Sustainable Strategy to Fight Hidden Hunger Using Food Waste: The Case of Aquatic Food Products

Abstract

In the current context of accelerating global warming, it is urgent to speed up actions to adapt to this problem. About one third of agri-food products are lost or underused, thus contributing further and unnecessarily to greenhouse gas emissions. This is a narrative review, based on exhaustive analysis of the literature dealing with the mechanisms, incidence, and historical aspects of hidden hunger, as well as technical and operational tools to fight it. The review gives an overview of the current situation regarding micronutrient deficiencies, called hidden hunger, in five minerals (iron, calcium, zinc, iodine, and selenium), and two vitamins (A and D), as well as a picture of overall mitigation actions and outcomes. Then, it gives a picture of available solutions regarding the raw material and the tools and methodologies currently used for agri-food waste valorization, with a focus on aquatic foodstuffs. Finally, a proposal for the use of agri-food waste to fight hidden hunger, food insecurity, and beyond, is advanced.

1. Introduction

While food waste has existed since the dawn of agriculture, its scale has escalated dramatically in recent history, especially since the revolution in food technology in the mid-19th century, due to inefficient management, inequitable distribution, logistical inefficiencies, and other reasons. However, for two decades, the Food and Agriculture Organization of the United Nations (FAO) has been warning about the unacceptably high level of global food loss or waste (~1.3 GT per year), which was estimated to be around one third of food produced for human consumption [1]. These losses and wastes generate between 8 and 10% of global greenhouse gas emissions [2]; therefore, reducing it will inevitably lead to a reduction in greenhouse gases, as well as food insecurity and unnecessary financial loss. According to Taneja et al. [3], the greatest losses are occurring in the production of fruits and vegetables (45%), followed by aquatic products (35%) and cereals (30%), then meat and dairy products (20% each). Nowadays, the concept of food waste is rather vague—some prefer “by-products”—and it is not clear if certain waste products used, albeit to a limited extent, as a source of biomolecules, as fertilizers, or as a source of energy, are included in waste. For this review, agri-food waste is broadly defined as any biomass from the agricultural or food supply chain that is not ultimately consumed by humans or animals, encompassing both edible food waste and inedible by-products, such as shells, bones, and peels.

On the other hand, over the two last decades, 700 to 800 million people have become undernourished [4], and the FAO estimated more than 6 million deaths in 2000 due to being underweight, affecting mainly young children, and to which deficiencies in iron, vitamin A, and zinc have contributed by about 40% [5] (see Supplementary Materials). Several global actions have been achieved; for example, during the summit of the United Nations in Rome in 1996, food safety was defined in four components: availability, accessibility, utilization, and stability, to which a fifth component, resilience, has been added since the COVID-19 pandemic. Another action was setting the Millennium Development Goals (8 MDGs) in 2000, which was followed by setting in 2015 Sustainable Development Goals (17 SDGs, and 169 targets for 2030). Global actions that began in the 1990s resulted in lowering the global undernourishment of around 200 million people in the mid-2010s, although an increase of about 4% in demography was observed during the same period. Then, an unexpected constant phase of food security status ran for a few years, before a dramatic increase in undernourishment (~100 million) due to the COVID-19 pandemic; fortunately, the trend in food insecurity is currently going downward [4].

The contribution of deficiency in micronutrients to undernourishment was anticipated early in 1947 by Sir Albert Howard: “Western civilization is suffering from a subtle form of famine, a famine of quality”. By that time, all vitamins and most essential minerals were known. The term “hidden hunger” (HH), which seems rather vague, but which is generally defined as being a deficiency of one or more micronutrients, was only introduced in 1994 by Houston [6], and nowadays the general literature reports at least 2 billion people affected by HH [7,8,9,10]. Women of reproductive age are the most affected group, especially in Africa, where likely more than half of the women suffer from deficiency in at least one micronutrient [11]. Young children are also highly affected, causing stunting, disability, and premature mortality [12]. For the women and the children and all people, remarkable successes have been achieved after efficient actions in the fight against HH. For example, there has been as much as a 92% decrease in iodine deficiency in Ethiopia between 1990 and 2017 [13]. This resulted in significant reductions in Disability-Adjusted Life Years (DALYs), which refers the sum of the years of life lost due to premature mortality and the years lived with a disability due to inadequate health conditions in a population.

This review provides a general overview of the current situation regarding global deficiencies in the main micronutrient contributors to HH, integrating the biological, technical, historical, and managerial aspects of the issue. The multidimensional analysis of the hidden hunger issue has allowed us to build and propose a comprehensive, sustainable, and flexible approach to the recovery of agri-food waste, particularly food waste of aquatic origin. The aim is to contribute to accelerating the transition to a healthier and more sustainable economy.

2. Methodology

The methodology used to prepare this review is summarized in Figure 1.

The first step involved identifying relevant publications based on the presence of targeted keywords in their titles, using general databases. Sometimes, the presence of keywords in the title/abstract was also explored when searching for specific information. The results were sorted, and the most relevant publications were selected, i.e., 282 publications.

Then, in a second round of literature analysis, a more in-depth examination of the selected publications was achieved, resulting in the selection of 96 publications cited in the review.

3. Results and Discussions

3.1. The Current Situation of Hidden Hunger

Figure 2 illustrates the biological activities of the main micronutrients that can lead to HH [14,15,16,17,18,19,20].

The most affected people are preschool-aged children due to the needs for growth, as well as women of reproductive age due to additional reproductive demands, and menstrual losses, particularly in the case of iron. Iron is involved in many biological processes, such as oxygen transport, oxidation of nutrients, and defense against xenobiotics ingested, inhaled, or absorbed through the skin, among other biological activities. Insufficient iron intake triggers disorders, especially anemia, the severity of which increases in parallel to the extent of the deficiency [21]. This is a concern in both developed and developing countries, with a global anemia prevalence in preschool-age children during the period 1993 to 2005 ranging from 22% to 67%, and in women of reproductive age from 19% to 57%, pregnant women being more affected than non-pregnant women [22]. The situation did not improve between 2000 and 2023, with a decrease in the overall average incidence of anemia among pregnant women from 40.3% to 35.5% and an increase among non-pregnant women from 28.7% to 30.5% [23].

Calcium is also involved in many biological processes, such as bone and protein structures, coagulation, cell signaling, etc., and its deficiency is historically linked to rickets and extends to less visible disorders dealing with bone health and other biochemical processes. According to Qu et al. [24], 500 million people are affected by osteoporosis and by over 8.9 million fractures annually, which contributes to the global health and economic burden due to HH. This is also the case for zinc, the deficiency of which affects one in six persons and up to one in four in some regions, according to Wessells and Brown [25]. Zinc deficiency is less visible than those of iron and calcium, even if zinc exhibits significant biological activities, including catalytic and structural activity in hundreds of proteins [26]. Iodine, which is also a major source of HH, including the highly visible goiter and cretinism, has quite a narrow interval of physiological concentration, and both excess and deficiency triggers disorders, dealing in both cases with thyroid gland function and associated neural circuits. According to Houston [6], Goiter was mentioned more than 2800 years BC in Chinese texts, as well as its remedy by seaweed. Whatever the veracity of this information, nowadays, iodine deficiency seems to concern approximately 2 billion people, including more or less severe clinical symptoms [17]. Another important mineral is selenium, which was discovered approximately 200 years ago and was considered toxic until it was identified as a cofactor of glutathione peroxidase, and later recognized as a micronutrient in the 1960s. Besides its role in antioxidant defense, selenium plays many other biological roles, including activities in immunity and endocrine systems, and may involve 25 selenoproteins that have been identified until now [8]. The global incidence of selenium deficiency was estimated to be 14% [27], and about 60 million people suffer from Keshan disease, a pathology that is associated with selenium deficiency and which was discovered in the 1930s in China in regions where the soil contains very low selenium concentrations [28].

As for the contribution of vitamins to HH, vision problems linked to vitamin A deficiency, especially xeropthalmia, has been known for a long time. According to Sommer [29], night blindness is mentioned in the Egyptian Ebers papyrus, as well as the remedy, which consists of applying a few drops of fluids from roasted sheep liver to the patient’s eyes. Currently, 140 to 250 million people are at risk of vitamin A deficiency and between 250,000 and 500,000 children deficient in vitamin A have lost their sight, half of whom died within the following year [30,31]. Vitamin D differs from the micronutrients mentioned above in that its production is primarily due to its cutaneous synthesis in the skin triggered by solar UVB radiation. The dietary component is therefore small, and its deficiency is mainly due to insufficient sun exposure. This deficiency, which appears to affect a significant portion of the global population, over 50% according to some authors [19], is responsible for rickets in children and for osteopenia and osteoporosis, among other disorders in adults [19,32,33].

In summary, the situation concerning HH is rather dramatic, with an incidence of deficiency in each of the seven micronutrients targeted here ranging from 15 to over 50% of the general population, and a higher cumulative incidence. This dramatic situation must be nuanced by the fact that deficiency may be mild, moderate, severe, or critical. However, even if there are only 10% severe cases, it still approaches a billion people. Encouragingly, trends indicate a gradual decline in HH that is being observed, both at global and national levels, thanks to the actions undertaken in recent decades. According to Lin et al. [34], the global incidence of iodine deficiency decreased by 13.3% between 1990 and 2019, i.e., an estimated annual percentage change (EAPC) of 0.7% /year, which agrees with the decrease reported by Hana et al. [35]. This is slightly higher that the decrease in global iron deficiency (EAPC of 0.55%/year) and markedly lower than global vitamin A deficiency (EAPC of 3.15%/year) [35]. The decline in the incidence of vitamin A deficiency has been associated with a similarly significant decline in the associated DALY rates between 1990 and 2019 [36]. More interestingly, as mentioned above, a remarkable success was reported for iodine deficiency (92% decrease) in Ethiopia from 1990 to 2017 [13]. This ascertains that it works when the means are put in place, although, as stated by the authors, there is still a need for further efforts in improving food security, especially the accessibility and utilization of nutrient-rich foods.

3.2. Strategies for Fighting Hidden Hunger

Overall, four main (conventional or emerging) approaches to fight HH are used, either at the global or national levels. The first is supplementation, which is implemented with a micronutrient in the form of tablets, pills, or other forms, regularly over a certain period of time [21,37]. The administered doses exceed nutritional requirements, which can lead to interference with the digestion, absorption, and metabolism of other micronutrients. This is due to competition for binding to enzymes, transporters, and other biomolecules. In the case of minerals, the supplementation approach would be useful for reducing human exposure to heavy metals as well, such as zinc and selenium against lead [38], and zinc and iron against cadmium [39]. Mineral/vitamin interference also occur, such as iron/vitamin A or B2 [37]. In any case, the approach has proven to be, to some extent, effective, particularly for iron and vitamin A deficiency, even though it requires significant technical and financial resources. It also faces acceptability issues: some people refuse to take mineral formulations due to cultural or religious beliefs, or due to a lack of information.

Food fortification, which consists of adding a micronutrient to a foodstuff, is also a long-standing approach. Well-established strategies are the use of iodine in sodium chloride introduced in the 1920s, and the addition of iron to wheat flour, which has taken place for over half a century. Food fortification with iodine, folate (vitamin B9), zinc, iron, and vitamin A have significantly contributed to the reduction in HH, although some discrepancies in effectiveness exist, especially in the case of iron and vitamin A [11]. Here, too, there are implementation constraints, i.e., financial resources, technical expertise, accessibility in rural areas, etc.

Biofortification, which developed mainly from the 1980s to the 1990s, consists of selecting crops rich in one or more micronutrients through conventional crossbreeding or introducing genes of interest using biotechnology. Both methods aim at improving the bioavailability of the target micronutrient(s), either directly in planta by increasing its content or indirectly by reducing inhibitors or increasing enhancers of its bioavailability, in planta or by another means [8]. Biofortification has had several successes, such as golden rice rich in beta-carotene, a precursor to vitamin A [40], iron-enriched cassava, nutrient-enhanced tomatoes, and omega 3-fortified oilseed crops [10]. Biofortification has also significantly contributed to the reduction in HH over the past decades.

The food to food fortification (F2FF) approach stems from the Flour Fortification Initiative in 2002, which initially targeted wheat and was later extended to corn, rice, and other foodstuffs in the mid-2010s. A definition of F2FF and a practical framework for its implementation and effectiveness evaluation have recently been proposed [41]. For example, Famuyide et al. [42] mixed wholegrain pearl millet with moringa leaves (both rich in minerals, especially iron), baobab fruit (rich in mineral absorption enhancers such as organic acids, especially ascorbic acid), and mango and papaya (rich in β-carotene, among others beneficial food ingredients). After an appropriate process and using an in vitro model for assessing the bio-accessibility of zinc and iron, i.e., the extent of liberation of micronutrients from the food matrix to be candidates for intestinal absorption, the authors were able to achieve a significant increase in zinc and iron bio-accessibilities. More interestingly, Rani et al. [43] succeeded in increasing the hemoglobin concentration of iron-deficient children fed with a mungbean-based meal to which fresh guava, a potent source of ascorbic acid, was added.

Here too, there are many constraints, but the approach indeed constitutes a real opportunity for value chain development. The F2FF method is scientifically and technologically less demanding than the other three methods, as it does not require genetic engineering or chemical synthesis, but it still requires knowledge of the physico-chemistry and nutritional quality of the food constituents concerned. It specifically requires expertise in the art of communication, to explain to the general public how to complement their diet with micronutrients by mixing certain foods with others, easily and at a lower cost, without neglecting the environmental cost. Most importantly, since food waste and by-products, such as fish bones or peels, contain the same nutrients and micronutrients as the consumed parts, they are the next frontier of F2FF.

3.3. Strategies for the Rational Valorization of Agri-Food Waste

To accelerate the actions for reducing HH and food insecurity, a robust and sustainable strategy is needed that provides all the necessary safety guarantees for both the consumer and the environment. There is abundant and generally inexpensive raw material that may be useful for this purpose, as well as many implementing tools and methodologies.

3.3.1. Opportunities for Waste Valorization

Agri-food waste, which represents approximately one third of global resources [1], ensures the accessibility of this widely available raw material. According to Wani et al., the losses occur in a decreasing rank during consumption (36%), production and storage (24% each), retail, distribution and packaging, accounting for the remainder of losses during the food chain [44]. Figure 3 proposes a comprehensive strategy for valorizing agri-food waste, in two processing rounds including all food resources to produce micronutrient platforms and/or other beneficial food constituents, or other ingredients for all kinds of uses (agronomy, cosmetics, energy, etc.).

The ultimate goal of this valorization is zero waste, which is possible, since the chemical composition of food waste is similar to that of the edible parts. Actually, the waste may be even richer in vitamins and minerals, which are found primarily in cell walls and seed coats that are the least consumed parts of foods of plant origin. Aquatic product waste is rich in calcium, iodine, iron, fat-soluble vitamins, protein, chitin, and other compounds of high commercial value [45,46,47,48]. To ensure the success of the approach, it is necessary to design robust and sustainable strategies for collecting specific waste at all levels of the food chain, then its processing, storage, and transport. It also is necessary that the safety of the final products is ensured. The ease of access to global databases concerning the chemical composition of foodstuffs is a real opportunity [49,50], since it allows for the rapid identification of foodstuffs rich in specific micronutrients or beneficial food constituents.

3.3.2. Nutritional Potential of Raw Materials

The mineral content of plant-based foods in general depends on the mineral content of soil and on food preparation practices, particularly the possible release of minerals from processing equipment and cookware used for food preparation. In addition, particularly high levels exist in one or another essential mineral in certain plants. For example, finger millet contains as much as 344 mg calcium/100 g of edible grains [51], and dry baobab leaves as much as 2.46 g calcium/100 g [52]. The iron content in many plants is similar to or even higher than in meat and fish; for example, on a dry basis, millet contains about 11 mg iron/100 g, and barley, sorghum, peas, and soybean grains contain more than 5 mg iron/100 g [53]. The content of zinc is between a 3 and 9 mg/100 g serving of almonds, cashews, pumpkin seeds, and beans [54]. Selenium is mainly provided by animal foodstuffs, although it is widely present in plant-based foods, sometimes in relatively high amounts, like in beans and buckwheat [55,56]. The same is true for iodine, which is found mainly in aquatic food products or in micro-algae [57,58]. Actually, well-chosen keywords and a few clicks are enough to identify foods rich in one or another micronutrient.

The challenge while dealing with foodstuffs of plant origin and associated waste is finding the right balance between stimulators and inhibitors of mineral bioavailability in raw materials. Phytates, the phosphorus reserve in plants, are major contributors to global anemia, due to their strong chelating capacity of mono- and divalent minerals, especially iron and zinc [59]. Oxalates are also an issue [60], and to a lesser extent, weak chelates of minerals like phenolic compounds and dietary fibers. It is also necessary to ensure the absence, or at least the presence at acceptably low/safe levels, of undesirable compounds, including anti-nutritional factors, natural toxins and pesticide residues, and above all contaminants such as mycotoxins.

The bioavailability of essential minerals from plants is low or very low due to certain interactions (see below) and oxidants within food matrices, all hindering their access to the intestinal mucosa or converting them into unabsorbable chemical forms. Iron, for example, is specifically absorbed as Fe(II) or as heme [21]; thus, iron in plant foodstuffs is easily trapped by phytates and other chelators or Fe(II) is oxidized into Fe(III), which is not recognized by the membrane transporters. Ultimately, only a low part of vegetal iron is absorbed by digestive mucosa, which explains why populations that consume the least animal foodstuffs are the most affected by iron deficiency.

Like plant-based foodstuffs, animal-based foodstuffs have a double face. The nutritional advantage consists of being the main sources of several essential minerals, like iron, zinc, selenium, and iodine, thanks to higher bio-availabilities than those of minerals from plant foods. In addition, animal-based foodstuffs are important sources of vitamins, especially vitamin B12 and fat-soluble vitamins. Aquatic food products, which are both a major source of waste, offer the greatest potential for economic valorization, as they are a notable source of calcium, iron, iodine, phosphorus, chitin, proteins, bioactive peptides, etc. [46,47,48,49]. In addition, animal foodstuffs are valuable sources of essential amino acids, especially lysine. The safety challenge of animal foodstuffs is the presence, in particular in those of aquatic origin, of anthropogenic organic and inorganic contaminants, such as mercury, lead, cadmium, dioxins, and dioxin-like substances, PCB, PAH, PFAS, heterocyclic amines, nitrosamines, acrylamides, microplastics, etc. [61,62,63,64,65,66,67,68]. It is noteworthy that human exposure to some of these contaminants, such as lead and dioxins, has decreased to some extent during the last decades in some areas due to strict regulations.

3.3.3. Extraction Technologies and Recovery Processes

Alongside the abundant raw materials of plant or animal origin, there is no shortage of methods for their valorization, from which it is, however, necessary to build solid, sustainable, and profitable strategies that will accelerate the transition to sustainable economies. A strategy is needed that will strive for zero waste while guaranteeing the security and durability of products, which can be nutrients or micronutrients, enzymes and bioactive peptides, oils and added-value fatty acids, beneficial bioactive molecules (phenolics, carotenoids, dietary fibers, etc.), chitin or chitosan, energy source molecules, etc. The whole raw matter can actually be fully valorized.

Focusing on aquatic foodstuffs, Figure 4 shows two typical processes applied in this sector.

The first one (Figure 4A) shows how omega-3 long chain fatty acids (ω₃-LCFA) are extracted, especially regarding aquatic food products, eicosapentaenoic acid (EPA-C22:5), and docosahexaenoic acid (DHA-C22:6). Omega 3 LCFAs have been proven to have health-beneficial effects since the observations performed in Greenlandic Inuit populations in the 1970s and are called “Eskimo paradox”, i.e., high lipids and high cholesterol intake but few cardiovascular diseases [74]. Global fish oil production has been estimated at 771 kilo tons in 2023 [75] and the market of ω₃-LCFA at about $2.5 billion [76], although it is difficult to obtain valid information about the markets. In addition, there are currently a large number of w₃-LCFA-enriched foods, such as FOSHU in Japan, nutraceutics in North America, and functional foods in the European Union.

Overall, oils are extracted from fish either by conventional or emerging techniques. The former consists of physical and chemical treatments (Figure 4A), with concern about residues of organic solvents, such as hexane in the latter case. Fortunately, solvent-based chemical treatments are minor processes in this sector, unlike plant oil extraction. Emerging techniques, such as supercritical fluid extraction and enzyme-, microwave-, ultrasound- and pulsed electric field-assisted extraction processes, are developing rapidly because they offer the advantages of allowing better yields, not generating harmful residues, and being more sustainable [77,78,79,80,81]. Then, the oil is refined by chemical and physical treatments (acids, bases, filtration, distillation, etc.) to achieve an omega 3 fatty acid content of approximately 30%. The extracts can be further enriched in omega 3 FA, up to about 55%, after specific additional treatments. Some waste generated during the process, such as residues and aqueous phases, fish oil wax, and non-omega 3 fatty acids, can be valorized as molecules of interest or as an energy source. Those from the refining stages, which can be loaded with contaminants, cannot be consumed.

The aquatic foodstuffs waste (heads, viscera, skin, skeleton, skin, scales) account globally from 30 to 70% [45,46,47,48], and can be fully valorized, as mentioned below. For example, 1000 tons of salmon waste can produce 239 tons of protein and 157 tons of oil, and the remainder (604 tons) can still be recovered into molecules of interest or as a source of energy [82]. Fish viscera can be used to produce enzymes after a series of physical and chemical treatments, i.e., homogenization, centrifugation, heating, filtration, precipitation, and aqueous dissolution [83].

The second interesting example is that of shellfish, the valorization of which needs to be rationalized for efficient improvement (Figure 4B). The global volume of shellfish waste was recently estimated at 6 to 8 megatons/year, and it could be 25% to 100% more profitable than cereal waste [45]. Solid shellfish waste can be valorized into minerals, lipids, and other bioactive compounds, such as organic acids after fermentation, chitin, and its deacetylated chitosan. Aqueous shellfish waste is also an interesting source of proteins and bioactive peptides harboring anti-inflammatory, antimicrobial, antifungal, and anti-cancer activities [44,45,72,73].

Rational valorization of aquatic foodstuffs waste will undoubtedly create wealth and jobs, and a likely significant return on investment, provided that the process and products are properly controlled. Some tools such as a Sankey diagram [84,85] would be useful to track the flow of waste, thus splitting waste into valuable outputs, including, among others, oils, proteins, and minerals, and consequently highlighting the profitability.

3.4. A Proposal for How to Valorize FW to Fight HH, Food Insecurity, and Beyond

We have shown above that the overall situation of HH in particular and food insecurity in general is worrying and that global warming is alarming. We have also shown that agri-food waste raw material is abundant and that the tools and methodologies for its recovery are available as well, with a closer look at aquatic food products, and the same is certainly true for other agri-food products.

Figure 5 proposes a rational and sustainable strategy for the valorization of AFW, integrating the important elements identified during the review of the literature. This PDCA method is very familiar and could be useful for industrial managers of food quality and security.

The strategy may be adapted to one or another agri-food waste to be valorized. Actually, many research groups recently already explored these profitable and sustainable valorization methods [83,86,87,88,89,90,91,92,93,94].

For example, Raak et al. [88] reported an interesting methodology to valorize waste from both sunflower oil and whey from industrial sectors as interesting sources of bioactive lipids and high-nutritional-value proteins. These authors also rightly emphasized the need to respect product quality and security standards. Similarly, Darko et al. [92] proposedsignificant materials and methodologies to obtain added-value food ingredients from waste from vegetables, fish, meat, and dairy products. The emerging technologies, such as machine learning, artificial intelligence, and the internet of things, could also be useful in achieving the objectives [93,94], provided, of course, that the task of distinguishing truth from falsehood is not too burdensome, since global digital resources contain too much information.

The approach to be implemented must be both cross-cutting and vertical, the former including as much agri-food waste as possible, taking into account feasibility and industrial viability involving as many stakeholders as possible. In a continuum from raw material to consumer, the consumer is in fact a stakeholder at every link in the chain. Financial resources are a primary need, which must be seen as profitable investments, along with a solid methodology, both of a fundamental and of an operational type, using well-defined indicators of performance. Figure 5 mentions some key points that characterize the four steps of the Deming ring, as far as agri-food waste valorization is concerned. The Plan phase involves identifying the team, the target(s), the resources, and the program schedule and tasks. The Do phase involves implementing the plan and identifying improvements to be made. The Check phase is probably the most important, because it deals with the feasibility and the viability of the system, and assumes the responsibility of the product security concern. For this, the HACCP methodology is necessary for any process aiming at producing foods or feeds. In this step, an assessment of economic and environmental impact has also to be achieved. The final phase (Act) involves recording the achievements and establishing an improved future plan, based on up-stream collected data, especially during the Do phase.

Importantly, in our opinion, citizens must be at the heart of the agri-food waste recovery system. The vertical approach of this strategy must mobilize skills in a hierarchical, complementary, and participatory manner, ultimately leading to the best decision. Citizens are stakeholders in every stage of the process, as students, researchers, producers, processors, traders and distributors, managers, communicators, as consumers, and, above all, as voters who can influence political decisions.

4. Concluding Remarks

This review provides an overview of the situation on hidden hunger regarding global micronutrient deficiency, at least the micronutrients that have attracted the most attention from the scientific community, and associated pathological disorders have been briefly mentioned. The review integrates fundamental methodologies with applied ones, in order to engage as many stakeholders as possible. The strategies are applicable at both the household level (citizens) and the industrial scale (manufacturers), provided they understand the what, the why, and the how of the system in question. The main objective of the work was to demonstrate the great potential of agri-food waste valorization to combat hidden hunger, food insecurity, climate change, and environmental degradation. Raw materials are abundant, and there is no shortage of effective and sustainable tools and methodologies for valorizing this waste. We hope that the proposed strategy will be useful to stakeholders in developing robust fundamental and industrial programs, which will undoubtedly accelerate the transition to a healthy and sustainable economy.

The widespread implementation of this approach and its improved versions will undoubtedly accelerate the reduction in HH, food insecurity, and global greenhouse gas emissions. It will also aid in achieving (or approaching) some of the 2030 Sustainable Development Goals, such as no poverty, zero hunger, good health and well-being, decent work and economic growth, industry, innovation, technology and infrastructure, and responsible consumption and production.