Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach.

Literature data on the bioavailability of various Mg forms provide scarce information on the best Mg salt to be used in animal and human supplementation. This study aimed to investigate the bioavailability of different forms of Mg in rats using Mg stable isotopes. Eighty male Wistar rats aged 6 weeks were fed a semi-purified Mg-depleted diet for three weeks. The rats were then randomised into ten groups and received, for two more weeks, the same diet repleted with Mg (550 mg Mg/kg) as: oxide, chloride, sulphate, carbonate, acetate, pidolate, citrate, gluconate, lactate or aspartate. After 10 days of Mg-repleted diet, the rats received orally 1.8 mg of an enriched 26Mg. Faeces and urine were then collected for 4 consecutive days. Isotope ratios in faeces and urine were determined. The Mg absorption values obtained varied from 50% to 67%. Organic Mg salts were slightly more available than inorganic Mg salts. Mg gluconate exhibited the highest Mg bioavailability of the ten Mg salts studied. Urinary 26Mg excretion varied from 0.20 mg to 0.33 mg, and feeding with the organic pidolate, citrate, gluconate and aspartate salts resulted in higher urinary 26Mg excretion than with inorganic salts. Ultimately, 26Mg retention was higher in the rats receiving the organic salts such as gluconate, lactate and aspartate than in those receiving the inorganic salts. Taken together, these results indicate that 26Mg is sufficiently bioavailable from the ten different Mg salts studied in the present experiment, although Mg gluconate exhibited the highest bioavailability under these experimental conditions.

Five-week intake of short-chain fructo-oligosaccharides increases intestinal absorption and status of magnesium in postmenopausal women.

Fermentable carbohydrates have been shown to be nondigestible by human enzymes in the small intestine but are fermented extensively in the large bowel to short-chain fatty acids (SCFAs), which can increase mineral absorption. It has been shown that feeding such carbohydrates including short-chain fructo-oligosaccharides (sc-FOSs) increases intestinal magnesium (Mg) absorption in animals, but their beneficial impact on Mg absorption in humans still remains to be established. Therefore, this work aimed to investigate the effect of moderate daily doses of sc-FOSs (10 g/day) on the intestinal absorption and status of Mg in postmenopausal women without hormone replacement therapy (HRT). Eleven healthy postmenopausal women aged 59 +/- 6 years (mean +/- SD) received for 5 weeks sc-FOS or sucrose (placebo) treatments according to a randomized, double-blind, crossover design separated by a washout period of at least 3 weeks. Subjects ingested 87.5 mg of stable isotope 25Mg together with a fecal marker. Subsequently, feces were collected for 5-7 days. An inductively coupled plasma mass spectrometer (ICP/MS) was used for 25Mg stable isotope measurements in feces, urine, and blood. Mg levels were assessed also at the beginning and at the end of each treatment in plasma, erythrocytes, and urine. These measurements allowed for the determination of net intestinal Mg absorption and Mg status. The results show that the addition of 10 g sc-FOS to the diet increased Mg absorption by 12.3%, from 30.2 +/- 5.0% (placebo treatment) to 33.9 +/- 7.2% (sc-FOS treatment; mean +/- SD; p < 0.02). This increase in intestinal Mg absorption was accompanied by an increase in plasma 25Mg level and led to a higher urinary 25Mg excretion. This is the first time that such an effect is shown in humans. The overall conclusion of this work is that the ingestion of moderate doses of sc-FOS did improve intestinal Mg absorption and status in postmenopausal women. Because of the important role of Mg in many cellular functions, such Mg absorption improvement may be particularly interesting when the dietary intake of Mg is limited.

Parathyroid hormone-related peptide might stimulate calcium secretion into the milk of goats.

Parathyroid hormone-related peptide (PTHrP) has been shown to stimulate the placental calcium pump in pregnant ewes. Recent studies also suggest a physiological role for this peptide during lactation. In the present work, we have studied the possible role of synthetic human PTHrP(1-34), (1-86) and (140-173) fragments on calcium, inorganic phosphorus and magnesium secretion into milk of four adult goats in early lactation. This was done by measuring differences in calcium, inorganic phosphorus and magnesium concentrations in the carotid artery and superficial epigastric vein, the concentration of these minerals in milk and milk production. Both PTHrP(1-34) and (1-86) fragments stimulated calcium, inorganic phosphorus and magnesium uptake by the mammary gland and secretion into milk, without any significant effect on milk production. Therefore PTHrP might have important physiological roles in the pregnant and/or lactating female, by regulating calcium transport through the placenta and mammary gland.

Relation between serum lipoperoxide concentrations and iron or copper status over one year in Cuban adult men.

The aims of this study were to determine the relations between iron and copper status and lipid peroxidation at different periods over one year in low-income and low-energy intake healthy subjects. The study was conducted in 199 middle-aged healthy Cuban men from March 1995 to February 1996. Iron status was assessed by the determination of serum ferritin, transferrin saturation, whole blood hemoglobin and iron intakes. Copper status was evaluated by the determination of serum copper and copper intakes. Serum thiobarbituric acid substances (TBARS) determination was used as an index of lipid peroxidation. Rank correlations were observed between serum TBARS concentrations and iron or copper status indices at different periods. In period 3 (end of the rainy season), serum TBARS and ferritin concentrations were maximum whereas blood hemoglobin levels and iron intake were minimum. Serum TBARS concentrations were significantly higher than the reference values of the laboratory whereas, iron and copper status were within the reference ranges. These results suggested that iron and copper status may be associated with lipid peroxidation in subjects without metal overloads and that variations over the year needed to be taken in account.

Mineral supplementation of white wheat flour is necessary to maintain adequate mineral status and bone characteristics in rats.

This experiment was designed to compare the effect of ingestion of a wheat flours on mineral status and bone characteristics in rats. White flour was tested either without further mineral supplementation or with Mg, Fe, Zn and Cu supplementation. The flour diets were compared to a control purified diet. Four groups of 10 male Wistar rats each were fed one of the experimental diets for 6 wk and mineral status and tissue retention as well as bone characteristics were determined. As expected, mineral intake, except for calcium, was significantly lesser in rats fed the white flour diet than in the other groups. The rats fed the white flour diet had the lowest food intake, weight gain, fecal excretion and intestinal fermentation. The most important result was that Mg and Fe status were drastically lower in rats fed the white flour diet than in those fed whole flour or control diets. The status of these both elements were significantly improved by the mineral supplementation of white flour. There were no major significant differences between mineral-supplemented white flour and whole flour groups in mineral status. Furthermore, bone mineral densities (total, metaphyseal and diphyseal) were significantly lower in rats fed white flour diet compared to the other diet groups, while no significant difference was observed between the mineral-supplemented white flour, whole flour or control diet groups. In conclusion, the present work shows clearly the importance of mineral-supplementation of white wheat flour to sustain an adequate intake of minerals. Our results indicate also that the whole wheat flour did not negatively alter mineral bioavailability, in comparison to mineral supplemented white flour. Clinical studies are still needed to confirm these rat results in human.

Contribution of milk to iodine intake in France.

A survey based on 838 samples of milk obtained from 537 dairies covering 70 of 95 districts in France was organized to assess iodine content of milk and its contribution to total intake. Iodine levels were significantly higher in winter than in summer. Very low iodine contents (less than 25 micrograms I/kg) were found in the eastern part of the country (the Vosges, Jura, and the Alpes) and the Massif Central. During milk processing, much of the iodine is lost in the whey. The other significant sources of dietary iodine are fish and eggs. Iodized salt is sold only to households and not to industry. Even if about 20% of the iodine is lost over the first 3 mo, salt remains the main source for this trace element. It is concluded that, if iodized salt is not provided systematically for both domestic and agro-industrial use, then milk may be the most important source of iodine. This key role may explain seasonal and geographical variations in the frequencies of goiter in France.

Comparative study of copper and zinc metabolism in cattle and camel.

At an experimental farm, five camels and five cows were fed a similar basal diet for 6 mo. They received oral trace element supplementation for 3 mo (day 22-112). This supplementation included zinc, copper, selenium, manganese, iodine, and cobalt, and corresponded to twice the requirements generally recommended for cows. Plasma copper and zinc concentrations were significantly lower in the camels (61 micrograms/100 mL for copper and 38 micrograms/100 mL for zinc) than in the cows (111 and 83, respectively). The supplementation had no effect on plasma zinc concentration in the camels in spite of the low observed values in this species. Liver copper concentration at the beginning of the trial was lower in the camels (9 ppm) than in the cows (35 ppm), and stayed at lower levels during the entire supplementation period. There was no clear difference in fecal excretion of copper and zinc between the camels and the cows. The results suggested that trace element requirements are lower in camels than in cows and that camels regulate their plasma zinc concentration at a very low level (< 40 micrograms/100 mL).

Stimulatory effect of inulin on intestinal absorption of calcium and magnesium in rats is modulated by dietary calcium intakes short- and long-term balance studies.

Previous studies have shown that short-term intake of fermentable oligosaccharides (OS), including inulin, can increase mineral intestinal absorption in humans and animals. While the stimulatory effect of these substances on intestinal magnesium (Mg) absorption is generally high and consistent, their effect on calcium (Ca) seems to depend on experimental conditions, particularly the duration of fermentable OS intake. The aim of this study was to determine how the short- and long-term dietary Ca intake may modulate the effect of inulin on Ca absorption. Sixty male Wistar rats, weighing 275 g, were randomized into two groups to receive or not 10% of inulin in their diet. Each group was divided into three sub-groups to receive one of the following dietary Ca levels 0.25%, 0.50% and 0.75% in their food. The animals were fed fresh food and water ad libitum for 40 days. Apparent intestinal absorptions of Ca and Mg were determined at D13 and D36 of the experiment. As expected, inulin feeding increased Ca and Mg absorption in both periods at all dietary Ca levels. However, the effect of inulin on intestinal Ca absorption was dependent on dietary Ca levels and on experiment duration. In the short-term period, the inulin effect was prominent in the groups receiving high or low Ca levels, but in long-term period inulin improved intestinal Ca absorption much more in the group receiving the low Ca level. In addition, efficiency of intestinal absorption of Ca and Mg (%) was negatively affected by Ca intake levels. These results show that the beneficial effect of inulin on intestinal Ca absorption may be more marked in cases where the Ca intake is low or where the organism's Ca requirement is high. Further studies are required to confirm these results in humans.

The emergence and treatment kinetic of cobalt deficiency in the sheep.

The emergence and treatment kinetic of the vitamin B12 deficiency was studied in 4 adult male Texel sheep bearing rumen fistulas. A natural meadow-grass, low in cobalt (0.04 mg/g of dry matter) was distributed freely to the animals. After the emergence of the vitamin B12 deficiency, the animals received every day a 10 ml solution containing 0.5 mg of cobalt in the rumen. The ingestion of a cobalt-deficient hay provoked a great decrease in the synthesis of vitamin B12 during the first week. The serum content decreases more slowly, the deficiency threshold being reached after 7 weeks. A serious deficiency is apparent 10 weeks after the deficient diet was first distributed. The treatment applied to the animals has a rapid and spectacular effect. The synthesis returns to normal 72 hours after the start of intraruminal cobalt infusions. The animals are no longer deficient after 24 to 28 hours of treatment.

The mineral and trace element composition in French food items and intake levels in France.

A table was made of the composition of mineral and trace elements in different classes of French food items. The P, Ca, Mg, Fe, Cu, Zn, Mn, I and Se contents of the main categories of food are presented. The mineral and trace element intakes of the average French consumer were calculated from national survey data concerning all food items purchased by households. The intakes and the sources of the different elements are given related to the energy. These results were calculated for male and female adults receiving 2700 kcal and 2000 kcal, respectively, and compared with the recommended dietary allowances (RDA). Phosphorus and calcium intakes were adequate, as was iron for men. The intakes of Mg, Cu, Mn were between 80 and 100% of the RDA. For Zn, I, Se the intakes were lower (50-80% of the RDA). The iron deficiency observed in women is serious, and the selenium deficit in men may induce real biochemical subdeficiencies with clinical consequences.

Studies of the changes in systemic copper metabolism and excretion produced by the intravenous administration of trithiomolybdate in sheep.

1. The effects of intravenous trithiomolybdate administration on the fate of 64Cu and on stable Cu metabolism were examined in sheep held in metabolism cages and fed on a low-Cu diet supplying 2.95 mg Cu/animal per d. 2. In Expt 1 the injection of trithiomolybdate, 30 mg molybdenum/sheep per d for 5 d, greatly increased plasma Cu levels and more than doubled the faecal Cu excretion. Urinary Cu excretion was unaffected. The disappearance from plasma of 64Cu injected during the trithiomolybdate administration was slowed although faecal 64Cu excretion was increased more than threefold. 3. In Expt 2 trithiomolybdate, 10 and 30 mg Mo/sheep per d for 3 d, was administered 22 h after the injection of 64Cu. Radioactivity reappeared immediately in plasma and faecal 64Cu excretion was increased. 4. In both experiments the 64Cu and the increased stable Cu in plasma were associated with albumin. 5. The experiments explain the effectiveness of thiomolybdates as 'decoppering' agents and provide a model for some of the systemic effects seen in ruminants exposed to increased dietary Mo. The experiments support the view that the thiomolybdates, by causing the appearance of new ligands, alter the distribution of Cu in tissues and cause an overall depletion.

Iodine nutrition in ewes. 2. Effects of low to high iodine intake by ewes on the I content of biological fluids and plasma immunoglobulins G in newborn lambs.

1. In two experiments samples of blood and organs were taken from newborn and young lambs born to five groups of ewes that received different dietary iodine (I) levels. Dietary I contents (mg/kg dry matter [DM]) in pregnancy and lactation, respectively, were: Experiment 1--0.36 and 0.26 for group C, 2.01 and 1.94 for group D; Experiment 2--0.13 and 0.12 for group A, 0.22 and 0.20 for group B, 10.77 and 8.88 for group E. 2. I intake of ewes had no effect on birthweight, body weight gain, or mortality between birth and wk 2 of life. No difference between the groups was recorded in the weights of brain, heart, lungs, and liver of lambs killed at birth. However, the weight of both the thyroid lobes in lambs from group E was lower than that of the other groups. The I content of the thyroid lobes of lambs from group A was 30-40% lower than that of the other groups. 3. The plasma inorganic iodine (PII) of lambs from birth to d42 of life was affected by ewe I intake, except for groups A and B, during the first 16 h of life. The PII of lambs increased with the I intake via milk in each group. The ratio of PII of lambs at birth/PII of ewes at d7 prepartum was 3.77, 2.96, 1.68, 1.39 and 8.62, respectively, for groups A, B, C, D and E. 4. The high I intake by group E ewes induced a higher plasma T4 concentration in lambs at birth. The decrease in plasma immunoglobulins G (IgG) recorded for the lambs in this group might be explained by this increase in plasma concentration.

Biochemical parameters useful for the diagnosis of mild molybdenosis in sheep.

Three groups of ten young ewes (29 kg) received a basal diet or a diet enriched in sulphur (3 g/kg DM) or sulphur (3 g/kg DM) plus molybdenum (13 mg/kg DM). The total plasma copper increased in the S + Mo group. The trichloracetic acid (TCA) insoluble copper fraction of this group rose sharply from the second week of experiment. A decrease in ceruloplasmin oxidase activity could be detected in non-saturating or saturating substrate conditions in the enzyme assay, either with paraphenylenediamine or o-dianisidine as substrate. It was concluded that the decrease was due to failure of synthesis rather than inhibition. The plasma TCA insoluble copper fraction is thus the earliest and most reliable parameter for molybdenosis diagnosis in sheep.

Comparison of the efficiency of zinc injected as metal or oxide for zinc deficiency treatment in sheep.

Efficiency of zinc injection as metal or oxide suspended in purified oil has been compared with control in three groups of seven ewes (39 kg). The zinc injected as oxide is liberated more rapidly from the injection site and the plasma zinc reachs a higher level than with zinc metal. However the effect of zinc metal injection lasts longer. Plasma copper behaves as an inflammation index. It rises more with zinc oxide injection. Both forms, metal or oxide are well tolerated by sheep without any side effect. Zinc oxide may be injected for more intensive but shorter treatment when zinc metal offers the best delayed effect.

The influence of sulfur supplementation (methionine and sulfate) on the zinc availability of a poor diet in sheep.

A poor hay, with a low proteic level, decreases the zinc availability in lambs. Increasing the sulfur level with methionine and sulfate, of such a diet, enhances zinc absorption. However, sulfur is not the only factor limiting zinc availability in a hypoproteic diet.

Iodine nutrition in ewes: effects of low to high iodine intake on iodine content of biological fluids in pregnant and lactating ewes.

In a first experiment, 2 groups of 46 and 47 multiparous ewes received diets which provided an iodine intake of 0.36 and 0.26 mg/kg dry matter (group C) and, 2.01 and 1.94 mg/kg (group D), respectively, for pregnancy and lactation. In a second experiment, 3 groups of 10 nulliparous ewes received diets which provided an I intake of 0.13 and 0.12 mg/kg dry matter (group A), 0.22 and 0.20 mg/kg dry matter (group B), and 10.77 and 8.88 mg/kg dry matter (group E), respectively, for pregnancy and lactation. Observations and sampling were carried out on the ewes from the first third of pregnancy to the 2nd and the 6th week of lactation. The diets provided adequate nutrition for pregnant and lactating ewes. Dietary I content had no effect on the dry matter intake, the size or the weight of the litter and the length of pregnancy. Plasma inorganic iodine (PII) was less affected by the I intake during lactation than during pregnancy. The excretion of I in milk induced a decrease in PII between pregnancy and lactation. The I in urine expressed as microgram I/g creatinine was largely affected by the intake. Colostrum I was 6.7, 4.0, 1.2, 1.3 and 1.5 times higher in groups A, B, C, D and E than the I in milk collected 1 week postpartum. Milk iodine (MI) content and the ratio MI/PII were markedly dependent on the I intake. During pregnancy, plasma T4 concentration decreased for each group. Plasma T4 concentration remained low during lactation in the low I intake group, whereas it increased at the same time in the other groups. The plasma T3 concentration decreased at the 6th week of lactation in the highest I intake group. Experimental values showed that 0.12 mg I/kg dry matter induced depletion in the I stocks of pregnant and lactating ewes, whereas an I intake above 10 mg I/mg dry matter disturbed the metabolism of thyroid hormones.

A zinc-deficient diet for ruminants: diagnosis and treatment of deficiency.

A zinc deficient diet which is not semi-synthetic was tried on 20 male Limousin X Romanoff three and a half month-old sheep weighing 36 kg on average. This diet was composed of strawy hay sprayed with caramel containing urea and minerals. Compared to hay alone this diet is more appetizing to lambs and more equilibrated as to energy level and soluble nitrogen utilization. The deficiency appeared within a week in zinc plasma and progressed clinically within 100 days. The plasmic free zinc and alkaline phosphatase were not better criteria for the deficiency diagnosis than total plasmic zinc. Supplementing the diet to 50 or even 100 mg Zn/kg DM was insufficient to suppress the deficiency. Zinc injection, by contrast, restored zincemia to normal in ten days. Zinc deficiency treatment by oral route should be reconsidered.

The influence of dietary sulphur, molybdate and copper on the absorption, excretion and plasma fraction levels of 99Mo in sheep.

The effect of increased dietary sulphur, copper and molybdate on the metabolism of 99Mo administered via the rumen or duodenum was examined. Duodenally administered 99MoO4= was efficiently and rapidly absorbed and excreted via the urine; dietary modifications did not alter this pattern although increased dietary S increased the excretion rate. The passge of 99MoO4= through the rumen led to chemical modification, so that, particularly at high S levels, most of the radioactivity remained in the feces; increased dietary Mo led to increased absorption whereas increased copper decreased absorption. Incorportion of radioactivity into the TCA insoluble plasma fraction was shown with increased dietary S and particularly when both dietary S and Mo were increased. The compatiblity of the results with the hypothesis of ruminal thiomolybdate formation and subsequent reaction with dietary or tissue copper is discussed.

A semi-automated method for the determination of iodine in plants.

A method for the determination of iodine in plants is described. This method involves destruction of organic matter by alkaline incineration and automated spectrophotometric determination of iodide based on the Sandell and Kolthoff's reaction. The mean recovery of 131I was 93.4% (S.D. = 3.19)). For replicate analyses of different plant material, the coefficient of variation is between 3 and 5%.

Iodine Content of Dairy Milk in France in 1983 and 1984.

Iodine concentrations were determined in 848 samples of milk from tanks of 537 dairy factories collected in 1983 and 1984 during winter and summer. Industrial processing, like pasteurization, UHT sterilization and spray-drying, had no effect on iodine concentrations. Of the samples of bovine milk, 94.7% ranged between 10 to 250 µg/kg. Iodine in bovine milk averaged 97 and 93 µg/kg in the winter of 1983 and 1984, and 44 and 23 µg/kg in the summer of 1983 and 1984. The frequency of iodine concentrations above the 500 µg/kg limit was 0.5% in 1983 and 0.3% in 1984. Iodine in ovine milk varied from 116 to 1183 µg/kg. Of the ovine milk samples 53.3% were above 500 µg/kg. Thus the iodine content of milk, is not yet a health problem in France.