Plant-based and vegetarian diets: an overview and definition of these dietary patterns.

PURPOSE: This paper aims to present an overview of the definitions of "plant-based and "vegetarian diets" adopted by different organizations worldwide, proposing new standard definitions and discussing the notion of vegetarianism as a restrictive dietary pattern. METHODS: An extensive literature review on the different definitions of vegetarian and plant-based diets was conducted. Definitions of different international vegetarian and vegan organizations were also taken into account. Objective definitions for vegetarian and plant-based diets, as well as for their subcategories, were proposed. Other aspects related to how vegetarian diets are viewed and defined were also discussed. RESULTS: We proposed that a vegetarian diet should be defined as "a dietary pattern that excludes meat, meat-derived foods, and, to different extents, other animal products". This definition would include, among others, ovolactovegetarian and vegan diets. The proposed definition for a plant-based diet was "a dietary pattern in which foods of animal origin are totally or mostly excluded". Other types of diets, such as flexitarian and pescetarian diets, could be considered plant-based. A vegetarian diet should not be considered restrictive. Instead, terms such as alternative or non-conventional could be used to define it and to distinguish it from the conventional diet adopted by most of the Western population. CONCLUSION: This paper was able to elaborate objective definitions of vegetarian and plant-based diets. Standardizing nomenclatures may reduce misinterpretation and confusion in this field of study.

Morally admirable or moralistically deplorable? A theoretical framework for understanding character judgments of vegan advocates.

Over the last decade, vegan advocates have become a growing minority. By arguing against animal-product consumption and imposing the virtue-loaded call to "go vegan," advocates have posed a direct challenge to the mainstream dietary ideology (termed "carnism") in hopes of positive social change. As a consequence, while vegan advocates may be admired for their morality and commitment, they may also be derogated with moralistic traits such as arrogance and overcommitment. We call this mixed-valence perception the "vegan paradox" and propose a theoretical framework for understanding it. Next, we develop a future research agenda to test and apply our framework, and inquire vegan advocacy for ethical, health, and environmental aims. Using the perspective of the idealistic vegan advocate as a reference point, we discuss the roles of the advocate's motives for change (i.e., the effectiveness of moral persuasion), the advocate's call for change (i.e., radical versus incremental change), the target's moral and carnist identification, and source attributes of the advocate. Lastly, we qualify our framework by highlighting further conceptual and methodological considerations.

Moralistic stereotyping of vegans: The role of dietary motivation and advocacy status.

Ambivalent attitudes exist toward vegans: While people may admire vegans' moral aims and commitment, they may also derogate vegans for seeming arrogant and overcommitted. These latter negative perceptions may undermine the effectiveness of efforts to reduce meat consumption for health, animal-welfare, and sustainability benefits. In the present research, we investigated the role of a vegan's motivation (animal ethics vs. health) in moralized attitudes toward vegans among omnivorous participants through two preregistered studies. In Study 1 (N = 390), we found that a vegan advocate motivated by animal ethics (vs. health) was seen as more moral but not as more arrogantly overcommitted. In Study 2 (N = 1177), we found that animal ethics (vs. health) vegans were seen as both more arrogantly committed and more morally committed, but that relative moral commitment perceptions were attenuated when vegans were described as actively advocating. Both advocating (vs. non-advocating) vegans and animal ethics (vs. health) vegans were generally seen as less socially attractive by omnivores due to stronger attributions of arrogant overcommitment, and a lower social attractiveness was associated with a lower willingness to eat less animal products. Our findings inform ongoing debates within the vegan movement about the effectiveness of signaling moral commitment in promoting plant-based diets.

CALIOP retrieval of droplet effective radius accounting for cloud vertical homogeneity.

Monitoring cloud droplet effective radius (re) is of great significance for studying aerosol-cloud interactions (ACI). Passive satellite retrieval, e.g., MODIS (Moderate Resolution Imaging Spectroradiometer), requires sunlight. This requirement prompted developing re retrieval using active sensors, e.g., CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). Given the highest sensitivity of vertically homogeneous clouds to aerosols that feed to cloud base, here CALIOP profile measurements were used for the first time to quantify cloud vertical homogeneity and estimate cloud re during both day and night. Comparison using simultaneous Aqua-MODIS measurements demonstrates that CALIOP retrieval has the highest accuracy for vertically homogeneous clouds, with R2 (MAE, RMSE) of 0.72 (1.75 µm, 2.25 µm), while the accuracy is lowest for non-homogeneous clouds, with R2 (MAE, RMSE) of 0.60 (2.90 µm, 3.70 µm). The improved re retrieval in vertically homogeneous clouds provides a basis for possible breakthrough insights in ACI by CALIOP since re in such clouds reflects most directly aerosol effects on cloud properties. Global day-night maps of cloud vertical homogeneity and respective re are presented.

Gender differences in meat consumption and openness to vegetarianism.

Understanding gender differences in meat consumption can help strengthen efforts to improve the sustainability of eating patterns. Compared to women, men eat more meat and are less open to becoming vegetarian. Simply considering between-gender differences, however, may overlook meaningful within-gender heterogeneity in how masculine and feminine identities associate with eating behavior. Distinguishing between specific types of meat is also important, given that some meats (e.g., beef) pose greater challenges to sustainability than do other meats. Through a highly powered, preregistered study (N = 1706), we investigated the predictive value of traditional gender role conformity and gender identity centrality for meat consumption frequency and openness to becoming vegetarian. Greater conformity to traditional gender roles predicted more frequent consumption of beef and chicken and lower openness to vegetarianism among men but offered no predictive value among women. No effects were observed for pork or fish consumption. Among women, greater traditional gender role conformity and gender identity centrality were associated with openness to becoming vegetarian for health reasons. Among men, lower traditional gender role conformity was associated with openness to becoming vegetarian for environmental reasons. These findings suggest that understanding meat consumption calls for greater distinctions between specific types of meat as well as deeper consideration of within-gender heterogeneity.

Pro-environmental behavior predicts adherence to plant-based diets.

Plant-based diets are beneficial to human health and environmental sustainability but suffer from low rates of adherence. For example, many people who self-identify as vegetarian sporadically eat meat and eventually give up their vegetarian diet entirely. We theorize that valuing a lifestyle of pro-environmental behaviors can enable people to adhere to a plant-based diet more successfully. In the current survey study, we tested this prediction among plant-based dieters for two outcomes: short-term adherence (for the past three days) and future-intended dietary adherence (intention to continue one's diet for the next 1-2 years). Over and above other dietary, motivational, and demographic factors, pro-environmental behavior positively predicted both short-term and future-intended adherence to plant-based diets. Moreover, pro-environmental behavior mediated links between (a) connectedness to nature and dietary adherence and (b) political ideology and dietary adherence. These findings highlight pro-environmental behavior as a tool for explaining and predicting adherence to plant-based diets.

Can a pandemic make people more socially conservative? Political ideology, gender roles, and the case of COVID-19.

The first months of 2020 rapidly threw people into a period of societal turmoil and pathogen threat with the COVID-19 pandemic. By promoting epistemic and existential motivational processes and activating people's behavioral immune systems, this pandemic may have changed social and political attitudes. The current research specifically asked the following question: As COVID-19 became pronounced in the United States during the pandemic's emergence, did people living there become more socially conservative? We present a repeated-measures study (N = 695) that assessed political ideology, gender role conformity, and gender stereotypes among U.S. adults before (January 25-26, 2020) versus during (March 19-April 2, 2020) the pandemic. During the pandemic, participants reported conforming more strongly to traditional gender roles and believing more strongly in traditional gender stereotypes than they did before the pandemic. Political ideology remained constant over time. These findings suggest that a pandemic may promote the preference for traditional gender roles.

Taste and health concerns trump anticipated stigma as barriers to vegetarianism.

Meat-eaters report that a number of barriers inhibit them from going vegetarian-for example, perceiving vegetarian diets to be inadequately nutritious, too expensive, unfamiliar, inconvenient, inadequately tasty, and socially stigmatizing. However, research identifying which barriers uniquely predict meat-eaters' openness to going vegetarian is lacking from the current literature. In the present research, accordingly, we conducted a highly powered, preregistered study (N = 579) to identify which barriers uniquely predict openness to going vegetarian. We focused specifically on anticipated vegetarian stigma, given recent qualitative evidence highlighting this attitude as an influential barrier. That is, do meat-eaters resist going vegetarian because they fear that following a vegetarian diet would make them feel stigmatized? Being of younger age, more politically conservative, White, and residing in a rural community predicted greater anticipated vegetarian stigma among meat-eaters. Frequentist and Bayesian analyses converged, however, to suggest that anticipated vegetarian stigma was not a significant predictor of openness to going vegetarian. The strongest predictors of openness were perceived tastiness and perceived healthfulness of vegetarian dieting. These factors-but not anticipated stigma-furthermore explained why men (compared to women) and political conservatives (compared to liberals) were particularly resistant to going vegetarian.

Unexpected rise of ozone in urban and rural areas, and sulfur dioxide in rural areas during the coronavirus city lockdown in Hangzhou, China: implications for air quality.

The outbreak of coronavirus named COVID-19, initially identified in Wuhan, China in December 2019, has spread rapidly at the global scale. Most countries have rapidly stopped almost all activities including industry, services and transportation of goods and people, thus decreasing air pollution in an unprecedented way, and providing a unique opportunity to study air pollutants. While satellite data have provided visual evidence for the global reduction in air pollution such as nitrogen dioxide (NO2) worldwide, precise and quantitative information is missing at the local scale. Here we studied changes in particulate matter (PM2.5, PM10), carbon monoxide (CO), NO2, sulfur dioxide (SO2) and ozone (O3) at 10 urban sites in Hangzhou, a city of 7.03 million inhabitants, and at 1 rural site, before city lockdown, January 1-23, during city lockdown, January 24-February 15, and during resumption, February 16-28, in 2020. Results show that city lockdown induced a sharp decrease in PM2.5, PM10, CO, and NO2 concentrations at both urban and rural sites. The NO2 decrease is explained by reduction in traffic emissions in the urban areas, and by lower regional transport in rural areas during lockdown, as expected. SO2 concentrations decreased from 6.3 to 5.3 µg m-3 in the city, but increased surprisingly from 4.7 to 5.8 µg m-3 at the rural site: this increase is attributed both to higher coal consumption for heating and emissions from traditional fireworks of the Spring Eve and Lantern Festivals during lockdown. Unexpectedly, O3 concentrations increased by 145% from 24.6 to 60.6 µg m-3 in the urban area, and from 42.0 to 62.9 µg m-3 in the rural area during the lockdown. This finding is explained by the weakening of chemical titration of O3 by NO due to reductions of NOx fresh emissions during the non-photochemical reaction period from 20:00 PM to 9:00 AM (local time). During the lockdown, compared to the same period in 2019, the daily average concentrations in the city decreased by 42.7% for PM2.5, 47.9% for PM10, 28.6% for SO2, 22.3% for CO and 58.4% for NO2, which is obviously explained by the absence of city activities. Overall, we observed not only the expected reduction in some atmospheric pollutants (PM, SO2, CO, NO2), but also unexpected increases in SO2 in the rural areas and of ozone (O3) in both urban and rural areas, the latter being paradoxically due to the reduction in nitrogen oxide levels. In other words, the city lockdown has improved air quality by reducing PM2.5, PM10, CO, and NO2, but has also decreased air quality by augmenting O3 and SO2.

When vegetarians eat meat: Why vegetarians violate their diets and how they feel about doing so.

Many people who self-identify as vegetarian actually eat meat on occasion. Surveys documenting this phenomenon have become abundant over the past two decades, and recent studies have begun to explain why some vegetarians are more likely to violate their diets than others are. However, qualitative research detailing the experiences of vegetarians eating meat is sparse. In the current study, we surveyed 243 vegetarians, 124 (51%) of whom indicated that they have eaten meat since going vegetarian. Of these 124 participants, 108 provided written narratives about their experiences eating meat, which we analyzed. Participants were most likely to eat meat at family gatherings and on special occasions; to eat meat in order to make a social situation flow more smoothly; and to react negatively to having eaten meat. Participants' narratives suggest that vegetarianism may be best conceived as a social identity, beyond just a diet. Some vegetarians reported that they view their diets as flexible guidelines, rather than rigid rules they ought to follow without exception. This study is the first, to our knowledge, to document in detail how vegetarians reflect on their experiences eating meat.

The role of social identity motivation in dietary attitudes and behaviors among vegetarians.

People go vegetarian for a variety of reasons-most commonly motivated by concerns about animals, health, ecology, religion, or some combination of these motivations. Largely missing from existing perspectives on vegetarian motivation, however, is consideration of how construing vegetarianism as a social identity may motivate vegetarian-relevant behavior. We advance that the desire to adopt and affirm a vegetarian identity and to see this identity in a positive light may represent an overlooked, but meaningful, source of motivation for vegetarianism. In the current study (N = 380), we tested the predictive values of animal, health, ecological, religious, and social identity motivations among vegetarians for a variety of attitudes and behaviors. Over and above other motivational factors and the centrality and salience of being a vegetarian, social identity motivation uniquely predicted several relevant outcomes, including the tendency to violate one's vegetarian diet. These findings suggest that the desire to adopt and affirm a vegetarian identity may be a unique and meaningful motivation underlying one's choice to forgo meat.

Satellite retrieval of cloud condensation nuclei concentrations by using clouds as CCN chambers.

Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day.

Improving our fundamental understanding of the role of aerosol-cloud interactions in the climate system.

The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth's clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol-cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol-cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol-cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.

Persistent sulfate formation from London Fog to Chinese haze.

Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

Remote Sensing of Droplet Number Concentration in Warm Clouds: A Review of the Current State of Knowledge and Perspectives.

The cloud droplet number concentration (N d) is of central interest to improve the understanding of cloud physics and for quantifying the effective radiative forcing by aerosol-cloud interactions. Current standard satellite retrievals do not operationally provide N d, but it can be inferred from retrievals of cloud optical depth (τ c) cloud droplet effective radius (r e) and cloud top temperature. This review summarizes issues with this approach and quantifies uncertainties. A total relative uncertainty of 78% is inferred for pixel-level retrievals for relatively homogeneous, optically thick and unobscured stratiform clouds with favorable viewing geometry. The uncertainty is even greater if these conditions are not met. For averages over 1° ×1° regions the uncertainty is reduced to 54% assuming random errors for instrument uncertainties. In contrast, the few evaluation studies against reference in situ observations suggest much better accuracy with little variability in the bias. More such studies are required for a better error characterization. N d uncertainty is dominated by errors in r e, and therefore, improvements in r e retrievals would greatly improve the quality of the N d retrievals. Recommendations are made for how this might be achieved. Some existing N d data sets are compared and discussed, and best practices for the use of N d data from current passive instruments (e.g., filtering criteria) are recommended. Emerging alternative N d estimates are also considered. First, new ideas to use additional information from existing and upcoming spaceborne instruments are discussed, and second, approaches using high-quality ground-based observations are examined.

Satellite Observations of Precipitating Marine Stratocumulus Show Greater Cloud Fraction for Decoupled Clouds in Comparison to Coupled Clouds.

This study examines the relationships between marine stratocumulus clouds (MSC) coupling state with the ocean surface, their precipitation rate and fractional cloud cover (CF). This was possible by developing a novel methodology for satellite retrieval of the clouds coupling state. Decks of overcast MSC were reported in previous studies to break up often as their precipitation rate increases significantly, thus reducing CF and cloud radiative effect substantially. Here we show that decks of precipitating decoupled MSC have larger CF compared to similarly precipitating coupled MSC. The difference in CF between decoupled and coupled clouds was found to increase with precipitation rate, up to nearly doubling the CF of the heaviest precipitating decoupled MSC. This suggests that decoupling is a feature related to higher cloud radiative effect in precipitating MSC.

The psychology of vegetarianism: Recent advances and future directions.

Whereas vegetarianism has long garnered attention from nutritional science and philosophy, psychological research exploring this eating behavior has emerged only in the past few decades. Six years ago, Ruby (2012) reviewed the extant literature on the psychology of vegetarianism, showcasing its promise as "a blossoming field of study." In the time since, this line of research truly has blossomed, as subsequent work has addressed prior knowledge gaps and initiated new lines of inquiry. While evidence on previously studied topics of dietary motivation, moral values, gender, differences between vegetarians and vegans, barriers to dietary change, and disordered eating has continued to expand, new lines of research on identity, social experiences, flexitarianism, culture, and prospective vegetarianism have emerged. Recent psychometric advancements, moreover, have constructed useful measures to assess relevant constructs. The current review synthesizes this amalgam of research, identifying emergent themes and highlighting promising directions for future inquiry.

Development and validation of the Dietarian Identity Questionnaire: Assessing self-perceptions of animal-product consumption.

In navigating decisions about what to eat, people both construct and rely on a food-choice identity. Yet food choice is multifaceted, as people apply different dietary schemas to different types of food, engaging various domains of food-choice identity. In this paper, we focus on dietarian identity: one's thoughts, feelings, and behaviors with respect to consuming or eschewing animal products (here, pertaining to red meat, poultry, fish, eggs, and dairy). First, we draw upon Rosenfeld and Burrow's (2017a) Unified Model of Vegetarian Identity in order to develop a Dietarian Identity Questionnaire (DIQ). Second, we validate the DIQ's factor structure, construct validity, internal consistency, test-retest reliability, and replicability. Lastly, we highlight directions for the use of the DIQ in future research.

Vegetarian on purpose: Understanding the motivations of plant-based dieters.

Much recent research has explored vegetarians' dietary motivations, recurrently highlighting the significant influence they exert on how people view themselves and others. For vegetarians and other plant-based dieters, dietary motivations have been theorized to be a central aspect of identity. Yet not all plant-based dieters are motivated to follow their diets; rather, some face aversions and constraints. In this paper, we propose that motivations, aversions, and constraints constitute three distinct reasons for consuming a plant-based diet. After conceptually distinguishing motivations from aversions and constraints, we critically evaluate the advantages and disadvantages of two conceptual frameworks that exist for studying these motivations systematically: the ethical-health framework and the Unified Model of Vegetarian Identity (UMVI) motivational orientations framework. Importantly, these frameworks serve different purposes, and their suitability often depends on the research question at hand. Particularly given an increasing prevalence of plant-based dieting, cultivating a more holistic understanding of these two frameworks is necessary for advancing this discipline. Directions for future research are discussed.

The unified model of vegetarian identity: A conceptual framework for understanding plant-based food choices.

By departing from social norms regarding food behaviors, vegetarians acquire membership in a distinct social group and can develop a salient vegetarian identity. However, vegetarian identities are diverse, multidimensional, and unique to each individual. Much research has identified fundamental psychological aspects of vegetarianism, and an identity framework that unifies these findings into common constructs and conceptually defines variables is needed. Integrating psychological theories of identity with research on food choices and vegetarianism, this paper proposes a conceptual model for studying vegetarianism: The Unified Model of Vegetarian Identity (UMVI). The UMVI encompasses ten dimensions-organized into three levels (contextual, internalized, and externalized)-that capture the role of vegetarianism in an individual's self-concept. Contextual dimensions situate vegetarianism within contexts; internalized dimensions outline self-evaluations; and externalized dimensions describe enactments of identity through behavior. Together, these dimensions form a coherent vegetarian identity, characterizing one's thoughts, feelings, and behaviors regarding being vegetarian. By unifying dimensions that capture psychological constructs universally, the UMVI can prevent discrepancies in operationalization, capture the inherent diversity of vegetarian identities, and enable future research to generate greater insight into how people understand themselves and their food choices.