126 The nutrition handbook for food processors intake is close to normal. It does not increase after a meal or decrease during short-term fasting and has been shown to correspond poorly with reported dietary intakes. In some studies of copper depletion, serum copper responses have been absent even in the presence of other biochemical or physiological changes. 3 Serum copper is known to be altered by a number of factors not directly related to copper status. Concentrations are low in infancy and rise to adult levels over the first 4-6 months, or longer following a low birth weight. In adult women. serum copper concentration is generally higher than in men, and is further raised during pregnancy and by oestrogen treatments. There is also a normal diurnal variation with a slight peak in the morning. Plasma copper fluctuates with age. and is raised in a number of other conditions including exercise, rheumatoid arthritis, dilated cardiomyopathy and anticonvulsant chemotherapy. Between 60 and 95%o of serum copper is associated with caeruloplasmin, so serum copper levels often mirror those of caeruloplasmin. Normal levels of serum or plasma caeruloplasmin protein are 180-400ug/mL Like serum copper, caeruloplasmin has shown variable responses to marginal depletion. Its concentration and activity fall with severe copper deficiency and return to normal with copper repletion; but because of its role as an acute phas protein, caeruloplasmin concentration in the plasma reflects oxidative status more reliably than copper status. Copper depletion may be masked by caeruloplasmin elevated in response to exercise, infection or inflammation, liver disease, malig- nancy and MI. Like serum copper, normal caeruloplasmin values also vary with age and gender, and during pregnancy Erythrocyte copper/zinc SOD concentration is normally 0.471 t 0.067 mg/g protein. SOD activity has appeared in some studies to be more sensitive than ceruloplasmin to changes in copper status, while in other studies its activity has fallen with depletion but failed to respond to repletion. Copper/zinc SOD activ- ity has been reported to rise in response to physical exercise. As an antioxidant enzyme, SOD is likely to respond to conditions of oxidative stress. A further com- plicating factor is that SOD measured in erythrocytes is unlikely to reflect short- term changes in dietary intake owing to the 100-day lifetime of erythrocytes Leucocyte copper has been found to decline along with other indices of copper status. Platelet copper has been shown to decline with copper depletion and to recover with copper repletion. However, there are not yet sufficient experi- mental data to confirm the validity of leucocyte or platelet copper as indicators of suboptimal copper status. DAO has been indicated in some studies of copper depletion as a possible marker of copper status. Its measurement is currently difficult cause of its extremely low levels in plasma. Furthermore, its use as an indicator may be limited because it is elevated during pregnancy, after heparin treatment and in some conditions of intestinal damage A valid functional index must respond sensitively, specifically and predictably to changes in the dietary supply or stores of copper, and must be measurable and accessible for measurement. Validation of a candidate marker would require status and also, ideally, between copper status and health measures. ss d copper demonstration of a cause and effect relationship between the marker anintake is close to normal.17 It does not increase after a meal or decrease during short-term fasting and has been shown to correspond poorly with reported dietary intakes.52 In some studies of copper depletion, serum copper responses have been absent even in the presence of other biochemical or physiological changes.53 Serum copper is known to be altered by a number of factors not directly related to copper status. Concentrations are low in infancy and rise to adult levels over the first 4–6 months, or longer following a low birth weight. In adult women, serum copper concentration is generally higher than in men, and is further raised during pregnancy and by oestrogen treatments.54 There is also a normal diurnal variation with a slight peak in the morning. Plasma copper fluctuates with age, and is raised in a number of other conditions including exercise, rheumatoid arthritis, dilated cardiomyopathy and anticonvulsant chemotherapy. Between 60 and 95% of serum copper is associated with caeruloplasmin, so serum copper levels often mirror those of caeruloplasmin.11 Normal levels of serum or plasma caeruloplasmin protein are 180–400mg/ml.17 Like serum copper, caeruloplasmin has shown variable responses to marginal depletion. Its concentration and activity fall with severe copper deficiency and return to normal with copper repletion; but because of its role as an acute phase protein, caeruloplasmin concentration in the plasma reflects oxidative status more reliably than copper status. Copper depletion may be masked by caeruloplasmin elevated in response to exercise, infection or inflammation, liver disease, malig￾nancy and MI.55 Like serum copper, normal caeruloplasmin values also vary with age and gender, and during pregnancy.23 Erythrocyte copper/zinc SOD concentration is normally 0.471 ± 0.067 mg/g protein.50 SOD activity has appeared in some studies to be more sensitive than caeruloplasmin to changes in copper status, while in other studies its activity has fallen with depletion but failed to respond to repletion.56 Copper/zinc SOD activ￾ity has been reported to rise in response to physical exercise.57 As an antioxidant enzyme, SOD is likely to respond to conditions of oxidative stress. A further com￾plicating factor is that SOD measured in erythrocytes is unlikely to reflect short￾term changes in dietary intake owing to the 100-day lifetime of erythrocytes. Leucocyte copper has been found to decline along with other indices of copper status.51 Platelet copper has been shown to decline with copper depletion and to recover with copper repletion.56 However, there are not yet sufficient experi￾mental data to confirm the validity of leucocyte or platelet copper as indicators of suboptimal copper status. DAO has been indicated in some studies of copper depletion as a possible marker of copper status.58 Its measurement is currently difficult because of its extremely low levels in plasma. Furthermore, its use as an indicator may be limited because it is elevated during pregnancy, after heparin treatment and in some conditions of intestinal damage. A valid functional index must respond sensitively, specifically and predictably to changes in the dietary supply or stores of copper, and must be measurable and accessible for measurement. Validation of a candidate marker would require demonstration of a cause and effect relationship between the marker and copper status and also, ideally, between copper status and health measures.59 126 The nutrition handbook for food processors