Bioavailability of Iron from Cereal Products Enriched with Dried Shittake Mushrooms ( Lentinula edodes ) as Determined by Iron Regeneration Efficacy Method in Female Rats

Abstract

Lentinula edodes shiitake mushrooms are rich sources of iron, which in addition to their relatively high nutritive value are also characterized by high contents of biologically active components. However, recommendation of products prepared on the basis of dried shiitake mushrooms and introduced to the diet as sources of iron requires a precise determination of bioavailability of this element. The purpose of this study was to assess the bioavailability of iron from cereal products with the addition of dried shiitake mushrooms using the iron regeneration efficacy method in Fe-deficient female rats. Feeding products with 10% and 20% addition of dried shiitake to female rats with a previously evoked Fe deficiency resulted in a gradual repletion of lowered Fe indices, including an increase in blood hemoglobin concentration and serum and liver Fe levels to values comparable to those of the control group. Bioavailability of iron from cereal products enriched with dried shiitake mushrooms is comparable to that of Fe(II) gluconate.

Introduction

I ron is a microelement essential for life. As a component of heme, it plays an important role in the functioning of hemoproteins, such as hemoglobin, myoglobin, catalase, and cytochromes of the respiratory chain or cytochrome P-450 variants. This metal is also contained in non-heme proteins, such as aconitase, ferrochelatase, and ribonucleotide reductase.¹ Iron homeostasis in mammals is maintained by the delicate equilibrium between the absorption of this element in the intestines and its storage, mainly in hepatocytes and cells of the reticuloendothelial system.^2,3 At insufficient iron intake, first a negative Fe balance and a reduction of reserves occur, without significant changes in hemoglobin levels. At prolonged negative Fe balance, when the Fe reserves are reduced considerably, Fe deficiency anemia develops, as reflected in reduced blood hemoglobin and related heme indices.⁴ On the other hand, excess free iron may be toxic to the organism, because of involvement of Fe in the production of free radicals that damage proteins, lipids, and DNA.^1,2 Maintenance of an appropriate iron homeostasis in the organism is particularly essential because deficiency of this element leads to anemia, whereas its excess induces serious disorders, such as primary iron accumulation (hemochromatosis) and secondary iron accumulation in the organism.^5

–8 Women are a group in the population especially at risk of iron deficiency. According to estimates in countries of Central and Eastern Europe iron deficiency anemia is found in approximately 16% of women of childbearing age and in 20% of pregnant women.⁹

Iron bioavailability from foods is determined by many factors, both external factors connected with the composition of the food matrix and endogenous factors related to organism conditions (body Fe reserves). External factors are connected mainly with the physical and chemical form, including oxidation rate, which determines the solubility of the compound and its interactions with components of the diet.¹⁰ Bioavailability of non-heme iron is enhanced by ascorbic acid and by muscle tissue coming particularly from meat, fish, and poultry, as well as by organic acids, including citric and lactic acids.^11
–13 A significant role in iron absorption is also played by fats, particularly saturated fats. To date several factors have also been identified that limit the absorption of non-heme iron. These factors include phytates, polyphenols, and phosphates, mainly in combination with calcium, as well as minerals, such as manganese and zinc. Some authors^14

–17 have suggested that food rich in dietary fiber may reduce iron absorption by binding it.

In the case of plant origin products, iron is found mainly in cereal products produced by high grinding processing as well as dry legume seeds and certain leafy vegetables; however, its bioavailability is low (1–8%). According to numerous researchers,^18

–21 mushrooms are also rich sources of iron, e.g., Lentinula edodes shiitake mushrooms, which in addition to their relatively high nutritive value are also characterized by high contents of biologically active components.^22

–25 Iron found in mushrooms is present in the non-heme form. Unlike many vegetable sources of iron, mushrooms do not contain phytates, which reduce the body's ability to absorb iron, and the presence of vitamin C in mushrooms will probably enhance its absorption. The bioavailability of the iron from mushrooms is expected to be higher than from plants and cereals.²⁶

However, recommendation of products prepared on the basis of dried shiitake mushrooms and introduced to the diet as sources of iron requires a precise determination of bioavailability of this element. The purpose of this study was to assess bioavailability of iron from products with an addition of dried shiitake mushrooms using the iron regeneration method in Fe-deficient female rats because data concerning bioavailability of iron from both L. edodes shiitake mushrooms and products with their addition are scarce.

Materials and Methods

Experimental animals and diets

The experiment was conducted in two stages. In the first stage the investigations were conducted on 34 Wistar female rats 6 weeks old, with a mean body weight of 120.25 ± 3.49 g, coming from laboratory breeding at the Laboratory of Toxicology, Poznań University of Medical Sciences, Poznań, Poland (approved by the Ethics Committee in Poznań). In the second stage 26 animals were used, with a mean body weight of 211.93 ± 12.73 g. Animals were kept in individual semimetabolic cages in a room with a 12-hour light/dark cycle and at a temperature of 21 ± 2°C and relative humidity of 65%. The level of food consumption was monitored every day, and once a week animals were weighed. Throughout the experiment animals, apart from test diets, received water ad libitum. Following the method of Fitzpatrick et al.,²⁷ the increment of animals' body weight after the consumption of 100 g of diet was adopted as a measure of efficiency of feeding.

Cereal products in the form of biscuits (CS0, CS1, and CS2) were produced by baking corn flour and with addition of milk with a 2% fat content, margarine, and olive oil. In the case of products CS1 and CS2, a portion of flour was replaced with ground, dried shiitake mushrooms added at 10 g/100 g of flour and 20 g/100 g of flour, respectively. Water was added in order to obtain an adequate consistency of the product. Products were baked at 160°C for 15 minutes.

In the experiment producing Fe deficiency, semisynthetic diets as a control and deficient diets were used, based on the AIN-93M diet.²⁸ Semisynthetic diets were composed of casein (protein content of approximately 90%) as a source of protein at 20%, soybean oil as a source of fat at 7%, wheat starch at 53% and sucrose at 10% as a source of carbohydrates, potato starch as a bulk substance at 5%, vitamin premix at 1%, and mineral premix at 4%. Mineral premix was modified in terms of iron content, whereas in the experiment aiming at producing iron deficiency in animals, this element was eliminated and replaced with an equivalent amount of wheat starch. Fe(II) gluconate was the source of iron in the control diet. Fe(II) gluconate was also added, in an amount ensuring the coverage of the requirement for this element in experimental animals, to tested products with the addition of dried mushrooms and to the product with no addition of dried mushrooms.

In order to estimate the degree of utilization of iron by animals from diets in the second experiment apart from cookies, control and deficient diets were also used, as the reference groups. The analytically determined chemical composition of the diets is presented in Table 1.

Table 1.

Analytically Determined Chemical Compositions of Diets

	Mean ± SEM
	Deficient	Control	CS1	CS2	CS0
Energy (MJ/100 g)	1.65 ± 0.15^a	1.67 ± 0.22^b	2.05 ± 0.26^b	1.93 ± 0.19^b	2.09 ± 0.11^b
Dry matter (g/100 g)	92.2 ± 0.23^a	93.0 ± 0.02^b	94.5 ± 0.10^b	95.0 ± 0.20^b	95.2 ± 0.02^b
Protein (g/100 g)	9.88 ± 1.05^a	10.2 ± 0.45^b	6.94 ± 0.09^b	8.27 ± 0.12^b	6.22 ± 0.043^b
Fat (g/100 g)	6.91 ± 0.13^a	7.4 ± 0.41^b	23.6 ± 0.33^b	20.4 ± 0.07^b	24.5 ± 0.11^b
Carbohydrates (g/100 g)	73.4 ± 0.23^a	73.3 ± 0.32^b	62.7 ± 0.59^b	61.5 ± 0.86^b	63.6 ± 0.55^b
Crude ash (g/100 g)	1.98 ± 0.23^a	2.1 ± 0.13^b	1.66 ± 0.03^b	1.84 ± 0.01^b	1.44 ± 0.01^b
Iron (mg/kg)	11.8 ± 1.1^a	51.6 ± 9.9^b	45.1 ± 3.3^b	47.1 ± 1.7^b	43.7 ± 2.5^b

Mean value with different superscript letters in each column are significantly different at P < .01.

Deficient diet, AIN-93M diet without Fe; control diet, AIN-93M diet; CS1 and CS2, cereal products with, respectively, 10% and 20% shiitake mushroom added; CS0, cereal products without addition of shiitake mushroom.

Experimental design

For 28 days, following a 3-day adaptation period, 24 animals received the Fe-deficient diet AIN-93M (no iron added in the mixture of mineral salts). At the same time a group of 10 females received a standard diet AIN-93M (complete diet) throughout the experiment (Fig. 1). After 31 days four animals were selected at random from each group, and from blood collected from their tails intravital indices of Fe level were determined: hemoglobin, hematocrit value, and blood serum Fe concentration. Next, after Fe deficiency had been diagnosed, animals were sacrificed using sodium thiopental, and blood was collected directly from the heart to a test tube containing dipotassium EDTA, while blood serum was collected to a test tube for clotting tests in order to accurately measure the effectiveness of producing systemic Fe deficiency. The following indices of Fe balance were determined: total iron binding capacity (TIBC), erythrocytes, hemoglobin, hematocrit value, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and blood serum Fe concentration, as well as the liver and kidney Fe content.

FIG. 1.

Diagram of the experiment.

After iron deficiency had been diagnosed in the animals, a 26-day experiment was conducted assessing bioavailability of Fe from products with an addition of dried shiitake mushrooms. Ten animals were given test diets (biscuits with a 10% and 20% addition of shiitake), and 16 females were administered control diets: five females, biscuits with no dried mushrooms added; five females, the Fe-deficient diet AIN-93M; and six females, the complete semisynthetic diet AIN-93M. After the planned test diet feeding was completed, on the last day of the experiment animals were sacrificed, and next blood and internal organs (liver, spleen, kidneys, and heart) were collected for biochemical analyses. The hemoglobin level, hematocrit value, erythrocyte content, MCV, MCH, MCHC, blood serum Fe concentration, and TIBC were determined.

Analysis of biochemical parameters and Fe content in blood and serum of female rats

Because of the very limited amount of blood collected from tails of experimental animals, a Reflotron^® apparatus (Roche Diagnostic Inc., Basel, Switzerland) was used in intravital determinations. The iron content and TIBC in blood serum were determined by colorimetry at a wavelength of 623 nm using a Vitalab^® Flexor apparatus (Vital Scientific NV, Dieren, The Netherlands). Values of morphological indices were determined using a hematological analyzer (Sysmex K-1000, TAO Medical Electronics Co., Kobe, Japan). The conductometric method was applied to calculate and analyze the corpuscle size. The hematocrit measurement method was based on the assumption that the height of impulses generated by corpuscles is proportional to corpuscle volume. Hemoglobin was determined by the photometric cyanmethemoglobin method using a 540 nm filter.

Analysis of Fe content in internal organs of animals

Livers and kidneys were collected for analyses. Analytical samples of 1 g of these organs were mineralized using the wet method in a spectrally pure concentrated nitric acid (Merck, Darmstadt, Germany) (65% HNO₃, ISO grade) in a MARS-5 system microwave (CEM Corp., Matthews, NC, USA). The clear mineralized sample obtained was transferred quantitatively to 25-mL flasks made from polypropylene and made up to the mark with deionized water. Next the mineralized sample was diluted five- or 10-fold with deionized water in the case of Fe assay from liver samples, whereas for Fe assays from kidney samples, it was threefold. The content of Fe was determined by the flame atomic absorption spectrometry method at a wavelength of 248.3 nm and slit width of 0.15 nm. Iron determinations were conducted using a spectrometer (model AAS-3, Carl-Zeiss, Analytik Jena AG, Jena, Germany). The accuracy of the method was assured by simultaneous analysis of the certified reference material (pig kidney, BCR-186, Community Bureau of Reference, Brussels, Belgium), which reached 99.6%.

Statistical analysis

All statistical calculations were performed using the STATISTICA™ PL version 8.0 software by StatSoft (Tulsa, OK, USA). Basic descriptive statistics were calculated for the above-mentioned parameters. Results presented in this study constitute arithmetic means of at least three independent series of measurements taken in two replications. Values of means for analyzed traits in groups of animals were compared taking into account the type of diet consumed, applying the analysis of variance for factorial designs, and differences between groups were evaluated by Fisher's LSD test.

Differences at P < .01 between groups in the analysis of variance for factorial designs were marked in tables between columns using different letters.

Results

The aim of the first stage of the experiment was to produce iron deficiency in female animals in order to assess the bioavailability of this nutrient from products enriched with dried shiitake mushrooms. Table 2 presents the overall nutritional indices, body and internal organ masses, and the iron status indices in female rats after 28 days of experimentation (the first stage aiming at producing Fe deficiency). In this experiment a significantly higher diet intake, Fe intake, and body mass gain were observed in the control rats in comparison to the Fe-deficient rats, while feeding efficiency ratio and internal organ masses were not different between these groups. Feeding of female rats with a diet deficient in Fe (25% recommended amount) resulted in a significant decrease in the concentrations of hemoglobin (by 15%), hematocrit value (by 5%), blood serum Fe (by 35%), hepatic Fe (by 70%), and Fe level in kidneys (by 55%). Moreover, MCV and MCH in blood of females fed the deficient diet were also significantly reduced.

Table 2.

Overall Nutritional Indices, Body and Internal Organ Masses, and Iron Status Indices in Female Rats After 28 Days of Experimentation

	Experimental group
Variable	Deficient diet	Control diet
Feed intake (g/28 days)	428.26 ± 3.41^a	608.38 ± 4.75^b
Body mass gain (g/28 days)	68.75 ± 7.04^a	93.50 ± 5.07^b
Feeding efficiency ratio (g/100 g)	14.09 ± 1.51^a	13.59 ± 0.75^a
Dietary Fe intake (mg/kg of diet)	5.07 ± 0.04^a	27.38 ± 0.21^b
Liver (g)	5.76 ± 0.52^a	5.73 ± 0.28^a
Kidneys (g)	1.62 ± 0.16^a	1.60 ± 0.10^a
Spleen (g)	0.41 ± 0.04^a	0.47 ± 0.04^a
Heart (g)	0.71 ± 0.06^a	0.70 ± 0.06^a
TIBC (μg/dL)	625.00 ± 148.62^a	522.00 ± 131.52^a
RBCs (× 10¹²/l]	8.50 ± 0.37^a	7.61 ± 0.12^b
Hemoglobin (g/dL)	12.08 ± 1.20^a	13.98 ± 1.06^b
Hematocrit (%)	40.20 ± 0.67^a	41.80 ± 0.55^b
MCV (fL)	47.22 ± 2.28^a	54.95 ± 0.33^b
MCH (pg)	15.25 ± 0.75^a	18.10 ± 2.25^b
MCHC (g/dL)	32.28 ± 0.21^a	32.93 ± 4.08^a
Serum Fe (μg/dL)	177.75 ± 68.18^a	276.00 ± 53.22^b
Liver Fe (μg/g dm)	330.31 ± 65.52^a	1,025.11 ± 157.28^b
Kidney Fe (μg/g dm)	164.35 ± 18.78^a	302.10 ± 44.17^b

Mean values with different superscript letters in each column are significantly different at P < .01.

MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; RBC, red blood cell; dm, dry matter; TIBC, total iron binding capacity.

Table 3 presents the overall nutritional indices, body and internal organ masses, and indices of iron status in female rats after 26 days of experiment (stage II). As can be seen, a significantly lower feed intake, body mass gain, and feeding efficiency ratio were observed for rats fed diets containing products with (CS1 and CS2) and without (CS0) the addition of dried shiitake mushrooms. The dietary iron intake was a consequence of dietary Fe content and feed intake and decreased in the groups in the following order: control, CS2, CS1, CS0, deficient. Final body and internal organ masses were in most cases similar, with slightly higher values being recorded for the groups with the applied deficient diet and AIN-93M diet. A 26-day feeding of female Wistar rats (with evoked Fe deficiency) with diets containing 10% and 20% addition of dried shiitake mushrooms (CS1 and CS2, respectively) resulted in the restoration of the Fe status, which was reflected in the changes of Fe indices, such as a decrease of serum TIBC (to the level found in the control), and an increase of hemoglobin and hematocrit values to the level comparable to that of the control. Also, the MCV, MCH, and MCHC indices were significantly higher in comparison to the Fe-deficient group, but lower than in the control group. Moreover, an upward trend for the serum Fe level was observed, while the liver Fe content in groups fed diets with the addition of shiitake mushrooms was considerably higher than that recorded at the beginning of experiment and in the CS2 group even reached the level found in the control group. The liver Fe level of rats fed the CS1 diet (10% shiitake addition) was slightly lower than that in the group fed products with no dried mushrooms added. In rats fed the Fe-deficient diet, a considerable worsening of Fe status was found, which was manifested in an increase of TIBC index and a decrease in all the biochemical Fe indices.

Table 3.

Overall Nutritional Indices, Body and Internal Organ Masses, and Indices of Iron Status in Female Rats After 26 Days of Experimentation (Stage II)

	Experimental group
Variable	CS1	CS2	CS0	Deficient	Control
Feed intake (g/26 days)	363.1 ± 17.03^b	324.2 ± 24.79^a	347.4 ± 38.73^ab	464.6 ± 24.75^c	457.8 ± 24.88^c
Body mass gain (g/26 days)	8.50 ± 3.11^a	4.60 ± 3.21^a	3.67 ± 1.53^a	13.50 ± 6.36^ab	20.00 ± 7.69^b
Feeding efficiency ratio (g/100 g)	2.37 ± 0.97^a	1.46 ± 1.13^a	1.09 ± 0.54^a	2.87 ± 1.22^ab	4.31 ± 1.43^b
Dietary Fe intake (mg/kg of diet)	16.30 ± 0.76^b	18.61 ± 1.42^c	14.52 ± 1.62^b	5.50 ± 0.29^a	20.60 ± 1.12^d
Liver (g)	6.09 ± 0.20^b	5.59 ± 0.51^ab	5.17 ± 0.65^a	6.00 ± 0.41^ab	5.95 ± 0.49^b
Kidney (g)	1.49 ± 0.10^ab	1.50 ± 0.14^ab	1.32 ± 0.19^a	1.62 ± 0.13^b	1.59 ± 0.15^b
Spleen (g)	0.45 ± 0.06^bc	0.46 ± 0.03^bc	0.35 ± 0.05^a	0.40 ± 0.03^ac	0.51 ± 0.05^c
Heart (g)	0.68 ± 0.02^ab	0.66 ± 0.09^a	0.62 ± 0.09^a	0.79 ± 0.12^b	0.72 ± 0.07^ab
TIBC	608.0 ± 26.00^a	505.5 ± 108.19^a	546.0 ± 106.1^a	811.5 ± 19.09^b	489.00 ± 42.43^a
RBCs ( × 10¹²/L)	8.36 ± 0.15	8.30 ± 0.67	8.65 ± 0.62	6.11 ± 2.39	7.40 ± 1.02
Hemoglobin (g/dL)	13.55 ± 0.31^b	13.62 ± 0.66^b	13.63 ± 0.47^b	8.84 ± 3.39^a	13.96 ± 1.67^b
Hematocrit (%)	43.68 ± 0.50^b	43.80 ± 2.12^b	43.87 ± 3.57^b	26.34 ± 5.32^a	39.98 ± 5.53^b
MCV (fL)	52.27 ± 1.00^bc	53.22 ± 2.53^bc	50.72 ± 0.56^b	43.07 ± 0.07^a	54.07 ± 1.08^c
MCH (pg)	16.22 ± 0.22^b	16.50 ± 0.76^b	15.82 ± 0.61^b	14.47 ± 0.07^a	18.92 ± 0.46 ^c
MCHC (g/dL)	31.04 ± 0.55^ab	30.98 ± 0.49^a	31.18 ± 1.50^ab	31.50 ± 0.28^b	35.00 ± 0.91^c
Serum Fe (μg/dL)	200.2 ± 62.06	176.4 ± 36.73	168.6 ± 34.39	163.5 ± 9.19	236.6 ± 35.89
Liver Fe (μg/g dm)	805.8 ± 136.71^b	1,035 ± 59.77^bc	1,139 ± 177.8^c	132.5 ± 32.62^a	1,048 ± 207.9^c
Kidney Fe (μg/g dm)	252.2 ± 37.63	253.5 ± 53.56	266.9 ± 61.21	161.8 ± 69.66	296.8 ± 29.48

abc

Mean values with different superscript letters in each column are significantly different at P < .01.

In view of the findings that the Fe-deficient female rats consumed much lower amounts of diets with products with an addition of shiitake, in comparison to semisynthetic diets, while they were able to replenish their depleted Fe stores, it can be concluded that bioavailability of Fe from shiitake is relatively high, comparable to Fe from the reference source used, Fe(II) gluconate.

Discussion and Results

Sources of iron required for the appropriate functioning of an organism include foodstuffs and deposited reserve iron. Large amounts of iron are found in such foodstuffs as liver, wheat bran, soybeans, and spinach. Their value as sources of iron varies considerably. Dietary fiber, phytates, tannins, theine (caffeine in tea), and oxalic acid reduce the absoprtion of iron—not only endogenous, but also introduced to the diet in the form of a supplement. At present different strategies are being applied, aimed at enhancing the availability of iron, mainly from plant origin food, being the basis for the diet, e.g., in developing countries. These strategies include in particular increasing the consumption of ascorbic acid by promotion of consumption of fruits and vegetables, being good sources, and addition of meat to food, mainly red meat as the so-called meat factor, as well as enzymatic degradation of phytic acid.²⁹

Availability of iron is also determined by its form, which determinesthe solubility of this compound and its interactions with components of the diet.¹⁰ The most advantageous form of supplementation of iron deficiency is to use natural foodstuffs rich in that nutrient. Thus a crucial element in this respect has been the introduction of the so-called functional food, which resembles in its form traditional food and exhibits an advantageous action consisting in the improvement of health and well-being and/or reduced risk of diseases. Thanks to the certification by the Food and Drug Administration of safe compounds placed on the GRAS (Generally Recognized as Safe) list, food enrichment became possible. Functional food, enriched with iron, can be a way in managing the Fe deficiency anemia prevalent in developing countries, particularly in the poorest regions of the world. However, there are still no studies concerning the bioavailability of iron from food enriched in that microelement. One of the alternatives for the enrichment of products with a synthetic form of iron may be foods with an addition of natural raw materials rich in that nutrient, e.g., dried shiitake (L. edodes). It is believed that these mushrooms, apart from their documented health properties,^22

–25 are also characterized by good nutritive value, manifested in high contents of dietary fiber and vitamins B as well as micro- and macroelements such as K, Mg, P, Zn, Fe, and Cu.^18
–20 However, to recommend the introduction of products enriched with dried shiitake mushrooms to the diet as products being sources of readily available iron, it is first required to precisely determine the bioavailability of this element.

Bioavailability in relation to minerals is defined as the degree to which a consumed nutrient, released from combinations found in food, may be absorbed in the alimentary tract and utilized by the body.³⁰

In the assessment of bioavailability of iron from a diet or supplement under in vitro conditions, different experimental methods are applied, e.g., methods using isotopes (radioactive and stable isotopes) evaluating the rate of absorption of these markers or models using animals with evoked deficiency of this nutrient, evaluating the rate of supplementation of deficiency (e.g., the repletion/slope ratio method, hemoglobin regeneration assay).³¹

In the experiment conducted in this study, female Wistar rats were fed for 4 weeks a diet with Fe deficit (approximately 25% of the recommended value) in order to produce Fe deficiency. After the deficiency was diagnosed, animals were fed for 26 days diets with products with addition of dried shiitake mushrooms in order to determine Fe bioavailability from these products, in comparison to the control diet containing the equivalent amount of Fe given in the reference form, such as Fe(II) gluconate. Feeding female rats Fe-deficient diet (approximately 25% of the recommended amount) for 28 days resulted in the depletion of Fe stores, which was confirmed by changes in a range of Fe indices, such as morphological blood indices (hemoglobin, hematocrit value, MCV, MCH) as well as the serum, liver, and kidney Fe concentrations. Also, a lower body mass gain was observed in Fe-deficient rats. This confirms findings reported by Campos et al.³² that a diet deficient in iron may result in a reduction of growth rate of rats and that this depends on the species of animals, their sex, and their age, as well as the physiological condition of the organism (pregnancy, lactation). Reduced consumption of the diet and feeding efficiency ratio with a deepening iron deficiency in rats was also reported by Pallares et al.³³

Feeding products with 10% and 20% addition of dried shiitake for 26 days successively to the Fe-deficient female Wistar rats resulted in a gradual repletion of the decreasd Fe stores. This was evidenced by significant changes in the major indices of body Fe status, such as an increase in blood hemoglobin concentration in group CS1 (by 53%) and in group CS2 (by 54%), an increase in the serum Fe concentration to the level comparable to that in the control group, and an increase in hepatic Fe content in groups CS1 and CS2 by 508% and 680%, respectively, in relation to the Fe-deficient group. It was noticed that already a 10% addition of dried shiitake mushrooms to a cereal product significantly replenished the body Fe status in the Fe-deficient rats. The levels of biomarkers of Fe status were comparable both in the group of animals fed products with 10% addition of dried shiitake mushrooms and in the group with 20% addition.

In conclusion, feeding Fe-deficient female rats products with an addition of dried shiitake mushrooms resulted in almost complete replenishment of reduced iron stores in a relatively short period of time (26 days). In the light of the obtained results, it can be concluded that the bioavailability of Fe from products enriched with dried shiitake mushrooms is relatively high, even comparable to that of the reference Fe source, Fe(II) gluconate. Therefore, the addition of dried shiitake mushrooms to cereal snacks may extend the range of functional products used in nutrition prevention measures, for example, for individuals with depleted iron status.

Footnotes

Acknowledgment

This study was partly financed from research funds in the years 2005–2008 as research project number 2 P06T 080 29.

Author Disclosure Statement

No competing financial interests exist.

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