Iron Absorption from an Iron-Fortified Follow-Up Formula with and without the Addition of a Synbiotic or a Human-Identical Milk Oligosaccharide: A Randomized Crossover Stable Isotope Study in Young Thai Children.

BACKGROUND: Previous studies showed that pre- and probiotics may enhance iron absorption. Probiotics combined with prebiotics (synbiotics), including human-identical milk oligosaccharides (HiMOs), are commonly added to infant and follow-up formula (FUF). Whether these additions enhance iron absorption from iron-fortified commercial milk formula is uncertain. OBJECTIVES: We determined the effect of adding 1) a synbiotic [galacto-oligosaccharide [GOS] + Limosilactobacillus reuteri (L. reuteri)] or 2) the HiMO 2'-fucosyllactose (2'FL) to iron-fortified FUF on iron absorption in young Thai children. METHODS: In a randomized, controlled, single-blinded (participants) crossover study, 82 Thai children aged 8-14 mo were enrolled to consume single servings (235 mL) of FUF with isotopically labeled ferrous sulfate (2.2 mg iron) with 1) the synbiotic (400 mg/100 mL GOS and L. reuteri DSM 17938), 2) the HiMO 2'FL (100 mg/100 mL), and 3) without synbiotic and 2'FL (control) in random order and a 3-d washout period between administrations. Fractional iron absorption [FIA (%)] was assessed by measuring erythrocyte incorporation of isotopic labels 14 d (n = 26) and 28 d (n = 76) after consumption of the last test FUF. RESULTS: Median (IQR) FIA from iron-fortified FUF with the synbiotic [8.2 (5.2, 12.9)%] and with 2'FL [8.4 (5.5, 14.1)%] did not differ from the control FUF [8.1 (4.8,14.7)%] (synbiotic compared with control, P = 0.24; 2'FL compared with control, P = 0.95). FIA from all FUF did not differ when measured after 14 and 28 d of erythrocyte incorporation (Time, P = 0.368; FUF, P = 0.435; Time × FUF, P = 0.937). Fecal pH and hemoglobin were negatively associated with FIA. CONCLUSIONS: In young Thai children, the addition of a synbiotic (GOS + L. reuteri) or 2'FL to iron-fortified FUF did not impact FIA from a single serving. The study was registered at clinicaltrials.gov as NCT04774016.

Galacto-oligosaccharide preconditioning improves metabolic activity and engraftment of Limosilactobacillus reuteri and stimulates osteoblastogenesis ex vivo.

A probiotic-related benefit for the host is inherently linked to metabolic activity and integration in the gut ecosystem. To facilitate these, probiotics are often combined with specific prebiotics in a synbiotic formulation. Here, we propose an approach for improving probiotic metabolic activity and engraftment. By cultivating the probiotic strain in the presence of a specific prebiotic (preconditioning), the bacterial enzymatic machinery is geared towards prebiotic consumption. Today, it is not known if preconditioning constitutes an advantage for the synbiotic concept. Therefore, we assessed the effects galacto-oligosaccharide (GOS) addition and preconditioning on GOS of Limosilactobacillus reuteri DSM 17938 on ex vivo colonic metabolic profiles, microbial community dynamics, and osteoblastogenesis. We show that adding GOS and preconditioning L. reuteri DSM 17938 act on different scales, yet both increase ex vivo short-chain fatty acid (SCFA) production and engraftment within the microbial community. Furthermore, preconditioned supernatants or SCFA cocktails mirroring these profiles decrease the migration speed of MC3T3-E1 osteoblasts, increase several osteogenic differentiation markers, and stimulate bone mineralization. Thus, our results demonstrate that preconditioning of L. reuteri with GOS may represent an incremental advantage for synbiotics by optimizing metabolite production, microbial engraftment, microbiome profile, and increased osteoblastogenesis.

A systematic review of iodine intake in children, adults, and pregnant women in Europe-comparison against dietary recommendations and evaluation of dietary iodine sources.

CONTEXT: Adequate iodine intake is essential throughout life. Key dietary sources are iodized salt and animal products, but dietary patterns in Europe are changing, for example toward lower salt intake and a more plant-based diet. OBJECTIVE: To review iodine intake (not status) in European populations (adults, children, and pregnant women) to identify at-risk groups and dietary sources. DATA SOURCES: PubMed, Embase, and Cochrane databases, as well as European national nutrition surveys were searched for data on had iodine intake (from dietary assessment) and sources of iodine, collected after 2006. DATA SELECTION: In total, 57 studies were included, comprising 22 national surveys and 35 sub-national studies. Iodine intake data were available from national surveys of children aged <10 years (n = 11), 11-17 years (n = 12), and adults (n = 15), but data from pregnancy were only available from sub-national studies. RESULTS: Iodine intake data are lacking-only 17 of 45 (38%) European countries had iodine-intake data from national surveys. Iodine intake reported from national surveys was below recommendations for: (1) children aged <10 years in 2 surveys (18%), (2) boys and girls aged 11-17 years in 6 (50%) and 8 (68%) surveys, respectively, and (3) adult men and women in 7 (47%) and 12 (80%) surveys, respectively. In pregnant women, intake was below recommendations except where women were taking iodine-containing supplements. Just 32% of national surveys (n = 7) included iodized salt when estimating iodine intake. Milk, dairy products, fish, and eggs were important contributors to intake in many countries, suggesting limited sources in plant-based diets. CONCLUSION: Results are limited by the challenges of dietary assessment for measuring iodine intake. Future national surveys should include iodine intake. Policy makers should consider dietary sources alongside any iodized salt policies when considering methods for improving population iodine intake. SYSTEMATIC REVIEW REGISTRATION: PROSPERO 2017 CRD42017075422.

Iron Bioavailability from Ferrous Ammonium Phosphate, Ferrous Sulfate, and Ferric Pyrophosphate in an Instant Milk Drink-A Stable Isotope Study in Children.

Ferrous ammonium phosphate (FAP) is an iron salt that has been developed for the fortification of food matrices sensitive to color and flavor changes. The objective of the study was to measure iron absorption from FAP in young children and compare it to a previous evaluation of FAP in young women. A double-blind randomized crossover study with two parallel arms was used to evaluate the iron absorption from FAP added to reconstituted milk powder in comparison to that from ferrous sulfate (FeSO4) and ferric pyrophosphate (FePP). Iron absorption was measured in 39 children aged 3- to 6-years-old using erythrocyte incorporation of stable Fe isotopes (57Fe, 58Fe). The geometric mean iron absorption in iron replete children from FAP, FeSO4 and FePP from milk was 8.3%, 7.6% and 2.1%, respectively. Iron absorption from FAP and FeSO4 fortified milk was not significantly different (p = 0.199); however, it was significantly higher than from FePP fortified milk (p < 0.001). Iron bioavailability from FAP and FePP relative to FeSO4 (relative bioavailability (RBV)) was 110% and 33%, respectively. The RBV of FAP (110%) in iron replete children was higher than previously reported RBV (71%) in mainly iron deficient women. The difference in iron status between the children and women in the respective studies may explain the different RBV values and is discussed.

Iron Bioavailability from Infant Cereals Containing Whole Grains and Pulses: A Stable Isotope Study in Malawian Children.

BACKGROUND: Compared with infant cereals based on refined grains, an infant cereal containing whole grains (WGs) and pulses with adequate amounts of ascorbic acid to protect against absorption inhibitors could be a healthier source of well-absorbed iron. However, iron absorption from such cereals is uncertain. OBJECTIVE: We measured iron bioavailability from ferrous fumarate (Fefum) added to commercial infant cereals containing 1) refined wheat flour (reference meal), 2) WG wheat and lentil flour (WG-wheat-lentil), 3) WG wheat and chickpea flour (WG-wheat-chickpeas), and 4) WG oat flour (WG-oat) and from ferrous bisglycinate (FeBG) added to the same oat-based cereal (WG-oat-FeBG). METHODS: In a prospective, single-blinded randomized crossover study, 6- to 14-mo-old Malawian children (n = 30) consumed 25-g servings of all 5 test meals containing 2.25 mg stable isotope-labeled iron and 13.5 mg ascorbic acid. Fractional iron absorption (FIA) was assessed by erythrocyte incorporation of isotopes after 14 d. Comparisons were made using linear mixed models. RESULTS: Seventy percent of the children were anemic and 67% were iron deficient. Geometric mean FIA percentages (-SD, +SD) from the cereals were as follows: 1) refined wheat, 12.1 (4.8, 30.6); 2) WG-wheat-lentil, 15.8 (6.6, 37.6); 3) WG-wheat-chickpeas, 12.8 (5.5, 29.8); and 4) WG-oat, 9.2 (3.9, 21.5) and 7.4 (2.9, 18.9) from WG-oat-FeBG. Meal predicted FIA (P ≤ 0.001), whereas in pairwise comparisons, only WG-oat-FeBG was significantly different compared with the refined wheat meal (P = 0.02). In addition, FIAs from WG-wheat-lentil and WG-wheat-chickpeas were significantly higher than from WG-oat (P = 0.002 and P = 0.04, respectively) and WG-oat-FeBG (P < 0.001 and P = 0.004, respectively). CONCLUSION: In Malawian children, when given with ascorbic acid at a molar ratio of 2:1, iron bioavailability from Fefum-fortified infant cereals containing WG wheat and pulses is ≈13-15%, whereas that from FeBG- and Fefum-fortified infant cereals based on WG oats is ≈7-9%.

Impact of Ascorbic Acid on the In Vitro Iron Bioavailability of a Casein-Based Iron Fortificant.

A new iron-casein complex (ICC) has been developed for iron (Fe) fortification of dairy matrices. The objective was to assess the impact of ascorbic acid (AA) on its in vitro bioavailability in comparison with ferrous sulfate (FeSO4) and ferric pyrophosphate (FePP). A simulated digestion coupled with the Caco-2 cell culture model was used in parallel with solubility and dissociation tests. Under diluted acidic conditions, the ICC was as soluble as FeSO4, but only part of the iron was found to dissociate from the caseins, indicating that the ICC was an iron chelate. The Caco-2 cell results in milk showed that the addition of AA (2:1 molar ratio) enhanced iron uptake from the ICCs and FeSO4 to a similar level (p = 0.582; p = 0.852) and to a significantly higher level than that from FePP (p < 0.01). This translated into a relative in vitro bioavailability to FeSO4 of 36% for FePP and 114 and 104% for the two ICCs. Similar results were obtained from water. Increasing the AA to iron molar ratio (4:1 molar ratio) had no additional effect on the ICCs and FePP. However, ICC absorption remained similar to that from FeSO4 (p = 0.666; p = 0.113), and was still significantly higher than that from FePP (p < 0.003). Therefore, even though iron from ICC does not fully dissociate under gastric digestion, iron uptake suggested that ICCs are absorbed to a similar amount as FeSO4 in the presence of AA and thus provide an excellent source of iron.

Iron bioavailability from bouillon fortified with a novel ferric phytate compound: a stable iron isotope study in healthy women (part II).

Bouillon cubes are widely consumed and when fortified with iron could contribute in preventing iron deficiency. We report the development (part I) and evaluation (current part II) of a novel ferric phytate compound to be used as iron fortificant in condiments such as bouillon. Ferric pyrophosphate (FePP), is the compound of choice due to its high stability in foods, but has a modest absorption in humans. Our objective was to assess iron bioavailability from a novel iron fortificant consisting of ferric iron complexed with phytic acid and hydrolyzed corn protein (Fe-PA-HCP), used in bouillon with and without an inhibitory food matrix. In a randomised single blind, cross-over study, we measured iron absorption in healthy adult women (n = 22). In vitro iron bioaccessibility was assessed using a Caco-2 cell model. Iron absorption from Fe-PA-HCP was 1.5% and 4.1% in bouillon with and without inhibitory matrix, respectively. Relative iron bioavailability to FeSO4 was 2.4 times higher than from FePP in bouillon (17% vs 7%) and 5.2 times higher when consumed with the inhibitory meal (41% vs 8%). Similar results were found in vitro. Fe-PA-HCP has a higher relative bioavailability versus FePP, especially when bouillon is served with an inhibitory food matrix.

Reducing the burden of iron deficiency anemia in Cote D'Ivoire through fortification.

BACKGROUND: Iron deficiency anemia (IDA) is highly prevalent in the Cote d'Ivoire and has severe health and economic consequences. In this paper, we apply a health economic model to quantify the burden of IDA, and the contribution of nationwide mandatory iron fortification of wheat flour and voluntary iron fortification of condiments to the reduction of this burden. METHODS: The analysis for the population from 6 months to 64 years builds on published reviews and publicly available datasets and is stratified by age-groups and socioeconomic strata using comparative risk assessment model. RESULTS: Without the impact of these fortification strategies, the annual burden of IDA is estimated at 242,100 disability adjusted life years (DALYs) and 978.1 million USD. Wheat flour and condiment fortification contributed to a reduction of the IDA burden by approximately 5% each. CONCLUSION: In places with high prevalence of malaria and other infectious diseases, such as the Côte D'Ivoire, food fortification as a nutritional intervention should be accompanied with infectious disease prevention and control. The findings of this study provide additional input for policy makers about the magnitude of the impact and can support the conception of future fortification strategies.

The bioavailability of iron picolinate is comparable to iron sulfate when fortified into a complementary fruit yogurt: a stable iron isotope study in young women.

PURPOSE: A technological gap exists for the iron (Fe) fortification of difficult-to-fortify products, such as wet and acid food products containing polyphenols, with stable and bioavailable Fe. Fe picolinate, a novel food ingredient, was found to be stable over time in this type of matrix. The objective of this study was to measure the Fe bioavailability of Fe picolinate in a complementary fruit yogurt. METHODS: The bioavailability of Fe picolinate was determined using stable iron isotopes in a double blind, randomized cross-over design in non-anemic Swiss women (n = 19; 25.1 ± 4.6 years). Fractional Fe absorption was measured from Fe picolinate (2.5 mg 57Fe per serving in two servings given morning and afternoon) and from Fe sulfate (2.5 mg 54Fe per serving in two servings given morning and afternoon) in a fortified dairy complementary food (i.e. yogurt containing fruits). Fe absorption was determined based on erythrocyte incorporation of isotopic labels 14 days after consumption of the last test meal. RESULTS: Geometric mean (95% CI) fractional iron absorption from Fe picolinate and Fe sulfate were not significantly different: 5.2% (3.8-7.2%) and 5.3% (3.8-7.3%) (N.S.), respectively. Relative bioavailability of Fe picolinate versus Fe sulfate was 0.99 (0.85-1.15). CONCLUSION: Therefore, Fe picolinate is a promising compound for the fortification of difficult-to-fortify foods, to help meet Fe requirements of infants, young children and women of childbearing age.

Longitudinal Changes of Mineral Concentrations in Preterm and Term Human Milk from Lactating Swiss Women.

An adequate mineral supply to preterm infants is essential for normal growth and development. This study aimed to compare the mineral contents of human milk (HM) from healthy mothers of preterm (28-32 weeks) and full term (>37 weeks) infants. Samples were collected weekly for eight weeks for the term group (n = 34) and, biweekly up to 16 weeks for the preterm group (n = 27). Iron, zinc, selenium, copper, iodine, calcium, magnesium, phosphorus, potassium, and sodium were quantitatively analyzed by Inductively Coupled Plasma-Mass Spectrometry. The mineral contents of both HM showed parallel compositional changes over the period of lactation, with occasional significant differences when compared at the same postpartum age. However, when the comparisons were performed at an equivalent postmenstrual age, preterm HM contained less zinc and copper from week 39 to 48 (p < 0.002) and less selenium from week 39 to 44 (p < 0.002) than term HM. This translates into ranges of differences (min-max) of 53% to 78%, 30% to 72%, and 11% to 33% lower for zinc, copper, and selenium, respectively. These data provide comprehensive information on the temporal changes of ten minerals in preterm HM and may help to increase the accuracy of the mineral fortification of milk for preterm consumption.

Health effects of micronutrient fortified dairy products and cereal food for children and adolescents: A systematic review.

INTRODUCTION: Micronutrient (MN) deficiencies cause a considerable burden of disease for children in many countries. Dairy products or cereals are an important food component during adolescence. Fortification of dairy products or cereals with MN may be an effective strategy to overcome MN deficiencies, but their specific impact on health in this age group is poorly documented. METHODS: We performed a systematic review and meta-analysis (registration number CRD42016039554) to assess the impact of MN fortified dairy products and cereal food on the health of children and adolescents (aged 5-15 years) compared with non-fortified food. We reviewed randomised controlled trials (RCT) using electronic databases (MEDLINE, EMBASE, Cochrane library; latest search: January 2018), reference list screening and citation searches. Three pairs of reviewers assessed 2048 studies for eligibility and extracted data. We assessed the risk of bias and applied GRADE to rate quality of evidence. RESULTS: We included 24 RCT (often multi MN fortification) with 30 pair-wise comparisons mainly from low- and middle income countries. A very small and non-significant increase of haemoglobin values emerged (0.09 g/dl [95%-CI: -0.01 to 0.18]; 13 RCT with iron fortification; very low quality of evidence). No significant difference was found on anaemia risk (risk ratio 0.87 [95%-CI: 0.76 to 1.01]; 12 RCT; very low quality), but a significant difference in iron deficiency anaemia favouring fortified food was found (risk ratio 0.38 [95%-CI: 0.18 to 0.81]; 5 RCT; very low quality). Similar effects were seen for fortified dairy products and cereals and different fortification strategies (mono- vs. dual- vs. multi-MN). Follow-up periods were often short and the impact on anthropometric measures was weak (low quality of evidence) Very low quality of evidence emerged for the improvement of cognitive performance, functional measures and morbidity. CONCLUSIONS: Fortification of dairy products and cereal food had only marginal health effects in our sample population from 5-15 years. Further evidence is needed to better understand the health impact of fortified dairy products and cereals in this age group. SYSTEMATIC REVIEW REGISTRATION: The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 26 May 2016 (registration number CRD42016039554).

Iron bioavailability from fresh cheese fortified with iron-enriched yeast.

PURPOSE: An iron-enriched yeast able to lyse at body temperature was developed for iron fortification of chilled dairy products. The aim was to evaluate iron (Fe) absorption from iron-enriched yeast or ferrous sulfate added to fresh cheese. METHODS: Two stable isotope studies with a crossover design were conducted in 32 young women. Fe absorption from fresh cheese fortified with iron-enriched yeast (2.5 mg 58Fe) was compared to that from ferrous sulfate (2.5 mg 57Fe) when ingested with fresh cheese alone or with fresh cheese consumed with bread and butter. Iron absorption was determined based on erythrocyte incorporation of isotopic labels 14 days after consumption of the last test meal. RESULTS: Geometric mean fractional iron absorption from fresh cheese fortified with iron-enriched yeast consumed alone was significantly lower than from the cheese fortified with FeSO4 (20.5 vs. 28.7 %; p = 0.0007). When the fresh cheese was consumed with bread and butter, iron absorption from both fortificants decreased to 6.9 % from the iron-enriched yeast compared to 8.4 % from ferrous sulfate. The relative bioavailability of the iron-enriched yeast compared to ferrous sulfate was 0.72 for the cheese consumed alone and 0.82 for cheese consumed with bread and butter (p = 0.157). CONCLUSIONS: Iron from iron-enriched yeast was 72-82 % as well absorbed as ferrous sulfate indicating that the yeast lysed during digestion and released its iron.

Influence of the consumption pattern of magnesium from magnesium-rich mineral water on magnesium bioavailability.

It is generally considered that the absorption of Mg is inversely related to the ingested dose. The objective of the present study was to determine if the mode of administration (bolus v. consumption throughout the day) could influence Mg bioavailability from Mg-rich natural mineral water comparing the same nutritional Mg amount (126 mg). Using a 2 d cross-over design, twelve healthy men were asked to drink 1·5 litres Mg-rich mineral water either as 2 × 750 ml or 7 × 212 ml throughout the day. Two stable isotopes ((25)Mg and (26)Mg) were used to label the water in order to distinguish both regimens. Fractional apparent Mg absorption was determined by faecal monitoring and Mg retention was determined by measuring urinary excretion of Mg isotopes. Higher Mg absorption (50·7 (SD 12·7) v. 32·4 (SD 8·1) %; P = 0·0007) and retention (47·5 (SD 12·9) v. 29·0 (SD 7·5) %; P = 0·0008) from Mg-rich mineral water were observed when it was consumed in seven servings compared with larger servings. Thus, regular water consumption throughout the day is an effective way to increase Mg bioavailability from Mg-rich mineral water.

Skin bioavailability of dietary vitamin E, carotenoids, polyphenols, vitamin C, zinc and selenium.

Dietary bioactive compounds (vitamin E, carotenoids, polyphenols, vitamin C, Se and Zn) have beneficial effects on skin health. The classical route of administration of active compounds is by topical application direct to the skin, and manufacturers have substantial experience of formulating ingredients in this field. However, the use of functional foods and oral supplements for improving skin condition is increasing. For oral consumption, some dietary components could have an indirect effect on the skin via, for example, secondary messengers. However, in the case of the dietary bioactive compounds considered here, we assume that they must pass down the gastrointestinal tract, cross the intestinal barrier, reach the blood circulation, and then be distributed to the different tissues of the body including the skin. The advantages of this route of administration are that the dietary bioactive compounds are metabolized and then presented to the entire tissue, potentially in an active form. Also, the blood continuously replenishes the skin with these bioactive compounds, which can then be distributed to all skin compartments (i.e. epidermis, dermis, subcutaneous fat and also to sebum). Where known, the distribution and mechanisms of transport of dietary bioactive compounds in skin are presented. Even for compounds that have been studied well in other organs, information on skin is relatively sparse. Gaps in knowledge are identified and suggestions made for future research.

A compartmental model of magnesium metabolism in healthy men based on two stable isotope tracers.

The aim of this study was to build a compartmental model of magnesium (Mg) kinetics by using data collected from six healthy adult men after oral administration of 26Mg and intravenous administration of 25Mg. Blood, urine, and feces were collected for 12 days after administration of the isotopes. Isotopic ratios were determined by inductively coupled plasma-mass spectrometry. Data were analyzed for each subject using SAAMII. We began with a compartmental model previously proposed (Avioli LV and Berman M. J Appl Physiol 21: 1688-1694, 1966) and developed an alternative approach to resolve the discrepancy between model-predicted curves and experimental data. This analysis enables the exploration of 25% of total body Mg that exchanges rapidly from plasma compartment with two extraplasma pools. One of the extraplasma compartments contains 80% of the exchangeable Mg with a transport rate of 48 +/- 13 mg/h. The second exchanges 179 +/- 88 mg of Mg/h. The model permitted estimation of kinetic parameters as well as fractional Mg absorption and fecal endogenous excretion.

Comparison of stable-isotope-tracer methods for the determination of magnesium absorption in humans.

BACKGROUND: The double-labeling (DL) method for determining magnesium absorption is less cumbersome than is the fecal monitoring method, which has been used most often, but it has not been validated. OBJECTIVE: The aim of this study was to compare methods and several sampling protocols for determining magnesium absorption to establish a simple and reliable alternative to the fecal monitoring approach. Fecal monitoring was used as the standard against which the DL methods based on urine data (DLU), plasma data (DLP), and plasma kinetics with the use of a deconvolution analysis (DP) were compared. DESIGN: Six healthy adult men received 70 mg (26)Mg orally and 30 mg (25)Mg intravenously. Multiple blood samples and complete urine and fecal samples were collected over 12 d. Stable-isotope ratios were determined by inductively coupled plasma mass spectrometry. RESULTS: Results from DLU were not significantly different from the fecal monitoring reference value (0.48 +/- 0.05; +/- SD) when based on 3-d urine pools from 72 to 144 h (0.54 +/- 0.04) and when based on the 24-h urine pools from 48 to 72 h (0.49 +/- 0.06), 72 to 96 h (0.51 +/- 0.11), and 96 to 120 h (0.50 +/- 0.06). Results with the DLP method 72 h after isotope administration also compared well with those with the fecal monitoring method (0.54 +/- 0.09). Magnesium absorption was 0.47 +/- 0.06 with the DP method, which also agreed with the fecal monitoring value. CONCLUSIONS: The DL methods are an alternative to fecal monitoring when applied within the appropriate time intervals. Therefore, DLU-the simplest and least invasive approach-is recommended for determining magnesium absorption.

Meal effect on magnesium bioavailability from mineral water in healthy women.

BACKGROUND: Magnesium intakes in many industrialized countries are below recommended daily allowances. Magnesium-rich mineral water may contribute to coverage of magnesium requirements by providing significant amounts of natural, energy-free, bioavailable magnesium. OBJECTIVE: The objectives were to determine magnesium bioavailability from magnesium-rich (110 mg/L) mineral water in healthy subjects when consumed alone and to evaluate the effect of simultaneous meal consumption. DESIGN: Magnesium bioavailability was measured in 10 healthy women with the use of a crossover design. Stable magnesium isotopes ((25)Mg and (26)Mg) were administered orally with mineral water, which was consumed with or without a meal. Apparent magnesium absorption was determined by fecal monitoring, and magnesium retention was determined from urinary excretion of magnesium isotopes. RESULTS: The mean (+/-SD) magnesium absorption from mineral water consumed alone was 45.7 +/- 4.6% (range: 40.2-55.5%) and was significantly greater (P = 0.0001) when it was consumed with a meal (52.3 +/- 3.9%; 46.2-60.2%), a relative difference of 14.4%. Magnesium retention also was significantly greater (P = 0.0004) when mineral water was consumed with a meal (41.5 +/- 4.2%; 35.2-50.6%) than when consumed alone (37.4 +/- 4.0%; 33.1-47.0%), a relative difference of 11.0%. CONCLUSIONS: In healthy young women, approximately 50% of the magnesium from magnesium-rich mineral water was absorbed when consumed alone. Magnesium bioavailability from mineral water is enhanced when the water is consumed with a meal, perhaps because of a slower gastrointestinal transit time, the presence of digestion products from the meal, or both. Regular consumption of magnesium-rich mineral water could make a valuable contribution to magnesium requirements.