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All the authors have made substantial contribution in drafting the article. KY contributed in conception and designing of study, interpretation of results and final approval of the manuscript. GR wrote the protocol, analysed data and reviewed the manuscript. RK was involved in analysis and interpretation of data. KV contributed in revising the article critically and in final approval of the manuscript. SS was involved in research selection, writing and critically revising the manuscript.
In developing countries there is a need for simple and cost-effective strategies to reduce the prevalence of iron deficiency anemia. The objective of the current systematic review is to summarize how cooking food in iron pots or iron ingots can increase the blood hemoglobin level and iron content of the food. Literature search was conducted using databases namely PubMed, Google Scholar, Medline-Ovid, IndMed, Cochrane library, World Health Organization bulletin and by cross-referencing articles. Thirteen researches were found to be suitable for inclusion in this systematic review. Four studies reported significant increase in blood hemoglobin levels while others reported only a minor increase. Significant improvement in amount of iron in food and iron bioavailability was also observed when food was cooked using iron pot or ingots. This can be used as a strategy for reduction of iron deficiency anemia. However, more research is required to understand the efficacy of this approach.
One-fifth of the global population is affected by IDA, in spite of the availability of several approaches that addresses the same [ 14 ]. An earlier systematic review by Geerlings et al reported that use of iron pot for preparing food may help to overcome the iron deficiency anemia in developing countries [ 15 ]. In India an action-oriented and cost-effective intervention is needed to reduce anemia especially among the vulnerable population, with minimal requirement for active compliance of individuals. Use of iron pot or ingot for cooking is considered as one such intervention that targets the whole family instead of individual level intervention. They cultural acceptability, given the history of usage of iron utensils for cooking in India. Herein, the motive of this systematic review of scientific literature was to study the impact of using iron-containing cookware (iron pot and ingot) for cooking on hemoglobin level amongst individuals and on the iron content of the food.
Despite the national and international anemia prevention programmes, the burden of IDA still remains high. Iron supplementation despite being the primary strategy to combat IDA in India; however, there is no substantial abatement in the anemia prevalence within the country. Moreover, effectiveness of iron supplementation largely depends on the delivery of supply chain system and compliance of the target recipients [ 8 ]. In addition, supplementing with iron can cause unwanted side-effects including gastro intestinal symptoms like nausea, vomiting, pain abdomen and constipation [ 9 ]. Staple food fortification is alos considered as one of the major economical intervention [ 6 ]. However, this intervention is also largely dependent on supply chain system and involvement of large- and small-scale manufacturers of rice to comply with iron fortification at production site [ 10 ]. Therefore, the daily requirement of dietary iron intake is difficult to meet. The main etiological factor for nutritional anemia is the low dietary iron intake and it’s low availability [ 11 , 12 ]. In developing countries, easy accessibility of iron and vitamin C-rich food remains uncertain, however cereals and beverages like tea and coffee which contains polyphenols, phytates and tannins, are often dietary staples [ 13 ].
A number of stakeholders or sectors namely health, agriculture, industry, education, and communication can contribute to prevent anemia among general population. There are various preventive strategies for IDA which include dietary improvement, food fortification, biofortification, iron supplementation, nutrition counselling, integration with other micronutrient control programme and antiparasitic treatment [ 6 ]. The reduction of anemia (IDA) is a global challenge which is more profound in developing countries. In India, the Ministry of Family and Health Welfare (MoHFW), revamped the existing National Iron Plus Initiative (NIPI) in the year 2018 as Integrated National Plus Initiative – Anemia Mukt Bharat to combat anemia [ 7 ]. The program focusses on providing iron folic acid supplementation along with deworming to improve the hemoglobin status among various age groups of both genders, i.e., children (6-59 months, 5-9 years), adolescent (10-19 years), pregnant and lactating women and females of reproductive age (20-49 years) [ 9 ].
Iron deficiency occurs predominantly due to malnutrition and it is commonly observed in a section of people with rapid rate of growth [ 4 ]. IDA has its adverse effects on cognitive and motor development, which leads to low productivity and fatigue [ 5 ]. Thus, it is important to address this public health problem.
Anemia, characterized by ‘low blood-hemoglobin concentration’, is a key public health concern prevalent among low, middle as well as high-income countries, worldwide [ 1 ]. Almost 1.62 billion people are affected from anemia, which approximates to 24.8% of the world’s population [ 2 ]. According to the Global Database on anemia, it is most frequent among children of preschool-age (47.4%), followed by pregnant (41.8%) and non-pregnant (30.2%) women [ 2 ]. There are various underlying causes of anemia, of which the most significant contributor is iron deficiency anemia (IDA). It is supposed that fifty percent of anemia instances are attributed to deficiency of iron [ 2 ]. As per National Family Health Survey-4 (2015-2016) India, the prevalence of IDA is more common in the rural setup as compared to the urban areas [ 3 ].
The primary outcome measure was the blood hemoglobin level to evaluate the efficacy of using iron-containing cookware for cooking food. Other hematological parameters (like serum ferritin) were also taken into account, if available.
Two reviewers individualistically completed methodology quality assessment of involved randomized control trials using “Cochrane Collaboration’s tool for assessing risk of bias in randomised trials” [ 17 ]. This tool assessed quality of the included studies on six criterias of bias; selection, detection, performance, reporting, attrition, and other bias. No methodology quality assessment was done for laboratory studies.
The title and abstracts of selected articles were reviewed by two independent authors for suitability. The articles which were identified as relevant by both the authors were considered for the final review. Disagreement between the authors were sorted out after discussion or opinion from the third author was obtained for the inclusion of the articles. Extracted data included: sample size, study design, location, period, intervention done and findings of the study.
Randomized trials and experimental studies assessing the outcomes of cooking in iron-containing cookware on blood hemoglobin status of individuals and on the total amount of iron in food items were included. The original research articles with accessibility to full text and published in English language, from 1991 till December 2020, were included.
A systematic literature search of randomized and non-randomized trials was performed by two authors using scientific databases such as PubMed, Google Scholar, Medline-Ovid, IndMed, Cochrane library and bulletin of World Health Organization. The search strategy comprised of free texts and Medical Subject Headings (MeSH) such as - ‘iron pots’, ‘iron utensils’, ‘iron vessels’, ‘iron ingot’, ‘iron’ AND ‘cooking’, ‘cooking and eating utensils’ AND ‘iron deficiency anemia’; ‘prevention of iron deficiency’ and ‘anemia’. Various combinations of these keywords were used for literature search. The bibliographies of the selected articles were also referred to find further relevant studies.
The initial literature search resulted in total 123 articles, from which 13 articles were finally included for the systematic review [20-32]. The PRISMA flow diagram of selection and exclusion of studies is depicted in . All included studies except one were conducted outside India [20]. Four studies were reported from Cambodia [19-22], two studies from Malawi [23-24], two from Brazil [25-26], one study each from Ethiopia [27], Benin [28], China [29] and USA [30]. Randomized, non-randomized or basic experimental trials on iron content of food items, published between 1991 to 2020 were included. Nine studies were randomized controlled studies which considered change in hemoglobin level as the proxy parameter to assess the change in iron status [18,19,21-23,25-28]. Of these nine articles, four performed laboratory testing to check for the change in quantity of iron in food cooked using iron-containing cookware [20,24,29,30]. Methodological quality assessment was done for nine randomized control studies ( & ). Overall quality of studies was high, nevertheless, allocation concealment bias was highest among all the biases. Least amount of bias was observed in random allocation generation. However, unclear risk of bias was found among few articles for some parameters.
The sample size varied from 27 to 407 in the reviewed articles [18,19,21-23,25-27]. Of the 13 studies included, 9 were conducted among human subjects and four were purely laboratory-based studies to assess the change in iron content of the food. The total sample size for the nine studies were 2096 subjects. Across all the studies the participants were children, adolescents and women. In the four-laboratory based studies food was cooked in different pots or with iron ingots and difference in iron content was measured [20,24,29,30].
Method used for hemoglobin estimation was Hemocue (point of care testing using digital hemoglobinometer) in six of the studies [21-23,26-28], hemoglobinometer in one study [25], one study did not mention the method of estimation [19], one study used plasma optical emission spectroscopy [20] and for rest of the studies atomic absorption spectrophotometry method was used [24,26,29,30].
The duration of studies varied from 16 weeks to 12 months. Four studies reported a significant increase in hemoglobin levels [18,21,25,27] while others reported only a slight increase [21,24,25,28,30]. The highest change in hemoglobin was observed in the study by Adish et al. in 1993, where an increase of 1.7g/dl in hemoglobin level from baseline to endpoint (12 months) was observed (95% CI 1.1-1.6g/dl); followed by a change of 0.8g/dl in the study on preschoolers, in which iron pot was used for 4 [18,27]. Minimum change in blood hemoglobin levels was seen, i.e. 0.03g/dl, post 16 weeks of intervention, for another group of preschoolers [26]. No significant change in mean blood hemoglobin levels was observed in children below 12 years of age during follow-up. For children >12 years of age, mean hemoglobin increased significantly among consistent iron pot users after 6-weeks and 20-weeks of follow-up (95% CI: 0.86-12.74; p=0.04) [23]. This study was conducted in high malaria prevalence region of Malawi. No difference in blood hemoglobin levels were reported across both the genders on using iron-containing cookware (iron pot or ingot[16,23,24,25,27,28].
Sharieff et al showed decline in prevalence of IDA between both the groups (cast iron pot users and blue steel pot users) post-intervention but this reduction was not statistically significant [28]. In another cluster randomized clinical trial, schools were provided with iron pots for meal preparation at school for the participants (preschoolers). In this group, prevalence of anemia decreased from 12.2% to 8.5% after 16-weeks of intervention. Preschoolers who were anemic at the baseline, were found to be non-anemic by the end of intervention (p< 0.001) [26]. Similar trend was also observed in a study which showed decrease in anemia prevalence from starting (73%) to study endpoint (54%), i.e., by 4 months of supplementing snacks (made using cauliflower greens with either bengal gram flour, or soyabean, or cowpea and laddoos made from garden cress and sesame seeds), cooked in iron pot (p<0.05) [18].
Decrease in anemia prevalence was also observed in the group that used iron ingot for cooking food [21]. Overall, anemia reduced by 46% in intervention group where participants were using the ingot daily for 12 months. Hemoglobin concentrations were >1.18 g/dL (95% CI: 9.1-14.6; p<0.001) amongst iron ingot intervention group women when compared to control group [21]. Contrarily, another randomized control trial did not observe any significant difference in mean blood hemoglobin between iron-ingot or iron supplement group compared to controls after 12-months [22].
Experimental studies demonstrated change in total iron quantity of food items cooked using iron pot or iron ingot. Some of the studies reflected a significant rise in total content of iron in the food preparations post cooking in iron pots and iron ingots [13,18,20,27,29]. Highest increase in iron content was observed in meat and vegetable preparations when compared to legumes [27]. Amount of iron doubled in meat and vegetables and increased by 1.5 times in legumes when cooked in iron pots, as compared with other two pots. Iron content of the pea pastes was 3.3 times higher (21.4±1.0 mg) when prepared in iron pot in comparison to peas prepared in clay pot (p<0.05) [29].
Lemon water made using iron ingot had more iron content (p<0.001) than the controls made without the ingot [20]. Comparison of apple and spaghetti sauces prepared in both iron and non-iron pots, showed a significant increase in the content of iron in apple sauce prepared in iron pot (p>0.05) [30].
Participants were also enquired regardingacceptability of iron pot for cooking purpose [23,24,31]. Participants were provided with either iron or aluminum pots, some of the participants preferred aluminum pots and not iron pot because former were lighter in weight, smaller in size and had flat base [31]. Notably, it was observed that the number of meals being cooked in the aluminum pot decreased significantly over 17-weeks, however, no significant change was found in households using iron pot for cooking (p=0.001). No change in mean acceptability score for aluminum pot was observed over time but there was a significant decline in acceptability score for iron pot in 17-weeks, i.e., from 13.7 to 11.4 (range 1-20) (p=0.001) [31]. Also, the percentage of people considering iron pot of good quality decreased significantly by the end of the study from 63% to 40% (p=0.04). The major reason for this decline in acceptability was the physical attributes of the pot, i.e., rusting, heaviness of the pot and three leg pot (which were distributed by a researcher). The primary reasons for acceptability of iron pots mentioned by the participants were that it heats up early, saving time and fuel; food was being easily prepared, and the durability of the pot [31]. On the other hand, iron pots were being replaced by aluminum pots because the latter were cheap, light weight, rust-resistant and readily available [32].
Compliance was also seen regarding the use of iron ingot for cooking. Initially, participants were advised regarding maintaining dryness and cleanliness of iron ingot after cooking, to avert rust formation. The compliance of iron ingot throughout the study period was high, as 94 percent of participants were daily using the iron ingot [21].