Achieving a balanced and diverse diet remains a challenge for many people, contributing to an ongoing burden of micronutrient de-ﬁciencies, particularly in low-income settings. Fortiﬁcation or dietary diversiﬁcation are common food-based approaches. We conducted a scoping review to: 1) ﬁnd evidence on whether combined food–based strategies are more effective than single strategies, and 2) understand how strategies implemented together could complement each other to achieve optimal nutritional impact on populations. Peer-reviewed articles selected (n ¼ 21) included interventions or observational studies (n ¼ 13) and reviews (n ¼ 8). We found little evidence of an added nutritional impact. On the other hand, it is apparent that fortiﬁcation and dietary diversiﬁcation target different types of settings (urban compared with rural) and foods (that is, low priced compared with highly priced). Further research is needed to understand the complementarity of these approaches and establish evidence of the effectiveness of combined strategies to foster policy adoption.
Keywords: food diversity, fortiﬁcation, biofortiﬁcation, hidden hunger, nutritional impact, integrated food-based strategies
Micronutrient deﬁciencies continue to pose a major global public health problem, particularly in low- and middle-income countries (LMICs), contributing to impaired linear growth of children, reduced immunocompetence, and suboptimal cogni-tive development, thereby impeding the development of both individuals and societies. A recent study estimates that 1 in 2 preschool aged children, and 2 in 3 women of reproductive age are deﬁcient in 1 vitamins or minerals . Despite data gaps, global estimates based on the analysis of existing national sur-veys reveal that vitamin A deﬁciency in children has improved in East Asia but remains high in South Asia and Africa . The extent of zinc deﬁciency remains uncertain due to limited data, but it is estimated to affect >20% of children living in LMICs . Universal iodization of salt has signiﬁcantly reduced iodine deﬁciency, but there are 25 countries in which mild to moderate forms of iodine deﬁciency remain prevalent . In addition, folate deﬁciency is still a major issue, linked to an estimated 260,100 neural tube defects (including ~175,000 stillbirths and neonatal deaths) . Anemia continues to affect an estimated 41.6% of children and 32.6% of women of repro-ductive age globally, with data suggesting iron deﬁciency to be an important, but not the only cause [6,7].
Efforts to combat the burden of these deﬁciencies over many decades have included a range of nutrition-speciﬁc and nutrition-sensitive interventions  which can be broadly grouped into four categories: micronutrient supplementation; fortiﬁcation A. Bechoff et al.
(including biofortiﬁcation); dietary diversiﬁcation; and public health and disease control (Figure 1). Fortiﬁcation and dietary diversiﬁcation fall under food-based strategies whereas the other two strategies are part of a health approach. These strategies were ﬁrst described at the International Conference on Nutrition, organized by the FAO and WHO in December 1992 . Bio-fortiﬁcation—referred to as micronutrient-enhanced crops by the European Commission—was not developed at this time, but was included in later guidelines . Food-based approaches to improve micronutrient status focus on the consumption of foods that are either naturally rich in micronutrients or have been enriched through fortiﬁcation .
We distinguish different forms of fortiﬁcation depending on the process and the stage at which micronutrients are added. With industrial fortiﬁcation, home fortiﬁcation or food-to-food fortiﬁcation, micronutrients are added at the site of processing or point of use (consumption), whereas in biofortiﬁcation, micronutrient content is increased during cultivation, generally using conventional breeding techniques or micronutrient-enhanced fertilizers. Dietary diversiﬁcation involves increasing the range of foods consumed to better meet the requirements for macro- and micronutrient intake. Although food fortiﬁcation focuses on increasing the content of one or more speciﬁc nutri-ents in staple foods, dietary diversiﬁcation typically relates to the introduction or more frequent consumption of nonstaple foods in existing diets.
Industrial fortiﬁcation and biofortiﬁcation have gained most attention in nutritional policies, but concerns have been raised about whether promoting fortiﬁcation as a standalone approach could divert policy makers from other strategies such as supporting diverse and healthy diets [12,13]. Fortiﬁcation strategies could lead to a limited impact on micronutrient deﬁciencies, because food fortiﬁcation is often with a limited number of micronutrients (for example, iodized salt or vitamin A fortiﬁed oils), and there are constraints to the amount of micronutrients in biofortiﬁed foods that can be achieved through breeding. Likewise, there are chal-lenges linked to the implementation of dietary diversiﬁcation as a single strategy, as foods naturally rich in micronutrients are often unaffordable for the poorer segments of societies, and linear pro-gramming analyses suggest that local foods may be unable to meet nutrient requirements for some population groups in some settings [14–16]. Moreover, producers in rural settings often face various constraints to produce diversiﬁed commodities, and the effects of production diversity on smallholder farming households’ diets varies between settings [17,18].
To accelerate progress in improving micronutrient status of populations globally, policy recommendations have called for integrating food-based approaches [6,9]. Despite a body of evi-dence to support the impact on nutritional status of food-based strategies taken separately, there is a knowledge gap about the effectiveness of those actions used in combination . We hy-pothesize that combining food fortiﬁcation with diversiﬁcation of diets would lead to improved nutritional outcomes compared with strategies focusing on either approach alone. The objective of this article is to evaluate the combination, and potential complementarity, of fortiﬁcation and dietary diversiﬁcation to improve the micronutrient status of populations.