Redefining healthy diets?

In the US, only 7 [O'Hearn et al. 2022] to 12%  [Araújo et al. 2019] of the adults are in a state of optimal cardiometabolic health. Two on three Americans are either overweight or obese (30% overweight and 42% obese, incl. 9% of severely obese) [Fryar et al. 2020], while one on two is expected to become obese and one on four severely obese by 2030 [Ward et al. 2019]. The US is not an isolated case. In Ireland, for instance, >80% of older adults are abdominally obese, >50% being at high cardiometabolic risk [FSA Ireland 2021]. Both chronic diseases and nutritional deficiencies are ravaging public health worldwide [Nelson et al., 2018]. Dietary change is obviously needed but current strategies are inadequate. The dietary guidelines have been introduced decades ago but have remained largely similar in their setup over time. Clearly, they have not been successful in their mission and are thus to be seen as failed policy
Given that nutritional epidemiology of chronic disease (NECD) has commonly been used to formulate implausible conclusions and overstate the evidence [Cofield et al. 2010; Schoenfeld & Ioannidis 2013; Ioannidis 2018], the way dietary advice has been constructed and practiced in the US since the 1980s has been criticized as 'untrustworthy', lacking evidence and rigor [Guyatt 2019; Johnston 2019]. Worse, it may have to be seen as a class-based construct that merely tells us what already healthy people (white, educated, middle-class professionals) believe a 'healthy diet' is [Hite 2018]. 
'Preventive' public health nutrition displays all three signs of arrogance, being (1) aggressively assertive (pursuing symptomless individuals in the general citizenry), (2) presumptuous (confident it does more good than harm), and (3) overbearing (attacking those who question the value of its recommendations) [cf. Sackett, 2002]. Taken together, dietary guidelines describe opinion but fail to provide meaningful information about true diet-chronic disease relationships. Some argue that - in the case of insufficient evidence - it may as well be wiser to ignore them altogether [Marantz et al. 2008]. 
Examples of overstated claims relate to further restriction of ASFs [see elsewhere] and sodium [Graudal et al. 2017; Graudal & Jürgens 2018; Mente et al. 2021; Ezekowitz et al. 2022], and some of the alleged protective effects on some of the specific health outcomes ascribed to calorie counting [Fernandes et al. 2019], 'Mediterranean' dieting [Rees et al. 2019], fruits and vegetables [Young et al. 2002; Møller et al. 2003; Crane et al. 2011; Kaiser at al. 2014; McEvoy et al. 2015; Duthie et al. 2018; Peluso et al. 2018; WCRF 2018, Key et al. 2020; Alami et al. 2022], whole-grains and fiber [Ho et al. 2012; Peery et al. 2012; Yang et al. 2012; Clark & Slavin 2013; Kelly et al. 2017; Guo et al. 2020; Marshall et al. 2020; Sadeghi et al. 2020], intake of antioxidants [Huggins & Simsolo 2021; Luo et al. 2021], or polyunsaturated fat [Ramsden et al. 2013; Hamley et al. 2017; Hanson et al. 2020], which are either non-existent or likely too small to be a game changer in a context of Western diets and lifestyles.

Too zealous adherence is not necessarily harmless
As a result of an excessive insistence on the restriction of ASFs [see elsewhere], devout adoption of the 'plant-based' eating message may not be without consequences for vulnerable groups [see elsewhere]. It may, for instance, lead to overly restrictive diets, especially when co-occurring with food allergies that require their own exclusionary measures [Protudjer & Mikkelsen 2020]. Also, it is likely that the increase of 'protein alternatives' will result in higher ingestion of processing contaminants and anti-nutritional compounds [Banach et al. 2022]. Concern has been raised related to elevated intakes of some plants (or algae), and their derived products, without the proper culinary treatments, as for the cooking of red beans [Food Safety News 2021]. 
In some cases, this could lead to exaggerated intakes of cariogenic sugars [Weerasinghe 2021], fructose [Gugliucci 2017; Amani & Fatima 2020; Geidl-Flueck & Gerber 2023], mycotoxins [Arroyo-Manzanares et al. 2019; Eskola et al., 2020; De Colli et al. 2021; Mihalache et al. 2022; Mihalache et al. 2022], toxic chemicals and heavy metals [Kumar & Sharma 2021; Vogel et al. 2021; Snoj Tratnik et al. 2022], pesticide residues [Wykhuys et al. 2020], plant-derived toxins and anti-nutritional factors [Ames 1990; Gee et al. 1996; Kassie et al. 1996; Patel et al. 2002; Truong et al. 2010; Baasanjav-Gerber et al. 2011; Latté et al. 2011; Gilani et al. 2012; Al Hasan et al. 2016Bressan & Kramer 2016; Felker et al. 2016; Mithöfer & Maffei 2016; Bernardino & Parmar, 2017; Gong et al. 2017; Malakar et al. 2017], phyto-oestrogens [Setchell et al. 1997; North et al. 2000; Allred et al. 2001; Tuohy 2003; Wagner et al. 2008; Siepmann et al. 2011; Marini et al. 2012; Westmark 2013; Upson et al. 2015, 2016a,b, 2019; Lee et al. 2019; Bredsdorff et al. 2020], allergens, even in cooked legumes [Dölle-Bierke et al. 2022; Abrams & Gerstner 2015], oils, omega-6 fatty acids, and OXLAMs [Pearce & Dayton 1971; Simopoulos 2002; Ghosh et al. 2006; Novak et al. 2008; Alvheim et al. 2012; Ramsden et al. 2013, 2016; DiNicolantonio 2014; Schlörmann et al., 2015; Kim et al. 2017; Mamounis et al. 2017; Saeed & Naz 2019; Yamashima et al. 2020; Grootveld et al. 2021; McGinnis & Ji 2021; Quin et al. 2021Wang et al. 2022], and acrylamide [Amrein et al. 2005; Schlörmann et al., 2015]. 
Some of these concerns are more worrying than others, many of which being based on isolated studies, experimental models, or weak evidence. Causal interpretations are often not warranted and the data should be contextualized and subjected to rigorous risk assessment. Evidently, the harm or healthfulness of plant-based diets will largely depend on the type of food items chosen [Satija et al. 2016; Kim et al. 2020; Gallagher et al. 2021; Oncina-Cnovas et al. 2021; Gehring et al. 2021; Asfura-Carrasco et al. 2022; Petermann-Rocha et al. 2023; Wang et al. 2023]. Also, individual health status should not be overlooked. For patients with non-alcoholic fatty liver disease, for instance, high fruit consumption can exacerbate steatosis, dyslipidemia, and glycemic control [Alami et al. 2022].
Nutritionism as an alibi for ultra-processing
The above-mentioned reductionist view on what constitutes a healthy diet leads to nutritionism and the setting of agendas [Scrinis 2013; Leroy et al. 2022]. This is being promoted and amplified by food corporations that consistently benefit from a methodology that favours the fragmented analysis of single nutrients and foods. As such, it has 'diverted attention from the study of the ingredients, additives, and processing techniques used in the manufacture of ultra-processed foods', while it 'has also obscured the broader social, commercial, and ecological determinants of dietary health' [Scrinis 2020]. The impact of ultra-processed foods on various environmental dimensions is indeed very substantial [Scott 2018; Fardet & Rock 2020Seferidi et al. 2020; Anastasiou et al. 2022]. In Brazil, impact of dietary change on change in greenhouse gas emissions, water footprint, and ecological footprint was ascribed to ultra-processed foods, while there was no change in these environmental indicators for unprocessed or minimally processed foods [da Silva et al. 2021]. 
There have been deliberate attempts by multinational corporations [e.g., WBCSD 2021] and their associated researchers to create confusion about the food category of ultra-processed foods, for instance by conflating it with 'processed foods' in general or by claiming that the category is too vague to be workable [Lawrence 2022]. The problem, however, should not be restricted to the simple degree of processing (in many cases, processing may be beneficial), so that a more comprehensive description is needed. The inferior quality of their ingredients is at least as important, if not more so, as ultra-processed foods are 'mostly constructed from a narrow range of cheap, extracted, refined and fractionated ingredients (for example, sugars, starches, vegetable oils, protein isolates, milk powders and mechanically separated meat), while lacking in whole, intact and fresh, ingredients' [Scrinis & Monteiro 2022]. As such, they are typified by a high degree of 'artificialization at the food level', based on the use of additives (e.g., colourants, flavours, artificial sweeteners, and emulsifiers). In addition to those technological criteria, ultra-processed foods are typically generated by transnational corporations 'to create branded, convenient (durable, ready-to-consume), attractive (hyper-palatable) and highly profitable (low-cost ingredients) food products often designed to displace all other food groups' [Monteiro et al. 20182019]. They 'bypass the body's satiety signals and elicit quasi-addictive behaviours' [Scrinis & Monteiro 2022]. As the social level, they tend to replace the rich experiences of shared traditional meals with a plethora of often individualized ready-made products, leading to both mindless eating and further atomization of society [Anastasiou et al. 2022]. Aggressive marketing, greenwashing, and nutri-washing, are used to 'drive up demand and create new food cultures, construct global supply chains to obtain cheap ingredients, and use extensive packaging that encourages mass production, long-distance transportation, and waste related to their consumption' [Seferidi et al. 2020]. As such, they reinforce the position of large corporations, to the detriment of smallholder production [Baker et al. 2020]. Within the food and drink portfolio of the world's largest food corporation, 70% of the items could be considered as junk food [Evans 2021Nestle 2021]. 

The share of ultra-processed foods in the diets of adults in high-income countries has been estimated at 17-39% of the total caloric intake [Anastasiou et al. 2022; Bertoni Maluf et al. 2022], and at 13-21% for Brazil [Nilson et al. 2022]. In the US, 71% of packaged foods are ultra-processed, i.e., 'industrial formulations made entirely or mostly from substances extracted from foods (oils, fats, sugar, starch & proteins)’ [Baldridge et al. 2019]. In the US, UK, and Australia, ultra-processed foods represent 70-80% of the diet in the top fifth of consumers of these products [Scrinis & Monteiro 2022]. Children in the Anglosphere now even obtain 55-65% of their caloric intake from ultra-processed foods, such as crisps, biscuits, juices and sodas, while the intake level in low- and middle-income countries is already at 18-35% [Khandpur et al. 2020]. Total energy consumed from ultra-processed foods by US youths (2-19 years) increased from 61% to 67% between 1999 and 2018 [Wang et al. 2021]. In France, intake is estimated at 35% for adults and 46% for children [Fardet et al. 2021]. The situation is expected to worsen globally due to aggressive marketing and the capturing and co-opting of policies, science, and civil society [Mialon & da Silva Gomes 2019; Moodie et al. 2021]. To make matters worse, they are disproportionally consumed by lower socioeconomic groups that already suffer from disbalanced nutrition [Baker et al. 2020].
Nutrient Profiling Systems (NPS) only seem to aggravate the situation, exaggerating the risks associated with ASFs and underestimating the risks associated with ultra-processed foods [Ortenzi et al. 2022]. It comes as no surprise that such nutrient-centric dietary models and Front-of-Pack labels (e.g., NutriScore or Health Stars) are usually embraced by food corporations [e.g., Nestlé 2020]. On the Spanish market, for instance, 1/4 and 1/2 products within the favourable NutriScore categories A and B, respectively, are ultra-processed foods [Romero Ferreiro et al. 2021]. Such models require small sacrifices but meanwhile associate the harms of the foods they produce with high energy density and elevated concentrations of specific nutrients (sodium, sugar, saturated fat, etc.), which can be conveniently addressed through what is the core expertise of such corporations: ultra-processing. Products are then reformulated to somewhat reduce the levels of some of these nutrients (e.g., with synthetic sweeteners, salt replacers, texturizers, flavouring agents), or by adding ingredients with a healthy aureole (e.g., fibre or vitamins). This says little about true improvement of the healthiness of a food. The adverse consequences of ultra-processed foods are generally independent of dietary quality or patterns, which undermines the idea that reformulation would mitigate against negative health outcomes [Dicken & Batterham 2022]. In some cases, such interventions may even be potentially harmful, for instance when adding artificial sweeteners [Dalenberg et al. 2020; Debras et al. 2022Suez et al. 2022], when using emulsifiers in fat-lowering formulations [Sandall et al. 2020; Viennois et al. 2020], or when generally restructuring the food matrix through ultra-processing [Fardet 2016]. 

In France, not only 2/3 of conventional industrial foods are to be categorized as ultra-processed, but also half of the products that are labelled as organic [Davidou et al. 2021]. Typically, they are based on refined oils, extracts, starches, and/or sugars. Similarly, the market for 'plant-based' mock ASFs [see elsewhere] has been embraced by large food multinationals, given that such foods are usually highly processed concoctions [Bohrer 2019], yet can be greenwashed based on narratives relating to 'planetary health' [see elsewhere]. In a French cohort study, vegetarians and vegans (especially those who started such diets more recently) had a higher intake of ultra-processed products than meat eaters, driven by a higher consumption of mock foods [Gehring et al. 2021]. 
Ways forward?

Future health policies should not only limit themselves to understanding  'the role of the various dietary dimensions that mediate health (i.e, nutrients, foods, and dietary patterns)' but also 'account for the role of social, commercial, and ecological determinants of health' [Scrinis 2020]. As an alternative to monolithic top-down approaches, proposing a narrow view on what may constitute a healthy diet [see elsewhere], a reappraisal of our various ancestral diets and culinary legacies may be considered as a more constructive way forward. This has the potential to provide a myriad of fallback options that allow for personal and cultural needs and preferences [Best & Ward 2020]. In contrast, foods that are typically associated with the historically recent 'Western diet' (dating back a mere 4-5 generations), warrant suspicion. This is the case for high intake of sugar [Avena et al. 2008; Yang et al. 2014], refined grains [Swaminathan et al. 2021], often as high-carb/high-fat concoctions with seed oils.
Efforts to correct public health will need to deal with those dietary factors that trigger a metabolic state of hyperinsulinemia, chronic inflammation, and abnormalities of the vascular endothelium. Based on strength of association and mechanistic insights, the latter responses may not only have to be considered as the most important markers for diseases of modernity, but also as potential causes of metabolic dysfunction [Kohrt et al. 1993; Bao et al. 1996; Wang et al. 2007; Rajendran et al. 2013; Chen et al. 2015; Tsoupras et al. 2018; Adeva-Andany et al. 2019]. In that respect, it is not fully understood to which degree specific foods negatively affect metabolic health in a clear and causal manner. However, it is known that the consumption of ultra-processed foods generally leads to higher energy intake levels and weight gain compared to an unprocessed diet [Hall et al. 2019], and there are increasing concerns about their constituents and biochemical make-up [e.g., Fardet 2016]. 

In fact, the harmful effects of Western foods may be less a matter of poor nutritional value than of the impact of ultra-processing as such [Bonaccio et al. 2022], largely through food matrix degradation [Fardet & Rock 2022], effects on the gut microbiome [Zinöcker & Lindseth 2018], and addictive eating [Gearhardt & Difeliceantonio 2022]. Consumption of ultra-processed foods can result in inflammatory responses ("fast food fever") [Myles, 2014; Hoffman 2022], reduced water intake [Galastri Baraldi et al. 2021], overeating due to soft textures [Forde et al. 2020] and altered glycemic responses [Fardet 2016], and harmful effects due to a higher intake of colourants, artificial sweeteners, flavours, emulsifiers, products from chemical hydrogenation, and various neo-formed substances [Dalenberg et al. 2020Sandall et al. 2020Viennois et al. 2020Debras et al. 2022Neumann & Fasshauer 2022Scrinis & Monteiro 2022Suez et al. 2022Vissers et al. 2022]. Harmful contaminants, e.g. endocrine-disrupting chemicals in the abundant packaging materials, could also play a role [cf. Diamanti-Kandarakis et al. 2009; Buckley et al. 2019]. For plant-based 'meat', for instance, a weakened gastrointestinal digestive function and lower digestibility has been found in mice, when compared to real meat [Xie et al. 2022].

In parallel to the avoidance of nutrient-poor and hyperpalatable foods, the concept of adequate essential nutrition serves as a meaningful foundation of public health, as protein and micronutrient deficiencies are still of major concern globally, including both the West and low- and middle-income countries [Bailey et al. 2015; Keats et al., 2019]. Adequate protein, vitamins, and mineral intake levels represent the true nutritional challenges for mid-century [Medek et al. 2017; Nelson et al., 2018]. Public health policies should take this unambiguous data as their main mission, rather than overemphasizing findings derived from nutritional epidemiology of chronic disease, and all of the problems that come with that [see elsewhere].

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