Minerals in the News
from The Mineral People™
Vol 4, Issue 4, April 2006

 

 

CALCIUM ABSORPTIVE EFFICIENCY IS POSITIVELY RELATED TO BODY SIZE
Barger-Lux, Heaney RP
J Clin Endocrinol Metab 2005; 90(9):5118-20.

The efficiency of calcium absorption is more important to calcium balance than calcium intake. All is not known about the causes of absorption variability. This study looks into the relationship between body size and calcium absorption efficiency.
The study was conducted at an inpatient metabolic unit in an academic health sciences center. The study included 178 women of average age 50.2 years. Calcium absorption fraction was measured via dual tracer method. Observed values were expressed as residuals from predicted values for each woman’s actual calcium intake, using the previously published relationship between intake and absorption. The absorption residuals were significantly positively correlated with height, weight, and surface area, and after adjusting for estrogen status, these body size variables accounted for about 4% of the total variability. The magnitude of this effect is such that a woman 1.8 meters in height would absorb 30% more calcium from a given intake than a woman 1.4 meters tall.


 

 

CALCIUM FORTIFICATION SYSTEMS DIFFER IN BIOAVAILABILITY
Heaney RP, et al
J Am Diet Assoc 2005; 105(5):807-9

This study tries to compare the bioavailability of calcium from two different fortification systems used in orange juice. Study design was randomized crossover, within-subject. The study subjects were 25 healthy premenopausal women in an academic health sciences center. The dosage of calcium was 500 mg in two different commercially available orange juice products, taken at breakfast after an overnight fast. One product uses calcium citrate malate as its fortification system, while the other uses a combination of tricalcium phosphate and calcium lactate. The main outcome measure was the area under the curve (AUC) for the increase in serum calcium seen from 0 to 9 hours after ingesting the calcium source. The AUC for the calcium citrate malate product was 48% greater than that seen for the tricalcium phosphate/calcium lactate product. These results indicate that equivalent calcium contents on a nutritional label do not guarantee equivalent nutritional value. Manufacturers should be encouraged to provide bioavailability information on their fortified products.

 

DIETARY IRON DEFICIENCY INDUCES VENTRICULAR DILATION, MITOCHODRIAL ULTRASTRUCTURAL ABERRATIONS AND CYTOCHROME C RELEASE: INVOLVEMENT OF NITRIC OXIDE SYNTHASE AND PROTEIN TYROSINE NITRATION.
Don F, et al
Clin Sci (Lond). 2005; 109(3):277-86

Iron deficiency results in multiple health problems, including problems involving the cardiovascular system. The mechanism by which iron deficiency damages the cardiovascular system needs to be elucidated. This study examines the effect of dietary iron deficiency on cardiac ultrastructure mitochondrial cytochrome c release, NOS (nitric oxide synthase) and several stressrelated protein molecules, including protein nitrotyrosine, the p47phox subunit of NADPH oxidase, caveolin-1 and RhoA.
Male weanling rats were fed with either a control or an iron-deficient diet for 12 weeks. The rats on the iron-deficient diet were found to have increased heart weight and size over the control group. Left ventricular dimension and chamber volume were significantly larger in the iron deficient group. Iron deficient ventricular tissues revealed mitochondrial swelling and abnormal sarcomere structure. Cytochrome c release was enhanced, and protein expressions of endothelial NOS and inducible NOS , and protein nitrotyrosine formation were elevated in the cardiac tissue of the iron deficient group. NADPH oxidase, caveolin-1, and RhoA expression were upregulated in the ventricular tissue of the iron deficient. These results suggest that iron deficiency may induce cardiac hypertrophy, characterized by aberrant mitochondrial and irregular sarcomere organization – accompanied by increased reactive nitrogen species and RhoA expression.

 

IRON STATUS OF FEMALE COLLEGIATE ATHLETES INVOLOVED IN DIFFERENT SPORTS.
Sareen S. Gropper, et al.
Biological Trace Element Research, Vol 109, 206, pp 1-13.

This study involved 70 female athletes, ages 18-15, who were involved in collegiate cross-country track, tennis, softball, swimming, soccer, basketball, and gymnastics. No significant differences were seen in mean hemoglobin, hematocrit, serum iron, total iron-binding capacity, transferrin saturation, and ferritin were found among the teams. All of the mean concentrations of each parameter for every team were inside normal ranges. Several athletes, however, from a variety of spots had suboptimal iron status indices. Seventeen athletes with low serum ferritin concentrations (<15mcg/L), also exhibited low serum iron (<60mcg/L) and low transferrin saturation (<16%). Thirteen of the athletes failed to consume ⅔ of the RDA for iron and exhibited suboptimal serum concentrations of ferritin, iron, and/or transferrin saturation. Out of nine athletes taking iron supplements, one exhibited suboptimal iron status. In summary, nonanemic iron depletion was seen among the female collegiate athletes in all sports, and the female athlete should continue to be individually and routinely evaluated fro nutritional deficiencies throughout their athletic careers.

 

ABNORMAL DEVELOPMENT AND INCREASES 3-NITROTYROSINE IN COPPER-DEFICIENT MOUSE EMBRYOS.
Beckers-Trapp ME, et al.
Free Radic Biol Med, 2006; 40(1):35-44.

Copper deficient rat embryos are characterized by low superoxide dismutase activity and high superoxide anion concentrations, and result in brain and heart anomalies. High superoxide anions can lead to the formation of the strong biological oxidant, peroxynitrite. In the study, embryos from copper-adequate and copper-deficient dames were cultured in media that were adequate or deficient in copper. After 48 hours, the copper-deficient exhibited brain and heart anomalies, as well as a high incidence of yolk sac vasculature abnormalities. Protein nitration(3-nitrotyrosine levels) were markedly higher in the copper deficient’s anterior neural tube epithelium. Correction of the deficiency did not ameliorate the abnormal development, but did decrease the 3-nitrotyrosine levels mentioned. Study shows that copper-deficiency compromises oxidant defense and increases protein nitration and may contribute to copper-deficiency-induced teratogenesis.

 

IRON BIOAVAILABILITY FROM FORTIFIED FLUID MILK AND PETIT SUISSE CHEESE DETERMINED BY THE PROPHYLACTIC-PREVENTIVE METHOD
Salgueiro J, et al.
Biological Trace Element Research, Vol 109, pp 91-96, 2006.

This study measures the iron bioavailabity of micronized ferric orthophosphate when used to fortify low fat fluid milk enriched with calcium and Petit Suisse cheese using the prophylactic-preventive method in rats. There were four groups of rats in the study, a basal diet group (control diet; 6.5 ppm Fe), a reference standard diet (ferrous sulfate micronized; 18.2 ppm Fe), a basal diet with fortified milk supplying the iron (17.9 ppm Fe, from micronized ferric orthophosphate), and a basal diet with iron fortified Petiti Suisse as the iron source (18 ppm Fe from micronized ferric orthophosphate). The iron bioavailability for the groups were calculated as the ratio between the mass of iron incorporated into the hemoglobin during the study and the total iron taken in per animal. The relative bioavailability, as compared to the reference standard of micronized ferrous sulfate was 61% and 69% for the milk source and cheese source respectively (both containing the micronized ferric orthophosphate). These are considered to be of medium bioavailability.