Redefining healthy diets?

In the US, only 12% of the adult population are in  a state of optimal metabolic health [Araújo et al. 2019]. 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]. In Ireland, >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]. 
 
Moreover, '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], 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], 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 lead to overly restrictive diets, especially when co-occurring with food allergies that require their own exclusionary measures [Protudjer & Mikkelsen 2020]. Moreover, concern has been raised related to elevated intakes of some plants (or algae), and their derived products, without the proper culinary treatments or context (e.g., for nuts or legumes). 
 
In some cases, this could lead to exaggerated intakes of cariogenic sugars [Weerasinghe 2021], mycotoxins [Arroyo-Manzanares et al. 2019; Eskola et al., 2020; De Colli et al. 2021], toxic chemicals and heavy metals [Kumar & Sharma 2021; Vogel et al. 2021], 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; Bressan & 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 [Abrams & Gerstner 2015], 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], and acrylamide [Amrein et al. 2005; Schlörmann et al., 2015].
 
Some of these concerns are more worrying than others, which are based on isolated studies or weak evidence. Once more, just as is the case for ASFs, 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].
 
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]. This is being promoted and amplified by food corporations that consistently benefit from a methodology that favors 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]. 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].
 
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. 2018]. 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]. 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]. Children in the Anglosphere now 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].
 
It comes as no surprise that nutrient-centric dietary models and Front-of-Pack labels (e.g., NutriScore or Health Stars) are usually embraced by food corporations. 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, flavoring agents), or by adding ingredients with a healthy aureole (e.g., fiber). 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 labeled 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, yet can be greenwashed based on narratives relating to 'planetary health' [see elsewhere].
 
Ways forward?

Future health policies should not only limit themselves to understanding  'the role of the various dietary dimensions that mediate health (ie, 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., Viennois et al. 2020].

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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