Effect of daily versus twice weekly long-term iron supplementation on iron absorption and status in iron-deficient women: a stable isotope study.

OBJECTIVES: This work aims at studying the effect of daily versus twice weekly long-term Fe supplementation on Fe absorption and status in Fe-deficient women. DESIGN AND METHODS: The study design is a randomized controlled open study carried out in the Internal Medicine Department, CHU de Clermont-Ferrand, France. Twenty-four young women participated in this study and were randomized into two groups: Group 1 received 50 mg Fe daily, and group 2 received 50 mg Fe twice weekly for 3 months. On day 10 (D10) and on day 90 (D90) of Fe supplementation, blood samples were obtained, and women received orally about 5 mg of 57Fe, and blood was sampled at different times over 24 h. The 57Fe absorption was evaluated by calculating the areas under the curves (AUC). Fe and oxidative stress status were also assessed. RESULTS: 57Fe absorption was similar in both groups on D10 but was greatly decreased in Group 1 and remained high in Group 2 on D90. Fe status was more improved in Group 1 than in Group 2. Oxidative stress status remained statistically unchanged. CONCLUSIONS: Our study shows that daily Fe supplementation is able to correct an Fe deficiency much more than twice weekly Fe supplementation in young women.

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.