Calcium, zinc, and iron bioavailabilities from a commercial human milk fortifier: a comparison study

Adding human milk fortifiers (HMF) to human milk (HM) is one way of overcoming the nutrient deficits found in the latter. In this study, the bioavailabilities of calcium, zinc, and iron in S-26/SMA HMF added to HM were compared with those in HM fortified with various bovine milk proteins: alpha-lactalbumin, colostrum, caseinate, casein phosphopeptides, and whey protein concentrate. The bioavailability of each mineral was assessed using an in vitro digestion/Caco-2 cell culture model. Calcium and zinc uptake by the cells was traced with radioisotopes; iron uptake was assessed via cell ferritin levels. Samples were prepared on an equal protein content basis and with added calcium, but no zinc or iron was added. Results revealed that calcium uptake from HM + S-26/SMA was not different from any of the HM fortified with the bovine milk proteins, except for unfortified HM and HM + colostrum in which calcium uptake was significantly lower (-89 and -38%, respectively). Uptake of zinc and iron were significantly higher for HM + S-26/SMA than for the other HM + fortifiers.     

The effect of dairy products on iron availability.

Many researchers report substantial reductions in iron availability when dairy products are consumed with solutions of iron. Yet other studies indicate that dairy products have little effect on iron availability when added to complex meals. The conflicting data may be due to differences in the technique used to measure availability, species of animal used, form of iron in the diet, and meal composition. Human studies show superior bioavailability of iron in human milk when compared with cow's milk. Definitive causes for the differences between human and cow's milk have not been identified. Human milk contains lower amounts of casein, phosphate, and calcium, components thought to inhibit iron absorption. More work is needed to identify the factors that influence iron-dairy interactions. The nutritional benefits provided by dairy products outweigh the slight inhibitory effect they may have on iron availability.     

Bioavailability of iron in goat milk compared with cow milk fed to anemic rats

Bioavailabilities of iron from dehydrated whole and skim goat milk were investigated using iron-deficient rats. Hemoglobin regeneration efficiencies were determined as the percent conversion of dietary iron into hemoglobin. The respective hemoglobin regeneration efficiencies for groups fed whole goat milk, whole cow milk, skim goat milk, and skim cow milk were 50.6, 13.1, 26.0, and 13.0%, indicating that iron bioavailability of goat milk was greater than cow milk. However, rats fed each milk had negative net increases in hemoglobin concentrations, implying that the iron contents of each milk were not adequate. For animals consuming whole goat milk supplemented with ferrous sulfate, the slope relating hemoglobin iron gained versus iron intake was .95. Respective bioavailabilities relative to ferrous sulfate were 54, 14, 28, and 14% for the four sources of milk. Iron bioavailability of goat milk is superior to cow milk when fed to anemic rats.     

Counteracting the inhibitory effect of tea on the in-vitro availability of iron from cereal meals

Studies were carried out on the in-vitro availability of iron to determine the effect of addition of tea, milk and ascorbic acid to a standard cereal meal in all possible combinations. The availability of iron from the cereal meal was low (3.92%). Tea, when added to the meal, had a significant depressing effect on available iron (2.56%). Addition of 100 mg ascorbic acid or 200 g milk completely counteracted the inhibitory effect of tea, and addition of both ascorbic acid and milk brought about an even greater enhancement in the in-vitro availability of iron than when either was added alone. This investigation reveals that milk is as effective a factor as ascorbic acid in counteracting the depressing effect of tea on in-vitro iron availability.     

Predicting relative concentrations of bioavailable iron in foods using in vitro digestion: New developments

In vitro methods have been developed for the prediction of iron bioavailability from foods and supplements. The dialyzability method measures dialyzable iron, released during a simulated gastrointestinal digestion, as an index of iron bioavailability. A new setup, that involves six-well plates and a ring insert that holds the dialysis membrane, is proposed for the application of the dialyzability method with the objective to increase efficiency and to allow testing small-volume samples. A series of solutions (water, ascorbic acid, and phytate), liquid foods (fresh milk and condensed milk), and solid foods (bread + meat meal, corn flakes), were tested in the presence or absence of added iron and digested with the new setup and the setup previously described for the dialyzability method. In both cases, percent dialyzable iron in each treatment remained similar (P > 0.05). These results suggest that the new setup can be employed in future applications with similar food matrices of the dialyzability method.     

In vitro bioavailability of iron from wheat flour fortified with ascorbic acid, EDTA and sodium hexametaphosphate, with or without iron

A laboratory scale technology was developed to fortify wheat flour with absorption promoters of iron, such as ascorbic acid, disodium ethylenediaminetetraacetic acid (NaEDTA) and with a stabilizer, sodium hexametaphosphate (SHMP), with or without iron. The in vitro bioavailability of iron in food (Indian bread, chapathi) prepared with the wheat flour fortified at 60 mg of iron/kg in the presence (1:1 molar ratio) or absence of the three chemical additives was tested. NaEDTA and ascorbic acid enhanced the in vitro bioavailability of native iron from Indian bread while SHMP had no effect. All three additives showed a trend of enhancing the in vitro bioavailabilty of total iron (native and added iron) from iron fortified chapathis. The predicted bioavailability of iron in man from Indian bread containing ascorbic acid or NaEDTA was twice as high than that with wheat flour alone or that with SHMP (8%). Similar enhancing effects of these two compounds were shown with iron-fortified wheat flour. It is concluded that wheat flour fortified with ascorbic acid or NaEDTA, either with or without iron, can enhance the predicted bioavailability of both native and added iron in man.     

In vitro bioaccessibility of iron and zinc in fortified fruit beverages

Iron and zinc bioaccessibility was estimated in the in vitro gastrointestinal digests of six different fortified fruit beverages (Fb) containing iron and/or zinc and/or skimmed milk (M). Solubility values can be used to establish trends in relative bioavailability of iron and zinc, as the first stage towards mineral bioavailability comprises solubility in the intestinal tract. FbFe, FbFeM and FbFeZnM samples showed iron bioaccessibility above 88%, differing ( P  < 0.05) from those of FbFeZn (53%). In turn, FbZn, FbFeZn and FbZnM samples presented higher zinc bioaccessibility (above 68%), differing ( P  < 0.05) from those of FbFeZnM (48%). The presence of milk-derived caseinophosphopeptides (CPPs) formed during gastrointestinal digestion in dairy samples does not increase iron or zinc bioaccessibility in FbFeM or FbZnM vs. FbFe or FbZn, but it is hypothesised that the negative interacting effect of zinc upon iron bioaccessibility when co-supplemented in these fruit beverages is overcome in the presence of CPPs, which favour iron solubility more than in the case of zinc.     

The impact of processing on phytic acid,in vitro soluble iron and Phy/Fe molar ratio of faba bean (Vicia faba L.)

BACKGROUND: Faba bean is one of the important legumes in Asian countries. It is also a major source of micronutrients in many rural areas. Unfortunately, the bioavailability of iron from faba bean is low because it is present as an insoluble complex with food components such as phytic acid. The influence of soaking, germination and fermentation with the expectation of increasing the bioavailability of iron was investigated. RESULTS: Fermentation treatments were most effective in decreasing phytic acid (48–84%), followed by soaking at 10 °C after preheating (36–51%). Steeping faba beans for 24 h at 25 °C had the least effect on the removal of phytic acid (9–24%). With increased germination time at 30 °C, phytic acid progressively decreased from 9 to 69%. Most wet processing procedures, except soaking after wet preheating, caused losses of dry matter and iron (8–15%). In vitro iron solubility, as a percentage of total iron in soaked faba bean after dry preheating, was significantly higher than in raw faba bean (P < 0.05). Fermentation and germination did not have significant effects on the solubility of iron. CONCLUSION: The expected improvement of iron bioavailability levels due to lower phytic acid was not confirmed by increasing levels of in vitro soluble iron. Soaking, germination and fermentation can decrease phytic acid in faba bean. However, results from in vitro solubility measurement of iron showed little improvement of iron bioavailability in fermented and germinated faba beans over untreated raw faba beans (P < 0.05). It seems that componets of dietary fibre other than phytic acid are more important in binding iron. Probably, a complex association between dietary fibre and iron is the reason for the poor bioavailability of iron in faba bean. Copyright © 2009 Society of Chemical Industry     

Relative Bioavailability of Dietary Iron from Three Processed Soy Products

The relative bioavailability of iron from soy flour (SF), freeze-dried soy beverage (SB) and soy concentrate (SC) was determined utilizing a hemoglobin repletion bioassay. Weanling male rats were fed a low iron depletion diet (3.5 ppm Fe) for 4 wk. For the next 2 wk groups of rats were fed repletion diets containing 0, 6, 12, or 18 ppm added iron from ferrous sulfate, SF, SB, or SC. Slope ratio analysis revealed that the relative iron bioavailabilities from SC (92%) and SF (81%) were not different from the reference standard, ferrous sulfate added to a casein-based diet, whereas that from SB (66%) was significantly less (P<0.01) than the inorganic source of iron. Analysis of results at individual iron levels suggested an iron bioavailability of SC>SF>SB.     

Iron-Enriched Bread: Interaction Effect of Protein Quality and Copper on Iron Bioavailability

These studies examined the bioavailability of iron in iron-enriched breads. The test breads also contained added protein in the form of gluten, soy or nonfat dry milk. Bioavailability was assessed based on net hemoglobin synthesis in rats initially made iron deficient and then fed bread-based diets containing 38.5 ppm iron (NRC requirement for rat, 35 ppm) and 3.75, 5.00, or 6.25 ppm copper (NRC requirement for rat, 5 ppm). More hemoglobin was synthesized on milk-supplemented (83 mg/mg iron) and on soy-supplemented (85 mg/mg iron) bread diets than on gluten-supplemented (59 mg/mg iron) bread diets. Copper appeared to have no influence on hemoglobin regeneration or on hepatic iron accumulation under the conditions of this experiment.     

添加共沉淀氢氧化铁对牛乳品质的影响

以共沉淀氢氧化铁用于杀菌牛乳中铁的强化,研究共沉淀氢氧化铁的不同添加量对牛乳感官品质的影响及在4℃贮藏过程中理化指标(pH值、TBA值)的变化。结果表明：5.3mg/100g及其以下的铁添加量的样品感官品质较好;添加共沉淀氢氧化铁的样品pH值增大,且铁添加量越多,pH值增加越多;在贮藏期间,各样品pH值变化不大,TBA值呈上升趋势,不同铁添加量的样品TBA值差异不显著;贮藏8d后,铁添加量≤5.3mg/100g的样品液中铁含量达添加量的89%。因此,以共沉淀氢氧化铁作为牛乳铁强化剂可行。     

Calcium Bioavailability from Ripening Cheddar Cheese

Calcium bioavailability to rats was compared from CaCl₂ (28 mM), CaCO₃, fresh milk, milk adjusted to pH 5.35, and Cheddar cheese. The cheese was manufactured from pasteurized bovine milk and all doses were labeled extrinsically with ⁴⁵Ca and ⁴⁷Ca and administered orally to rats. One label (⁴⁵Ca) was added to milk before cheese manufacture and the other (⁴⁷Ca) was added to the cheese 24 h prior to dosing. Calcium bioavailability was determined by: 1) absorption measured by whole body counting, and 2) availability for bone metabolism assessed by bone radioactivity measurements. Calcium absorption averaged 76.8% and was not affected by length of ripening (p>0.05). Absorption from CaCl₂, CaCO₃, fresh milk, milk at pH 5.35, and the cheeses was similar. The two methods gave similar estimates of relative bioavailability. The ratio of ⁴⁷Ca absorption to ⁴⁵Ca absorption for any cheese sample was significantly greater than 1, indicating extrinsic labels added after processing may overestimate Ca absorption from cheese.     

Effect of Partial Phytate Removal and Heat upon Iron Bioavailability from Soy Protein-Based Diets

The effect of heat and partial phytate removal upon in vivo iron bioavailability from soy protein was studied by chick hemoglobin repletion. Iron repletion diets were formulated with unheated and heated soy protein isolates and phytate-reduced soy protein isolates, with and without iron supplementation. Heating at 120°C for 20 min, 75% phytate reduction and 20 mg/kg iron supplementation improved iron bioavailability by 65-77%, 6-11% and 10-17%, respectively. These beneficial effects were interpreted in terms of promoting protein and protein-Fe-phytate complex digestion and release of endogenous and added iron.     

Addition of milk or caseinophosphopeptides to fruit beverages to improve iron bioavailability?

A study has been made of the influence of caseinophosphopeptides (CPPs) added to a fruit beverage versus milk based fruit beverages upon iron retention, transport and uptake, using a combined simulated gastrointestinal digestion/Caco-2 cell system. Grape concentrate, orange concentrate, and apricot puree were used for sample formulation. Eight samples were assayed with/without added Fe sulphate (3 mg/100 ml fruit beverage) and/or added Zn sulphate (1.6 mg/100 ml fruit beverage), with/without skimmed milk (11% v/v). The addition of milk to fruit beverages exerted a positive effect on iron retention, transport and uptake versus fruit beverages, and this effect was greater than that of CPPs added to soluble fractions of fruit beverages. The addition of CPPs to soluble fractions of fruit beverages improved iron transport. Iron supplementation increased Fe retention, transport and uptake – the effect being more notable in samples with milk. Zinc supplementation did not affect Fe retention, transport or uptake.     

Iron-Lactoferrin Complex Reduces Iron-Catalyzed Off-flavor Formation in Powdered Milk with Added Fish Oil

Abstract: The iron–lactoferrin complex (FeLf) is useful for dietary iron supplementation. However, the effects of FeLf on iron‐catalyzed off‐flavors in lipid‐containing food products have not been reported. In this study, we investigated the effects of FeLf on off‐flavors development during the production and storage of powdered milk with added fish oil. Powdered milk samples were formulated with FeLf or iron (II) sulfate, then stored at 37 °C for 5 mo. A sensory evaluation revealed that FeLf delayed the development of oxidized flavor and reduced metallic taste in the powdered milk compared with iron (II) sulfate. Headspace gas chromatography–mass spectrometry analysis showed that oxidized volatile compounds, such as pentanal, hexanal, heptanal, octanal, 1‐penten‐3‐one, (Z)‐4‐heptenal, (E, E)‐2,4‐heptadienal, and (E)‐2‐octenal, were less developed in the powdered milk containing FeLf than in that containing iron (II) sulfate. Iron and lactoferrin (Lf) were retained in the high‐molecular‐weight (>10000 Da) fraction of the reconstituted FeLf‐containing powdered milk after its manufacture and storage, whereas the antigenicity of Lf was lost after ultrahigh‐temperature processing at 120 °C for 5 s. These results suggest that FeLf reduces the iron‐catalyzed off‐flavors that develop during the production and storage of powdered milk. The stable iron‐holding property of FeLf contributes to the inhibition of oxidized and metallic volatile formation, although the loss of Lf antigenicity did not affect the stability of FeLf and the iron‐catalyzed formation of off‐flavors in the powdered milk. Consequently, FeLf is a suitable candidate for the simultaneous supplementation of a single food with iron and fish oil. Practical Application: The supplementation of food products with iron and fish oil is a useful approach to redressing their inadequate intake in many populations. The iron–lactoferrin complex can protect food products against the off‐flavors caused by iron‐catalyzed lipid oxidation. Our results show that the iron–lactoferrin complex is useful for the simultaneous fortification of foods and nutraceuticals with iron and fish oil because this complex also reduces the formation of iron‐catalyzed off‐flavors in powdered milk enriched with fish oil.     

Effect of Fermentation on Iron, Zinc, and Calcium Availability from Iron-fortified Dairy Products

ABSTRACT: Iron, zinc, and calcium dialyzability and ascorbic acid (AA) concentrations were determined in milk, acidified milk, or yogurt fortified with ferrous sulfate (FS) or iron bis-glycinate (FBG) with or without AA addition in a 4:1 AA:Fe molar ratio. Milk fermentation or acidification caused an increase in iron availability from both iron sources. Highest availability values were obtained for fermented products with added AA (18-fold increase compared to milk). AA oxidation during fermentation was minor. However, at 14 d of cold storage, AA degradation was close to 50% in FS-fortified yogurt and 35% in FBG-fortified yogurt. Nevertheless, iron dialyzability remained constant. Lactic acidification and fermentation also increased Zn availability, but Ca dialyzability was hardly increased by either treatment. AA addition did not modify Zn or Ca availability.     

Effects of dietary proteins on iron bioavailability—A review

In this review we have summarized the iron bioavailability literature dealing with protein (or major dietary protein source) effects and proposed a mechanism for these effects compatible with existing empirical data. Data from studies employing a variety of approaches are fairly consistent in showing that meats enhance non-heme iron absorption while plant, milk and egg proteins depress it. The variable, and sometimes opposite, effects of different proteins on iron bioavailability may be explained by the following proposed mechanism: (1) protein enhances iron bioavailability by releasing peptides during digestion which form soluble, low molecular weight complexes that readily release iron to mucosal receptors; (2) protein depresses iron bioavailability by releasing peptides which form insoluble complexes with iron or which form soluble complexes that do not release iron to mucosal receptors. Data from the literature, including our own evidence, which support the above hypothesis are discussed.     

Trace elements and their distribution in protein fractions of camel milk in comparison to other commonly consumed milks.

Studies on camels' milk, whether with respect to concentration or bioavailability of trace elements from this milk, are limited and warrant further investigation. The object of this study was to analyse the concentration and distribution of zinc, copper, selenium, manganese and iron in camel milk compared to those in human milk, cows' milk and infant formula under similar experimental conditions. Camels' milk and cows' milk were collected from local farms, human milk samples were obtained from healthy donors in Kuwait and infant formula was purchased locally. Milk fractionation was performed by ultra-centrifugation and gelcolumn chromatography. The concentration of trace elements was analysed by atomic absorption spectrometry and that of protein was determined spectrophotometrically. The concentration of manganese and iron in camels' milk was remarkably higher (7-20-fold and 4-10-fold, respectively) than in human milk, cows' milk and infant formula. The zinc content of camels' milk was higher than that of human milk but slightly lower than in cows' milk and infant formula. The concentration of copper in camels' milk was similar to that of cows' milk but lower than in human milk and infant formula. The selenium content of camels' milk was comparable to those of other types of milk, Approximately 50-80% of zinc, copper and manganese in camels' milk were associated with the casein fraction, similar to that of cows' milk, The majority of selenium and iron in camels' milk was in association with the low molecular weight fraction, It is recommended that camels' milk be considered as a potential source of manganese, selenium and iron, perhaps not only for infants, but also for other groups suspected of mild deficiency of these elements. Further investigations are required to confirm this proposal.     

Iron-Fortified Infant Cereals

Infants are particularly susceptible to iron deficiency and related anemia due to their high growth rates and the low iron content of breast milk and most unfortified weaning foods. Cows' milk also is poor in iron, and certain forms of cows' milk cause blood and thus iron loss from the gastrointestinal tract. Iron-fortified cereal-based complementary foods – infant cereals – are recommended to supply the iron needs of older infants. Fortified infant cereals contain much more iron than other fortified cereal products – up to ten or fifteen times as much. Highly or slightly soluble iron salts have excellent bioavailability, but affect color and reduce chemical stability, so these iron salts are not commonly used to fortify infant cereals. Insoluble sources of iron, such as the iron phosphates, were used historically to fortify infant cereals, but these sources have very poor bioavailability. Infants depending on these cereals for iron suffered from high rates of iron deficiency and anemia.

Elemental iron of small particle size, particularly electrolytic iron, currently is the generally accepted vehicle for infant cereal fortification. Iron-fortified cereal made with electrolytic iron reduces iron deficiency and related anemia in several settings but unfortunately is not fully protective in all. Ascorbic acid is a known enhancer of iron bioavailability but ascorbic acid is heat-labile and ascorbic activity declines rapidly during storage. Nonetheless, adding ascorbic acid during processing appears to improve the availability of electrolytic iron and thus the reliability of iron-fortified infant cereal as a means of preventing iron deficiency in older infants.     

Preparation,characterization, bioavailability in vitro and in vivo of tea polysaccharides–iron complex

The task of this study was to prepare a complex of tea polysaccharides (TPS) with ferric iron and research its bioavailability in vitro and in vivo. Optimum condition for preparing tea polysaccharides–iron complex (TPIC) was as follows: TPS and FeCl₃ with a weight ratio of 1:2.4, reacted in a water bath at 60 °C for 3 h, generating an iron content for TPIC of 14.60 %. The digestion in vitro experiment showed that availability of TPIC was sufficient. Then, iron bioavailability in vivo of TPIC was evaluated by the rat hemoglobin-repletion bioassay with ferrous sulfate (FeSO₄) as the positive control. Results indicated that at the end of 21 days’ iron regeneration phase, the values of hemoglobin (Hb) concentration, free erythrocyte protoporphyrin (FEP), serum iron (SI) concentration, and mean cell hemoglobin (MCHC) of rats supplemented with FeSO₄ and TPIC increased quickly to those of normal ones. If the bioavailability of FeSO₄ was given 100 % with Hb concentration, SI concentration and MCHC as the evaluation index, respectively, bioavailability of TPIC were in the range of 101.85–116 %. These results demonstrate that TPIC is a good iron supplement source for increasing uptake and bioavailability in the body.