use of D-S NDCs to identify the nutritional problem responsible for poor performance and determine nutritionally treatable causes. Although four indicator-specific sets of D-S NDCs commonly used in the nutritional assessment of anemia, albumin, treatment adequacy and hypertension were identified and referenced, seven codes were consistently repeated. These D-S NDCs were (1) altered nutritional biochemistry integrity; (2) absence of/limited nutritional service; (3) deficit in nutrition knowledge; (4) imbalance of nutrient/fluid; (5) nutrition misinformation; (6) toxicity of nutrient/nutrient end-product; and (7) possibility of developing a specific disease. Thus, in ESRD, use of D-S NDCs shows the implicit role of the registered dietitian in disease prevention, management of altered nutrient disposition, and patient education.

Indicators of vitamin and mineral status in athletes' blood: a review

This review examines the hypothesis that vitamin and mineral status in athletes is inadequate for optimal sports performance. The review is based on indicators determined from blood and on studies published since 1980. Most of the studies did not find micronutrient status in athletes to be different from untrained controls. The serum ferritin concentration in females was lower than in males (27 vs. 78 micrograms.L-1), and the prevalence of low serum ferritin concentration was higher in female athletes than in untrained female controls (37 vs. 23%). Supplementation of water-soluble vitamins and iron was associated with an improvement in the corresponding indicators. Excluding a few studies with mildly anemic subjects, improvements in indicators of micronutrient status were not associated with enhanced athletic performance. Consequently, the levels of indicators of micronutrient status seen in athletes' blood were apparently compatible with optimal physical performance.

Observations on the nutrient intakes of eating-dependent nursing home residents: underutilization of micronutrient supplements

OBJECTIVE

To estimate the intakes of essential nutrients by eating-dependent nursing home residents (EDR).

METHODS

This study was done in a 190 bed VA nursing home. Thirty-four EDR were selected for the study. Clinical data base which included age, sex, primary diagnosis, body mass index, albumin, hematocrit, activities of daily living status, decubitus ulcer medications and use of multivitamin/trace mineral supplement were recorded from the medical records. Caloric and essential nutrient intakes were determined over a 3-day period by a registered dietitian.

RESULTS

Seventy percent (24/34) residents in the study group were underweight (body mass index < 23 kg/m2), 26% were hypoalbuminemic (serum level < 3.5 g/dl), 50% were anemic (hematocrit < 37%); and 38% had pressure ulcers. In 88% EDR, the dietary intakes of three or more essential nutrients were below 50% of the RDA. Most frequent and severely deficient were zinc, copper, and vitamin B6. Despite the inadequate essential micronutrient intakes in the majority of EDR, only 35% received a multivitamin supplement and only 3% received a trace mineral supplement. A survey of 30 other VA nursing homes indicated generally similar findings to those in the Milwaukee facility with regard to the high frequency for eating-dependence, and the low frequency for administration of multivitamin and trace mineral supplements.

CONCLUSIONS

Despite eating supervision and assistance, the majority of EDR have inadequate intakes of numerous essential macro- and micronutrients. The deficient micronutrient intakes could be normalized by administration of a multivitamin/trace mineral supplement daily. Nevertheless, only a minority of EDR in VA nursing homes currently receive such a supplement.

Alteration of circulating micronutrients with overt and occult infections in anaemic Guatemalan preschool children

Clinical and laboratory data to define conditions of apparent health, localised infection or inapparent infection were available for 74 anaemic Guatemalan preschool children in the baseline phase of a clinical trial of the effect of iron and vitamin A on haematological status to be correlated with serum levels of four circulating micronutrients--iron, zinc, copper and retinol--known to be influenced by activation of the acute-phase reaction. Upon enrolment, only 29.7% of the children were free of all evidence of infection, 36.5% had one or more localised conditions detected on clinical examination, and 33.8% had an elevated white cell count and/or sedimentation rate, without localising features. These were classified as 'inapparent infections'. With respect to the healthy children, levels of iron, zinc, and retinol declined and copper generally increased in the four categories of clinical infections (acute respiratory infection, dermal infections, conjunctivitis, and 'other') but were also displaced in inapparent infections. Some activation of the acute-phase response in anaemic children may occur in the absence of clinical findings. Care must be taken in interpreting circulating micronutrient levels in relation to nutritional status in such population.

Malnutrition in AIDS

Malnutrition, weight loss, and chronic diarrhea are common findings in patients infected with human immunodeficiency virus (HIV), and many traditional and nontraditional dietary approaches have been suggested. This article examines the mechanisms and pathophysiology of wasting in HIV, and the evidence for malnutrition of protein, energy, and micronutrients in patients with the acquired immunodeficiency syndrome (AIDS). The article concludes with a review of dietary therapy in AIDS patients.

Pathways to the impairment of human nutritional status by gastrointestinal pathogens

Gastrointestinal pathogens are of three varieties, those that can, and often do, take the life of the host, those that infect transiently and rarely are life-threatening, and those (parasites) that establish a relatively prolonged residence or colonization of the host's alimentary tract. In the case of the second form, if infections are recurrent, both catabolic effects during the episode and failure to digest foods and/or absorb nutrients results. Similarly, catabolic wastage through activation of the acute phase response, and interference with the host's acquisition of nutrients by maldigestion, malabsorption, intestinal losses and competition with the parasite burden can impair growth and nutrition with helminthic infections. Growth and nutrition with respect to all of the macronutrients and virtually all of the micronutrients have been documented to be adversely affected by gastrointestinal pathogens. For its burgeoning importance as a worldwide health problem, both with the HIV virus as a direct intestinal pathogen and with the opportunistic gut infections occurring in the immunocompromised host, AIDS represents the emerging context of the impairment of nutritional status by intestinal pathogens.

[Evaluation of nutritional status of adult middle class healthy subjects. Energy and protein intake, anthropometry, blood biochemical tests, and immunocompetence tests]

Nutritional status was assessed in 151 middle-class healthy adult individuals (69 medical students, 18-29 y, 34 males, 35 females); 48 university personnel, 30-49 y, 24 males, 24 females; and their older relatives, 34 subjects, 50-79 y, 19 males, 15 females) living in Botucatu, S. Paulo. Methods included anthropometric measurements, energy and protein intakes, blood biochemical analyses and cutaneous delayed hypersensitivity tests. Anthropometric measurements showed higher values in men, with the exception of the triceps skinfold thickness (higher in women) and of the arm fat area (higher in the older age female groups); aging seemed to be associated with increases of weight, arm muscle variables and with arm fat accumulation in women and with increases of arm muscle variables in men. The values for anthropometric measurements were in general higher than those found in other Brazilian studies; on the other hand, they approximate to but do not entirely agree with the data representative of the international referential adult population: differences were mainly concerned with body weight and upper arm muscle parameters, which were lower in our sample. As regards energy intake, values found in subjects under 50 years of age were lower than the recommended dietary allowances; averages found for protein intake were above the level recommended by WHO/FAO/UNU (1985). The mean values for serum proteins and lipids were similar to those of referential data. As regards the hypersensitivity tests, it was found that none of the individuals challenged with four antigens (PPD, Candidin, Vaccinia and phytohemagglutinin) presented less than two positive skin reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Laboratory tests and nutritional assessment. Protein-energy status

1. There is no one definitive laboratory test, group of tests, or indices that are satisfactory for the assessment of protein-calorie status. 2. Clinical evaluation remains the simplest, most widely available, most reproducible, and wisest method. It is satisfactory for the majority of clinical situations. 3. The laboratory should be used selectively and to complement clinical evaluation. Routine testing must be relegated to research protocols. 4. Always include some assessment of inflammation (for example, C-reactive protein, erythrosedimentation rate [ESR]), because its presence affects the interpretation of all the other tests. 5. The pathophysiologic effects of the underlying disease, especially in hospitalized patients, will affect the interpretation of every one of the laboratory tests. 6. Nutritional status often impacts more on the interpretation of commonly performed laboratory tests than laboratory tests impact on the assessment of nutrition.

Energy expenditure and body composition in patients with anorexia nervosa

Blood biochemistry, body composition, and resting energy expenditure were studied in 25 patients with anorexia nervosa admitted to hospital during a period of 18 months. The patients' ages ranged from 12.9 to 17.2 years, and the abnormal feeding history from 3 to 12 months. Blood chemistry values were in the normal range, but fat body mass and lean body mass were reduced and extracellular water volume was expanded beyond normal values. Resting energy expenditure was reduced to 49% to 91% of values predicted by the Harris-Benedict equations. Substrate use after overnight fast indicated an abnormally high use of carbohydrates. Significant correlations were found between extracellular water volume and triceps skin-fold thickness, mid-arm muscle circumference and lean body mass, and substrate use and weight loss as a percentage of initial weight. We suggest that these simple anthropometric measurements can be used to assess and monitor the refeeding of patients with anorexia nervosa.

Effects of dietary copper on human autonomic cardiovascular function

Heart rate and blood pressure responses during supine rest, orthostasis, and sustained handgrip exercise at 30% maximal voluntary contraction were determined in eight healthy women aged 18-36 years who consumed diets varying in copper and ascorbic acid content. Copper retention and plasma copper concentration were not affected by diet. Enzymatic, but not immunoreactive, ceruloplasmin was lower (p less than 0.05) after the low copper and high ascorbic acid diet periods. Diet had no effect on resting supine heart rates, orthostatic responses in heart rate and blood pressure, or standing resting blood pressure. Systolic and diastolic blood pressures were increased significantly (p less than 0.05) during the handgrip test at the end of the low copper and ascorbic acid supplementation periods. Also, the ratio of enzymatic to immunoreactive ceruloplasmin decreased significantly during these dietary treatments. The mean arterial blood pressure at the end of the handgrip test was negatively (p less than 0.0004) correlated with the ceruloplasmin ratios. These findings indicate a functional alteration in human blood pressure regulation during mild copper depletion.

Measurement of vitamin C in blood components by high-performance liquid chromatography. Implication in assessing vitamin C status

The fact that platelets, PMN leukocytes, and MN leukocytes concentrate ascorbic acid suggests that vitamin C has an important role in their physiological functions. The question still remains as to which one of the cells best reflects vitamin C status. The ascorbic acid content of PMNs and platelets correlates positively with plasma concentration and supplementation with vitamin C, as shown in Evans et al. They also found that MN leukocytes, in contrast, do not show any such relationship; however, MN leukocytes maintain the highest levels of ascorbic acid and play a very important function in immunocompetence. We have found that with a limited number of subjects, ascorbic acid content of MN and PMN leukocytes correlates positively with plasma ascorbic acid, but there was no correlation between platelets and plasma ascorbic acid (unpublished results). Therefore, further work is necessary to evaluate these three blood components for the best cellular marker of vitamin C status. We have developed a reversed-phase HPLC method for ascorbic acid that can be used in conjunction with our cellular differential centrifugation technique for the determination of ascorbic acid in relatively pure blood cell fractions. The chromatographic method is simple, sensitive, and automated. It clearly resolves ascorbic acid, which is the major form of the vitamin found in vivo and is not prone to interference by sugars, carbohydrates, or nucleotides.

Distribution of vitamins A and E in blood and liver of rats depleted of vitamin A or vitamin E

Young Sprague-Dawley male rats (n = 150) were fed a semipurified diet, either without vitamin A (VA), without vitamin E (VE) or supplemented with both vitamins A and E (control). At the end of weeks 0, 1, 3, 5, 6, 7, 8 and 9, groups of rats were anesthetized with methoxyflurane, and blood was collected by cardiac puncture until the rat was exsanguinated. The liver was excised. Whole blood (WB) from each rat was fractionated into plasma (PLA), leukocytes (LEU), platelets (PLT) and erythrocytes (RBC). Each blood component was extracted with heptane and livers were extracted with CHCl3/CH3OH (2:1, v/v). The extracts were analyzed for VA and VE by high performance liquid chromatography. The relationship among blood components in the loss of VA was PLT = LEU greater than WB greater than PLA. The relationship among blood components in the loss of VE was PLA greater than RBC greater than WB greater than LEU = PLT. VA and VE levels in other blood components decreased precipitously between weeks 0 and 4 in the animals placed on deficient diets. These results and correlation analyses between vitamin contents of blood components and of livers indicate inadequacies for the use of certain blood components as monitors of lipid-soluble vitamin status in the rat.

Trace element metabolism in the fetus and neonate

The effects of trace metal nutrition on the fetus and neonate have been described. Since very little research has been done with the human fetus and neonate, much of our knowledge must be extrapolated from animal studies. In addition, most of the work centres around the effects of copper and zinc nutrition. Nutritional requirements (when known) for both enteral and total parenteral feeding of certain trace metals, as well as the bioavailability, have been discussed. Finally, methods of assessment of trace metal nutritional status have been discussed. These include direct measurement of metal concentrations and determination of biochemical indicators, such as metal-dependent enzyme activities--both of which are static indicators of nutritional status, and functional assessment of nutritional status which is a dynamic measure of trace metal nutrition and includes tests measuring the effects of metal nutrition on the function of cells, tissues, organs, and the host in general.

Assessment of nutritional status: functional indicators of pediatric nutriture

The author speaks to the need to update our conceptual approach and our technical capacities for nutritional status assessment and to devise innovative ways to apply them to pediatric practice. The article discusses and evaluates conventional, static indices of nutriture and the importance of history and the physical examination. Focus is then placed on the concept of the functional assessment of nutritional status and its potential for clinical use.

Biochemical, metabolic, and clinical role of copper in human nutrition

Veterinary nutritional science has embraced the study of copper for decades, but copper has languished as an orphan among human nutritionists because of the obscurity of clinical copper-deficiency states in man. As medical investigators, we may have gone down a long road, missing the forest for the trees. Indeed, overt copper-deficiency syndromes in humans have been recognized since the 1960s, and the list of contributing factors is expanding. Unwise self-medication with megadoses of zinc, for instance, might produce a mini-epidemic of copper deficiency. Moreover, induced copper deficiency may someday prove to be a legitimate therapeutic intervention in some disease states. But, the influence of subtle differences in dietary intakes of copper on human health may be much more important than frank copper depletion. Moreover, the recognition of disordered copper metabolism simulating a deficiency state--as occurs in Menkes' KHS and in variant Elhers-Danlos syndrome--has important implications. The full description of the relationship that thionein and other intracellular proteins might have in the etiology of these alterations has yet to be written. The elegance of the interplay of biochemical defects, physiological dysfunction, and clinical manifestations in copper metabolism is virtually unmatched in nutritional biology; yet, our present abilities to determine human copper status are limited. Now that it is clear that intracellular redistribution as well as total-body depletion can effect the disruption of copper-dependent functions, a concerted effort to improve status assessment through the use of functional indices should become a high priority. Finally, the pursuit of the bases of copper's involvement in host defenses, antiotoxidant protection and carbohydrate metabolism--functions in which clear links to established mammalian cuproenzyme are at present elusive--should provide exciting substrate for investigators for years to come.

Changes in plasma zinc content after exercise in men fed a low-zinc diet

For 30 days five healthy men aged 23-57 yr consumed a diet adequate in zinc (8.6 mg/day); they ate a low-zinc diet (3.6 mg/day) for the next 120 days and then received a zinc-supplemented (33.6 mg/day) diet for 30 days. Copper intake was constant at 1.8 mg/day. Aerobic capacity was determined periodically during each diet period. Relative zinc balance (% of control) declined during depletion (r = -0.28, P less than 0.009). Pre- and postexercise zinc concentrations decreased when dietary zinc was restricted (r = -0.61, P less than 0.0001 and r = -0.78, P less than 0.0001) and increased with supplementation (r = 0.61, P less than 0.008 and r = 0.76, P less than 0.0003, respectively). Both plasma zinc and hematocrit increased (P less than 0.01) after maximal exercise. To minimize the effect of hemoconcentration during exercise, the van Beaumont quotient (J. Appl. Physiol. 34: 102-106, 1973) was calculated using pre- and postexercise hematocrit and plasma zinc. The initial quotient of 1.8 +/- 1.8% (mean +/- SE) declined (P less than 0.05) to -7.4 +/- 2.3% during depletion. With zinc repletion, the quotient increased to 6.9 +/- 3.6%, which was greater (P less than 0.05) than the quotient in depletion but similar to the initial quotient. The quotient was a strong predictor (r = 0.71, P less than 0.0005) of the change in relative zinc balance during zinc depletion. In contrast, no changes were found in plasma copper content. These data suggest that zinc mobilization from tissues is impaired during zinc depletion, and they validate the use of the van Beaumont quotient as an index of change in body zinc stores.