David B. Milne

Increased cholesterol in plasma in a young man during experimental copper depletion

Signs of copper depletion were produced in a healthy man by an amount of dietary copper (0.83 mg/day) similar to that in some contemporary diets. Urinary and fecal loss of copper exceeded intake. Plasma copper, ceruloplasmin, and superoxide dismutase activity in erythrocytes decreased. Cholesterol in plasma increased, and hematologic indices were unchanged. Lipid metabolism may be a more sensitive index of copper nutriture than are changes in hematology. The findings support the hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease.

Copper intake and assessment of copper status

The diagnosis of marginal copper deficiency has not been perfected despite an increased understanding of the physiologic roles of copper. The use of nonstandardized procedures and the effects of factors other than copper nutriture have impeded identification of an ideal indicator of copper nutritional status in humans. A review of studies of experimental copper deprivation conducted in adult humans over the past 12 y indicated that between 1.0 and 1.25 mg Cu/d is needed by adults for copper maintenance for periods of up to 6 mo and that < or = 2.6 mg Cu/d for periods of up to 42 d is not sufficient for recovery from copper deprivation. Copper-containing enzymes in blood cells, such as erythrocyte superoxide dismutase and platelet cytochrome-c oxidase, may be better indicators of metabolically active copper and copper stores than plasma concentrations of copper or ceruloplasmin because the enzyme activities are sensitive to changes in copper stores and are not as sensitive to factors not related to copper nutriture.

Dietary Magnesium Deficiency Induces Heart Rhythm Changes, Impairs Glucose Tolerance, and Decreases Serum Cholesterol in Post Menopausal Women

Objective: To determine whether or not dietary magnesium restriction to about 33% of the Recommended Dietary Allowance (RDA) causes changes in glucose, cholesterol and electrolyte metabolism that could lead to pathologic consequences. Design: The length of the experiment was 136 days. Subjects were fed a basal Western-type diet that provided 4.16 mmol (101 mg) magnesium per 8.4 MJ (2000 kcal) for 78 days then replenished with magnesium by supplementing the diet with 200 mg magnesium as the gluconate per day for 58 days. If a subject exhibited adverse heart rhythm changes before 78 days of depletion were completed, she entered the repletion period early. Setting: The metabolic research unit of the Grand Forks Human Nutrition Research Center. Subjects: A total of 14 post menopausal women were recruited by advertisement throughout the United States. Thirteen women (ages 47 to 75 years) completed the study. Results: During magnesium depletion, heart rhythm changes appeared in 5 women and resulted in 4 prematurely entering the magnesium repletion period (42 to 64 days of depletion instead of 78). Three women exhibited atrial fibrillation and flutter that responded quickly to magnesium supplementation. Magnesium deprivation resulted in a non-positive magnesium balance that became highly positive with magnesium repletion. Magnesium deprivation decreased red blood cell membrane magnesium, serum total cholesterol and erythrocyte superoxide dismutase concentrations, increased the urinary excretion of sodium and potassium, and increased serum glucose concentration. Conclusions: Magnesium balance may be a suitable indicator of magnesium depletion under experimental conditions. Magnesium deficiency resulting from feeding a diet that would not be considered having an atypical menu induces heart arrhythmias, impairs glucose homeostasis, and alters cholesterol and oxidative metabolism in post menopausal women. A dietary intake of about 4.12 mmol (100 mg) Mg/8.4 MJ is inadequate for healthy adults and may result in compromised cardiovascular health and glycemic control in post menopausal women.

Effects of dietary copper on human autonomic cardiovascular function

SummaryHeart 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<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<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<0.0004) correlated with the ceruloplasmin ratios. These findings indicate a functional alteration in human blood pressure regulation during mild copper depletion.

Low Dietary Zinc Alters Indices of Copper Function and Status in Postmenopausal Women

OBJECTIVES To better define the relationship between dietary zinc and copper for humans so that sound recommendations for intakes of these elements can be made. METHODS A study was conducted to ascertain the effect of moderately excessive and deficient intakes of zinc on copper metabolism and use in humans fed low and luxuriant amounts of copper. Twenty-one postmenopausal women housed in a metabolic unit completed the study as designed. After a 10-d equilibration period in which they were fed a diet providing 31.5 micromol (2 mg) Cu and 91.8 micromol (9 mg) Zn/8.4 MJ (2000 kcal), the women were divided into two groups. One group was fed a diet containing 15.7 micromol (1 mg) Cu/8.4 MJ (2000 kcal), and the other group was fed a diet containing 47.2 micromol (3 mg) Cu/8.4 MJ (2000 kcal). After equilibration, both groups were fed the basal diet providing 45.9 micromol (3 mg) Zn/8.4 MJ (2000 kcal) for 90 d; this was followed by another 10-d equilibration period before dietary zinc was increased to 811 micromol (53 mg)/8.4 MJ (2000 kcal) for 90 d. RESULTS The women were in positive copper balance only when the diet provided 47.2 micromol (3 mg) Cu and 811 micromol (53 mg) Zn/d. Immunoreactive ceruloplasmin concentrations and platelet cytochrome-c oxidase activity on a platelet number basis were significantly lower and the ratio between enzymatic and immunoreactive ceruloplasmin was significantly higher during low dietary than during high dietary zinc intake. Serum cholesterol was higher in subjects fed 15.7 micromol (1 mg) Cu/d than in those fed 47.2 micromol (3 mg) Cu/d. Total and low-density lipoprotein cholesterol concentrations decreased with zinc supplementation. Whole-blood glutathione concentration and erythrocyte glutathione peroxidase activity were lower during high than during low dietary zinc intake. CONCLUSIONS The findings indicate that an inadequate intake of zinc (45.9 micromol/d; 3 mg/d) was more effective than a moderately high intake of zinc (811 micromol/d; 53 mg/d) in inducing changes associated with a decreased copper status in postmenopausal women. Furthermore, the findings indicate that copper status indicators might be useful in evaluating changes in zinc status in humans, and an intake of 15.7 micromol (1 mg)/d of copper may be inadequate for postmenopausal women.

The Interaction Between Dietary Fructose and Magnesium Adversely Affects Macromineral Homeostasis in Men

Objective: Studies with rats have found that an interaction between fructose and magnesium affects macromineral metabolism; high dietary fructose significantly increased kidney calcification in both male and female rats, particularly when dietary magnesium was low. This study tests the hypothesis that an interaction between dietary fructose and magnesium adversely affects macromineral homeostasis in men. Methods: Eleven men aged 22 to 40 years were fed a mixed, Western diet for four 42-day dietary periods in which dietary magnesium was either approximately 170 or 370 mg/day and dietary fructose was either 4% or 20% of energy. A decaffeinated beverage containing high fructose corn syrup replaced cornstarch, bread and rice in the low fructose diet to give the high fructose diet. Results: High dietary fructose significantly (p<0.01) increased magnesium balance during both low and high dietary magnesium intakes. Ultrafilterable and ionized serum magnesium also apparently were related to magnesium and fructose intakes; they were higher when fructose was fed and when Mg intakes were high. High fructose depressed calcium balance: the effect tended to be more marked when dietary Mg was low. High dietary fructose also significantly (p<0.005) decreased phosphorous balance. Urinary phosphorous losses were significantly (p<0.001) higher when high dietary fructose was fed. High dietary fructose also increased the concentration of serum alkaline phosphatase (p<0.005). Conclusion: These findings indicate that dietary fructose adversely affects macromineral homeostasis in humans and suggest further studies to see if a high fructose diet coupled with low dietary magnesium and marginal calcium leads to bone loss.

Effect of copper intake on balance, absorption, and status indices of copper in men

Indices of Cu status were measured in 8 men fed diets low in Cu (0.89±0.10 mg/day), for periods ranging from 105 to 120 days. One man showed Cu depletion signs of significantly decreased plasma Cu, 8.7 μmole/L, at the end of depletion, vs 12.1 μmole/L during equilibration and 11.0 μmole/L at the end of repletion, and decreased RBS superoxide dismutase (SOD), 705 U/g Hgb at the end of depletion vs 3619 U/g Hgb at the end of repletion. Two others exhibited similar trends. Copper absorption by the men was not affected by the amount of dietary Cu. However, endogenous excretion of Cu during depletion was 50% of that during the control period (1.00±0.20 vs 0.50±0.17 mg Cu/d, p<0.0002) for control and depletion periods, respectively. Intakes of below 0.9 mg/d apparently result in signs of Cu depletion in healthy adults. Sex differences need to be considered when determining the effect of Cu depletion on various indices of Cu status.

Plasma trace elements and cognitive function in older men and women: The Rancho Bernardo study

Objective. This study examines the sex-specific associations of plasma concentrations of iron, copper, and zinc with cognitive function in older community-dwelling adults.Design: Cross-sectional study.Setting: 1988–92 follow-up clinic visit.Participants: 602 men and 849 women (average age=75 ±8 years) who were community-dwelling and not clinically demented.Measurements: Blood samples were assayed for trace elements and 12 cognitive function tests were administered. Sex-specific analyses were adjusted for age, education, alcohol consumption, smoking, exercise, and estrogen use in women.Results. Men and women differed significantly in education and alcohol intake (p’s<0.001), concentrations of plasma iron, copper and zinc (p’s<0.001) and scores on 11 of 12 cognitive function tests (p=0.04 to <0.001). Regression analyses showed significant inverted U-shaped associations in men;both low and high iron levels were associated with poor performance on total and long-term recall and Serial 7’s (p’s=0.018, 0.042 and 0.004, respectively) compared to intermediate concentrations. In women, iron and copper concentrations had inverse linear associations with Buschke total, long and short-term recall and Blessed scores (p’s<0.05). Zinc was positively associated with performance on Blessed Items (p=0.008). Analyses comparing cognitive function using categorically defined mineral concentrations yielded similar sex specific results.Conclusion. Optimal trace element concentrations may exist for optimal cognitive function in older adults, and these levels may differ by sex and cognitive function domain.

EFFECTS OF ASCORBIC ACID SUPPLEMENTS AND A DIET MARGINAL IN COPPER ON INDICES OF COPPER NUTRITURE IN WOMEN

Biochemical indicators of copper status were studied in young women housed in a metabolic unit for 135 days. The women were fed a diet low in Cu (0.67 mg/d), that was supplemented with 1.5 g of ascorbic acid and variable amounts of copper. Copper balance was not significantly affected by diet. Plasma copper and monoamine oxidase, and erythrocyte superoxide dismutase were not affected by dietary copper or by ascorbic acid. Enzymatic (CpENZ), but not immunoreactive (CpRID), ceruloplasmin was lower at the end of low copper intake and high ascorbic acid intake periods. The specific activity of ceruloplasmin (CpENZ/CpRID) was significantly lower at the end of the ascorbic acid period (1.26) than at either the end of control (1.81) or repletion (1.80) periods, and slightly lower than after only low copper intake (1.44). Cytochrome-c oxidase activities in platelets and leukocytes were significantly affected by copper intake, but not ascorbic acid intake. These findings indicate that the specific activity of ceruloplasmin and cytochrome-c oxidase activity of platelets and white cells may be sensitive indicators of copper status, and that ascorbic acid supplements do not markedly affect commonly measured indices of copper metabolism, except for the specific activity of ceruloplasmin in young women.

Some Magnesium Status Indicators and Oxidative Metabolism Responses to Low-Dietary Magnesium Are Affected by Dietary Copper in Postmenopausal Women

OBJECTIVE A study with human volunteers was conducted to ascertain whether a low intake of copper (Cu) would exacerbate the response to a deficient intake of magnesium (Mg). METHODS Nineteen postmenopausal women, age 47 to 78 y, completed a metabolic unit study as designed. For 162 d, nine women were fed a diet containing 1.0 mg of Cu/2000 kcal and 10 women were fed 3.0 mg of Cu/2000 kcal. Diets contained 99 or 399 mg of Mg/2000 kcal for 81 d in a randomized, double-blind, crossover design. Differences were considered significant when statistical analysis yielded P </= 0.05. RESULTS Magnesium balance was highly positive when the dietary magnesium was high but non-positive when dietary magnesium was low. Copper balance was more positive when dietary copper was high than when it was low. Plasma ionized magnesium was decreased by magnesium deprivation. Several variables measured indicated that low dietary copper affected the response to magnesium deprivation or vice-versa. Red blood cell magnesium was lower when dietary copper was low than when it was high. When dietary magnesium was low, serum copper was lower in the women fed marginal copper than in those fed luxuriant copper. When dietary magnesium was high, low dietary copper did not affect serum copper. Magnesium deprivation decreased red blood cell superoxide dismutase when dietary copper was luxuriant; when dietary copper was low, magnesium deprivation did not have much of an effect. Apolipoprotein A1 was lowest when dietary magnesium and copper were low. The order in which the magnesium restriction occurred affected the response of a number of variables to this treatment including concentrations of serum magnesium and total and low-density lipoprotein cholesterol. CONCLUSIONS The findings indicated that, in short-term magnesium depletion experiments, the response to depletion can be influenced by other dietary factors including copper intake and a high magnesium intake before depletion, and that 100 mg of Mg/d is inadequate for postmenopausal women.