Impact of oil fortification with iron in the prevention of anemia—A systematic review

Abstract

Micronutrient malnutrition has gained its significant influence on public health and a role in the worldwide disease burden in recent years. Through fortification, the nutritional profile of staple foods is enhanced, making them more nutritious and beneficial for consumption. This systematic review aims to assess the impact of oil fortification with iron in anemia prevention. Electronic search through five databases and additional resources was performed by using the appropriate keywords. Out of 13,948 records that were identified, one double-blind randomized controlled trial done among Swiss women met eligibility criteria. Selected study focused on women aged between 18 and 40 years with low serum ferritin, evaluating the impact of iron-fortified low-fat margarine. This study is registered in PROSPERO (CRD42023420044). Intervention showed an increase in body iron stores with both compounds, namely, sodium iron ethylenediaminetetraacetate (NaFeEDTA) and micronized ground ferric pyrophosphate (MGFePP); however, NaFeEDTA fortification demonstrated a two to three times greater impact compared to MGFePP fortification. Findings suggest that fortification, specifically with certain iron compounds, can be a useful tactic for enhancing iron status, particularly in people with low iron stores. The only included study under this review revealed that adding iron to low-fat margarine helped boost iron levels in women with low blood iron. Findings revealed that oil fortification with NaFeEDTA showed superior efficacy over MGFePP. Further research is warranted to investigate the feasibility of fortifying edible oils with iron, exploring reasons for both potential success and challenges, thus curbing the public health issue of iron deficiency.

Background

Anemia is a significant health issue affecting women and children across India. According to the National Family Health Survey (NFHS-4 and NFHS-5), over half (53%) of women in their reproductive years suffer from anemia, and nearly 58% of children under five are impacted. These alarming statistics highlight the pressing need for effective strategies to tackle this widespread nutritional deficiency and improve the health and well-being of these vulnerable groups[1] Micronutrient malnutrition, also known as “hidden hunger,” has gained its significant influence on public health and role in the worldwide disease burden in recent years. Micronutrients are vital vitamins and minerals that the body needs in trace levels to support healthy growth, development, and overall health. Iron, vitamin A, iodine, zinc, and several B vitamins are examples of common micronutrients.[2] Micronutrient deficiencies pose a significant threat to the physical and mental well-being of millions of people. To combat this issue, fortification emerges as a vital strategy. Fortification involves augmenting staple foods, including rice, wheat flour, oils, milk, and salt, with critical vitamins and minerals like iron, iodine, zinc and vitamins A and D. These nutrients may have been absent in the original composition of the food or may have been lost or reduced during processing.[2]

Through fortification, the nutritional profile of these staple foods is enhanced, making them more nutritious and beneficial for consumption. This approach to fortification is firmly grounded in scientific research, demonstrating its efficacy in addressing micronutrient deficiencies and promoting better health outcomes.[3] Moreover, its implementation is financially prudent, offering a cost-effective means to reach a wide segment of the population. Its scalability ensures that its benefits can extend to various socioeconomic strata, making it an adaptable solution for nations facing similar nutritional challenges.[4]

Crucially, the sustainability of food fortification is a key factor in its favor. Once integrated into the production and distribution of staple foods, fortification can continue to provide lasting nutritional advantages to the population. This not only contributes to immediate health improvements but also establishes a foundation for long-term well-being.[5,6]

In a global context, food fortification stands out as a globally relevant intervention. Its potential impact on combating micronutrient deficiencies holds promise for widespread application across diverse countries and regions.[7] By enriching staple foods with essential nutrients, food fortification addresses a critical concern and nurtures healthier populations.[8]

A recent study conducted by the International Market Analysis Research and Consulting Group (IMARC), a leading market research firm, unveils that India’s annual oil consumption amounts to 24 million metric tonnes (MMT).[9] The utilization of these oils is distributed between the organized sector (19 MMT) and the unorganized sector (5 MMT). Primary domestically cultivated edible oils encompass rapeseed, soy, cottonseed, and groundnut oil. Edible oils play an essential role in Indian households, with a widespread adoption of 99%. Notably, palm oil takes the lead in consumption at 38%, with soybean oil closely following at 22%.[10] India has a history of fortification, particularly with Vanaspati, fortified with vitamins A and D for over 70 years since 1953 to enhance nutritional value.[11] The Food Safety and Standards Authority of India (FSSAI) has recently in 2018 recommended a standardized approach to oil fortification, possibly becoming mandatory in the future.[12]

Anemia is widespread among Indian women and children. The average annual per capita oil consumption in India stands at 14.43 kg.[13] Fortifying oil with iron could effectively reach a large portion of the intended population. While there is substantial evidence supporting oil fortification with vitamins, such evidence is lacking for iron fortification. For instance, research has extensively demonstrated the effectiveness of oil fortification with vitamins, such as vitamins A and D, in improving overall health outcomes and reducing deficiency-related conditions. However, studies specifically investigating the impact of iron fortification in edible oils, particularly in terms of its efficacy in addressing iron deficiency and related health outcomes, are relatively limited.

To tackle this deep-rooted problem of anemia, we aimed to study the impact of oil fortification with iron in the prevention of anemia.

Materials and Methods

Criteria for considering studies for this review

Types of studies: Only experimental study designs, i.e., randomized, quasi-randomized, and cluster-randomized studies, were included in this review. Observational studies were excluded in this review and exclusively included published articles written in English and all non-English studies were excluded.

Search strategy

Electronic searches: A search was carried out in the following electronic databases using a set of keywords. PUBMED, EMBASE, WEB OF SCIENCE, SCOPUS, and Cochrane Library (CENTRAL) were searched for relevant records. These databases from their inception till date were searched. The search in each database was completed in April 2023 (Supplementary material).

Searching other resources

We contacted subject experts to identify unpublished and ongoing studies. We contacted authors of published trials to clarify or provide additional information if the criteria for methodological assessment are not explicit in their publication.

Ethical consecration

This Systematic Review followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).[14] This study is registered in PROSPERO (CRD42023420044).

Quality assessment

To examine the potential bias within the studies encompassed by this review, two individual authors conducted an independent evaluation of the articles’ quality. Our assessment employed the revised Cochrane risk-of-bias tool, encompassing domains such as the generation of random selection, allocation concealment, blinding procedures for participants and personnel, blinding of outcome assessment, management of incomplete outcome data, and prevention of selective reporting. Any uncertainties or inquiries were directed to the original authors of the articles. Studies demonstrating over four biases in the risk assessment, characterized by unclear or uncertain methodologies and outcomes, were subsequently excluded.[15]

Data analysis

Screening articles: The data extraction was carried out independently by two investigators with a predesigned data extraction tool. The data extraction tool contains details of authors, year of publication, relevant information related to research questions, PICO (population, intervention, comparison, and outcome), etc.

Data synthesis

As the review had only one eligible study, meta-analysis was not performed and the results are depicted as a narrative synthesis.

Population: Children (aged 6–59 months), 5–9 years of aged children, 10–19 years of aged adolescent girls and boys, pregnant women, women of reproductive age (20–24 years), and lactating mothers (0–6 months of a child).

Intervention: Oil fortification with iron

Comparison

1. Oil fortified with iron alone or in combination with other micronutrients versus unfortified oil (no micronutrients added)

2. Oil fortified with iron alone or in combination with other micronutrients versus no intervention or any other intervention.

Outcome

• Anemia

• Iron deficiency

• Hemoglobin concentration

• Iron status.

  1. Anemia (defined as hemoglobin (Hb) below the WHO cutoff adjusted for altitude as appropriate or as defined by the study authors)

  2. Iron deficiency and iron status (as defined by study authors, based on a biomarker of iron status)

  3. Hemoglobin concentration (g/L).

Result

A total of 13,948 records were identified through PubMed, Embase, Web of Science, Scopus, and Cochrane Library. Out of these records, 7109 records were duplicates and were excluded. The remaining 6839 records were screened based on title and abstract match. Here, 6776 records were excluded as they were either an observational study, non-published article, or non-English articles. The remaining 63 records underwent a full-text review, and 62 records had unmatched age criteria, were non-oil fortified studies, or had outcomes other than anemia, iron-deficiency, hemoglobin concentration, or iron status. Thus, only one article matched the criteria and was included for the review [Figure 1].

Figure 1.

PRISMA flow diagram for study inclusion and screening process

In the course of our research, additional resources were thoroughly searched in ProQuest, Open Grey, Shodhganga, and Science.gov databases; however, no relevant records were found. In Shodhganga, none of the 40739 articles were pertinent to our subjects. In Open Grey, 158 records were unmatched with all criteria. In science.gov, out of the 428 articles, none were relevant to our topic.

In Table 1, Andersson et al.’s 2010 the comparison between the two intervention groups (MGFePP and NaFeEDTA) was emphasized to evaluate the relative efficacy of these iron fortificants, a primary objective of the study. While both groups showed improvements compared to the placebo, NaFeEDTA significantly increased serum ferritin (SF) levels and reduced transferrin receptor (TfR) concentrations compared to both the placebo and MGFePP, highlighting its superior performance. Directly comparing the intervention groups provides clearer insights into their relative effectiveness and aligns with the study’s goal of identifying the more effective fortificant.[16]

Table 1.

Study design, population, sample size, intervention, control, and duration of the included study

Study		Study design		Population		Sample size		Intervention		Control		Duration
Andersson et al., 2010[16]		RCT		Women 18 to 40 years		n=142 Women were assigned—48 allocated to Placebo, 47 allocated to MGFePP, 46 allocated to NaFeEDTA (one case was excluded because of elevated CRP. CRP here was four times higher than normal)		The 20-g low-fat margarine was fortified with MGFePP or with NaFeEDTA		The 20-g low-fat margarine that contained no added iron)		32 weeks

RCT=Randomized control, MGFePP=Micronized ground ferric pyrophosphate, NaFeEDTA=Sodium iron ethylenediaminetetraacetate, CRP=C-reactive protein

After rigorous screening based on our inclusion criteria, one article was included in this systematic review. This study evaluated the effectiveness of fortifying low-fat margarine with iron in a double-blind randomized controlled trial. Swiss women aged between 18 and 40 years (n = 142) with serum ferritin concentrations less than 25 microgram/L were the population under consideration. Three groups of women were randomized to receive either 20 g margarine, 14 mg of additional iron in the form of NaFeEDTA or MGFePP, or a placebo per day. [Table 1].

Andersson et al.’s 2010 randomized controlled trial, which we referenced, entailed 142 women aged between 18 and 40 years. The study investigated the impact of iron fortification on hemoglobin levels over a 32-week period. The participants were divided into three groups: placebo, MGFePP, and NaFeEDTA. The intervention included fortifying 20 g of low-fat margarine with iron, while the control group received non-fortified margarine. Hemoglobin concentrations were measured at 0 and 32 weeks for each group. Results showed minimal changes in hemoglobin levels, with the placebo group exhibiting a negligible decrease of 0.0012 g/L, the MGFePP group showing a slight decrease of 0.0004 g/L (P = 0.589), and the NaFeEDTA group experiencing no change (P = 0.28). Overall, the study suggested that iron fortification did not significantly impact hemoglobin levels over the specified duration [Table 2].[16]

Table 2.

Hemoglobin details of included study

Study		Study design		Population		Sample size		Intervention		Control		Duration		Hb (g/dL)				Criteria
														1st time point (TP)		2nd time point
Andersson et al., 2010[16]		RCT		Women 18 to 40 years		n=142 Women were assigned-48 allocated to Placebo, 47 allocated to MGFePP, and 46 allocated to NaFeEDTA		The 20 g low-fat margarine was fortified with MGFePP or with NaFeEDTA		The 20-g low-fat margarine that contained no added iron)		32 weeks		Placebo (n=48) 0 week 13.5±0.9		Placebo (n=48) 32 weeks 13.5±0.9 Change -0.0012		Hemoglobin concentration <12 g/dL is defined as anemia.
														MGFePP (n=47) 0 week 13.7±0.9		MGFePP (n=47) 32 weeks 13.7±0.7 Change -0.0004 P=0.589
														NaFeEDTA (n=46) 0 week 13.6±0.9		NaFeEDTA (n=46) 32 weeks 13.6±0.9 Change 0 P=0.28

RCT=Randomized control, MGFePP=Micronized ground ferric pyrophosphate, NaFeEDTA=Sodium iron ethylenediaminetetraacetate, CRP=C-reactive protein

RCT with 142 women, aged between 18 and 40, revealed significant serum ferritin increases in the NaFeEDTA group (P < 0.0001) over 32 weeks, while the MGFePP group showed a nonsignificant increase (P = 0.0985). MGFePP did not lead to a significant improvement in SF compared to the placebo, though it did help improve body iron stores. However, NaFeEDTA significantly increased SF levels. [Table 3].

Table 3.

Serum ferritin and transferrin receptor (TfR) level details of the included study

Study		Study design		Population		Serum ferritin (microg/L)				Definition		TfR (mg/L)				Definition
						1st time point (TP)		2nd time point (TP)				1st time point (TP)		2nd time point (TP)
Andersson et al., 2010[16]		RCT		Women 18 to 40 years		Placebo (n=48) 0 week 10.9±7.4		Placebo (n=48) 32 weeks 11.9±9.6 Change -0.0006		Serum ferritin concentration <15 microgram/L is defined as iron deficiency		Placebo (n=48) 0 week 3.5±1.3		Placebo (n=48) 32 weeks 3.7±1.8 Change: -0.000327		Elevated TfR is defined as a TfR concentration >4.4 mg/L.
						MGFePP (n=47) 0 week 11.6± 6.1		MGFePP (n=47) 32 weeks 14.8±11.8 Change -0.0029 P=0.0985				MGFePP (n=47) 0 week 3.4±1.4		MGFePP (n=47) 32 weeks 3.2±1.1 Change: -0.000169 P=0.0589
						NaFeEDTA (n=46) 0 week 12.9±6.6		NaFeEDTA (n=46) 32 weeks 23.4±13.5 Change 0.0067 P=<0.0001				NaFeEDTA (n=46) 0 week 3.4±1.2		NaFeEDTA (n=46) 32 weeks 2.9±0.9 Change: -0.000639 P=<0.0001

TfR=Reduced transferrin receptor, RCT=Randomized control, MGFePP=Micronized ground ferric pyrophosphate, NaFeEDTA=Sodium iron ethylenediaminetetraacetate, CRP=C-reactive protein

In Andersson et al.’s 2010 study involving 142 women, iron fortification in the form of NaFeEDTA significantly decreased transferrin receptor (TfR) levels (Change: -0.000639, P = <0.0001) over 32 weeks. The MGFePP group showed a modest decrease (Change: -0.000169, P = 0.0589), while the placebo group exhibited a slight increase in TfR concentrations (Change: -0.000327). These findings suggest varying impacts of iron fortification on TfR levels in different intervention groups. Both MGFePP and NaFeEDTA were effective in lowering elevated TfR concentrations, with NaFeEDTA showing stronger results. [Table 3].[16]

In Andersson et al.’s 2010 study with 142 women, iron fortification’s impact on body iron levels was observed over 32 weeks. The placebo group exhibited a slight change from 0.9+/-3.2 to 1.0+/-3.8 mg Fe/kg body weight (Change: -0.0063). Meanwhile, the NaFeEDTA group showed a significant increase from 1.6+/-2.9 to 4.3+/-2.3 mg Fe/kg (Change: 0.0275, P = 0.0016), suggesting a notable result of NaFeEDTA fortification on body iron stores compared to other interventions. Both interventions showed improvement in body iron stores compared to the placebo. However, NaFeEDTA was more effective, with a much greater improvement than MGFePP. [Table 4].[16]

Table 4.

Body iron and elevated TfR details of the included study

Study		Study design		Population		Body iron (mg Fe/kg body weight)				Definition		Prevalence of elevated TfR
						1st time point (TP)		2nd time point (TP)				1st time point (TP) n (%)		Difference from baseline (% units)
Andersson et al., 2010[16]		RCT		Women 18 to 40 years		Placebo (n=48) 0 week 0.9±3.2		Placebo (n=48) 32 weeks ± 3.8 Change: -0.0063		Depleted body iron is defined as a body iron store <0 mg Fe/kg body weight.		Placebo (n=48) 0 week 12 (25)		Placebo (n=48) 32 weeks Change: 1.3%
						MGFePP (n=47) 0 week 1.2±2.9		MGFePP (n=47) 32 weeks 2.2±3.3 Change: 0.0103 P=0.2199				MGFePP (n=47) 0 week 10 (21.3)		MGFePP (n=47) 32 weeks Change: -7.8% P<0.05
						NaFeEDTA (n=46) 0 week 1.6±2.9		NaFeEDTA (n=46) 32 weeks 4.3±2.3 Change: 0.0275 P=0.0016				NaFeEDTA (n=46) 0 week 9 (19.6)		NaFeEDTA (n=46) 32 weeks Change: -16.2% P<0.001

TfR=Reduced transferrin receptor, RCT=Randomized control, MGFePP=Micronized ground ferric pyrophosphate, NaFeEDTA=Sodium iron ethylenediaminetetraacetate, CRP=C-reactive protein

The prevalence of elevated transferrin receptor (TfR) concentrations was significantly reduced by fortification with NaFeEDTA, indicating its effectiveness in improving iron status compared to the placebo and MGFePP fortification. The prevalence of elevated transferrin receptor levels changed over 32 weeks. The NaFeEDTA group showed a substantial decrease from 19.6% to 3.4%, suggesting a notable effectiveness in lowering elevated transferrin receptor levels compared to other interventions. [Table 4].

In Andersson et al.’s 2010 study with 142 women, anemia prevalence changed over 32 weeks. The placebo group increased from 2.1% to 5.8%, MGFePP showed a modest rise from 4.3% to 5.4%, while NaFeEDTA decreased from 6.4% to 3.2%. These results suggest potential differences in the effectiveness of iron fortification interventions in addressing iron deficiency. [Table 5].[16]

Table 5.

Prevalence of anemia and iron deficiency of the included study

Study		Study design		Population		Anemia prevalence				Prevalence of iron deficiency
						1st time point (TP) n (%)		1st time point (TP) n (%)		1st time point (TP) n (%)		Difference from baseline (% units)
Andersson et al., 2010[16]		RCT		Women 18 to 40 years		Placebo (n=1) 0 week: 1 (2.1)		Placebo (n=48) 32 weeks Change: +5.8%		Placebo (n=48) 0 week 29 (60.4)		Placebo (n=48) 32 weeks Change: -11.8%
						MGFePP (n=2) 0 week: 2 (4.3)		MGFePP (n=47) 32 weeks Change: 1.1%		MGFePP (n=47) 0 week 28 (59.6)		MGFePP (n=47) 32 weeks Change: -16.7%
						NaFeEDTA (n=3) 0 week: 3 (6.4)		NaFeEDTA (n=46) 32 weeks Change: -3.2%		NaFeEDTA (n=46) 0 week 23 (50.0)		NaFeEDTA (n=46) 32 weeks Change: -32.8% P<0.05

MGFePP=Micronized ground ferric pyrophosphate, NaFeEDTA=Sodium iron ethylenediaminetetraacetate

In a study with 142 women, the prevalence of elevated transferrin receptor levels changed over 32 weeks. The placebo group decreased from 60.4% to 48.6%, MGFePP showed a reduction from 59.6% to 42.9%, and NaFeEDTA exhibited a substantial decrease from 50% to 17.2%. These results suggest potential effectiveness of iron fortification interventions, particularly with NaFeEDTA, in lowering the prevalence of elevated transferrin receptor levels in the studied population. While MGFePP did not show a significant reduction in iron deficiency, NaFeEDTA had a strong impact, significantly reducing its prevalence. [Table 5].

Iron and hemoglobin levels were assessed at three randomly selected time intervals between four and 28 weeks in addition to two predetermined time points (the baseline and the 32-week mark). When compared to women who got a placebo, those who received MGFePP or NaFeEDTA had higher body iron reserves (P < 0.05). When body iron reserves were fortified with NaFeEDTA, they increased two to three times more than when they were fortified with MGFePP (P < 0.05); this difference was especially pronounced in women whose baseline serum ferritin concentrations were less than 15 microgram/L (P < 0.05).

There was no drastic change in Hb in the three groups when they were compared at baseline with at 32 weeks. The serum ferritin increased in MGFePP and NaFeEDTA groups at 32 weeks compared to baseline. There was a mild increase in the placebo group also for the same comparison. TfR decreased in MGFePP and NaFeEDTA groups at 32 weeks vs baseline values, whereas in the placebo group, it showed a mild increase in values. Body iron drastically improved in MGFePP and NaFeEDTA groups at 32 weeks vs baseline, whereas the placebo group showed a mild increase.

The prevalence of depleted body iron refers to the percentage of individuals with body iron stores below a certain threshold, indicating a deficiency in iron levels. The prevalence of depleted body iron was assessed over 32 weeks. The NaFeEDTA group showed a significant decrease of 20.5% (from 23.9% to 3.4%), indicating a notable effectiveness in reducing the prevalence of depleted body iron compared to other interventions (Placebo: increase by 2%, MGFePP group: decrease in value by 4.8%).

Figure 2 outlines the domain-specific risk of bias assessment using the Cochrane risk-of-bias tool. Each domain was carefully evaluated based on predefined criteria. Random sequence generation (D1) was performed using a mixed-effect model to account for potential group-level variability introduced by randomization. This reduces the risk of selection bias and ensures robust estimation of intervention effects. Allocation concealment (D2) was performed by robust allocation concealment procedures. Randomization codes were securely sealed and inaccessible to both participants and investigators during the trial. Blinding of group assignments was maintained, with codes revealed only after all participants had completed the study and a blind review of the data had been conducted. This approach ensured that group allocation was not influenced by participant characteristics or investigator preferences, reducing the risk of selection bias and enhancing the validity of the trial findings. Blinding of participants and personnel (D3) was ensured by using identical intervention materials, reducing the risk of performance bias. Outcome assessment (D4) was blinded, and incomplete outcome data (D5) were addressed with a robust follow-up protocol, ensuring minimal risk of attrition bias. These measures collectively indicate a low risk of bias, enhancing the reliability of the study results.

Figure 2.

Risk of bias domains

The risk of bias is low in the randomized control trial study because the individual domains from D1 to D5 have been assessed the risk as low. This indicates that the trial was conducted with rigorous methods, minimizing potential biases. It suggests that the study results are likely reliable. It is important to note that a low risk of bias is contingent on a thorough understanding of the design [Figure 2].

Discussion

Studies have extensively explored the fortification of oils with vitamins and minerals, yet research specifically addressing iron fortification in oils remains scarce. While numerous studies have investigated iron fortification in various food sources, there has been only one study research focusing on fortifying oils with iron, which seriously hinders the generalizability of study findings.

The current study was a double-blinded randomized controlled trial that aimed to evaluate the effectiveness of iron fortification in low-fat margarine. Serum ferritin levels of less than 25 microg/L were seen in the 142 Swiss women, aged between 18 and 40. Three groups of women were randomly randomized to receive either 20 g of margarine with 14 mg of additional iron as NaFeEDTA or MGFePP on a daily basis, or a placebo. At baseline, the 32-week endpoint, and three randomly chosen time intervals between four and 28 weeks, measurements of hemoglobin and iron status were made.

Results showed increased body iron stores in women receiving MGFePP or NaFeEDTA compared to those receiving a placebo (P < 0.05). The increase in body iron stores with NaFeEDTA fortification was two to three times greater than with MGFePP fortification (P < 0.05), particularly notable in women with baseline SF concentrations <15 microg/L (P < 0.05).[9]

Fortifying oil with iron presents several challenges, and it is not a common practice for several reasons: 1. Reactivity: Iron is known to undergo chemical reactions, including oxidation, especially in the presence of air and moisture. Edible oils are susceptible to oxidation, and the addition of iron could accelerate this process, leading to rancidity and off-flavors in the oil. 2. Color Changes: Iron can cause discoloration in foods. When added to oils, it might contribute to undesirable color changes, affecting the appearance and consumer acceptance of the fortified oil. 3. Bioavailability: The form of iron used for fortification matters for its bioavailability. Iron exists in different forms, and not all forms are well absorbed by the human body. Certain forms of iron may not be bioavailable in oil, making the fortification less effective in addressing iron deficiency. 4. Taste and Odor: Iron fortification might introduce metallic tastes or odors to the oil, impacting the overall sensory qualities of the food prepared with the fortified oil. 5. Regulatory Considerations: The addition of iron to foods is subject to regulatory standards and guidelines. Regulatory authorities typically set limits on the types and amounts of fortificants that can be used in certain food items to ensure safety and efficacy.[16]

Iron fortification is a vital tool in combating anemia and iron deficiency, but it can sometimes have unintended side effects. Common issues include gastrointestinal discomfort, such as diarrhea, constipation, and bloating, often caused by changes in gut microbiota.[17,18,19,20] High doses of iron can increase the risk of infections like malaria and bacterial illnesses by promoting pathogen growth.[18,21,22] In children who are not iron-deficient, it may slow growth and potentially affect cognitive and motor development, although more research is needed.[18] Additionally, iron can interfere with the absorption of other nutrients, like zinc and copper, and contribute to oxidative stress and inflammation.[19,23] While these effects highlight the need for careful monitoring, tailoring fortification programs to specific needs can help maximize benefits while minimizing risks.

To overcome the limitations of iron fortification in edible oil, solutions include using encapsulation techniques to prevent oxidation and off-flavors, selecting highly bioavailable iron compounds, and employing flavor masking methods to mitigate metallic tastes.

While fortifying oil with iron might face challenges, iron fortification is commonly performed in other food products, where the issues mentioned above can be better managed. For example, iron is often added to cereals, flour, and other processed foods to address iron deficiency in populations. The choice of fortification strategy depends on the specific food matrix, the characteristics of the fortificant, and the intended nutritional outcome.

Limitations and recommendations

The current systematic review has followed the methodology adopted in the Cochrane Handbook for Systematic Reviews of Interventions.[24] However, a notable limitation lies in its singular focus, as only one such study is conducted, and exclusively in the context of margarine in only single population of a geographical location (Swiss women), potentially limiting the generalizability of findings to a broader scope of products or contexts.

A future study is warranted to investigate the feasibility of fortifying edible oils with micronutrients, exploring reasons for both potential success and challenges. Comprehensive global studies examining the efficacy of fortification across various edible oils and micronutrients are essential to establish evidence-based practices. The research should encompass a systematic analysis of chemical stability, bioavailability, and sensory attributes to inform sound recommendations. Rigorous experimental designs, including randomized controlled trials, should be employed to ensure robust data analysis. Collaboration with experts in nutrition and food science will enhance the scientific rigor and applicability of the study.

Conclusion

The study included under this review has revealed that adding iron to low-fat margarine helped boost iron levels in women with low blood iron. Although adding iron to foods like cereals is a common practice, fortifying iron in oil has its own limitations. Further high-quality trials are warranted to investigate the feasibility of fortifying edible oils with iron, thus curbing the public health issue of iron deficiency.

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Abbreviations

NaFeEDTA: Sodium iron ethylenediaminetetraacetate; MGFePP: Micronized ground ferric pyrophosphate; NFHS: National Family Health Survey; FSSAI: Food Safety and Standards Authority of India.

Author’s contributions

RH: Conceptual design, data curation, formal analysis, research, methods, writing - original draft, writing – revision and editing. BU: Conceptual design, data curation, formal analysis, research, methods, writing - revision and editing. MR: Conceptual design, methods, validation, supervision, writing - revision and editing. CC: Writing - revision and editing. VG: Conceptual design, methods, formal analysis, supervision, writing - revision and editing. JJ: Conceptual design, methods, supervision, writing – revision and editing. NAK: Data-extraction, writing - revision and editing. VV: Data-extraction, writing - revision and editing. AS: Data-extraction, writing - revision and editing. AB: Data-extraction, writing - revision and editing.

Data availability statement

All data analysed during this study are included in this published article.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

This study has been supported by the Indian Council of Medical Research, Ministry of Health and Family Welfare, New Delhi, Government of India.