Acid precipitation and food quality: Effects of dietary Al,Ca, and P on bone and liver characteristics in American black ducks and mallards

American black ducks (Anas rubripes) and mallards (A. platyrhynchos) were fed diets varying in concentrations of aluminum (Al), calcium (Ca), and phosphorus (P) for 10 weeks to identify toxic effects of Al under conditions representative of areas with acid precipitation. Femur and liver tissues were analyzed for Al, Ca, and P concentrations and structural characteristics. At two weeks of age, both species demonstrated pronounced differences in femur Al and P concentrations and femur mass from dietary Al and interaction between Ca:P regimen and Al; Low Ca:Low P enhanced Al storage and decreased P and mass in femurs. Femur Ca was lowest in the Low Ca:Low P regimen but was not affected by dietary Al. At 10 weeks, femur and liver Al continued to vary with dietary Al. Elevated Al and reduced Ca lowered modulus of elasticity. Femur P increased with elevated dietary P in black ducks. Elevated dietary P negated some of the effects of dietary Al on femur mass in black ducks. Reduced Ca concentrations weakened bones of both species and lowered both Ca and P. An array of clinical signs including lameness, discoloration of the upper mandible, complete and greenstick fractures, and death were responses to elevated Al and Ca:P regimen. Black ducks seemed to display these signs over a wider range of diets than mallards. Diets of 1,000 mg/kg Al had toxic effects on both species, particularly when combined with diets low in Ca and P.     

Trial monitoring of pesticides in wings of mallards and black ducks

Conclusions The results of the trial monitoring indicate that mallard and black duck wings are satisfactory monitoring media, that pesticidal residues were present in all pools, and that due to the variability in levels, the pool size should not be reduced from 25 wings unless there is a wing shortage. Differences in DDE residues between adult and immature wings of both species indicate that the age classification should be maintained in sampling. For analytical reasons, State identification will be necessary in nation-wide monitoring even though significant residue differences between New York and Pennsylvania wings were not demonstrated.     

Effects of dietary aluminum,calcium, and phosphorus on egg and bone of European starlings

Egg and bone of passerine birds nesting in acidified habitats may be affected by high levels of Al or P, or low levels of Ca. Nine treatments of three levels of dietary Al (target levels of 200, 1,000, and 5,000 g/g) and three levels of Ca:P (target levels of NN = 1.3% Ca: 0.9% P; LL = 0.19 Ca:0.45 P; LH = 0.19 Ca: 1.65 P) were fed to 16–17 starling pairs during two breeding seasons. Eggs of starlings fed the LH diet were smaller and weighed less than eggs from the NN and LL treatments. Treatment effects on thickness, strength, and weight of eggshells were not consistent between seasons, probably because of differences in actual dietary levels of Al, Ca, and P or in incubation intervals. In one season, birds fed the highest Al diet had thicker eggshells than those from the other Al treatments (no effect from Ca:P); the following season, eggshells from the NN and LH treatments were thicker and stronger than those from the LL treatment. Eggshells from the NN treatment weighed more than those from the other Ca:P treatments. Starlings on the LH diet had the strongest femurs, but the effect was interactive with different levels of dietary Al. Effects of Ca:P on egg and bone were more evident than Al effects.     

Changes in mineral composition of eggshells from black ducks and mallards fed DDE in the diet

Summary Diets containing 10 and 30 ppm (dry weight) DDE were fed to black ducks, and diets containing 1, 5, and 10 ppm (dry weight) DDE were fed to mallards. Among the results were the following changes in black duck eggshell composition: (a) significant increase in the percentage of Mg, (b) significant decreases in Ba and Sr, (c) increases (which approached significance) in average percentage of eggshell Na and Cu, (d) a decrease in shell Ca which approached significance, (e) patterns of mineral correlations which in some instances were distinct to dosage groups, and (f) inverse correlations in the control group between eggshell thickness Mg and Na.Changes in mallard eggshells were: (a) significant increase in percentage of magnesium at 5 and 10 ppm DDE, (b) significant decrease in Al at 5 and 10 ppm DDE, (c) a significant decrease in Ca from eggshells from the 10 ppm DDE group, and (d) an increase in average percentage of Na in eggshells from DDE dosed ducks which approached significance.     

Effects of dietary aluminum on chicks Gallus gallus domesticus with different dietary intake of calcium and phosphorus

Birds that feed in acidified areas may be exposed to an increased intake of aluminum, while their intake of calcium and phosphorus may simultaneously be low. In particular, juvenile birds foraging in acidified areas may suffer from increased effects of aluminum due to high demands of calcium. Day old chicks were fed six different diets where aluminum was combined with normal and low concentrations of dietary calcium and phosphorus for 14 days. The normal calcium-available phosphorus (Ca-P) level was 1.05%–0.45%, and the low dietary Ca-P level was 0.49%–0.21%. Aluminum was given in dietary levels of 0%, 0.13%, and 0.31%. Aluminum had no effects on growth, mortality, or hematocrit, but induced hypocalcemia.Bones accumulated more aluminum than kidneys. A high dietary concentration of aluminum (0.31%) increased the accumulation of aluminum twofold in bones and threefold in kidneys when the dietary concentration of calcium and phosphorus was halved. Opposed to the predictions, bone mineralisation was stimulated by an intermediate increase in dietary aluminum (0.13%) at both levels of dietary calcium and phosphorus. Bone stiffness was also stimulated at this dietary aluminum concentration, but only at the diet low in calcium and phosphorus. A high dietary aluminum concentration did not have any effect on bone stiffness or calcium concentration. Bone stiffness correlated positively with the calcium concentration in bone, and negatively with the aluminum concentration in bone. The effect of dietary aluminum on bone stiffness is probably caused by an alteration in bone mineralization, rather than by the presence of aluminum in bones.     

Effect of dietary calcium and phosphorus levels on the utilization of calcium,phosphorus, magnesium,manganese, and selenium by adult males

The effects of dietary calcium and phosphorus levels on the utilization of phosphorus, calcium, magnesium, manganese, and selenium by nine adult males were examined during a 39-day balance study. The dietary treatments were a moderate calcium-moderate phosphorus diet (MCaMP), a moderate calcium-high phosphorus diet (MCaHP), and a high calcium-high phosphorus diet (HCaHP). The moderate and high levels of phosphorus were 843 and 2443 mg daily, respecitvely; the moderate and high levels of calcium were 780 and 2382 mg daily, respectively. Subjects were unable to maintain positive balance in regard to phosphorus when fed the moderate level of phosphorus (MCaMP) but maintained positive balance in regard to phosphorus when fed the high level of phosphorus (MCaHP, HCaHP). The addition of more calcium to the high phosphorus diets resulted in significantly greater excretion of phosphorus in the feces but significantly less excretion of phosphorus in the urine by subjects. The dietary treatments affected urinary excretion of calcium, magnesium, and selenium significantly, but the effects were small or were compensated for by changes in fecal excretion of the minerals. Thus the dietary treatments had no significant effects on overall retention of calcium, magnesium, manganese, and selenium by these subjects.     

Influence of dietary phosphorus restriction on calcium and phosphorus metabolism in rats

The effect of dietary phosphorus (P) on calcium (Ca) and phosphorus metabolism was studied in young female rats. P levels in the semipurified diets ranged from 0.1 to 0.4% (w/w). A level of 0.4% P in the diet is recommended for rats. Kidney calcification was observed in rats fed the 0.4%-P diet whereas P restriction prevented this condition. Rats fed the diet containing 0.1% P, showed severe hypercalciuria, hypercalcemia, reduced growth and impaired bone mineralization. These effects did not occur when the diet contained 0.2 or 0.3% of P. This study suggests that in short-term studies P in the diet of female rats can be restricted to 0.2% so as to prevent nephrocalcinosis without affecting their development.     

Colon cancer and dietary fat, phosphorus, and calcium in Hawaiian-Japanese men

In a prospective cohort study, 8006 men of Japanese ancestry were examined from 1965 to 1968. A 24-h dietary recall questionnaire was administered to each subject as part of the baseline clinical examination. Dietary data were analyzed for intake of calcium, phosphorus, and total fat in 99 colon cancer cases and in 378 controls chosen from the cancer-free men. This was a nested case-control study design with 14-17 yr of prospective followup for colon cancer incidence. We found no significant association between dietary calcium intake and colon cancer risk. This held true whether phosphorus intake was low (less than 1032 mg/day) or high (greater than or equal to 1032 mg/day), and whether total fat intake was low (less than 61 g/day) or high (greater than or equal to 61 g/day). Adjusted-odds ratios were 0.7-1.4 across eight subgroups of low and high intakes of the three nutrients studied. These data do not support a recent hypothesis that calcium intake might be negatively associated with colon cancer risk, depending on the level of fat and phosphorus intake.     

Effects of dietary calcium, phosphorus and magnesium on intranephronic calculosis in rats

The effects of varying dietary levels of calcium, phosphorus and magnesium on the incidence and severity of intranephronic calculosis were studied. Renal calculi were induced by feeding female rats the AIN-76TM semipurified diet for 4 weeks. During this time period, dietary levels of 350, 450 or 550 mg calcium per 100 g diet did not influence the occurrence of urolithiasis. Increasing dietary magnesium levels from 50 to 350 mg was beneficial in preventing the occurrence of calculi if the diet contained 400 mg or less phosphorus. The protective effects of dietary magnesium were counteracted when dietary phosphorus levels were increased from 400 mg to 550 or 700 mg. If the dietary content of phosphorus and magnesium permitted the formation of renal calculi, the severity of the condition was also influenced by the dietary level of calcium. Some animal groups fed semipurified diets did not have microscopic or radiographic evidence of renal calculi but were found to have significantly elevated renal calcium values. It was suggested that these animals might be in a precalculus-forming state.     

Nephrocalcinosis caused by dietary calcium:phosphorus imbalance in female rats develops rapidly and is irreversible

Female rats fed the standardized AIN-76A diet develop kidney calcium deposits (nephrocalcinosis, NC). A low dietary Ca:P molar ratio is a primary factor in this disorder. The AIN-93G diet has a lower P content and higher Ca:P molar ratio and lowers the incidence of NC. To examine the early stages of NC induced by dietary Ca:P imbalance and the potential reversibility of this disorder, weanling female Sprague-Dawley rats were fed a modified AIN-93G test diet containing Ca:P at AIN-76A levels (NC-inducing diet) for 0.5-16 wk before necropsy, or were switched to AIN-93G control diet after 0.5-4 wk until necropsy at 16 wk. A dramatic increase in incidence and severity of NC was noted after 2 wk of feeding the test diet. NC was not reversible by switching to the control diet. As little as 0.5 wk of exposure to the test diet followed by 15.5 wk of consuming the control diet resulted in increased incidence and severity of NC compared with 16 wk of consuming the control diet. Short-term (as little as several days) feeding of an NC-inducing diet to female rats can lead to NC even if they are switched to an optimal diet.     

Influence of dietary calcium:phosphorus ratio on mineral excretion and nephrocalcinosis in female rats

The effects of dietary calcium (Ca) concentration and calcium: phosphorus (Ca:P) ratio on mineral balance and nephrocalcinosis were studied in female rats. In the first experiment there were two dietary Ca concentrations (0.25 and 0.50%, wt/wt) at two different Ca:P ratios (0.6 and 1.3). In the second experiment the diets were formulated to contain 0.40% P and either 0.13, 0.25, 0.50 or 0.75% Ca. The diets contained 0.03% magnesium (Mg). The fecal outputs of Ca, P and Mg were lower (P less than 0.01) after feeding low Ca diets than after feeding high Ca diets. Urinary excretion of P decreased with increasing dietary Ca and increased with increasing P intake. In rats fed the 0.25% Ca diets whole-body retentions of Ca and P were lower than in the rats fed 0.50% Ca. Both increases in dietary Ca from 0.13 to 0.50% and P from 0.20 to 0.40% elevated Ca and P content of kidneys as well as the degree of nephrocalcinosis. However, after feeding the highest Ca concentration (0.75%) nephrocalcinosis was essentially absent while kidney concentrations of Ca and P were relatively low. When compared with 0.50% Ca in the diet, 0.75% Ca increased group mean whole-body retention of Ca but lowered that of P. In individual rats the degree of nephrocalcinosis and the concentrations of minerals in kidney were positively correlated.     

Associations between dietary intake and urinary excretion of sodium, potassium, phosphorus, magnesium, and calcium

OBJECTIVES AND METHODS: The associations between dietary intake and urinary excretion of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P), and the major dietary sources derived from the urinary minerals were studied in a nutritional survey of 219 Japanese females aged 27-84 years, who completed anthropometric measurements, a one-day dietary record, and a 24 hr urine collection. RESULTS: The minerals excreted in the urine were significantly and positively correlated with each other, in which Na excretion was correlated with K and Ca excretion (r = 0.490 and r = 0.482, respectively, p < 0.01) and Ca excretion was correlated with Mg excretion (r = 0.526, p < 0.01). The ratios of urinary exertion to dietary intake of Na, K, Ca, Mg, and P were 81.5%, 62.7%, 24.5%, 21.7%, and 56.1%, respectively. The dietary intake and the urinary excretion of the minerals expressed per body weight (kg) were significantly and positively correlated (Na, r = 0.267; K, r = 0.460; Ca, r = 0.181; Mg, r = 0.245; P, r = 0.351, p < 0.01). Further examinations using chief component analysis for food intake showed several significant positive correlations, including between Na intake and the intake of vegetables, noodles, and seasonings (r = 0.332-0.381, p < 0.01); between K, Mg and P intake and the intake of vegetables, fruits, and potatoes (r = 0.332-0.533, p < 0.01); and between Ca intake and the intake of bread and dairy foods (r = 0.428, p < 0.01). In addition, significant positive associations were found between Na excretion and the intake of confectionaries, nuts, and seeds (r = 0.223, p < 0.01). Weak correlations were also found between K excretion and the intake of vegetables (r = 0.296, p < 0.01); between Ca and P excretion and the intake of meat, oil, and fats (r = 0.135, P < 0.05; r = 0.193, P < 0.01, respectively), and between Mg excretion and the intake of bread and dairy foods (r = 0.137, P < 0.05). CONCLUSIONS: Findings from this study indicate that, while urinary excretion of Ca and Mg is unlikely to be a reliable biochemical marker of dietary intake, the levels of urinary excretion of Na, K, and P can be reflective of the intake of salt, vegetables, and meats, respectively. The urinary excretion of the minerals, particularly Na, K, and Ca, may be highly linked to salt intake in Japanese females.     

White swans, black ravens, and lame ducks: necessary and sufficient causes in epidemiology

Several authors have used Popper's "white swan" example to support arguments for a falsificationist approach to epidemiology. The statement "all swans are white" cannot be verified by finding even a large number of white swans, but can be falsified by finding a single black swan. An analogous epidemiologic example that has been proposed is the hypothesis that a particular virus is a necessary cause of acquired immunodeficiency syndrome (AIDS). Such examples, however, have little relevance to science since scientific theories are not generalizations of facts; rather, they involve an understanding of the underlying processes that cause certain facts to occur. Furthermore, the "white swan" example is particularly inapplicable to epidemiology, since most factors of scientific or public health importance are neither necessary nor sufficient causes of disease. Nevertheless, epidemiologic research has achieved success in the understanding and prevention of disease. These points are exemplified by applying Rothman's model of causal constellations, which provides a conceptual basis for the development of epidemiologic theories.     

Influence of dietary calcium, phosphorus, zinc and sodium phytate level on cataract incidence, growth and histopathology in juvenile chinook salmon (Oncorhynchus tshawytscha)

To determine the influence of wide variations in dietary levels of calcium, zinc and phytic acid (as sodium phytate) on growth and cataract incidence, juvenile chinook salmon held at 10-11 degrees C were fed daily to satiation for 105 d one of nine purified diets containing one of three levels (grams/kilogram) of calcium (averaged 4.8, 17.7, 50.2), zinc (averaged 0.05, 0.15, 0.39) and phytic acid (1.62, 6.46, 25.8). Diets were formulated to have a calcium-phosphorus ratio of close to unity when considering phosphorus sources other than sodium phytate. High dietary phytic acid concentration (25.8 g/kg) depressed chinook salmon growth, food and protein conversion [protein efficiency ratio (PER)] and thyroid function, increased mortality, promoted cataract formation (zinc at 0.05 g/kg) and induced anomalies in pyloric cecal structure. Calcium at 51 g/kg (or phosphorus) exacerbated the effects of high dietary phytate and low dietary zinc on cataract incidence. Moreover, high dietary levels of calcium (48-51 g/kg) coupled with phosphorus significantly impaired the growth and appetite of low phytic acid (1.62 g/kg) groups and led to nephrocalcinosis in low and high phytic acid groups. Plasma zinc levels were directly related to dietary zinc concentration and inversely related to dietary phytic acid level. Calcium (51 g/kg) and/or phosphorus reduced zinc bioavailability when the diet concurrently contained 0.05 g zinc and 25.8 g of phytic acid per kilogram. It is concluded that zinc is essential for normal eye development in juvenile chinook salmon. Further, zinc deficiency could not be induced in chinook salmon fed diets with high ratios of calcium (or phosphorus) to zinc alone. This required the simultaneous presence of a strong mineral (zinc)-binding agent.