J. L. Greger

Mineral metabolism of rats fed various levels of aluminum hydroxide

The effect of ingesting nutritionally complete diets with added aluminum hydroxide (257 μg Al/g diet in study A and 1075 μg Al/g diet in study B) was assessed in two 67-d studies. Rats fed either 257 or 1075 μg Al/g diet accumulated significantly greater amounts of aluminum in their tibias, kidneys, and livers than control animals. However, the rats fed 1075 μg Al/g diet did not accumulate more aluminum in these tissues than rats fed 257 μg Al/g diet. After consuming the diets for 30–39 d, the rats fed 257 μg Al/g diet absorbed calcium, magnesium, and copper significantly less efficiently, and the rats fed 1075 μg Al/g diet absorbed phosphorus and calcium significantly less efficiently than control animals. After the rats had consumed the diets for 62–65 d, the additional aluminum hydroxide no longer affected the apparent absorption or tissue concentrations of phosphorus, calcium, magnesium, zinc, or iron. Rats fed 1075 μg Al/g diet had significantly higher concentrations of copper in their tibias, but significantly less total calcium, magnesium, and zinc in their tibias and livers and less total iron in their tibias than control animals. The reduced breaking strength of bones from the animals fed 1075 μg Al/g diet may reflect their slightly smaller size.

Manganese status, gut endogenous losses of manganese, and antioxidant enzyme activity in rats fed varying levels of manganese and fat

AbstractWe hypothesized that manganese deficient animals fed high vs moderate levels of polyunsaturated fat would either manifest evidence of increased oxidative stress or would experience compensatory changes in antioxidant enzymes and/or shifts in manganese utilization that result in decreased endogenous gut manganese losses. Rats (females in Study 1, males in Study 2,n = 8/treatment) were fed diets that contained 5 or 20% corn oil by weight and either 0.01 or 1.5 μmol manganese/g diet. In study 2,54Mn complexed to albumin was injected into the portal vein to assess gut endogenous losses of manganese. The manganese deficient rats:1.Had 30–50% lower liver, tibia, kidney, spleen, and pancreas manganese concentrations than manganese adequate rats;2.Conserved manganese through ≈70-fold reductions in endogenous fecal losses of manganese;3.Had lower heart manganese superoxide dismutase (MnSOD) activity; and4.Experienced only two minor compensatory changes in the activity of copper-zinc superoxide dismutase (CuZnSOD) and catalase. Gut endogenous losses of manganese tended to account for a smaller proportion of absorbed manganese in rats fed high-fat diets; otherwise fat intake had few effects on tissue manganese concentrations.

Zinc, copper and iron utilisation by chicks fed various concentrations of zinc

1. Zinc, iron and copper interactions were examined in chicks (New Hampshire X Single Comb White Leghorn) grown individually in stainless steel cages and fed on purified diets with three concentrations of zinc: control (37 mg Zn/kg), moderate (100 mg Zn/kg) and excess (2000 mg Zn/kg) in three studies. 2. Chicks given either moderate or excess zinc excreted more than twice as much 65Zn from a test diet as those fed on the control diet. Thus chicks given the moderate amount of zinc had concentrations of zinc in tissues similar to those of controls but chicks given excess zinc accumulated zinc in their tissues. 3. The specific activity of 65Zn in the tissues, especially in the bursa of Fabricius, of chicks given excess zinc was not reduced as much as would be predicted. Thus, ingestion of excess zinc appeared to reduce tissue turnover of 65Zn, especially in the bursa. However, humoral immune responses, as measured by antibody titres to sheep red blood cells, were not affected. 4. Chicks given excess zinc or pair-fed on the control diet retained less 59Fe from a test diet than chicks given control or moderate concentrations of zinc ad libitum. The iron concentrations in tibiae of chicks given excess zinc were depressed.

Zinc, iron, and copper contents of eggs from hens fed varying levels of zinc

Abstract We wanted to determine whether eggs which contained more zinc could be produced by fortifying the diets of hens with zinc. In two studies, hens fed very high levels of zinc (1762 or 1861 μg Zn/g diet) for 4 to 40 weeks produced eggs that contained 57–90% more zinc than eggs produced by hens fed control diets (28 or 26 μg Zn/g diet). Hens fed high levels of zinc (218 or 257 μg Zn/g diet) produced eggs that contained as much as 25% more zinc than eggs produced by hens fed control diets. Ingestion of excess zinc did not have consistent effects on the iron or copper content of eggs or on the zinc content of eggshells.

Iron metabolism in chicks fed various levels of zinc and copper

Abstract Four studies were conducted to determine the effect of high levels of zinc and copper on iron use of the chick. Chicks from the cross of New Hampshire x Single Comb White Leghorn were fed semi-purified diets with adequate (0.58–0.76 μmol Zn/g diet) and high (26.0–31.4 μmol Zn/g diet) levels of zinc and adequate (0.13–0.17 μmol Cu/g diet) and high (3.18–3.50 μmol Cu/g diet) levels of copper for 21 days. Fe-59 was fed in studies A–C and injected intraperitoneally in study D. Chicks fed high levels of zinc consistently showed decreased packed cell volumes and depressed concentrations of iron in livers and tibius. The anemia was not attributable to reduced feed and iron intakes. Chicks fed high rather than adequate amounts of zinc excreted 78% rather than 54% of an oral dose of Fe-59. The appearance of Fe-59 in plasma 1 hour after feeding the isotope decreased in chicks fed high rather than adequate levels of zinc. Ingestion of additional copper did not reverse the effects of ingesting high amounts of zinc on iron absorption. Ingestion of the high levels of zinc had minor effects on endogenous iron excretion. The ingestion of additional copper partially counteracted this effect.

Mineral metabolism of aging female rats fed various commercially available calcium supplements or yogurt.

The utilization of calcium from commercially available calcium supplements and yogurt and the effects of these calcium supplements on the utilization of other minerals were evaluated. Moderate and high levels (4 and 8 mg Ca/g diet) of calcium from four different sources of dietary calcium (yogurt, calcium phosphate dibasic, calcium magnesium chelate, and oyster shells) were fed to retired female breeder rats. Rats absorbed calcium equally efficiently from all four sources but ingestion of calcium phosphate dibasic tended to cause abnormal accumulation of calcium in kidneys. Ingestion of the calcium magnesium chelate improved calcium retention in bone but depressed the digestibility of the total diet. The elevation of dietary calcium did not affect tissue calcium levels or fecal β-glucuronidase activity but depressed the apparent absorption of phosphorus, increased kidney phosphorus levels, decreased tibia iron levels, and decreased the digestibility of the total diet.

Anemia induced by ingestion of excess zinc in chicks: importance of red blood cell turnover?

Abstract Three studies were conducted to determine whether ingestion of excess zinc induces anemia, at least partially, by increasing red blood cell fragility directly or through changes in copper-zinc—dependent superoxide dismutase (Cu-Zn-SOD). Chicks from the cross New Hampshire × Single Comb White Leghorn were fed adequate (0.72–0.76 μmol Zn/g diet) or high (22.60–25.17 μmol Zn/g diet) levels of zinc and adequate (0.11–0.14 μmol Cu/g diet) or high (3.13–3.45 μmol Cu/g diet) levels of copper. To assess whether excess zinc could induce a hemolytic anemia, we monitored red blood cell (RBC) Cu-Zn-SOD, RBC fragility in vitro, and erythrocyte t 1 2 in vivo. Cu-Zn-SOD activity was depressed among chicks fed excess zinc and the ingestion of extra copper restored Cu-Zn-SOD activities to the levels of the control chicks. However, lysis of erythrocytes in diluted saline (0.35% NaCl) was lower when chicks were fed high levels of zinc and the ingestion of extra copper further decreased lysis. With these counteracting influences, the lifespan of erythrocytes was not affected by any of the treatments in one study and was greater in chicks fed both high zinc and copper in another study. These data indicate that the anemia induced by excess zinc is not a hemolytic anemia.

Zinc, Iron and Copper Interactions in Humans, Rats and Chicks

The effect of iron on zinc metabolism is of interest because iron supplements and foods highly fortified with iron are used so frequently. However, in practical situations we think that supplemental zinc is more apt to affect iron metabolism, than vice versa. We base this comment on data collected in studies conducted with humans, rats and chicks.

Chloride, sodium and potassium utilization by subjects fed milk and calcium supplements

Abstract Eight adult males excreted on average 97%, 95% and 84% of their chloride, sodium and potassium intakes, respectively, in urine during a 56-day metabolic balance study. Variations in the levels and forms of chloride and calcium fed had no significant effects on apparent absorption or serum levels of chloride and sodium. Urinary chloride and sodium excretion were sensitive to seasonal changes. Apparent absorption of potassium was increased when subjects were fed supplemental calcium.