This was a cross-sectional analytical study using a mixed-methods approach (laboratory analysis and nutritional survey), conducted from November 4 to December 4, 2024. It aimed to collect data on the microbiological, physicochemical, and nutritional profiles of local porridges, as well as the dynamics of dietary iodine intake among breastfed children aged 6 to 24 months in the prefecture of Fria.

The study population consisted of breastfed children aged 6 to 24 months, for the assessment of their nutritional status and dietary iodine dynamics, as well as their mothers, from whom data were collected regarding dietary habits and preparation practices of local porridges.

Fria Prefecture, located in Lower Guinea within the administrative region of Boké, covers an area of 1811 km² and has approximately 82,000 inhabitants, with a population density of 45 inhabitants/km². It is crossed by the Konkouré River and lies 160 km north of Conakry. Historically, Fria is known for hosting Africa’s first alumina plant, built in 1957 by Péchiney. Connected to Conakry by road and rail, this industry was once a major economic driver. However, its closure had profound socio-economic repercussions, worsening food insecurity and nutritional vulnerability among the local population. Administratively, the prefecture is divided into four sub-prefectures (Baguinet, Banguingny, Fria-Centre, and Tormelin), along with several urban districts. Fria was selected as the study area due to the impact of the industrial crisis on food security and childhood malnutrition. This situation justifies a thorough analysis of the nutritional and socio-economic factors influencing feeding practices and hematoparasitic profiles in children under five years of age in the region [7] . As shown in Figure 1 , the map of the Prefecture of Fria highlights the enumeration zones

The study was conducted in collaboration with the National Office for Quality Control (ONCQ) and the Péchiney Hospital of Fria. The ONCQ, a public institution responsible for monitoring the quality of food and non-food products in the Republic of Guinea, operates a laboratory located in the Matoto municipality. This facility enabled the microbiological, physicochemical, and nutritional analyses of local porridges consumed by young children. Its technical expertise ensured scientific rigor and compliance with international food safety standards [8] .

The Péchiney Hospital of Fria, the main healthcare facility in the prefecture, houses a laboratory equipped for biochemical, serological, parasitological, and hematological testing. This laboratory was used to assess urinary iodine concentration (UIC), as well as TSH and T4 levels in children aged 6 to 24 months, in order to analyze their iodine status. The collaboration between these two institutions facilitated a comprehensive evaluation of the microbiological, nutritional, and biological dimensions of the study, ensuring a rigorous and multidisciplinary scientific approach [9] . As shown in Figure 2 , the map illustrates the location of the National Office of Quality Control and shows the image of the Péchiney Hospital in Fria.

The sample size was calculated using Schwartz’s formula for cross-sectional studies. Due to the absence of iodine deficiency prevalence data in the Guinea DHS 2018 and SMART 2022 surveys, a prevalence threshold of 5% was assumed for estimation purposes. The initial sample size was set at 384 participants. After adjusting for a non-response rate of 10%, the final sample size was increased to 423 children.

$N=\frac{Z^2\times p\left(1-P\right)}{d^2}$

With:

Household and child sampling was carried out using a stratified random sampling method based on two main criteria: geographical location (neighborhoods or villages) and the socioeconomic status of participants. This approach was adopted to ensure adequate representation of the various strata within the target population. The sample size was estimated considering the expected prevalence of iodine deficiency and the consumption of local porridges among children. A sample of between 300 and 500 breastfed children aged 6 to 24 months was selected to allow for statistically reliable and representative analyses. A 95% confidence interval was used for result interpretation. Additionally, a 10% anticipated non-response rate was included in the sample size calculation to ensure the validity of conclusions despite potential absences or refusals to participate.

The selection of porridge types consumed by children was based on a list of commonly used local ingredients, such as millet, maize, rice, sorghum, and other traditional cereals used in infant meals. The porridges included were selected based on their consumption frequency among households in the Fria prefecture, as established through a preliminary survey. Samples were collected directly from households to ensure the porridge analyzed reflected what children actually consumed. These samples were then transported to laboratories for microbiological, physicochemical, and nutritional analyses to assess their sanitary quality and nutritional value.

1) Urine (iodide measurement)

Morning fasting urine samples (5 to 10 ml) were collected from each child and immediately transferred to sterile containers for laboratory analysis.

2) Blood (to measure free thyroxine (Free T4) and thyroid-stimulating hormone (TSH))

A 3 to 5 ml venous blood sample was collected in a tube without anticoagulant to analyze thyroid hormone levels.

To collect local porridge samples, a volume of 100 to 200 ml was taken directly from households using sterile containers to avoid contamination. Samples were immediately stored at 4˚C to preserve their microbiological and nutritional integrity and transported to the laboratory for analysis. At the time of sampling, porridge preparation conditions were carefully recorded. This included checking for the addition of iodized salt, which could influence children’s iodine status, and the porridge cooking time, as duration may impact the nutritional value of foods. These data were collected to allow for a comprehensive analysis of how preparation methods affect the nutritional quality of porridges.

Urine samples were collected in sterile containers, preferably in the morning, and immediately stored at −20˚C until laboratory analysis. This preservation ensured the stability of iodine concentration in the urine, used as an indicator of the child’s iodine status.

Blood samples were collected via venipuncture, followed by centrifugation to separate the serum. The serum was then stored at −80˚C to allow for accurate analysis of free T4 and TSH levels, which reflect the functional status of the thyroid gland and the impact of iodine deficiency.

Mothers reported meal frequency and the types of porridges consumed, to better understand the children’s dietary habits.

Mothers were asked about the use of iodized salt in meal preparation and the administration of dietary supplements, such as vitamins or iodine-based products, which could influence the child’s nutritional status.

Observations were conducted to document porridge preparation practices, including mothers’ hand hygiene, the use of clean cooking utensils, and general cooking conditions, all of which can influence the microbiological and nutritional quality of porridges. These observations were recorded in the field to complement the data collected through the questionnaires.

Porridge samples were tested to detect the presence of microorganisms that could impact child health. These tests were conducted at the ONCQ laboratory using standard culture media and in accordance with international standards.

The detection of fecal coliforms evaluates fecal contamination and compliance with hygiene practices. The method used was plating on Violet Red Bile Dextrose Agar (VRBD) and incubation at 44˚C for 24 hours, according to ISO 4832:2006 [10] .

These are indicators of environmental contamination and possible hygiene lapses during porridge preparation. The method used was VRBD plating and incubation at 37˚C for 24 hours, also according to ISO 4832:2006 [10] .

Used to assess overall microbial load and the general microbiological quality of the porridges. Analysis was performed using deep plating on Plate Count Agar (PCA) and incubation at 30˚C for 72 hours, following ISO 4833-1:2022 [11] .

Testing for Salmonella is essential as it causes serious foodborne illnesses. The method used included pre-enrichment in Buffered Peptone Water (BPW), isolation on Salmonella-Shigella Agar (SS) at 37˚C for 24 to 48 hours, and biochemical confirmation in accordance with ISO 6579-1:2017/Amd 1:2020 [12] .

This pathogen can produce toxins responsible for food poisoning. The analysis involved plating on Baird-Parker Agar (BP), incubation at 37˚C for 24 to 48 hours, and confirmation via coagulase testing, in line with ISO 6888-1:2021 [13] .

Their presence can affect porridge quality and pose health risks through potential mycotoxin production. The method used was plating on Potato Dextrose Agar (PDA) and incubation at 25˚C for 5 days, following ISO 21527-1:2008 [14] .

This bacterium indicates fecal contamination and is a public health concern. The method involved enrichment in a non-selective broth, followed by plating on a selective medium such as EC Agar and incubation at 37˚C for 18 to 24 hours, according to ISO 16649-2:2001 [15] .

The physicochemical characteristics of porridges were analyzed to determine their composition and stability in compliance with applicable standards. These analyses included:

The pH measurement assessed the acidity or alkalinity of the porridges, influencing both preservation and digestibility. Analysis was performed using potentiometry with a pH meter, according to ISO 4316:1977 [16] .

Moisture determination is essential as high levels can promote microbial growth and shorten shelf life. The method used was oven drying (gravimetry) at 105˚C until constant weight, in line with ISO 712:2009 [17] .

Dry matter refers to the portion remaining after moisture removal, serving as a key indicator of nutrient concentration. The method was an indirect calculation by subtracting moisture content, as per ISO 712:2009 [17] .

Ash content indicates the total mineral and inorganic matter in porridges. The analysis was performed via incineration at 550˚C to 600˚C according to ISO 2171:2023 [18] .

1) Carbohydrates

The carbohydrate content was calculated by difference after determining the other components (moisture, proteins, fats, and ash). Carbohydrates are a major source of energy for the body. The analytical method is based on subtraction, following the FAO/WHO 2003 standard [19] .

2) Energy Value

The energy value of porridges was calculated using the Atwater conversion factors: 4 kcal/g for proteins, 9 kcal/g for fats, and 4 kcal/g for carbohydrates, as recommended by FAO/WHO 2003 [19] .

3) Fats

Fat content was determined using Soxhlet extraction with petroleum ether as a solvent, in accordance with AOAC 2000 [20] .

4) Proteins

Protein content was measured using the Kjeldahl method for total nitrogen, followed by conversion to protein using a factor of 6.25, as described by AOAC 2000 [20] .

1) Iodine

Iodine content in salt and porridges was determined using the iodometric titration method, in accordance with WHO/UNICEF/ICCIDD 2007 guidelines [21] .

2) Iron

Iron content was measured via atomic absorption spectroscopy (AAS) following AOAC 2000 [20] .

3) Zinc

Zinc was determined using AAS as described in AOAC 2000 [20] .

4) Vitamin A

Vitamin A content was analyzed using High Performance Liquid Chromatography (HPLC) as per AOAC 2000 [20] .

5) Calcium

Calcium was determined using titration with EDTA according to AOAC 2000 [20] .

6) Magnesium

Magnesium was measured using AAS as per AOAC 2000 [20] .

7) Starch

Starch content was analyzed enzymatically using AOAC 2000 [20] .

8) Cellulose

Cellulose content was determined by the Weende method according to AOAC 2000 [20] .

Urinary iodine concentration (UIC) was measured using the Sandell-Kolthoff reaction, following WHO/UNICEF/ICCIDD 2007 guidelines [21] .

Serum free T4 and TSH concentrations were determined using enzyme-linked immunosorbent assay (ELISA) kits, according to the manufacturer’s instructions [22] .

Goiter was assessed via palpation according to WHO 2001 criteria [23] .

Mean, standard deviation, and proportions were calculated for all variables of interest.

The results from Table 4 indicate that the samples of local porridge analyzed exhibit relatively low concentrations of total coliforms, ranging from 1 to 22 cfu/g. Higher concentrations were observed in samples E1, E7, E9, and E16, which could suggest variations in hygiene conditions during preparation or storage. Nonetheless, these values remain below the maximum criterion of 10³ cfu/g, in compliance with food safety standards. Regarding Staphylococcus aureus, concentrations ranged from 1 to 18 cfu/g. Although these levels are well below the safety limit of 100 cfu/g, the presence of this pathogenic bacterium indicates a potential risk of contamination by toxins, particularly if the porridge is stored at room temperature for prolonged periods.

Furthermore, the presence of spoilage microorganisms such as total aerobic mesophilic flora, total coliforms, yeasts, and molds, as well as the absence of contamination indicator germs like fecal coliforms, suggests that proper hygiene practices were not always consistently applied during preparation, and that storage conditions could be improved. This microbiological profile highlights the need for rigorous measures to ensure the sanitary safety of the products.

The results in Table 5 show that the local porridges have a relatively stable moisture content (%H) ranging from 12.02% to 13.78%, which contributes to a good consistency while preserving the nutrients. The dry matter (%MS), ranging from 86.22% to 87.98%, reflects a high concentration of nutrients, characteristic of porridges made from cereals. The ash content, indicative of mineral richness, ranges from 3.17% to 4.07%, which is consistent with expectations for this type of preparation. The pH, varying between 6.17 and 6.46, falls within a slightly acidic to neutral range, limiting microbial growth and promoting product stability. The lipid content (%L), ranging from 7.91% to 8.40%, provides essential energy intake. The carbohydrate content (%G), the main source of energy, ranges from 64.18% to 65.99%, while the protein content (%P), ranging from 10% to 10.59%, supports muscle growth. The starch content (%Ami), in line with the expected standards (57.76% to 59.39%), ensures an adequate supply of complex carbohydrates. The cellulose content, ranging from 0.26% to 0.59%, remains low, which is beneficial for digestibility in young children, while still contributing a moderate amount of dietary fiber essential for healthy intestinal transit. Finally, the energy value (VE) of the porridges, ranging from 369.47 to 393.13 Kcal/100 g, is slightly below the recommended threshold of ≥400 Kcal/100 g, suggesting that nutritional supplementation might be needed to fully meet the energy needs of children aged 6 to 24 months.

The results in Table 6 reveal that the iron content, ranging from 7.5 to 8.2 mg/100 g, falls within the recommended range (5 - 10 mg/100 g), which is essential for preventing infant anemia. Zinc concentrations, ranging from 4.2 to 4.9 mg/100 g, exceed the minimum required threshold (≥3 mg/100 g) and play a key role in immune development and growth. Calcium levels (300.43 to 306 mg/100 g) and magnesium levels (85.0 to 89.0 mg/100 g) meet the established standards, contributing to bone mineralization and cellular metabolism.

Furthermore, vitamin A levels, ranging from 310.66 to 316 µg ER/100 g, and iodine concentrations, ranging from 15.64 to 16.35 ppm, meet the nutritional requirements essential for maintaining vision, strengthening immunity, and supporting proper thyroid function. These results confirm that the porridges studied provide a balanced nutritional intake, suitable for the needs of growing children.

The results presented in Table 7 show that the iodine content of the 20 salt samples used in the preparation of porridge made from local flours for children aged 6 to 24 months ranged from 16.2 ± 0.1 ppm to 19.5 ± 0.3 ppm. Specifically, 40% of the samples had iodine levels between 16.2 and 17.8 ppm, while 60% showed higher concentrations, from 18.0 to 19.5 ppm. These values meet the minimum recommended threshold of 15 ppm, thereby ensuring an adequate iodine intake to prevent iodine deficiency disorders such as endemic goiter or delays in neurocognitive development in children. Iodine is an essential trace element required for the synthesis of thyroid hormones (thyroxine and triiodothyronine), which are crucial for energy metabolism regulation, growth, and brain development. However, even when measured levels are satisfactory, iodine stability in salt remains a critical factor. Improper storage particularly exposure to humidity, heat, or light can lead to significant losses, thereby reducing the effectiveness of iodized salt. It is therefore essential to promote proper storage practices, such as using airtight containers and avoiding unfavorable environments. Beyond the use of iodized salt, an integrated nutritional approach should be encouraged. Regular consumption of iodine-rich foods (such as marine fish, seafood, eggs, and dairy products) helps diversify intake sources and improves the micronutrient’s bioavailability, reducing the risk of deficiency. In comparison with the study by GOMINA ASSOUMANOU et al. conducted in 2011 in Benin, our results show both similarities and notable differences. In their survey, the average iodine content in table salt was 33.836 ± 17.046 ppm, significantly higher than in our study. Additionally, 86.24% of the analyzed samples had an iodine content ≥ 15 ppm, compared to 100% in our case. However, their study also revealed a non-negligible proportion of inadequately iodized salt (11.31% < 15 ppm and 2.45% at 0 ppm), which contrasts with our findings, where none of the samples fell below the critical threshold. Another important distinction is that although iodine levels in the Benin study were higher, only 54.74% of the samples were considered adequately iodized according to the 15 - 40 ppm standard, whereas all the samples analyzed in our study fell within this normative range. This difference may reflect better uniformity in iodization or stricter supply chain management in our study area. Thus, while both studies highlight the importance of iodized salt as a public health tool, our findings are distinguished by the consistency of the measured concentrations, all of which comply with current recommendations. This likely reflects better local control of iodization procedures or improved salt storage practices at the household level [27] .

The results presented in Table 8 reveal that the urinary iodine concentration (UIC) among the 20 children included in this study ranges from 110 ± 5 µg/L to 198 ± 3 µg/L. Of these, 45% had UIC levels between 110 and 150 µg/L, and 55% between 155 and 198 µg/L. These values all fall within the World Health Organization (WHO) recommended range of 100 - 199 µg/L, indicating an optimal iodine status in this population.

This finding aligns with WHO guidelines, which state that a median UIC of 100 - 199 µg/L in school-aged children and by extension in children under five years of age, according to some studies reflects adequate iodine intake at the population level. Maintaining this range is essential to effectively prevent iodine deficiency disorders, including neurocognitive development delays, thyroid dysfunctions, and, in severe cases, endemic cretinism in at-risk regions. Our findings may be compared to those of the study by Delange et al. (2002), conducted across 17 countries and involving over 55,000 individuals. That study reported that 48% of the populations examined had a median UIC within the 100 - 199 µg/L range, considered the optimal threshold. However, the same study also highlighted significant inter-country and inter-regional variability, with some records showing very high UIC values (up to 540 µg/L), reflecting potential excessive iodine intake in certain areas.

In contrast to these multicentric findings, where extreme UIC values were frequently observed, our data are more homogeneous and remain strictly within the recommended limits, with no cases below 100 µg/L or exceeding 200 µg/L. This narrower distribution around the mean likely reflects greater stability in iodine intake among the surveyed children, possibly due to the quality of iodized salt used in households as corroborated by the findings in Table 7 . Moreover, although our results follow the same trend as those of Delange et al. in terms of adequate iodine intake, our study stands out due to the absence of extreme cases, suggesting greater uniformity in iodine exposure. This indicates better control of the nutritional and environmental factors influencing urinary iodine levels in children [28] .

The results in Table 9 show that the free thyroxine (T4) concentrations measured in the 20 samples ranged from 11.0 ± 0.5 pmol/L to 22.0 ± 0.4 pmol/L, entirely within the established reference range of 10 to 23 pmol/L. Among these samples, 35% had concentrations between 11.0 ± 0.5 and 14.5 ± 0.4 pmol/L, while 65% showed values between 15.0 ± 0.6 and 22.0 ± 0.4 pmol/L. These findings indicate that all individuals studied exhibited free T4 levels consistent with physiological norms, suggesting normal thyroid function. Free thyroxine (T4) is a critical thyroid hormone that plays a key role in regulating metabolism and cellular energy production. Assessing its concentration within the reference interval is crucial for identifying potential thyroid abnormalities that could negatively impact overall health. In this context, the results support the notion of hormonal balance essential for proper metabolism, growth, and optimal development in the children included in the study. Such hormonally normal levels are particularly important to ensure healthy development, especially in a young population.

The TSH concentrations measured in the 20 samples, as presented in Table 10 , ranged from 1.3 ± 0.2 mIU/L to 3.2 ± 0.3 mIU/L, all within the established reference interval of 0.5 to 4.5 mIU/L. Among these, 30% of samples showed levels between 1.3 ± 0.2 and 1.8 ± 0.2 mIU/L, while 70% displayed values ranging from 2.0 ± 0.2 to 3.2 ± 0.3 mIU/L. These findings suggest overall stable thyroid function among the study subjects, with TSH concentrations consistent with physiological norms. Thyroid-stimulating hormone (TSH), also known as thyrotropin, plays a fundamental role in regulating the thyroid gland by stimulating the secretion of thyroid hormones T3 and T4, which are essential for maintaining metabolic balance and cellular energy production. The absence of elevated TSH levels in the study population is an important indicator of the absence of iodine deficiency or overt hypothyroidism. Elevated TSH levels typically reflect excessive stimulation of the thyroid gland, often associated with insufficient thyroid hormone production. These results thus indicate appropriate hormonal regulation in the children studied, which is critical for optimal metabolic development. From a public health perspective, these findings can help identify at-risk populations and guide preventive strategies, particularly in regions where iodine deficiency might be prevalent. Moreover, the crucial role of thyroid hormones in neurocognitive development and growth, especially in children, underscores the importance of maintaining normal hormonal balance. Our results differ from those reported by Xueqin Yan et al. (2023, China), who studied children under the age of five with elevated TSH levels at birth. In their sample, several groups exhibited TSH concentrations between 5 and over 20 mIU/L, indicating subclinical or congenital hypothyroidism. Their study noted an initial impact on growth (lower height z-scores), although these differences diminished with age. However, the developmental quotient (DQ) at two years did not significantly differ between groups. In contrast to Yan et al.’s findings, our study population showed no elevated TSH levels, reflecting normal thyroid status. This comparison highlights the importance of pathophysiological context: our study describes a population with no identified endocrine disorders, while Yan et al. Focused on children affected by or at risk for thyroid dysfunction [29] .