From 19 to 21 November 2014, the Rome Declaration on Nutrition, the outcome document of the Second International Conference on Nutrition (ICN2), noted that over two billion people suffer from micronutrient deficiencies and in particular vitamin A, iodine, iron, and zinc [1
]. The ICN2 Framework for Action [2
] and the subsequent United Nations General Assembly proclamation on the Decade for Action on Nutrition 2016–2025 [3
] have recommended urgent and significant action to combat micronutrient deficiencies. Food fortification, the addition of a nutrient(s) to a food to prevent or correct a demonstrated nutrient deficiency [4
], is promoted as a particularly effective strategy to combat micronutrient deficiencies [5
], though its effectiveness, risks, and ethical implications vary depending on the contexts associated with the deficiency it is addressing and the circumstances related to its implementation [7
However, food fortification is just one among many nutrition interventions available to combat micronutrient deficiencies. These interventions are commonly considered as belonging to either of two broad categories:
Nutrition-specific interventions (NSpI) “address the immediate causes of undernutrition, like inadequate dietary intake, and some of the underlying causes, like feeding practices and access to food” [8
]. Food fortification and nutrient supplementation are prominent examples of these interventions that can rapidly increase an individual’s and targeted population’s exposure to a nutrient(s) [9
Nutrition-sensitive interventions (NSeI) “can address some of the underlying and basic causes of malnutrition by incorporating nutrition goals and actions from a wide range of sectors. They can also serve as delivery platforms for nutrition-specific interventions” [8
]. Interventions may be located in sectors as diverse as agriculture [10
], education [11
], and social support [12
]. In contrast to nutrient-oriented interventions, they generally focus on promoting food and diet quality and diversity to support consumption of a healthy, balanced diet.
Whether or not to select food fortification as an intervention to combat a micronutrient deficiency will depend largely on the circumstances associated with this nutrition problem and what alternative interventions are available. In the short term, a NSpI such as food fortification may be well suited to treat an acute micronutrient deficiency. Alternatively, in a chronic situation, food-based NSeI are likely to be better suited to protect against and sustainably prevent micronutrient deficiencies. Over the longer term, food- and diet-based interventions are better able to tackle the co-existence of multiple micronutrient deficiencies, and deliver social and economic co-benefits [13
]. Generally, a strategically implemented combination of multiple interventions is recommended as the best approach to achieve nutrition’s full potential for health and development outcomes [8
]. As Uauy comments, “Fortification should be seen as complementary to food-based strategies and not as a replacement to dietary diversification, and can serve as a cost-effective measure to resolve micronutrient deficiencies until food-based approaches become feasible” [17
Evidence-informed policy and practice decisions are required to plan and implement nutrition policies and interventions. The WHO “Handbook for Guideline Development” [18
] explains that the WHO guideline recommendations need to be based on the best evidence available and that an effective approach for obtaining such evidence is to draw upon the findings of systematic reviews (SRs) of relevant interventions. A number of relevant and detailed SRs, guideline statements, and implementation actions to combat micronutrient deficiencies are available. Rationally, it would be expected that SRs would assess all available evidence for both NSpI and NSeI. In turn, these reviews would inform the development NSpI- or NSeI-aligned guideline statements and implementation actions. However, food policy-making is an inherently political process, especially given the contested views over the causes of, and solutions to, complex problems such as micronutrient deficiencies [7
]. For example, political processes may influence what evidence is collected, synthesized, and translated in the formulation of policies and interventions to combat micronutrient deficiencies. Our hypothesis was that the various nutrition interventions available to help combat micronutrient deficiencies are not equally represented in SRs, that this will impact the number and type of guidelines and policy statements formed and, finally, that this will translate into a skewed number and type of implemented actions for nutrition. As far as we know, the profile of and relationships among these three sets of resources have not been investigated. Thus, the aim of this research was to analyse the profile of nutrition interventions for combating micronutrient deficiency with particular focus on food fortification reported in existing SRs, guidelines and policy statements, and implementation actions for nutrition. The findings from this research can help inform the future planning of evidence synthesis, guideline development, and implementation actions for nutrition interventions to combat micronutrient deficiencies.
3.1. Systematic Reviews
The review selection process for SRs and SR protocols is outlined in Figure 1
. Searches of PubMed, TRIP, Epistemonikos, and Health Evidence retrieved 1183 records, of which 92 met our eligibility criteria (excluding records from the CDSR). In the CDSR, of 8484 records identified, 78 were included in this analysis. In total, 170 SRs and SR protocols (including one overview of SRs) were included that addressed primary micronutrient deficiencies, either through fortification or other methods, in any population.
Of the 170 included SRs and SR protocols, the majority addressed food fortification-only (n
= 29, 17.0%) or micronutrient supplementation-only interventions (n
= 108, 63.5%) (Table 1
Of the 29 fortification-only interventions, 14 involved fortification with multiple micronutrients and 15 involved single micronutrients (iron n = 5, iodine n = 4, zinc n = 3, vitamin A n = 1, vitamin D n = 1, and calcium and vitamin D n = 1). Vehicles for fortification included staple foods, maize flour, wheat flour, rice, salt, condiments, seasonings and various foods (e.g., milk, margarine for vitamin D, and point-of-use fortification of foods with micronutrient powders), as well as dairy and non-dairy beverages. The vast majority of the supplementation-only interventions involved single nutrients (n = 92) rather than multiple micronutrients (n = 16).
Some SRs and SR protocols addressed other interventions (n = 12, 7.0%) or a combined intervention (n = 21, 12.3%). Other interventions included food-based interventions (e.g., school feeding programs, dietary diversification, and modification strategies), targeted financial incentives (e.g., conditional cash transfer programs), agricultural interventions (e.g., household food production strategies), and education-based interventions. Combined interventions included fortification and supplementation (n = 6), fortification, supplementation and other interventions (n = 7), supplementation and other interventions (n = 3), and fortification and other interventions (n = 5).
All of the fortification-only and supplementation-only interventions were NSpI. More than half of the ‘other’ interventions addressed by SRs were NSpI, such as behaviour change interventions to promote improved breastfeeding and complimentary feeding, and food-based feeding program interventions. The remainder was made up of NSeI, such as those using agricultural or social security platforms.
3.2. Nutrition Guidelines and Policy Statements
69 of the 101 interventions in the eLENA met our inclusion criteria (Table 2
). Food fortification interventions included the fortification of staple foods such as flour and rice, iodisation of salt, and the use of multiple micronutrient powders for the fortification of foods in the home. One intervention involved biofortification of staple crops with iron, zinc, or vitamin A. Supplementation interventions included vitamins A, D, and E, zinc, iron, folic acid (in combination with zinc or iron), and calcium.
All interventions involving supplementation were classified as Category 1 or 2 interventions (n = 34). Of the fortification interventions, four of seven were Category 1 or 2 interventions, and three of seven were Category 3 interventions. A number of other relevant interventions were also identified. Other interventions included those addressing feeding practices, marketing of infant formula, nutrition assessment, nutrition education, sanitation, and financial incentives. All other interventions were classified as either Category 1 or Category 2 interventions (n = 28).
Of the 69 included interventions, the vast majority (n = 63, 91.3%) were NSpI. The remaining six interventions (8.7%) were NSeI (agricultural interventions n = 1, public health interventions n = 4, social welfare interventions n = 1). Five of the six NSeI interventions were classified as Category 1 or Category 2 interventions.
3.3. Implementation of Nutrition Actions
Thirty sub-topics in the WHO GINA database were included in our analysis. A total of 1646 nutrition actions were categorised under these sub-topics (Table 3
Some nutrition actions involved food fortification (n = 293, 17.8%) or micronutrient supplementation (n = 438, 26.7%), but more than half did not (n = 915, 55.6%). Vehicles for food fortification included rice, maize or corn flour, wheat flour, milk, condiments and seasonings, sugar, margarine, butter, and oil. Some actions involved multiple micronutrients, such as fortification of salt with iron, iodine, vitamin B12, folic acid, zinc, and vitamin A. A number of nutrition actions involved the addition of multiple micronutrient powders to foods in the home. Nutrition actions involving micronutrient supplementation involved single nutrients (zinc, iodine, iron and folic acid, iron, vitamin A, and calcium) or multiple micronutrients. Other nutrition actions included both NSpI and NSeI. Overall, the majority of actions were NSpI (n = 1169, 71.0%). The remaining 477 actions were NSeI (agricultural actions n = 22, public health actions n = 439, and other nutrition sensitive actions n = 16).
The findings from this analysis indicate that there is a substantial body of evidence reporting the use of food fortification as an intervention to combat micronutrient deficiencies. They also indicate that this evidence is translating into practice to a certain extent. A range of food fortification interventions are addressed by the SRs, guidelines and policy statements, and nutrition actions. All three forms of evidence synthesis and translation include interventions to combat vitamin A, iodine, iron, and zinc deficiencies noted with particular attention at ICN2 [1
Micronutrient supplementation is the dominant intervention type addressed in included SRs, protocols, guidelines, and policy statements. Systematic reviews and protocols related to NSpI, which are predominantly supplementation and fortification, are significantly more available than those related to NSeI alone or in combination with NSpI. The fact that there are significantly more guidelines, policy statements, and actions available related to NSpI than to NSeI alone or in combination with NSpI confirms our original hypothesis. These findings are consistent with a rational linear relationship pattern connecting the evidence synthesized from SRs, the development of guideline statements, and implementation actions, at least in relation to NSpI. However, further studies would be needed to confirm this.
The dominance of NSpI-related reviews and protocols, guidelines and policy statements, and actions relative to NSeI is not congruent with public health best practice, including recommendations by the United Nations International Children's Emergency Fund (UNICEF) [8
] and the WHO [14
], which encourage a strategic combination of evidence-informed interventions to combat micronutrient deficiencies. Consequently, policies and practices might not be as effective as they might be and may result in public health risks. Whereas NSpI are well suited to relatively quickly treat and prevent the physiological symptoms of micronutrient deficiencies, they may not address the underlying cause of the deficiency as NSeI would. Consequently, depending on the circumstances, NSpI may not be as effective, sustainable, or safe as NSeI [7
]. Concerns about risks associated with the potential for harmful dietary exposure resulting from food fortification interventions have been raised in the context of low- to middle-income countries [23
] as well as high-income countries [24
It was beyond the scope of this research to investigate specific explanations for the observed dominance of NSpI in general, and supplementation and fortification interventions in particular, among the interventions available to combat micronutrient deficiencies. However, the literature does provide examples where methodological orthodoxies and political factors can influence decision-making and result in the privileging of supplementation and food fortification interventions over NSeI. Methodologically, evidence synthesis orthodoxies typically rate the evidence obtained from studies using reductionist methods higher than evidence obtained from studies using more holistic methods. Investigations of relationships between single nutrients and single physiological outcomes are more amenable to reductionist methods than the inherently complex relationships that exist between NSeI and health outcomes [26
]. Politically, vested interests can preferentially support NSpI relative to NSeI, and this manifests in relatively greater likelihood that certain research agendas are pursued, certain research questions are posed, certain SRs are conducted, and certain interventions are implemented. For example, potential conflicts of interest that can arise with the planning of food fortification activities were identified in the WHO technical report, “Addressing and managing conflicts of interest in the planning and delivery of nutrition programmes at country level” [28
]. In the report, it was noted: “The private sector influences the political framing of the problem and the selection of appropriate policy responses (at international and national level) in the following areas: Reliance on private money; research investment and prioritization; underlying assumptions; selection of experts, advisers, and researchers; partnerships or donors pushing for fortification when it is not needed; de-prioritization of medium- and long-term solutions … (and at-risk areas include inadequacies when) … evaluating options (e.g., fortification versus other nutrition interventions)” [28
] (p. 22).
The strengths of this research included the novel nature of the investigation, the high quality databases from which the data were sourced and the critical analysis of the collective profile of these data, their inter-relationships, potential knowledge gaps, implications for public health nutrition practice, and future research priorities. Nonetheless, the potential for limitations with the collection and analysis of the data cannot be discounted. Comprehensive data on systematic reviews were collected from five key databases; however, it is possible that we missed relevant SRs. Similarly, we may have missed relevant nutrition guidelines and policy statements and actions that are being implemented but are not recorded in the eLENA and the GINA, respectively. In the GINA the data extraction was restricted to actions only and not policies. It is possible that, if policies had also been included, the findings may have differed to a certain extent. The decision not to include policies was based on the authors’ experience that the existence of a policy does not always lead to an action, and it was action that was the priority interest for this investigation. Additionally, in relation to the GINA, the search relied on the classifications in the website database rather than on original keyword search, so relevant results may have been missed. Despite quality assurance procedures being undertaken, it is possible there were inaccuracies regarding data extraction, coding, and interpretation during the data analysis component of the research. We did not assess the quality of individual reviews, guidelines, or actions included in the study, as this would have been beyond the scope of the research aim. We also did not investigate the reach and impact of individual interventions. Therefore, a food fortification intervention to modify the nutrient composition of the national food supply and an NSeI such as a local agriculture program were recorded as one intervention each, despite the reality that the former would have a significantly higher reach and impact.
To the authors’ knowledge this is the first study to investigate SRs, guidelines and policy statements, and actions by type of nutrition intervention to combat micronutrient deficiencies, as well as analyse the relationship between these three activities. A number of unanswered questions remain. Priority areas for future research include investigating the relationship between evidence synthesized for NSeI and what then is happening in policy and practice, especially if this can contribute to the informing of strategic combinations of interventions to combat micronutrient deficiencies; extending the investigation to analyse policy documents in the GINA; and investigating how and why there is a dominance of NSpI over NSeI in the observed SRs, guidelines and policy statements, and actions observed.