Putting the balance back in diet.

The notion of dietary balance is fundamental to health yet is not captured by focusing on the intake of energy or single nutrients. Advances in nutritional geometry have begun to unravel and integrate the interactive effects of multiple nutrients on health, lifespan, aging, and reproduction.

Biosynthetic constraints on amino acid synthesis at the base of the food chain may determine their use in higher-order consumer genomes.

Dietary nutrient composition is essential for shaping important fitness traits and behaviours. Many organisms are protein limited, and for Drosophila melanogaster this limitation manifests at the level of the single most limiting essential Amino Acid (AA) in the diet. The identity of this AA and its effects on female fecundity is readily predictable by a procedure called exome matching in which the sum of AAs encoded by a consumer's exome is used to predict the relative proportion of AAs required in its diet. However, the exome matching calculation does not weight AA contributions to the overall profile by protein size or expression. Here, we update the exome matching calculation to include these weightings. Surprisingly, although nearly half of the transcriptome is differentially expressed when comparing male and female flies, we found that creating transcriptome-weighted exome matched diets for each sex did not enhance their fecundity over that supported by exome matching alone. These data indicate that while organisms may require different amounts of dietary protein across conditions, the relative proportion of the constituent AAs remains constant. Interestingly, we also found that exome matched AA profiles are generally conserved across taxa and that the composition of these profiles might be explained by energetic and elemental limitations on microbial AA synthesis. Thus, it appears that ecological constraints amongst autotrophs shape the relative proportion of AAs that are available across trophic levels and that this constrains biomass composition.

'Dust you shall eat': The complex nutritional and functional considerations underlying a simple diet.

Animals assimilate macronutrients and mineral nutrients in specific quantities and ratios to maximise fitness. To achieve this, animals must ingest different foods that contain the needed nutrients or facilitate the digestion of those nutrients. We explored how these multidimensional considerations affect the desert isopods (Hemilepistus reaumuri) curious food selection, using field and laboratory experiments. Wild isopods consumed three-fold more macronutrient-poor biological soil crust (BSC) than plant litter. Isopods tightly regulated macronutrient and calcium intake, but not phosphorus when eating the two natural foods and when artificial calcium and phosphorus sources substituted the BSC. Despite the equivalent calcium ingestion, isopods performed better when eating BSC compared to artificial foods. Isopods that consumed BSC sterilised by gamma-radiation ate more but grew slower than isopods that ate live BSC, implying that ingested microorganisms facilitate litter digestion. Our work highlights the need to reveal the multifaceted considerations that affect food-selection when exploring trophic-interactions.

Evidence for protein leverage on total energy intake, but not body mass index, in a large cohort of older adults.

BACKGROUND: Protein leverage (PL) is the phenomenon of consuming food until absolute intake of protein approaches a 'target value', such that total energy intake (TEI) varies passively with the ratio of protein: non-protein energy (fat + carbohydrate) in the diet. The PL hypothesis (PLH) suggests that the dilution of protein in energy-dense foods, particularly those rich in carbohydrates and fats, combines with protein leverage to contribute to the global obesity epidemic. Evidence for PL has been reported in younger adults, children and adolescents. This study aimed to test for PL and the protein leverage hypothesis (PLH) in a cohort of older adults. METHODS: We conducted a retrospective analysis of dietary intake in a cohort of 1699 community-dwelling older adults aged 67-84 years from the NuAge cohort. We computed TEI and the energy contribution (EC) from each macronutrient. The strength of leverage of macronutrients was assessed through power functions ( TEI = µ * EC L ). Body mass index (BMI) was calculated, and mixture models were fitted to predict TEI and BMI from macronutrients' ECs. RESULTS: In this cohort of older adults, 53% of individuals had obesity and 1.5% had severe cases. The mean TEI was 7673 kJ and macronutrients' ECs were 50.4%, 33.2% and 16.4%, respectively for carbohydrates, fat, and protein. There was a strong negative association (L = -0.37; p < 0.001) between the protein EC and TEI. Each percent of energy intake from protein reduced TEI by 77 kJ on average, ceteris paribus. However, BMI was unassociated with TEI in this cohort. CONCLUSIONS: Findings indicate clear evidence for PL on TEI, but not on BMI, likely because of aging, body composition, sarcopenia, or protein wasting.

Mice Regulate Dietary Amino Acid Balance and Energy Intake by Selecting between Complementary Protein Sources.

BACKGROUND: A balanced intake of protein and constituent amino acids (AAs) requires adjustments to total food intake (protein leverage [PL]) and food selection to balance deficits and excesses (complementary feeding). We provided mice with choices of casein and whey, 2 protein sources that are complementary in AA balance, across a range of protein concentrations (P%) of digestible energy (DE). OBJECTIVES: We aimed to determine if: 1) PL operates similarly for casein and whey; 2) one protein source is preferred at control P%; 3) the preference changes as P% falls; and 4) AA intakes under control and low P% levels identify AAs that drive changes in protein selection. METHODS: Food intake and plasma fibroblast growth factor-21 (FGF21) concentrations were measured in mice at various P% (P7.5%-P33%). For direct comparisons, defined diets were used in which the protein source was either casein or whey. In food choice studies, mice had access to foods in which both casein and whey were provided at the same P% level at the same time. RESULTS: PL operated at different P% thresholds in casein (13%)- and whey (10%)-based diets, and the magnitude of PL was greater for casein. Although mice preferred casein under control conditions (P23%), a pronounced preference shift to whey occurred as P% fell to P13% and P10%. At low P%, increases in food intake were accompanied by increases in plasma FGF21, a protein hunger signal. Among AAs deficient in casein and enriched in whey, the intake of Cys was the most invariant as P% changed between P23% and P10%, appearing to drive the switch in protein preference. CONCLUSIONS: Mice selected between complementary protein sources, casein and whey, achieving stable total energy intake and regulated intake of AAs as P% varied. Supplementation of low P% casein diets with one whey-enriched AA, Cys, suppressed plasma FGF21 and total food intake.

Macronutrient composition of plant-based diets and breast cancer risk: the E3N prospective cohort study.

PURPOSE: Recent evidence suggests that plant-based diets may reduce the risk of breast cancer (BC). However, the macronutrient composition of plant-based diets and its potential impact on BC risk has not been well explored. This analysis investigated the association of macronutrient composition with BC risk across a spectrum of plant-based diet indexes using a multidimensional approach. DESIGN: This study followed 64,655 participants from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort from 1993 to 2014. Diets were evaluated using validated 208-item diet history questionnaires at baseline (1993) and follow-up (2005), to calculate adherence to the overall plant-based diet (PDI), healthful plant-based diet (hPDI), and unhealthful plant-based diet (uPDI). The association of macronutrient composition with BC risk was assessed via generalized additive time-dependent Cox models across different levels of these indexes. Response surfaces were generated to visualize compositional associations at the 25th, 50th, and 75th percentile of each index (low, moderate, and high). RESULTS: A total of 3,932 incident BC cases were identified during the 21-year follow-up. There was a significant association between macronutrient composition and BC risk for hPDI, uPDI, and PDI (all P < 0.001). Akaike information criterion favored the hPDI model for characterizing the association between macronutrients and BC. BC risk was highest for individuals with a lower hPDI score who also consumed a diet containing lower protein (10%), lower carbohydrate (35%), and higher fat (55%). The lowest risk of BC was observed in those with higher hPDI scores with the lowest intake of protein (10%). At higher PDI and uPDI, diets containing higher protein (30%) and fat (45%) had the highest BC risk. CONCLUSION: These results demonstrate a complex relationship between macronutrient composition, plant-based diet quality, and BC risk. Further research is needed to examine specific foods that may be driving these associations. REGISTRY: The protocol is registered at clinicaltrials.gov as NCT03285230.

Integrating isotopic and nutritional niches reveals multiple dimensions of individual diet specialisation in a marine apex predator.

Dietary specialisations are important determinants of ecological structure, particularly in species with high per-capita trophic influence like marine apex predators. These species are, however, among the most challenging in which to establish spatiotemporally integrated diets. We introduce a novel integration of stable isotopes with a multidimensional nutritional niche framework that addresses the challenges of establishing spatiotemporally integrated nutritional niches in wild populations, and apply the framework to explore individual diet specialisation in a marine apex predator, the white shark Carcharodon carcharias. Sequential tooth files were sampled from juvenile white sharks to establish individual isotopic (δ-space; δ13 C, δ15 N, δ34 S) niche specialisation. Bayesian mixing models were then used to reveal individual-level prey (p-space) specialisation, and further combined with nutritional geometry models to quantify the nutritional (N-space) dimensions of individual specialisation, and their relationships to prey use. Isotopic and mixing model analyses indicated juvenile white sharks as individual specialists within a broader, generalist, population niche. Individual sharks differed in their consumption of several important mesopredator species, which suggested among-individual variance in trophic roles in either pelagic or benthic food webs. However, variation in nutrient intakes was small and not consistently correlated with differences in prey use, suggesting white sharks as nutritional specialists and that individuals could use functionally and nutritionally different prey as complementary means to achieve a common nutritional goal. We identify how degrees of individual specialisation can differ between niche spaces (δ-, p- or N-space), the physiological and ecological implications of this, and argue that integrating nutrition can provide stronger, mechanistic links between diet specialisation and its intrinsic (fitness/performance) and extrinsic (ecological) outcomes. Our time-integrated framework is adaptable for examining the nutritional consequences and drivers of food use variation at the individual, population or species level.

Systems map of interventions to improve dietary intake of pre-school aged children: A scoping review.

Implementation and sustaining impact of early childhood nutrition interventions in practice remains a challenge. An understanding of the extent to which determinants across multiple levels of the food system are being addressed may improve success. This literature review aimed to synthesise the evidence on interventions targeting dietary intake and eating behaviours in preschool children using a systems approach. Eligible studies included intervention studies targeting the dietary intake of preschool children aged 2-5 years in high income countries, published in English after January 2000. Interventions were categorised to the Determinants of Nutrition and Eating (DONE) framework for children developed and evaluated by experts across multiple fields. The framework maps and ranks 411 factors driving eating behaviours and nutrition and can be used to systematically summarise determinants. DONE ranks each determinant for its perceived research priority. A total of 160 eligible studies were identified. Most interventions targeted interpersonal (n = 101, 63.1%) and individual (n = 85, 53.1%) level determinants, with fewer targeting environmental (n = 55, 34.4%) and policy level (n = 17, 10.6%) determinants. The most frequently addressed determinants were Parental Resources and Risk Factors (n = 85) and Children's Food Knowledge, Skills and Abilities (n = 67). These determinants had a Moderate research priority rating. Home Food Availability and Accessibility at the environmental level is classified as the highest research priority, however, only 15 of 160 interventions addressed this determinant. This review highlights home food availability and accessibility as potential leverage points for future interventions to improve children's dietary intake and eating behaviours.

Nutritional, environmental and economic impacts of ultra-processed food consumption in Australia.

OBJECTIVE: To quantify the full life cycle impacts of ultra-processed foods (UPF) for key environmental, economic and nutritional indicators to identify trade-offs between UPF contribution to broad-scope sustainability. DESIGN: Using 24-h dietary recalls along with an input-output database for the Australian economy, dietary environmental and economic impacts were quantified in this national representative cross-sectional analysis. Food items were classified into non-UPF and UPF using the NOVA system, and dietary energy contribution from non-UPF and UPF fractions in diets was estimated. Thereafter, associations between nutritional, environmental and economic impacts of non-UPF and UPF fractions of diets were examined using a multi-dimensional nutritional geometry representation. SETTING: National Nutrition and Physical Activity Survey 2011-2012 of Australia. PARTICIPANTS: Respondents (n 5344) aged > 18 years with 1 d of 24-h dietary recall data excluding respondents with missing values and outlier data points and under reporters. RESULTS: Australian diets rich in UPF were associated with reduced nutritional quality, high greenhouse gas emissions, energy use, and increased employment and income associated with the food supply chains. The environmental and economic impacts associated with the UPF portion of diets become more distinct when the diets are standardised to average protein recommendation. CONCLUSION: Increased consumption of UPF has socio-economic benefits, but this comes with adverse effects on the environment and public health. Consideration of such trade-offs is important in identifying policy and other mechanisms regarding UPF for establishing healthy and sustainable food systems.

Associations between protein to non-protein ratio and intakes of other dietary components in a cohort aged 65-75 years: the Nutrition for Healthy Living Study.

OBJECTIVE: Diets with a low proportion of energy from protein have shown to cause overconsumption of non-protein energy, known as Protein Leverage. Older adults are susceptible to nutritional inadequacy. The aim was to investigate associations between protein to non-protein ratio (P:NP) and intakes of dietary components and assess the nutritional adequacy of individuals aged 65-75 years from the Nutrition for Healthy Living (NHL) Study. DESIGN: Cross-sectional. Nutritional intakes from seven-day weighed food records were compared with the Nutrient Reference Values for Australia and New Zealand, Australian Guide to Healthy Eating, Australian Dietary Guidelines and World Health Organisation Free Sugar Guidelines. Associations between P:NP and intakes of dietary components were assessed through linear regression analyses. SETTING: NHL Study. PARTICIPANTS: 113 participants. RESULTS: Eighty-eight (59 female and 29 male) with plausible dietary data had a median (interquartile range) age of 69 years (67-71), high education level (86 %) and sources of income apart from the age pension (81 %). Substantial proportions had intakes below recommendations for dairy and alternatives (89 %), wholegrain (89 %) and simultaneously exceeded recommendations for discretionary foods (100 %) and saturated fat (92 %). In adjusted analyses, P:NP (per 1 % increment) was associated with lower intakes of energy, saturated fat, free sugar and discretionary foods and higher intakes of vitamin B12, Zn, meat and alternatives, red meat, poultry and wholegrain % (all P < 0·05). CONCLUSIONS: Higher P:NP was associated with lower intakes of energy, saturated fat, free sugar and discretionary. Our study revealed substantial nutritional inadequacy in this group of higher socio-economic individuals aged 65-75 years.

Testing for Protein Leverage in Patients with Gastric Bypass: A Pilot Study.

INTRODUCTION: Protein leverage (PL) is the phenomenon whereby a dominant appetite for protein drives overconsumption of energy with a decline in the ratio of protein to fat and carbohydrate in the diet. PL has been independently verified in several randomized control trials, and its predictions are supported by diet surveillance data. Our aim in the present study was to test whether surgical intervention through gastric bypass will ameliorate the PL effect. METHODS: Ten patients with gastric bypass (2-5 years postsurgical time) were given ad libitum access to study food comprising 10%, 15%, or 25% protein and no access to other foods for 3 days while controlling food palatability and variety. Food intake was measured, and energy and nutrient intakes were calculated. Body weight, blood chemistry, lipid profile, hormones (insulin, leptin, and ghrelin), and creatinine were determined before and after each experimental period. RESULTS: The gastric bypass patients in our study did not show evidence for protein intake regulation as predicted under PL but ate to constant total energy intake on the 10%, 15%, and 25% protein diets with protein intake varying significantly. Patients lost weight in the three study periods, but significant weight loss was observed only on the 15% protein diet. CONCLUSION: Our results suggest that gastric bypass might disengage the PL mechanism, thus ameliorating an appetite-specific mechanism that drives energy overconsumption in modern food environments.

Global associations between macronutrient supply and age-specific mortality.

Animal experiments have demonstrated that energy intake and the balance of macronutrients determine life span and patterns of age-specific mortality (ASM). Similar effects have also been detected in epidemiological studies in humans. Using global supply data and 1,879 life tables from 103 countries, we test for these effects at a macrolevel: between the nutrient supplies of nations and their patterns of ASM. We find that macronutrient supplies are strong predictors of ASM even after correction for time and economic factors. Globally, signatures of undernutrition are evident in the effects of low supply on life expectancy at birth and high mortality across ages, even as recently as 2016. However, in wealthy countries, the effects of overnutrition are prominent, where high supplies particularly from fats and carbohydrates are predicted to lead to high levels of mortality. Energy supplied at around 3,500 kcal/cap/d minimized mortality across ages. However, we show that the macronutrient composition of energy supply that minimizes mortality varies with age. In early life, 40 to 45% energy from each of fat and carbohydrate and 16% from protein minimizes mortality. In later life, replacing fat with carbohydrates to around 65% of total energy and reducing protein to 11% is associated with the lowest level of mortality. These results, particularly those regarding fats, accord both with experimental data from animals and within-country epidemiological studies on the association between macronutrient intake and risk of age-related chronic diseases.

Multidimensional associations between nutrient intake and healthy ageing in humans.

BACKGROUND: Little is known about how normal variation in dietary patterns in humans affects the ageing process. To date, most analyses of the problem have used a unidimensional paradigm, being concerned with the effects of a single nutrient on a single outcome. Perhaps then, our ability to understand the problem has been complicated by the fact that both nutrition and the physiology of ageing are highly complex and multidimensional, involving a high number of functional interactions. Here we apply the multidimensional geometric framework for nutrition to data on biological ageing from 1560 older adults followed over four years to assess on a large-scale how nutrient intake associates with the ageing process. RESULTS: Ageing and age-related loss of homeostasis (physiological dysregulation) were quantified via the integration of blood biomarkers. The effects of diet were modelled using the geometric framework for nutrition, applied to macronutrients and 19 micronutrients/nutrient subclasses. We observed four broad patterns: (1) The optimal level of nutrient intake was dependent on the ageing metric used. Elevated protein intake improved/depressed some ageing parameters, whereas elevated carbohydrate levels improved/depressed others; (2) There were non-linearities where intermediate levels of nutrients performed well for many outcomes (i.e. arguing against a simple more/less is better perspective); (3) There is broad tolerance for nutrient intake patterns that don't deviate too much from norms ('homeostatic plateaus'). (4) Optimal levels of one nutrient often depend on levels of another (e.g. vitamin E and vitamin C). Simpler linear/univariate analytical approaches are insufficient to capture such associations. We present an interactive tool to explore the results in the high-dimensional nutritional space. CONCLUSION: Using multidimensional modelling techniques to test the effects of nutrient intake on physiological dysregulation in an aged population, we identified key patterns of specific nutrients associated with minimal biological ageing. Our approach presents a roadmap for future studies to explore the full complexity of the nutrition-ageing landscape.

Normal diet ameliorates obesity more safely and effectively than ketogenic diet does in high-fat diet-induced obesity mouse based on gut microbiota and lipid metabolism.

Growing evidence supports the efficacy of ketogenic diets for inducing weight loss, but there are also potential health risks due to their unbalanced nutrient composition. We aim at assessing relative effectiveness of a balanced diet and ketogenic diet for reversing metabolic syndrome in a diet-induced C57BL/6J mouse model. Mice were fed high-fat diet to induce obesity. Obese individuals were then fed either ketogenic or balanced diets as an obesity intervention. Serum, liver, fat and faecal samples were analysed. We observed that both diet interventions led to significant decrease in body weight. The ketogenic intervention was less effective in reducing adipocyte cell size and led to dyslipidaemia. The composition of the gut microbiome in the balanced diet intervention was more similar to the non-obese control group and had improved functional attributes. Our results indicate intervention with balanced diets ameliorates obesity more safely and effectively than ketogenic diets in diet-induced obesity mouse model.

Does diet influence aging? Evidence from animal studies.

Nutrition profoundly influences the risk for many age-related diseases. Whether nutrition influences human aging biology directly is less clear. Studies in different animal species indicate that reducing food intake ("caloric restriction" [CR]) can increase lifespan and delay the onset of diseases and the biological hallmarks of aging. Obesity has been described as "accelerated aging" and therefore the lifespan and health benefits generated by CR in both aging and obesity may occur via similar mechanisms. Beyond calorie intake, studies based on nutritional geometry have shown that protein intake and the interaction between dietary protein and carbohydrates influence age-related health and lifespan. Studies where animals are calorically restricted by providing free access to diluted diets have had less impact on lifespan than those studies where animals are given a reduced aliquot of food each day and are fasting between meals. This has drawn attention to the role of fasting in health and aging, and exploration of the health effects of various fasting regimes. Although definitive human clinical trials of nutrition and aging would need to be unfeasibly long and unrealistically controlled, there is good evidence from animal experiments that some nutritional interventions based on CR, manipulating dietary macronutrients, and fasting can influence aging biology and lifespan.

A randomized clinical trial to investigate the effect of dietary protein sources on periodontal health.

AIM: The aim was to assess two macronutrient interventions in a 2 × 2 factorial dietary design to determine their effects on oral health. MATERIALS AND METHODS: Participants (65-75 years old) with a body mass index between 20 and 35 kg/m2 of a larger randomized control trial who consented to an oral health assessment were recruited. They had ad libitum access to one of four experimental diets (omnivorous higher fat or higher carbohydrate, semi-vegetarian higher fat or higher carbohydrate) for 4 weeks. The periodontal examination included periodontal probing depth (PPD), clinical attachment level (CAL), and bleeding on probing. Oral plaque and gingival crevicular fluid (GCF) were collected before and after the intervention. RESULTS: Between baseline and follow up, the number of sites with a CAL <5 mm (mean difference [MD] -5.11 ± 9.68, p = .039) increased and the GCF amount (MD -23.42 ± 39.42 Periotron Units [PU], p = .050) decreased for the semi-vegetarian high-fat diet. For the mean proportion of sites with PPD reduction of >1 mm and CAL gain of >1 mm, significant differences were calculated between the diets investigated. The clinical parameters were not associated with changes in the oral microbiota. CONCLUSIONS: The results of this study provided evidence that a semi-vegetarian high-fat diet provides benefits to clinical parameters of periodontal health. This study is registered in ClinicalTrials.gov (ACTRN12616001606471).

Firstborn sex defines early childhood growth of subsequent siblings.

Animal studies have shown that maternal resource allocation can be sex-biased in order to maximize reproductive success, yet this basic concept has not been investigated in humans. In this study, we explored relationships between maternal factors, offspring sex and prenatal and postnatal weight gain. Sex-specific regression models not only indicated that maternal ethnicity impacted male (n = 2456) and female (n = 1871) childrens postnatal weight gain differently but also that parity and mode of feeding influenced weight velocity of female (ß ± s.e. = -0.31 ± 0.11 kg, p = 0.005; ß ± s.e. = -0.37 ± 0.11 kg, p < 0.001) but not male offspring. Collectively, our findings imply that maternal resource allocation to consecutive offspring increases after a male firstborn. The absence of this finding in formula fed children suggests that this observation could be mediated by breast milk. Our results warrant further mechanistic and epidemiological studies to elucidate the role of breastfeeding on the programming of infant growth as well as of metabolic and cardiovascular diseases, with potential implications for tailoring infant formulae according to sex and birth order.

The geometry of resource constraint: An empirical study of the golden snub-nosed monkey.

Apposite conceptualization and measurement of resource variation is critical for understanding many issues in ecology, including ecological niches, persistence and distribution of populations, the structure of communities and population resilience to perturbations. We apply the nutritional geometry framework to conceptualize and quantify the responses of a temperate-living primate, the golden snub-nosed monkey Rhinopithecus roxellana to variation in resource quality and quantity and in nutrient requirements associated with seasonal environments. We present a geometric model distinguishing qualitative constraint, quantitative constraint and 'pseudo-constraint' whereby nutrient intakes resemble response to qualitative resource constraint but are in fact driven by variation in nutrient requirements. The model is applied to analyse nutrient intakes recorded in 164 full-day observations of monkeys from two populations, one wild and the other captive, across seasons. Additionally, we recorded the diet of a single animal over 32 consecutive days in the wild. Despite considerable differences in available resources, the captive and wild populations showed marked similarities in nutrient intakes, including indistinguishable amounts and ratios of ingested macronutrients during summer and autumn and strong year-round maintenance of protein compared to seasonally variable fat and carbohydrate intakes. These similarities suggest homeostatically regulated nutritional targets and provide reference points to identify factors driving population differences in macronutrient intake in winter and spring. Our framework enabled us to distinguish examples of quantitative, qualitative and 'pseudo-constraint'. We suggest that this approach can increase the resolution at which resource constraint is conceptualized and measured in ecological studies.

The future of human malnutrition: rebalancing agency for better nutritional health.

The major threat to human societies posed by undernutrition has been recognised for millennia. Despite substantial economic development and scientific innovation, however, progress in addressing this global challenge has been inadequate. Paradoxically, the last half-century also saw the rapid emergence of obesity, first in high-income countries but now also in low- and middle-income countries. Traditionally, these problems were approached separately, but there is increasing recognition that they have common drivers and need integrated responses. The new nutrition reality comprises a global 'double burden' of malnutrition, where the challenges of food insecurity, nutritional deficiencies and undernutrition coexist and interact with obesity, sedentary behaviour, unhealthy diets and environments that foster unhealthy behaviour. Beyond immediate efforts to prevent and treat malnutrition, what must change in order to reduce the future burden? Here, we present a conceptual framework that focuses on the deeper structural drivers of malnutrition embedded in society, and their interaction with biological mechanisms of appetite regulation and physiological homeostasis. Building on a review of malnutrition in past societies, our framework brings to the fore the power dynamics that characterise contemporary human food systems at many levels. We focus on the concept of agency, the ability of individuals or organisations to pursue their goals. In globalized food systems, the agency of individuals is directly confronted by the agency of several other types of actor, including corporations, governments and supranational institutions. The intakes of energy and nutrients by individuals are powerfully shaped by this 'competition of agency', and we therefore argue that the greatest opportunities to reduce malnutrition lie in rebalancing agency across the competing actors. The effect of the COVID-19 pandemic on food systems and individuals illustrates our conceptual framework. Efforts to improve agency must both drive and respond to complementary efforts to promote and maintain equitable societies and planetary health.

Projected effects on salt purchases following implementation of a national salt reduction policy in South Africa.

OBJECTIVE: To assess the contribution of different food groups to total salt purchases and to evaluate the estimated reduction in salt purchases if mandatory maximum salt limits in South African legislation were being complied with. DESIGN: This study conducted a cross-sectional analysis of purchasing data from Discovery Vitality members. Data were linked to the South African FoodSwitch database to determine the salt content of each food product purchased. Food category and total annual salt purchases were determined by summing salt content (kg) per each unit purchased across a whole year. Reductions in annual salt purchases were estimated by applying legislated maximum limits to product salt content. SETTING: South Africa. PARTICIPANTS: The study utilised purchasing data from 344 161 households, members of Discovery Vitality, collected for a whole year between January and December 2018. RESULTS: Vitality members purchased R12·8 billion worth of food products in 2018, representing 9562 products from which 264 583 kg of salt was purchased. The main contributors to salt purchases were bread and bakery products (23·3 %); meat and meat products (19 %); dairy (12·2 %); sauces, dressings, spreads and dips (11·8 %); and convenience foods (8·7 %). The projected total quantity of salt that would be purchased after implementation of the salt legislation was 250 346 kg, a reduction of 5·4 % from 2018 levels. CONCLUSIONS: A projected reduction in salt purchases of 5·4 % from 2018 levels suggests that meeting the mandatory maximum salt limits in South Africa will make a meaningful contribution to reducing salt purchases.