Malnutrition, defined by the World Health Organization as deficiencies, excesses, or imbalances in a person’s intake of energy and/or nutrients, contributes to a double burden within the developed world, where an increasing proportion of the population are either not meeting recommended nutrient intakes, suffering from diet-related chronic diseases, or both (1, 2). The relationship between adequate nutrition and the maintenance of health is well-established, with each nutrient playing important and integrated roles in metabolism and biochemistry, contributing to recommended levels of dietary intake to maintain health (3, 4). While most often attributed to excess caloric intake, diet-related disease pathogenesis also involves nutrient inadequacies, where intake and/or status is suboptimal (1, 2). This includes (but is not limited to) cardiovascular disease (CVD), type 2 diabetes (T2DM), obesity, some cancers (1, 2), and infectious disease, including COVID-19 (5, 6). Although some diet-related diseases show elevated prevalence across the population, demographic groups have specific nutrient requirements and diet-related health priorities, indicating that the relative importance of each nutrient may vary depending on age and sex, and for women, pregnancy and menopausal status. For example, vitamin D deficiency or insufficiency has been suggested to increase the global burden of disease overall (7), but has also been associated with osteoporosis in menopausal women (8), an increased risk for gestational diabetes in pregnant women (9), and increased susceptibility to respiratory infection in the older men and women (10). Folic acid supplementation is recommended pre- and during pregnancy due to the well-established increased risk of sub-optimal folate for foetal neural tube defects (11, 12).

The increase in diet-related disease prevalence in the developed world, including Australia and New Zealand, has been primarily attributed to the widespread over-consumption of foods that are both energy rich and nutrient poor (2, 13, 14), partly due to a large percentage of the diet made up of ultra-processed and/or discretionary foods and beverages in these countries. These foods are predominantly high in saturated fat, sodium, and added sugars, nutrients labelled to be of concern and recommended to limit across dietary guidelines globally (13). The diets also fail to meet food group recommendations and are consequently inadequate in meeting several macro- and micronutrient recommendations (13, 15); in Australia and/or New Zealand, common nutrient inadequacies include calcium, vitamin D, iron, selenium, zinc, folate, thiamin, and vitamin B12 (16–18). Other factors impacting suboptimal dietary choices include (but are not limited to) affordability and sustainability, with refined ingredients often cheaper than their whole-food counterparts (19), and an increasing movement towards plant-based diets, containing, for example, processed meat and dairy alternatives (20). There is evidence that increasing intake of key micronutrients has a measurable impact on public health, for example, via mandatory fortification of bread with folic acid to prevent neural-tube defects (12) and the universal iodisation of salt and bread to prevent iodine deficiency-related hypothyroidism and goitre (21, 22). Thus, there is a need to identify the nutrients that offer the greatest potential to address both malnutrition and diet-related disease in Australia and New Zealand.

Nutritional adequacy plays a key role in supporting health priorities for each demographic group. Reference intake values for each essential nutrient are provided by government recommendations, such as the US Dietary Reference Intakes (DRIs) (23), and the Nutrient Reference Values (NRVs) for Australian and New Zealand (3). The NRVs were developed to determine the average nutrient values needed by individuals and populations, with the majority last updated in 2006; the most recent update was 2017 (for sodium). While the NRVs provide intake recommendations for essential nutrients across the lifespan to maintain health, varying according to life stage, age, and sex, scientific evidence suggests that they may be outdated, with some nutrient requirements greater than prescribed (24, 25). Further, the NRVs include suggested dietary targets (SDTs) for some nutrients, where higher nutrient intake recommendations are provided to help support and prevent chronic disease, showcasing the importance of nutrients beyond overt malnutrition. For some of these nutrients, doses shown to reduce the risk of chronic disease (26) are at doses greater than those in the NRVs. Thus, there is a need to better understand the evidence-base related to nutrients of the highest priority for frank deficiency prevention, reduction of diet-related disease, and health promotion. This information plays an important role in informing food policy, dietary guidelines, food development and fortification programs to close nutrient gaps, prevent deficiency, improve the quality of the food supply, and better support public health across the lifespan.

The aim of this research was to develop and implement methodology for determination of the highest priority nutrients for each demographic group (based on age and sex, in alignment with the NRVs) in Australia and New Zealand. These nutrients can simultaneously support both nutrient adequacy and efforts to reduce diet-related disease. Further, the methodology can be applied globally to uncover and compare nutrient inadequacies and priority nutrients between countries.

For each demographic group, nutrient intake information from the most recent Australian [2011/12 (18)] and New Zealand [2008/09 (27), 2002 (28)] nutrition surveys were obtained, followed by the identification of health priorities, based on government-managed statistical and consultation with an expert (nutritional and dietary management) panel of PhD-qualified health care professionals. A detailed scope of high-level scientific evidence regarding the relationship of specific nutrients to health priorities was performed (systematic literature reviews (SLRs) of randomised controlled trials (RCTs) or prospective cohort studies), including any evidence that current recommended intakes may not be sufficient to support health (SLRs, RCTs, and nutrient balance studies). A quantitative scoring matrix was developed and used to determine the nutrients with the highest priority for each demographic group. For each nutrient and each demographic group, the scoring was based on: 1. the level of dietary inadequacy [percentage of the population with intake below the Estimated Average Requirement (EAR) or Adequate Intake (AI)]; 2. the presence of consistent evidence for increased requirements (compared to current EAR/Recommended Dietary Intake (RDI)/AI values); and 3. the degree of association with identified health priorities.

An overview of the methodology used is provided as a flowchart in Figure 1. The methodology included 4 steps to identify demographic groups for assessment, followed by the key health priorities, a shortlist of nutrients, and a final list of priority nutrients, per each demographic group. An assessment of priority nutrients for the total population was also performed. These steps are described in detail below.

The research presented here has highlighted the priority nutrients, or those with the highest potential to address the double burden of malnutrition and diet-related disease in Australia and New Zealand, at both the demographic group and population-level. Nutritional inadequacies (relative to current NRVs) were prevalent across all demographic groups, ranging from a minimum of 7 (children) to 16 (males and older adults), highlighting an important gap in intake vs. needs. While the number and specifics of priority nutrients varied between demographic groups, there was notable consistency in the nutrients found to be of highest importance across the demographic groups. Furthermore, this consistency was maintained when priority nutrient scoring was applied at the population level, with four nutrients featuring as the highest priority regardless of scoring method; these were vitamin D, calcium, omega-3 fatty acids, and magnesium. Dietary fibre and folate were also priority nutrients at the population level. The methodology adopted to uncover the highest priority nutrients was evidence-based and systematic and provides a novel approach that can be replicated for application on a global scale.

The highest priority nutrients at the population level arose due to not only overt inadequacy, but increased needs and health priorities, addressing both sides of the double burden of disease. While priority for each nutrient was based on the combination of scoring within each one of these domains, each priority nutrient showed variation in terms of which domain made the largest contribution to the total score. This suggests that the two major diet-related issues of malnutrition and diet-related disease are both independent and integrated; a nutrient inadequacy can be an issue due to its necessity for normal physiology, but might also contribute, either directly or indirectly, to the development of one or more diet-related diseases. For example, calcium had a relatively low number of health priority associations (4: bone growth in childhood and adolescence, bone maintenance in peri-menopausal and menopausal women, and healthy weight gain during pregnancy), and intakes associated with health benefits in these health priorities (120–1,200 mg/day in pregnancy) were comparable to recommended values. However, dietary inadequacy was high, with up to 94% not meeting the EAR, thus likely to exacerbate calcium-related disease prevalence. On the other hand, even if met, recommended intakes may not support optimal health or the prevention of diet-related disease. This is evidenced by the development of SDTs for some nutrients (3). For example, while no dietary inadequacy was identified for the omega-3 fatty acids, this nutrient had one of the highest scores for association with health priorities, has an SDT, showing that increased intakes are likely necessary to optimally support health. Regardless of the underlying mechanism, increased intakes are needed for each one of the priority nutrients, and a focus on these nutrients in public nutrition policy and messaging, including the promotion of foods supplying these nutrients, is needed. While previous efforts to uncover priority nutrients have been employed, including nutrition surveys and the development of SDTs (3), our research and scoring matrix integrates three key domains (inadequate intake, evidence for increased needs, and association with health priorities) related to nutrient intake and health to pinpoint the nutrients that may represent the biggest bottlenecks for public nutrition and disease reduction.

The specific priority nutrients identified for each demographic group contribute key information to the recommendations of policy makers, as well as health organisations and professionals, including GPs, nurses, and paediatric dietitians, to name a few. For example, Vitamin D emerged as a priority nutrient for all demographic groups. This finding is consistent with recent dietary intake and blood status data suggesting that the prevalence of vitamin D deficiency and insufficiency are critically high and potentially increasing, with a call for changes in policy to address this (17). However, vitamin D was the sole priority nutrient for pregnant and lactating women, indicating that a targeted focus within this demographic group may be warranted. Similarly, each demographic group was characterised by a unique set of priority nutrients, suggesting that these nutrients require specific attention to optimally support health within that group. For example, five (zinc, folate, omeg-3 fatty acids, vitamin D, and magnesium) of the six priority nutrients identified for males were associated with supporting the health priority of anxiety and depression in this demographic group. Despite identification as a health priority, anxiety and depression have been suggested to be largely overlooked and/or under-reported in adult males (139, 140), accentuating that the priority placement of these nutrients is warranted and has the potential to address the specific needs of each demographic group.

It is important to highlight that 22 nutrients were identified as having inadequate intake in at least one demographic group, despite Australia and New Zealand being developed countries. These nutrients included vitamin A, iron, and iodine, the primary nutrients of concern for deficiency on a global scale (141). Alongside a clear role in health and disease prevention, nutrient and food group inadequacies have significant economic implications, including both health-care costs and losses in productivity. A recent systematic review to assess the cost vs. benefit of folic acid fortification for the prevention of neural tube defects identified a return of 17.5 monetary units for each monetary unit spent, with doses above 300 μg/100 g showing the highest benefit (142). Research on the cost of iron deficiency for 10 developing countries suggested that the median value of annual physical productivity losses was around $2.32 per capita, or 0.57% of GDP, with median total losses (physical and cognitive combined) at $16.78 per capita, 4.05% of GDP (143). Not surprisingly, there is a cost benefit of addressing deficiency; it has been estimated that addressing micronutrient (iodine, iron, or vitamin A) deficiency via supplementation or fortification efforts produces an economic gain, of 4 to 37 US dollars per disability adjusted life-year (144). In America, $12.7 billion in direct health care costs was the estimated saving if all adults were to consume the US Food and Drug Administration Daily Reference Value for dietary fibre of 25 grams per day (145). Research to determine the cost benefit of addressing priority nutrients in Australia and other developed countries is needed.

In addition to a focus on specific priority nutrients, diet- and food-based recommendations can help to support their intake. Table 6 shows the major dietary sources for each of the population-level priority nutrients (3, 146); while folate and dietary fibre feature primarily in plant-based sources, the major dietary contributors of vitamin D and calcium are animal foods, while magnesium can be found in both. Despite the omega-3 fatty acids also being provided by both plant and animal foods, the forms are not synonymous and have different roles within the body. Further, while ALA (found in nuts and seeds) can be converted into DHA and EPA (found in fatty fish), the efficiency of this conversion is both low and varies among individuals, and much of the literature regarding health associations was focused on DHA, DPA, and EPA. Some foods also provide more than one priority nutrient, for example, fatty fish provide both omega-3 fatty acids and vitamin D, and dairy milk provides both calcium and magnesium. The identification and specific targeting of key foods providing priority nutrients may serve as a useful and effective way to address the lowest-hanging fruit for both malnutrition and diet-related disease burdens.

In theory, a balanced diet containing all core food groups, as well as fatty fish, should be able to provide all priority nutrients. However, there is a current trend towards plant-based diets to support health and sustainability, coupled with an increased use of and/or demand for plant-based meat and milk alternatives (147, 148). As these foods are often matched (to their animal-based counterpart) for use but not nutritional composition and/or adequacy (141, 149), these dietary patterns may lead to further increases in the inadequacy level of some of these key nutrients. This pattern may be of even greater importance given that the dietary intake data obtained for the current research was based on the most recent survey data available, now up to 20 years old; the intake of some nutrients may have declined even further with these shifts in dietary patterns. Concern has been expressed regarding the use of plant-based milk alternatives as a substitute for dairy milk, except for fortified soy milk, due to nutritional inequivalence (148, 150). In children, this substitution has been suggested to result in severe consequences for metabolic health (147). As calcium has been identified as having inadequate intakes in both Australia and New Zealand, for which the major dietary source is dairy products (Table 6) an increased shift from dairy milk to plant-based milks may further exacerbate these inadequacies (16, 18). Further, the dietary modelling used to develop the most recent Australian Dietary Guidelines produced dietary patterns that supported the intake of all essential nutrients except for vitamin D (151). These issues need to be addressed and taken seriously, particularly for dietary guidelines. There is a need to balance recommendations to meet nutrient adequacy with dietary shifts in plant-based eating for health as well as for environment for all demographic groups.

Rather than existing and acting in isolation, each dietary nutrient interacts and can act synergistically with other dietary nutrients, both within foods and inside the body following digestion and absorption (152, 153). While outside of the scope of this research, inadequacies in priority nutrients may impact the provision and activity of other nutrients. These interactions may also be involved in the associations identified for priority nutrients and selected health priorities. These factors are important considerations for future research as well as recommendations made by dietary guidelines.

This research has a number of strengths and limitations. First, the holistic and integrated approach of identifying priority nutrients is novel in its ability to determine the priority nutritional targets for both individual demographic groups, as well as the total population, addressing both sides of the nutritional double burden: malnutrition and diet-related disease. As current efforts focus on nutrient intake or health outcomes independently, they lack the ability to target both at the same time. Second, only high-level evidence [based on the NHMRC framework (42)] in nutrition was collected to ensure robustness in the study design and support the conclusions made. Third, the methodology described can be applied to other countries, to highlight nutrients that have importance on a global scale and allowing for comparisons in nutrient inadequacy and nutrient prioritisation. While some nutrients [such as vitamin D (7)] show widespread deficiency and many diet-related diseases are common throughout developed countries (such as cardiometabolic issues and cancer), each country is likely to be characterised by differing degrees of inadequacy for each nutrient, as well as specific nutrient inadequacies, depending on the food environment. In addition, leading causes of morbidity and mortality may differ between countries; for example, cardiovascular complications are a leading cause of maternal mortality in the US (154) but were not identified as such in Australia and New Zealand. Application of the methodology to additional countries and subsequent comparisons are warranted.

Although the most recent national nutrition survey data were utilised, the major limitation of the findings is the age of the most recent dietary intake data, collected in 2011–2012 for Australia, 2007–2008 for New Zealand adults, and 2003 for New Zealand children; and it is likely that dietary patterns have evolved and shifted since this time, indicating that a repeat of this research when new data become available will be essential. Regardless, the findings provide a proof-of-concept for the novel methodology presented; furthermore, given that many of the nutrient inadequacies identified are mimicked by current evidence worldwide (17, 155, 156), these findings remain relevant despite the age of the included data. In addition, while the level of nutrient inadequacy was a major aspect of the methodology, nutrient adequacy alone is not sufficient to prevent disease; there are many factors involved, including (but not limited to) physical activity, smoking and alcohol, social connection, and mental health and wellbeing. However, nutrient adequacy is a key part of any solution, and the current research was focused on nutrition. The methodology for the selection of health priorities was designed to identify disease categories regarded by authorities as being most pertinent to public health in Australia and New Zealand. While robust and specific, this approach does not consider individual diseases of significance within each disease category, nor additional health outcomes showing increasing significance. For example, a high prevalence of vitamin D deficiency was identified in patients with cancer sub-category of neuroendocrine neoplasms (157), and gastrointestinal diseases such as inflammatory bowel disease are both increasing in prevalence and involve malnutrition (158). Further iterations of the methodology can seek to include such diseases and their nutritional relationships. Finally, relating single nutrients to chronic disease outcomes has shortcomings, due to disease being complex and multifaceted in its causes and presentation. Food context, nutrient interactions, and overall dietary patterns play key roles in health, and should be taken into consideration when interpreting the findings presented here, though the NRVs tend to allow for these complex interactions when setting reference values. The overall opportunity lies in the translation of these priority nutrients to food and diet-based recommendations. In line with this, the study did not address non-nutritive dietary factors, which are additional mediators of disease (such as antioxidants), and should be considered in policies, guidelines, and/or strategies that use diet to address health priorities. Further research to understand the highest priority non-nutrients is required.

Multi-nutrient inadequacies within Australia and New Zealand were reported across all demographic groups, including nutrients with a direct link to increasing rates of diet-related disease. There is a need to revisit and revise nutrient and food-based recommendations, to ensure adequacy for the population, with a focus on priority nutrients that are more likely to impact health. Efforts to provide education and awareness about priority nutrients, to ensure that the current double burden of malnutrition and diet-related disease is alleviated, rather than exacerbated are warranted. Future research needs to focus on the identification and promotion of foods that contribute to priority nutrient intake, whilst also supporting sustainability efforts and taking into consideration cost. While this research was focused on the Australian and New Zealand populations, the methodology presented can be applied globally, to determine and communicate nutrients for prioritisation and nutrition, a fundamental cornerstone for the reduction of diet-related disease.

Publicly available datasets were analyzed in this study. This data can be found at: National Nutrition and Physical Activity Survey 2011–2012, https://www.abs.gov.au/statistics/health/health-conditions-and-risks/australian-health-survey-nutrition-first-results-foods-and-nutrients/latest-release and New Zealand Adult Nutrition Survey 2008–2009 and Children’s Nutrition Survey 2002, https://www.health.govt.nz/nz-health-statistics/surveys/past-surveys/nutrition-survey.

Ethical approval was not required for the study involving humans in accordance with the local legislation and institutional requirements. Written informed consent to participate in this study was not required from the participants or the participants’ legal guardians/next of kin in accordance with the national legislation and the institutional requirements.

CS: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. TC: Conceptualization, Methodology, Writing – review & editing. EB: Writing – review & editing. SM: Conceptualization, Methodology, Writing – review & editing. FF-M: Conceptualization, Funding acquisition, Methodology, Writing – review & editing.