Greenhouse gas emissions, cost, and diet quality of specific diet patterns in the United States

Exploring dietary patterns and their association with environmental sustainability and body mass index in children and adolescents: Insights from the National Food, Nutrition and Physical Activity Survey 2015-2016

OBJECTIVE

To adapt four dietary patterns for children and adolescents, and study their associations with sustainability (greenhouse-gas emissions-GHGE and land use-LU), and health (body mass index-BMI) indicators.

RESEARCH METHODS & PROCEDURES

Dietary intake of children (3-9y) and adolescents (10-17y) from the National Food, Nutrition and Physical Activity Survey 2015-2016, Portugal (n = 1153) was assessed through two non-consecutive interviews: one-day food diaries (children), and 24-h recalls (adolescents), using an automated multiple-pass method, including a picture book for portion sizes estimation. Adherence to the Eat-Lancet and World Health Organization (WHO) recommendations, Mediterranean and Atlantic diets were evaluated using adapted versions for pediatrics of the World Index for Sustainability and Health (WISH), Diet Quality Index (DQI), Mediterranean Diet Score (MDS) and Southern-European Atlantic Diet (SEAD), respectively. Diet-related GHGE and LU were estimated using the SHARP-Indicators database. BMI (measured) z-scores were classified according to WHO criteria. A standardized weighted health-sustainability composite index was created (BMI + 0.5*GHGE+0.5*LU). Adjusted linear regression models were computed.

RESULTS

WISH, DQI, MDS, and SEAD had weighted mean scores (range) of 50 (0-130), 24 (9-36), 20 (8-32), and 17 (8-32), respectively. All dietary patterns were associated with lower environmental impact, particularly in children, but not with BMI. Only MDS explained both health and sustainability indicators in childhood (composite index: sd.β = -0·223,95%CI:-0·347,-0·072,R2 = 25.1 %), and adolescence (composite index: sd.β = -0·159,95%CI:-0·315,-0·003,R2 = 31.3 %).

CONCLUSION

The Mediterranean diet was the most related to (higher) environmental sustainability and (lower) BMI. However, in children (not adolescents), the WISH, DQI, and SEAD showed then same associations.

Mexican national dietary guidelines promote less costly and environmentally sustainable diets

The 2023 Mexican Healthy and Sustainable Dietary Guidelines (HSDG 2023) were developed to include all dimensions of sustainability. Here we compare the environmental impact and cost of diets based on the HSDG 2023, current diets and the Mexican-adapted EAT healthy reference diet. Diets following HSDG 2023 are 21% less expensive, require 30% less land to be produced and have 34% less carbon emissions than current diets-particularly in Mexico City and other urban areas with higher prevalence of Westernized diets. This is driven by reduced animal-source food, especially red meat, and ultra-processed foods. In south-rural areas, the water footprint and cost of diets following HSDG 2023 were higher than those of current diets owing to increased intake of nuts, fruits and vegetables not offset by lower meat consumption (which is already close to recommendations). Diet environmental impact and cost could be further reduced with the Mexican-adapted EAT healthy reference diet compared with the HSDG 2023.

Augmenting the National Nutrition Data System to Promote Diet Sustainability Analyses

Research on sustainable diets has become an important and growing area of the nutrition field, but recent studies have pointed to a lack of sustainability metrics and methods that are hindering research and policy progress. To fill this gap, the White House National Strategy on Hunger, Nutrition, and Health calls for increased funding to improve metrics, data collection, and research to address all domains of sustainability, which include nutrition/health, economic, environmental, and social domains. Commodity recipe databases, such as the Food Commodity Intake Database (FCID), are important tools for conducting diet sustainability analyses because they translate mixed dishes from dietary surveys, such as the National Health and Nutrition Examination Survey (NHANES), into commodity ingredients. These ingredients have been linked to data on environmental impacts and economic costs from other databases, thus facilitating collaboration between nutrition researchers, environmental scientists, economists, and others. These linkages cannot be made with other components of the national nutrition data system, such as the Food Patterns Equivalents Database (FPED), because the disaggregated food groups from them are not relevant for examining environmental impacts. Although the NHANES is conducted on an ongoing basis, and FPED is continually updated, the FCID has not been officially updated since 2010. This severely limits advancements in sustainability research and related policy analyses. In this commentary, we argue that the federal government should promote this diet sustainability work by integrating a commodity recipe database into the national nutrition data system, and updating it on a regular basis, as it does with other component databases.

The knowledge, attitudes, and perceptions towards a plant-based dietary pattern: a survey of obstetrician-gynecologists

Background

Obstetricians-gynecologists (OB/GYNs) play a critical role for their pregnant patients during their perinatal period, but research on OB/GYNs knowledge, attitudes, and perceptions regarding plant-based dietary patterns (PBDP) and how this may influence recommendations to patients is lacking. An online cross-sectional survey was conducted to examine OB/GYN's knowledge, attitudes, and perceptions towards a PBDP.

Methods

Postcards were mailed in June 2023 to a convenience sample of 5,000 OB/GYNs across the US using a mailing list provided by the American College of Obstetricians and Gynecologists. Postcards had a brief study description and a QR code that linked to an online survey asking questions about demographics, behavior (e.g., nutritional habits), and other factors that may influence knowledge, attitudes, and perceptions towards a PBDP for their patients.

Results

Ninety-six OB/GYNs completed the full questionnaire (~2% response rate). Most (92%) felt that it is within an OB/GYN's role to incorporate nutrition education and counseling within practice. However, 72% felt inadequately trained to discuss nutrition and diet-related issues with patients. Despite a perceived lack of nutrition training, 86% reported that a PBDP was safe and health-promoting, and 81% reported that a well-planned PBDP could adequately meet all nutritional needs of pregnant and lactating patients.

Conclusion

Findings suggest that OB/GYNs are generally knowledgeable about the components and health benefits of a plant-based diets. However, nutrient adequacy misconceptions and lack of sufficient training to discuss nutrition with patients may result in OB/GYNs not recommending PBDPs to patients. These findings underscore the need to enhance OB/GYN graduate medical education and training by integrating education on PBDPs, therefore improving a clinician's ability to confidently and effectively counsel pregnant persons on this aspect of perinatal care.

The Impact of Sustainability Courses: Are They Effective in Improving Diet Quality and Anthropometric Indices?

There are studies on the effect of general nutrition education on diet quality and anthropometric measurements, while studies showing the effectiveness of sustainable nutrition education, which also addresses the effect of food on the environment, are quite limited. This study aimed to investigate the effects of sustainable nutrition education on diet quality, anthropometric measurements, and the carbon footprint (CFP) and water footprint (WFP) of diet. A total of 160 university students received 1 h of sustainable nutrition education for 6 weeks. Before, at the end of, and 2 months after the courses, 24 h food consumption records were taken to assess diet quality and CFP and WFP values of diet, and Mediterranean diet (MedDiet) and Healthy Eating Index (HEI)-2020 scores were evaluated. The results of the study showed that sustainable nutrition education increased MedDiet score by 1.86 points and HEI-2020 score by 7.38 points. This education program also decreased body weight, body mass index (BMI), fat mass, and neck circumference. Sustainability education has a positive impact on calcium, potassium, and magnesium intakes, a negative impact on vitamin B12 and zinc intakes, and no effect on total protein intake. Education resulted in a 22% reduction in CFP and a 10% reduction in WFP.

Perspective: The Place of Pork Meat in Sustainable Healthy Diets

The food systems sustainability framework has 4 domains: nutrition, economics, environment, and society. To qualify as sustainable, individual foods and total diets need to be nutrient-rich, affordable, environmentally friendly, and socially acceptable. Pork is the most consumed meat globally, providing high-quality protein and several priority micronutrients. With research attention focused on plant-based diets, it is time to assess the place of pork meat protein in the global sustainability framework. First, not all proteins are equal. The United States Department of Agriculture category of protein foods includes meat, poultry and fish, eggs, beans and legumes, and nuts and seeds. These protein sources have different protein digestibility profiles, different per-calorie prices, and different environmental footprints, measured in terms of greenhouse gas emissions. Second, most analyses of animal-source proteins combine beef, pork, and lamb into a single category of red meat. Beef, pork, and lamb have different nutrient profiles, different protein costs, and different impacts on the environment. Future analyses of nutrient density and monetary and carbon costs of alternative diets would do well to separate pork from beef, lamb, and chicken. There are also different profiles of global food demand. Prior analyses of global Food and Agriculture Organization Statistical Database food balance sheets joined with World Bank country incomes have consistently shown that rising incomes across lower- and middle-income countries (LMIC) create a growing demand for meat to replace traditional plant proteins. Most of the observed increase has been for pork and chicken rather than beef. This ongoing LMIC protein transition toward more animal proteins may be irreversible as long as incomes grow. The present analyses explore the place of pork in sustainable healthy diets worldwide, given the need for high-quality protein and the predictable patterns of global food demand.

Dietary quality and dietary greenhouse gas emissions in the USA: a comparison of the planetary health diet index, healthy eating index-2015, and dietary approaches to stop hypertension

BACKGROUND

The Planetary Health Diet Index (PHDI) measures adherence to the dietary pattern presented by the EAT-Lancet Commission, which aligns health and sustainability targets. There is a need to understand how PHDI scores correlate with dietary greenhouse gas emissions (GHGE) and how this differs from the carbon footprints of scores on established dietary recommendations. The objectives of this study were to compare how the PHDI, Healthy Eating Index-2015 (HEI-2015) and Dietary Approaches to Stop Hypertension (DASH) relate to (a) dietary GHGE and (b) to examine the influence of PHDI food components on dietary GHGE.

METHODS

We used life cycle assessment data from the Database of Food Recall Impacts on the Environment for Nutrition and Dietary Studies to calculate the mean dietary GHGE of 8,128 adult participants in the 2015-2016 and 2017-2018 cycles of the National Health and Nutrition Examination Survey (NHANES). Poisson regression was used to estimate the association of (a) quintiles of diet score and (b) standardized dietary index Z-scores with dietary GHGE for PHDI, HEI-2015, and DASH scores. In secondary analyses, we used Poisson regression to assess the influence of individual PHDI component scores on dietary GHGE.

RESULTS

We found that higher dietary quality on all three indices was correlated with lower dietary GHGE. The magnitude of the dietary quality-dietary GHGE relationship was larger for PHDI [-0.4, 95% CI (-0.5, -0.3) kg CO2 equivalents per one standard deviation change] and for DASH [-0.5, (-0.4, -0.6) kg CO2-equivalents] than for HEI-2015 [-0.2, (-0.2, -0.3) kg CO2-equivalents]. When examining PHDI component scores, we found that diet-related GHGE were driven largely by red and processed meat intake.

CONCLUSIONS

Improved dietary quality has the potential to lower the emissions impacts of US diets. Future efforts to promote healthy, sustainable diets could apply the recommendations of the established DASH guidelines as well as the new guidance provided by the PHDI to increase their environmental benefits.

Developing messages to encourage healthy, sustainable dietary substitutions: A qualitative study with US emerging adults

Prior research shows that adopting simple dietary substitutions (e.g., replacing beef with poultry or plant-based entrees) can improve dietary quality and reduce the negative environmental consequences of food production, but little is known about how to encourage people to adopt these substitutions. This study aimed to examine reactions to messages encouraging healthy, sustainable dietary substitutions among emerging adults ages 18-25. We conducted four online focus groups with a diverse sample of US emerging adults (n = 28; 61% female). Focus groups explored emerging adults' reactions to messages encouraging them to adopt three target dietary substitutions: replacing beef and pork with poultry and plant-based entrees; replacing juice with whole fruit; and replacing dairy milk with non-dairy milk. We transcribed discussions verbatim and adopted a thematic approach to analyzing the transcripts. Results showed that participants perceived messages to be most effective at encouraging the target dietary substitutions when the messages: encouraged specific, achievable dietary changes; linked these dietary changes to clear consequences; included personally relevant content; included statistics; were succinct; and used a positive tone. Across the target dietary substitutions, two message topics (small changes, big benefits, which emphasized how small dietary changes can have large positive health and environmental impacts, and warning, which discussed the negative health and environmental impacts of dietary choices) were generally perceived to be most effective. A few participants expressed doubt that the target dietary substitutions would have meaningful environmental impacts. Results suggest that campaign messages to encourage healthy, sustainable dietary substitutions may be more effective if the messages make the target dietary substitutions seem achievable and use statistics to clearly describe the positive impacts of making these changes.

Opportunities for Consistent and Holistic Metrics to Support Food Systems Transformation: A Summary of a Symposium Presented at Nutrition 2023

There is an urgent need for global food systems transformation to realize a future where planetary health reaches its full potential. Paramount to this vision is the ability of stakeholders across sectors to understand how foods and dietary patterns impact food systems inclusive of all domains of sustainability-environmental, nutrition/health, economic and social. This article is a synopsis of presentations by 3 food systems experts to share the latest science in a session entitled "How do you measure sustainability? Opportunities for consistent and holistic metrics to support food systems transformation" at the American Society for Nutrition's 2023 annual conference. As summarized here, global population data showing widespread malnutrition underscore the important role of dietary diversity through a balance of plant- and animal-source foods to achieve nutritionally adequate diets and reduce risk of noncommunicable diseases. Yet, recent international audits of countries, companies, and organizations and their sustainability targets largely demonstrate an underrepresentation of robust nutrition/health metrics to support public nutrition and health progress. Addressing limitations in diet-sustainability modeling systems provides a viable opportunity to accurately reflect the important contributions and trade-offs of diets across all domains of sustainability to ultimately support evidence-based decision making in advancing healthy food systems.

Reducing the carbon footprint of diets across socio-demographic groups in Finland: a mathematical optimisation study

OBJECTIVES

To characterise nutritionally adequate, climate-friendly diets that are culturally acceptable across socio-demographic groups. To identify potential equity issues linked to more climate-friendly and nutritionally adequate dietary changes.

DESIGN

An optimisation model minimises distance from observed diets subject to nutritional, greenhouse gas emissions (GHGE) and food-habit constraints. It is calibrated to socio-demographic groups differentiated by sex, education and income levels using dietary intake data. The environmental coefficients are derived from life cycle analysis and an environmentally extended input-output model.

SETTING

Finland.

PARTICIPANTS

Adult population.

RESULTS

Across all population groups, we find large synergies between improvements in nutritional adequacy and reductions in GHGE, set at one-third or half of the current level. Those reductions result mainly from the substitution of meat with cereals, potatoes and roots and the intra-category substitution of foods, such as beef with poultry in the meat category. The simulated more climate-friendly diets are thus flexitarian. Moving towards reduced-impact diets would not create major inadequacies related to protein and fatty acid intakes, but Fe could be an issue for pre-menopausal females. The initial socio-economic gradient in the GHGE of diets is small, and the patterns of adjustments to more climate-friendly diets are similar across socio-demographic groups.

CONCLUSIONS

A one-third reduction in GHGE of diets is achievable through moderate behavioural adjustments, but achieving larger reductions may be difficult. The required changes are similar across socio-demographic groups and do not raise equity issues. A population-wide policy to promote behavioural change for diet sustainability would be appropriate.

Commercial weight-loss diets, greenhouse gas emissions and freshwater consumption

BACKGROUND

Weight-loss attempts are widespread in the United States, with many using commercial weight-loss diet plans for guidance and support. Accordingly, dietary suggestions within these plans influence the nation's food-related environmental footprint.

METHODS

We modelled United States (US) per capita greenhouse gas emissions (GHGe) and water footprints associated with seven commercial weight-loss diets, the US baseline, and selected other dietary patterns. We characterised consumption in commercial weight-loss diets both via modelling from provided guidelines and based on specific foods in 1-week meal plans. Cradle-to-farmgate GHGe and water footprints were assessed using a previously developed model. GHGe results were compared to the EAT-Lancet 2050 target. Water footprints were compared to the US baseline.

RESULTS

Weight-loss diets had GHGe footprints on average 4.4 times the EAT-Lancet target recommended for planetary health (range: 2.4-8.5 times). Bovine meat was by far the largest contributor of GHGe in most diets that included it. Three commercial diets had water footprints above the US baseline. Low caloric intake in some diets compensated for the relative increases in GHGe- and water-intensive foods.

CONCLUSIONS

Dietary patterns suggested by marketing materials and guidelines from commercial weight-loss diets can have high GHGe and water footprints, particularly if caloric limits are exceeded. Commercial diet plan guidance can be altered to support planetary and individual health, including describing what dietary patterns can jointly support environmental sustainability and weight loss.

Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins: A Randomized Clinical Trial

Importance

Increasing evidence suggests that, compared with an omnivorous diet, a vegan diet confers potential cardiovascular benefits from improved diet quality (ie, higher consumption of vegetables, legumes, fruits, whole grains, nuts, and seeds).

Objective

To compare the effects of a healthy vegan vs healthy omnivorous diet on cardiometabolic measures during an 8-week intervention.

Design, Setting, and Participants

This single-center, population-based randomized clinical trial of 22 pairs of twins (N = 44) randomized participants to a vegan or omnivorous diet (1 twin per diet). Participant enrollment began March 28, 2022, and continued through May 5, 2022. The date of final follow-up data collection was July 20, 2022. This 8-week, open-label, parallel, dietary randomized clinical trial compared the health impact of a vegan diet vs an omnivorous diet in identical twins. Primary analysis included all available data.

Intervention

Twin pairs were randomized to follow a healthy vegan diet or a healthy omnivorous diet for 8 weeks. Diet-specific meals were provided via a meal delivery service from baseline through week 4, and from weeks 5 to 8 participants prepared their own diet-appropriate meals and snacks.

Main Outcomes and Measures

The primary outcome was difference in low-density lipoprotein cholesterol concentration from baseline to end point (week 8). Secondary outcome measures were changes in cardiometabolic factors (plasma lipids, glucose, and insulin levels and serum trimethylamine N-oxide level), plasma vitamin B12 level, and body weight. Exploratory measures were adherence to study diets, ease or difficulty in following the diets, participant energy levels, and sense of well-being.

Results

A total of 22 pairs (N = 44) of twins (34 [77.3%] female; mean [SD] age, 39.6 [12.7] years; mean [SD] body mass index, 25.9 [4.7]) were enrolled in the study. After 8 weeks, compared with twins randomized to an omnivorous diet, the twins randomized to the vegan diet experienced significant mean (SD) decreases in low-density lipoprotein cholesterol concentration (-13.9 [5.8] mg/dL; 95% CI, -25.3 to -2.4 mg/dL), fasting insulin level (-2.9 [1.3] μIU/mL; 95% CI, -5.3 to -0.4 μIU/mL), and body weight (-1.9 [0.7] kg; 95% CI, -3.3 to -0.6 kg).

Conclusions and Relevance

In this randomized clinical trial of the cardiometabolic effects of omnivorous vs vegan diets in identical twins, the healthy vegan diet led to improved cardiometabolic outcomes compared with a healthy omnivorous diet. Clinicians can consider this dietary approach as a healthy alternative for their patients.

Trial Registration

ClinicalTrials.gov Identifier: NCT05297825.

Simple dietary substitutions can reduce carbon footprints and improve dietary quality across diverse segments of the US population

Changing what foods we eat could reduce environmental harms and improve human health, but sweeping dietary change is challenging. We used dietary intake data from a nationally representative sample of 7,753 US children and adults to identify simple, actionable dietary substitutions from higher- to lower-carbon foods (for example, substituting chicken for beef in mixed dishes such as burritos, but making no other changes to the diet). We simulated the potential impact of these substitutions on dietary carbon emissions and dietary quality. If all consumers who ate the high-carbon foods instead consumed a lower-carbon substitute, the total dietary carbon footprint in the United States would be reduced by more than 35%. Moreover, if adopted, these substitutions would improve consumers' overall dietary quality by 4-10%, with benefits projected for all age, gender, and racial and ethnic groups. These results suggest that a 'small changes' approach could be a valuable starting point for addressing diet's impact on climate and health.

Greater adherence to the Dietary Guidelines for Americans is associated with lower diet-related greenhouse gas emissions but higher costs

Introduction

Few studies have evaluated the sustainability of popular diet patterns in the US, which limits policy action and impedes consumer efficacy to make sustainable dietary changes. This study filled this gap by evaluating the relationship between diet quality, greenhouse gas emissions (GHGE), and diet cost for plant-based, restricted carbohydrate, low grain, low fat, and time restricted diet patterns.

Methods

Dietary data were retrieved from the National Health and Nutrition Examination Survey (2011-2018, n = 8,146) and linked with data on GHGE and food prices from publicly available databases. Diet quality was measured using the Healthy Eating Index-2015. The present study (1) compared the mean diet quality, GHGE, and diet cost between diet patterns, (2) evaluated the association of diet quality to GHGE and diet cost for each diet pattern, and (3) estimated the contribution of food sources to GHGE and diet cost for each diet pattern.

Results

Higher diet quality was associated with lower GHGE for the general population and for most diet patterns (p < 0.01) except for the plant-based and time restricted diet patterns (p > 0.05). Higher diet quality was associated with higher cost for the general population and for all dietary patterns (p < 0.01) except the time restricted diet pattern (p > 0.05). Protein foods, mostly beef, accounted for the largest share of GHGE (29-40%) and diet cost (28-47%) for all diet patterns except plant-based.

Discussion

Higher diet quality was associated with lower GHGE but was often accompanied by higher diet cost. These sustainability trade-offs can help inform major policy discussions in the US and shed light on further research needs in the area of food systems transformation.