122 The nutrition handbook for food processors for enzyme function. Symptoms usually appear within the first months of life, and can result in death in early childhood. In clinical copper deficiency, the most common defects are: cardiovascular and haematological disorders including iron-resistant anaemia, neutropenia and thrombocytopenia; bone abnormalities including osteoporosis and fractures; and alterations to skin and hair texture and pigmentation.Immunological changes have also been indicated. 9.32These changes may be accompanied by depressed serum copper and blood cupro- enzymes, with caeruloplasmin concentrations observed at 30% of normal.6 It has been clearly demonstrated that very many of the changes induced by severe copper deficiency are also risk factors for ischaemic heart disease in humans. Human copper depletion studies have produced impaired glucose clearance, blood pressure changes, electrocardiographic irregularities and significantly increased LDL cholesterol with decreased HDL cholesterol. In copper-deficient animals, cardiovascular disorders observed include lesion and rupture of blood vessels, cardiac enlargement, myocardial degeneration and infarction(MI). It has been argued that copper deficiency is the only nutritional deficit known to affect adversely so many risk factors for ischaemic heart disease. The proposed link between copper deficiency and cardiovascular disease is supported by data gathered from studies of cardiovascular patients Post-mortem measurement of tissue copper has revealed lower-than-normal opper concentrations in ischaemic hearts, in the liver and heart of individuals with severe atherosclerosis, and in leucocytes of patients with highly occluded coronary arteries A variety of mechanisms may contribute to the cardiovascular effects of copper deficiency. There is evidence for alterations in the activity of copper- dependent enzymes, increased oxidative stress and damage to biomolecules, and interference with the maintenance of blood pressure. An interaction of these three mechanisms of damage has been proposed to have even further potential for harm.36 which need not be limited to cardiovascular defects. The adverse effects elicited by copper deficiency are numerous and as varied as the roles of copper in health. In the light of this, it has been proposed that long-term sub-clinical opper deficiency may contribute to the pathogenesis of a number of degenera- tive and inflammatory conditions. 37 5.6 Copper toxicity Copper toxicity is rare because levels in food and water are generally low and because increased dietary intake results in decreased absorption and increased excretion. Cases of both acute and chronic poisoning have, however, been reported. Acute toxicity has been known to result from accidental or deliberate consumption of copper salts and, more commonly, from contamination of drinks by copper containers. A 1957 report of contamination of cocktails stored for just two hours in a metal cocktail shaker was used in 1988 by US Environmental Pro- tection Agency(EPA)Office of Drinking Water to derive drinking water regula
for enzyme function. Symptoms usually appear within the first months of life, and can result in death in early childhood.31 In clinical copper deficiency, the most common defects are: cardiovascular and haematological disorders including iron-resistant anaemia, neutropenia and thrombocytopenia; bone abnormalities including osteoporosis and fractures; and alterations to skin and hair texture and pigmentation.23 Immunological changes have also been indicated.19,32 These changes may be accompanied by depressed serum copper and blood cuproenzymes, with caeruloplasmin concentrations observed at 30% of normal.6 It has been clearly demonstrated that very many of the changes induced by severe copper deficiency are also risk factors for ischaemic heart disease in humans. Human copper depletion studies have produced impaired glucose clearance,33 blood pressure changes,34 electrocardiographic irregularities and significantly increased LDL cholesterol with decreased HDL cholesterol.21 In copper-deficient animals, cardiovascular disorders observed include lesion and rupture of blood vessels, cardiac enlargement, myocardial degeneration and infarction (MI).33 It has been argued that copper deficiency is the only nutritional deficit known to affect adversely so many risk factors for ischaemic heart disease.35 The proposed link between copper deficiency and cardiovascular disease is supported by data gathered from studies of cardiovascular patients. Post-mortem measurement of tissue copper has revealed lower-than-normal copper concentrations in ischaemic hearts, in the liver and heart of individuals with severe atherosclerosis, and in leucocytes of patients with highly occluded coronary arteries.33 A variety of mechanisms may contribute to the cardiovascular effects of copper deficiency. There is evidence for alterations in the activity of copperdependent enzymes, increased oxidative stress and damage to biomolecules, and interference with the maintenance of blood pressure. An interaction of these three mechanisms of damage has been proposed to have even further potential for harm,36 which need not be limited to cardiovascular defects. The adverse effects elicited by copper deficiency are numerous and as varied as the roles of copper in health. In the light of this, it has been proposed that long-term sub-clinical copper deficiency may contribute to the pathogenesis of a number of degenerative and inflammatory conditions.37 5.6 Copper toxicity Copper toxicity is rare because levels in food and water are generally low and because increased dietary intake results in decreased absorption and increased excretion.38 Cases of both acute and chronic poisoning have, however, been reported. Acute toxicity has been known to result from accidental or deliberate consumption of copper salts and, more commonly, from contamination of drinks by copper containers.6 A 1957 report of contamination of cocktails stored for just two hours in a metal cocktail shaker was used in 1988 by US Environmental Protection Agency (EPA) Office of Drinking Water to derive drinking water regula- 122 The nutrition handbook for food processors
measuring intake of nutrients and their effects: the case of copper 123 tions which are still in place. Acute toxicity results, initially, in symptoms such as abdominal pain, nausea, vomiting and diarrhoea. These gastrointestinal effects are often sufficiently severe and prompt to prevent systemic toxicity which, like chronic copper poisoning, is associated with liver damage. Chronic toxicity has most often been caused by contaminated water supplies, and occasionally by contamination of haemodialysis equipment by copper parts The highest intake which has been shown experimentally to produce no adverse effects is defined as the No-Observed-Adverse-Effects-Level (NOAEL) While a NOael of 4 mg/ in drinking water has been observed for acute effects, a higher NOAEL of 10mg supplemental copper per day has been demonstrated to provoke no ill effect upon liver function after 12 weeks. 4 The IS Food and nutrition board have used the latter value to calculate a theoreti cal Tolerable Upper Intake Level (UL), defined as the highest level of daily intake considered likely to pose no threat to the health of almost all individuals. The UL is in agreement with the World Health Organizations provisional maximum tolerable daily intake(PTDD), an estimate of the amount that can be ingested daily over a lifetime without appreciable risk to health In drinking water, copper levels vary considerably depending on factors including the ph and hardness of the water supply and the length of piping. In some systems, copper salts are added to control the growth of algae. Suggested pper limits for copper in drinking water differ world-wide, and while some are based on health issues, others consider only aesthetic values. The issue is currently under review by several international groups. Table 5.3 shows current permissible levels of copper in drinking water, and recommended limits of total copper intake A number of disorders of copper homeostasis can result in toxicity leading to liver cirrhosis at dietary copper levels which are tolerated by the general popu lation. Copper-induced cirrhosis is mainly restricted to children, possibly because Table 5.3 Recommended limits of copper intake Reference Value Copper limit Source In drinking water( UK standard Water Quality)Regulation WHO standard 2.0 ines for Drinking Water Quality, EU standard 98/83L30,32-54 LXlImun EPA Drinking Water Regulations, 1988 contaminant Total intake(mg/d) Food and Nutrition Board. 2001 WHO PTDI 10.0(women) World Health Organization, 1996 12.0(men)
tions which are still in place.39 Acute toxicity results, initially, in symptoms such as abdominal pain, nausea, vomiting and diarrhoea. These gastrointestinal effects are often sufficiently severe and prompt to prevent systemic toxicity which, like chronic copper poisoning, is associated with liver damage. Chronic toxicity has most often been caused by contaminated water supplies, and occasionally by contamination of haemodialysis equipment by copper parts.40 The highest intake which has been shown experimentally to produce no adverse effects is defined as the No-Observed-Adverse-Effects-Level (NOAEL). While a NOAEL of 4 mg/l in drinking water has been observed for acute effects,41 a higher NOAEL of 10 mg supplemental copper per day has been demonstrated to provoke no ill effect upon liver function after 12 weeks.42 The US Food and Nutrition Board have used the latter value to calculate a theoretical Tolerable Upper Intake Level (UL), defined as the highest level of daily intake considered likely to pose no threat to the health of almost all individuals. The UL is in agreement with the World Health Organization’s provisional maximum tolerable daily intake (PTDI), an estimate of the amount that can be ingested daily over a lifetime without appreciable risk to health. In drinking water, copper levels vary considerably depending on factors including the pH and hardness of the water supply and the length of piping. In some systems, copper salts are added to control the growth of algae.16 Suggested upper limits for copper in drinking water differ world-wide, and while some are based on health issues, others consider only aesthetic values. The issue is currently under review by several international groups.39 Table 5.3 shows current permissible levels of copper in drinking water, and recommended limits of total copper intake. A number of disorders of copper homeostasis can result in toxicity leading to liver cirrhosis at dietary copper levels which are tolerated by the general population. Copper-induced cirrhosis is mainly restricted to children, possibly because Measuring intake of nutrients and their effects: the case of copper 123 Table 5.3 Recommended limits of copper intake Reference Value Copper limit Source In drinking water (mg/l) UK standard 3.0 Water Supply (Water Quality) Regulations, 1989 WHO standard 2.0 WHO Guidelines for Drinking Water Quality, 1993 EU standard 2.0 EU Directive 98/83 L330, 32–54 US maximum 1.3 EPA Drinking Water Regulations, 1988 contaminant level Total intake (mg/d) US UL 10.0 Food and Nutrition Board, 2001 WHO PTDI 10.0 (women) World Health Organization, 1996 12.0 (men)
124 The nutrition handbook for food processors of the lower capacity of their biliary excretory mechanisms. Indian Childhood Cirrhosis (ICC)is a fatal condition of copper metabolism which was, at one time, a major cause of infant mortality on the Indian subcontinent. ICC sufferers usually infants aged between 6 months and 5 years, are often found to have been exposed at an early age to milk contaminated with copper from untinned brass or copper vessels. High copper intake, however, is not thought to be the sole cause of the illness; both environmental and genetic components are thought to contribute. Cases of a similar infantile condition have been reported in Germany and in the Tyrol, Austria. Incidence of both ICC and Tyrolean Infantile Cirrhosis has dropped in recent years. One possible explanation is reduced use of brass vessels, while an alternative is the dilution of the responsible gene by increased population mobility and fewer consanguineous marriages. A rare inherited disorder of copper metabolism leads to Wilson's disease, in which copper cannot be properly transported out of the liver and so accumulates to toxic levels. When the hepatocytes die, copper is released into the plasma and deposited in other tissues including the central nervous system. Treatment of Wilsons disease is aimed at removing copper from the body and preventing its reaccumulation 5.7 General limitations in assessing nutrient intake As for any nutrient where deficiency and toxicity are issues, the reliable assess- ment of intake is paramount. The ultimate aim of defining optimal dietary intakes is hampered by difficulties in determining certain key facts, namely, individual copper intakes and status. Dietary intake can be assessed by a number of methods, involving either the recording of actual consumption(prospective) or the assess- ment by questionnaires of diet in the recent past (retrospective). At each stage in the application of any method, errors are introduced, producing as a result either a systematic bias or random deviations from the true values. Of the methods in ommon use, the weighed dietary record is widely accepted to be the most accu- rate, but it requires a considerable amount of co-operation from human subjects This disadvantage may give rise to substantial bias, most likely toward under reporting habitual dietary intakes. In clinical practice the most frequently used method of dietary assessment is the diet history, which is highly dependent on accurate recall by the individual. It is possible to verify these reports, to some extent, by independent methods. Under- and over-estimation of an individuals total food intake can be identified by measuring total energy expenditure, either directly, using the doubly-labelled water technique, or indirectly, by calculatin basal metabolic rate. Another check is a comparison of the individuals 24-hour urinary nitrogen output with the reported protein intake. The accuracy of these methods is limited either by the involvement of estimates, or by reliance on the assumption that body weight is constant One means of assessing nutrient requirements is the metabolic balance study The aim of a balance study is to compare the intake of a nutrient with the amount
of the lower capacity of their biliary excretory mechanisms.38 Indian Childhood Cirrhosis (ICC) is a fatal condition of copper metabolism which was, at one time, a major cause of infant mortality on the Indian subcontinent. ICC sufferers, usually infants aged between 6 months and 5 years, are often found to have been exposed at an early age to milk contaminated with copper from untinned brass or copper vessels.43 High copper intake, however, is not thought to be the sole cause of the illness; both environmental and genetic components are thought to contribute.44 Cases of a similar infantile condition have been reported in Germany and in the Tyrol, Austria.45,46 Incidence of both ICC and Tyrolean Infantile Cirrhosis has dropped in recent years. One possible explanation is reduced use of brass vessels, while an alternative is the dilution of the responsible gene by increased population mobility and fewer consanguineous marriages. A rare inherited disorder of copper metabolism leads to Wilson’s disease, in which copper cannot be properly transported out of the liver and so accumulates to toxic levels. When the hepatocytes die, copper is released into the plasma and deposited in other tissues including the central nervous system. 47 Treatment of Wilson’s disease is aimed at removing copper from the body and preventing its reaccumulation. 5.7 General limitations in assessing nutrient intake As for any nutrient where deficiency and toxicity are issues, the reliable assessment of intake is paramount. The ultimate aim of defining optimal dietary intakes is hampered by difficulties in determining certain key facts, namely, individual copper intakes and status. Dietary intake can be assessed by a number of methods, involving either the recording of actual consumption (prospective) or the assessment by questionnaires of diet in the recent past (retrospective). At each stage in the application of any method, errors are introduced, producing as a result either a systematic bias or random deviations from the true values. Of the methods in common use, the weighed dietary record is widely accepted to be the most accurate, but it requires a considerable amount of co-operation from human subjects. This disadvantage may give rise to substantial bias, most likely toward underreporting habitual dietary intakes.48 In clinical practice the most frequently used method of dietary assessment is the diet history, which is highly dependent on accurate recall by the individual. It is possible to verify these reports, to some extent, by independent methods. Under- and over-estimation of an individual’s total food intake can be identified by measuring total energy expenditure, either directly, using the doubly-labelled water technique, or indirectly, by calculating basal metabolic rate. Another check is a comparison of the individual’s 24-hour urinary nitrogen output with the reported protein intake. The accuracy of these methods is limited either by the involvement of estimates, or by reliance on the assumption that body weight is constant. One means of assessing nutrient requirements is the metabolic balance study. The aim of a balance study is to compare the intake of a nutrient with the amount 124 The nutrition handbook for food processors
Measuring intake of nutrients and their effects: the case of copper 125 leaving the body. A constant daily intake of the nutrient in question is provided throughout the study period, and collection of stools and urine are made. Crucial to the success of the investigation is the accuracy of measurement of intake and excretion. For this reason, balance studies demand careful planning and execu tion, good facilities for food preparation, sample collection and sample storage, and good laboratory services. A major limitation is that balance studies provide little information about nutrient transport or utilisation within the body Nutrient intake can also be assessed by the use of experimental diets with different mineral intakes. The use of experimental diets to determine nutrient requirements depends on the selection and measurement of a biochemical endpoint, to serve as a marker of nutrient sufficiency. However, experimental diets must be carefully constituted to minimise the possibility that other dietary components may modify absorption of the nutrient, or even influence directly e chosen marker. A limitation of this method is that it permits the estimation of the basal nutrient requirements, but not the amount needed to maintain bodily nutrient reserves Epidemiological studies such as the US Total Diet Study or the North/South Ireland Food Consumption Survey> are often carried out with the aim of esti mating the fraction of the population at risk from deficiency or excess intake Attempts are made to assess long-term average intake of populations from data gained using short-term measures of intake. Few studies have reported testing the validity of such an extrapolation, but a recent study which examined values cal culated from up to six samples, spaced over a year, found significant temporal variability for individual subjects. In addition, when the reliability of short-term (4-day) samples was estimated by comparing individual values to the aggregate value, results suggested that three short-term samples would be required to achieve a strong correlation(r=0.9)between short- and long-term values. Tra tional reliance on short-term measures for estimation of long-term copper status could produce erroneous result 5.8 Putative copper indicators Determination of copper status suffers from the lack of sensitive, reliable and easy measures for detecting marginal copper status. Copper levels in the hair, nails or saliva do not appear to reflect copper status. Urinary copper is normally extremely low, and although it can decline in extreme copper deficiency, this is usually seen only after changes are seen in other copper indices. In copper de- pletion and repletion studies, cuproenzyme activities have appeared relatively insensitive to change I The traditional and most commonly used putative indicator of copper status is serum or plasma copper. Under normal circumstances, strong homeostatic mechanisms maintain the range between 0. 64 and 1.56ug/ml. Although in severe copper depletion it has been known to fall to very low levels, and to recover upon copper repletion, it does not appear to reflect dietary levels when
leaving the body. A constant daily intake of the nutrient in question is provided throughout the study period, and collection of stools and urine are made. Crucial to the success of the investigation is the accuracy of measurement of intake and excretion. For this reason, balance studies demand careful planning and execution, good facilities for food preparation, sample collection and sample storage, and good laboratory services. A major limitation is that balance studies provide little information about nutrient transport or utilisation within the body.22 Nutrient intake can also be assessed by the use of experimental diets with different mineral intakes. The use of experimental diets to determine nutrient requirements depends on the selection and measurement of a biochemical endpoint, to serve as a marker of nutrient sufficiency. However, experimental diets must be carefully constituted to minimise the possibility that other dietary components may modify absorption of the nutrient, or even influence directly the chosen marker.23 A limitation of this method is that it permits the estimation of the basal nutrient requirements, but not the amount needed to maintain bodily nutrient reserves. Epidemiological studies such as the US Total Diet Study13 or the North/South Ireland Food Consumption Survey15 are often carried out with the aim of estimating the fraction of the population at risk from deficiency or excess intake. Attempts are made to assess long-term average intake of populations from data gained using short-term measures of intake. Few studies have reported testing the validity of such an extrapolation, but a recent study which examined values calculated from up to six samples, spaced over a year, found significant temporal variability for individual subjects.49 In addition, when the reliability of short-term (4-day) samples was estimated by comparing individual values to the aggregate value, results suggested that three short-term samples would be required to achieve a strong correlation (r = 0.9) between short- and long-term values. Traditional reliance on short-term measures for estimation of long-term copper status could produce erroneous results. 5.8 Putative copper indicators Determination of copper status suffers from the lack of sensitive, reliable and easy measures for detecting marginal copper status. Copper levels in the hair, nails or saliva do not appear to reflect copper status.50 Urinary copper is normally extremely low, and although it can decline in extreme copper deficiency, this is usually seen only after changes are seen in other copper indices.17 In copper depletion and repletion studies, cuproenzyme activities have appeared relatively insensitive to change.51 The traditional and most commonly used putative indicator of copper status is serum or plasma copper. Under normal circumstances, strong homeostatic mechanisms maintain the range between 0.64 and 1.56mg/ml.50 Although in severe copper depletion it has been known to fall to very low levels, and to recover upon copper repletion, it does not appear to reflect dietary levels when Measuring intake of nutrients and their effects: the case of copper 125