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my name is Jeidy Vallecillo and I am currently a senior attending Animo Inglewood Charter High School. My research question that I want to research about is ''the health risk of processed foods and why they showed be limited". The reason that I want to learn about this is because I want to know what we are putting in our bodies when we eat fast foods instead of a home cooked meal. And I want to inform others the dangerous of eating processed foods because we never know what it in them.

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Article 1: ''processed foods:nutrition, safety, and public health by national center for biotechnology information

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Article 1: ''processed foods:nutrition, safety, and public health by national center for biotechnology information

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this article talks about the different food systems that have led to the rapid evolution of food processing. It states that people are consuming these processed foods a lot more now since they are the easiest to get your hands on. But that consuming too much of this has led people to develop many diseases due to the high levels of salt, saturated and trans fat, and sugars. These processed foods led to many health complications like hypertension, cardiovascular diseases, and diabetes. The department of public health also recommends you to limit yourself into eating to much of processed foods and try eating more of a healthy diet to help improve in your health and nutrition.

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Processed Food: Nutrition, Safety, and Public Health

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Food processing comprises the activities involved during the transformation of raw materials from different origins (vegetable, animal) until a final product is achieved that is suitable for human consumption [1]. Food processing was traditionally developed with a focus on the long-time storage and transport of foods, using techniques such as cooking, curing, and smoking. However, the effective reduction in spoilage and pathogenic microorganisms achieved with processing techniques such as pasteurization and other heat treatment technologies has also allowed processed foods to become safer. Later development of food processing has also included strategies to increase the palatability and production of indulgent products [2].

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Article 2:" Ultra processed food exposure and adverse health outcomes" by The BMJ 

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Article 2:" Ultra processed food exposure and adverse health outcomes" by The BMJ 

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This article highlights the health risk that comes with consuming processed foods. When people consume too much processed foods it can led them to having many health complications down the line. like problems with their heart, diabetes, and it can also cause them to have mental health problems such as depression and anxiety. Studies have found that people who eat a lot of processed foods have a higher mortality rate and have identified over 30 health complications that it leds to people having. This article advises people to start looking at the amount of calories they are consuming from these processed foods and tells them to start making better choices for their body and their mental health.

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Objective To evaluate the existing meta-analytic evidence of associations between exposure to ultra-processed foods, as defined by the Nova food classification system, and adverse health outcomes.

Design Systematic umbrella review of existing meta-analyses.

Data sources MEDLINE, PsycINFO, Embase, and the Cochrane Database of Systematic Reviews, as well as manual searches of reference lists from 2009 to June 2023.

Eligibility criteria for selecting studies Systematic reviews and meta-analyses of cohort, case-control, and/or cross sectional study designs. To evaluate the credibility of evidence, pre-specified evidence classification criteria were applied, graded as convincing ("class I"), highly suggestive ("class II"), suggestive ("class III"), weak ("class IV"), or no evidence ("class V"). The quality of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework, categorised as "high," "moderate," "low," or "very low" quality.

Results The search identified 45 unique pooled analyses, including 13 dose-response associations and 32 non-dose-response associations (n=9 888 373). Overall, direct associations were found between exposure to ultra-processed foods and 32 (71%) health parameters spanning mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. Based on the pre-specified evidence classification criteria, convincing evidence (class I) supported direct associations between greater ultra-processed food exposure and higher risks of incident cardiovascular disease related mortality (risk ratio 1.50, 95% confidence interval 1.37 to 1.63; GRADE=very low) and type 2 diabetes (dose-response risk ratio 1.12, 1.11 to 1.13; moderate), as well as higher risks of prevalent anxiety outcomes (odds ratio 1.48, 1.37 to 1.59; low) and combined common mental disorder outcomes (odds ratio 1.53, 1.43 to 1.63; low). Highly suggestive (class II) evidence indicated that greater exposure to ultra-processed foods was directly associated with higher risks of incident all cause mortality (risk ratio 1.21, 1.15 to 1.27; low), heart disease related mortality (hazard ratio 1.66, 1.51 to 1.84; low), type 2 diabetes (odds ratio 1.40, 1.23 to 1.59; very low), and depressive outcomes (hazard ratio 1.22, 1.16 to 1.28; low), together with higher risks of prevalent adverse sleep related outcomes (odds ratio 1.41, 1.24 to 1.61; low), wheezing (risk ratio 1.40, 1.27 to 1.55; low), and obesity (odds ratio 1.55, 1.36 to 1.77; low). Of the remaining 34 pooled analyses, 21 were graded as suggestive or weak strength (class III-IV) and 13 were graded as no evidence (class V). Overall, using the GRADE framework, 22 pooled analyses were rated as low quality, with 19 rated as very low quality and four rated as moderate quality.

Conclusions Greater exposure to ultra-processed food was associated with a higher risk of adverse health outcomes, especially cardiometabolic, common mental disorder, and mortality outcomes. These findings provide a rationale to develop and evaluate the effectiveness of using population based and public health measures to target and reduce dietary exposure to ultra-processed foods for improved human health. They also inform and provide support for urgent mechanistic research.

Systematic review registration PROSPERO CRD42023412732.

Inclusion criteria and searches

We found no existing pooled analyses of randomised controlled trials during the pilot phase of this review. Consequently, we refined our search approach and scope to focus on observational epidemiological studies. Thus, we outlined inclusion criteria in accordance with the population, exposure, comparisons, outcomes, and study design (PECOS) reporting structure. 22 Eligible meta-analysis studies comprised human populations across the life course, irrespective of health status (population). We also considered meta-analysis studies that examined associations of dietary intake of ultra-processed foods, as defined by the Nova food classification system (exposure), comparing dose-response (continuous exposure) and/or non-dose-response (categorical only or categorical and continuous exposure) associations of dietary intake of ultra-processed foods (comparison), with any adverse health endpoint (outcome). Included in our review were observational epidemiological study designs (for example, prospective cohort, case-control, and/or cross sectional) that pooled categorical or continuous outcome data by using meta-analysis (study design).

The lead author (MML) did a systematic search across MEDLINE, PsycINFO, Embase, and the Cochrane databases for studies spanning the period from 2009 to June 2023 (last update). The year 2009 aligns with the initial publication of the details and principles of the Nova food classification system, which introduced the concept of ultra-processed foods. 23 We applied no language limitations.

To identify relevant meta-analysis studies, we used key search terms and variations of text words related to ultra-processed food or Nova and meta-analysis study design: ("ultra-processed food" OR UPF OR "Nova food classification system") AND ("meta-analysis" OR "systematic review"). The specific search strings for each database can be found in supplementary table A. We used Covidence systematic review software to do duplicate primary screening based on titles and abstracts (MML and EG) and duplicate secondary screening based on full text articles (MML and WM). We screened references cited within the eligible meta-analysis studies to identify any additional relevant meta-analysis studies (EG). Any disagreements between authors conducting eligibility screening were resolved through consensus. We included the most recent and/or largest meta-analysis study when multiple pooled analyses were available for the same adverse health outcome. This is consistent with the methods used in previous umbrella reviews. 24 25 26 In cases in which the most recent meta-analysis study examined non-dose-response and dose-response exposure to ultra-processed foods, we included both meta-analysed effect estimates.

Data extraction

We extracted characteristics of the original research articles included in the retained meta-analysis studies in duplicate by using a pre-piloted custom Microsoft Excel spreadsheet (MML, EG, SD, DNA, AJM, and SG). These data included details such as the outcome, spanning health domains such as mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. In addition, the data extraction encompassed details on the level of exposure comparison, distinguishing between dose-response (involving each additional serving per day or a 10% increment) and non-dose-response (encompassing categories such as high versus low, daily consumers versus not daily consumers, and frequent consumption versus no frequent consumption, as well as combinations of categories with continuous exposure including 1% or 10% increments). It also covered the total number of studies (original research articles), participants, and cases included in the pooled analysis. The extraction included effect estimates with 95% confidence intervals from both separate original research articles and those pooled from the meta-analysis studies, as well as the pooled effect size metric (hazard ratios, odds ratios, and risk ratios). Furthermore, we extracted details about the meta-analysis study, including the first author's name, publication year, original research study design, and competing interests and funding disclosures of meta-analysis study authors. We prioritised pooled estimates with the largest number of prospective cohorts, given that prospective studies guarantee temporality in epidemiological associations and strongly limit reverse causality bias. 27 Additionally, we extracted pooled estimates for related health outcomes that were meta-analysed together and separately (for example, metabolic syndrome and its individual components including low high density lipoprotein cholesterol and hypertriglyceridaemia). If information was missing or unclear in the meta-analysis studies, we obtained the data from the original research articles or directly requested it from the corresponding author(s) of those meta-analysis studies. If discrepancies existed between the data reported in the original research articles and the meta-analyses, we prioritised extracting data from the original research article.

Data analysis

Operating according to previously published methods and guidance, 28 29 we used a random effects meta-analysis model to reanalyse the effect estimates for each outcome. As part of our main reanalysis, we took the following steps: entry of separate effect estimates and the total number of participants and cases from the original research articles; recalculation of the pooled effect estimates using the original metric used by the meta-analysis study authors (hazard ratio, odds ratio, and risk ratio with 95% confidence intervals); recalculation of the P value; and recalculation of the between study heterogeneity using the I ² statistic. We also calculated 95% prediction intervals and assessed excess significance bias, small study effects, and the largest study significance (detailed below) as part of our reanalysis.

Terminology

We used the terms "direct" and "inverse" to describe the direction of observed associations between ultra-processed food exposure and adverse health outcomes, with "direct" referring to a higher risk associated with greater exposure and "inverse" referring to a lower risk. We chose these terms over "positive" or "negative" associations to avoid ambiguous interpretations.

Credibility and quality assessment of evidence and methods

Patient and public involvement

The study and manuscript development did not involve patients or the public owing to the absence of funding for this research.

Study characteristics

The range of adverse health outcomes reviewed across the 45 discrete pooled analyses included mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. All meta-analysis studies were published in the past three years, and none was funded by a company involved in the production of ultra-processed foods. The number of original research articles included in the pooled analyses was four on average and ranged from two to nine. The sum total number of participants included across the pooled analyses was 9 888 373 (ranging from 1113 17 to 962 593 48). Supplementary table F details the characteristics of the original research articles included in each of the pooled analyses, such as study design, population, and exposure measurement. Pooled analyses included estimates from original research articles that comprised either prospective cohorts (n=18), mixed study designs (n=15), or cross sectional designs (n=12). Most pooled analyses included adults as the main population, except for five, which included children and adolescents in examining mental health outcomes and respiratory conditions. 18 49 50 In 87% of pooled analyses, estimates of exposure to ultra-processed food were obtained from a combination of tools, including food frequency questionnaires, 24 hour dietary recalls, and dietary history, as reported in the meta-analysis studies. Six pooled analyses, pertaining to heart disease related mortality, 51 cancer related mortality, 51 respiratory conditions, 18 and non-alcohol fatty liver disease, 46 included estimates of exposure from food frequency questionnaires alone.

Each of the meta-analysis studies examined the non-dose-response associations between exposure to ultra-processed foods and adverse health outcomes. However, an additional analysis involving dose-response modelling of the ultra-processed food exposure variable was conducted in 13 pooled analyses across five meta-analysis studies. 40 42 43 47 51 The outcomes considered using this approach included all cause mortality and cardiovascular disease events, such as cardiovascular disease morbidity and mortality, associated with each increase in daily servings of ultra-processed food. 43 One meta-analysis study specifically pooled heart disease related deaths, such as ischaemic heart disease related mortality and cerebrovascular disease related mortality, with each 10% increase in total ultra-processed food exposure. 51 Additionally, associations for other outcomes, such as abdominal obesity, 42 overweight and obesity, 42 type 2 diabetes, 47 and breast, colorectal, and prostate cancers, 40 were modelled on the basis of each 10% increase in ultra-processed food exposure.

Results of syntheses

Figure 2 and figure 3 show the direction and sizes of effect estimates using equivalent odds ratios for both the non-dose-response and dose-response relations between exposure to ultra-processed foods and each adverse health outcome, respectively.

On the basis of the random effects model, 32 (71%) distinct pooled analyses showed direct associations between greater ultra-processed food exposure and a higher risk of adverse health outcomes at the significance level of P≤0.05 (supplementary table G). Additionally, of these combined analyses, 11 (34%) showed continued statistical significance when a more stringent threshold was applied (P<1×10 −6) (data not shown). These included the incidence of all cause mortality, 43 cardiovascular disease related mortality, 43 heart disease related mortality, 51 type 2 diabetes (dose-response and non-dose-response), 47 and depressive outcomes, 50 as well as the prevalence of anxiety and combined common mental disorder outcomes, 50 adverse sleep related outcomes, 49 and wheezing. 18

We found evidence of moderate (I ²=50-74.9%) to high (I ²≥75%) heterogeneity in 13 (29%) and eight (18%) of the 45 discrete pooled analyses, respectively (supplementary table G). The 95% prediction intervals were statistically significant for seven (25%) of the 28 pooled analyses with three or more original research articles (supplementary table G), including direct associations of greater ultra-processed food exposure with higher risks of all cause mortality, 43 cardiovascular disease related mortality, 43 common mental disorder outcomes, 50 Crohn's disease, 48 obesity, 42 and type 2 diabetes (dose-response). 47 Additionally, we found evidence of excess significance bias in nine (32%) of the 28 pooled analyses with three or more original research articles listed in supplementary table G. This bias was evident in associations between higher ultra-processed food exposure and all cause mortality (dose-response and non-dose-response), 43 hypertension, 44 abdominal obesity, 42 metabolic syndrome, 45 non-alcoholic fatty liver disease, 46 obesity (dose-response and non-dose-response), 42 and type 2 diabetes. 47 Small study effects were evident in five (18%) of the 28 pooled analyses with three or more original research articles, as indicated in supplementary table G. We observed these effects in associations between higher ultra-processed food exposure and all cause mortality (dose-response and non-dose-response), 43 breast cancer, 40 metabolic syndrome, 45 and obesity (dose-response). 42

Effect estimates from the largest original research article were nominally statistically significant for 28 (62%) pooled analyses (supplementary table G) and pertained to associations of greater ultra-processed food exposure with higher risks of all cause mortality (dose-response and non-dose-response), 43 cardiovascular disease related mortality (dose-response and non-dose-response), 43 heart disease related mortality (dose-response and non-dose-response), 51 central nervous system tumours, 40 adverse sleep outcomes, 49 common mental disorder outcomes, 50 asthma, 18 wheezing, 18 cardiovascular disease events (dose-response and non-dose-response), 43 low high density lipoprotein concentrations, 17 abdominal obesity (dose-response and non-dose-response), 42 hyperglycaemia, 17 metabolic syndrome, 45 non-alcoholic fatty liver disease, 46 obesity and overweight (dose-response and non-dose-response), 42 and type 2 diabetes (dose-response and non-dose-response). 47

Credibility and GRADE quality assessments

Quality assessment of individual meta-analysis studies using AMSTAR 2 tool

Although all of the authors of the meta-analysis studies used satisfactory literature search techniques (AMSTAR critical item 4) and accounted for the potential risk of bias in original research articles when interpreting and discussing their results (AMSTAR critical item 9), we considered the overall confidence in the results of seven meta-analysis studies to be low owing to lack of clarity as to whether the review methods were established before the conduct of the review (AMSTAR critical item 2) (supplementary table E). 17 40 41 42 44 45 51 Based on non-critical items, the confidence in the results of all meta-analysis studies was assessed as moderate. Notably, the most considerable limitations, for which all meta-analysis studies scored zero, were related to the review authors' failure to provide an explanation for their selection of study designs for inclusion in the review (AMSTAR item 3) and their omission of information on funding sources for the studies included in the review (AMSTAR item 10). 39

Principal findings

Our umbrella review provides a comprehensive overview and evaluation of the evidence for associations between dietary exposure to ultra-processed foods and various adverse health outcomes. Our review included 45 distinct pooled analyses, encompassing a total population of 9 888 373 participants and spanning seven health parameters related to mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. Across the pooled analyses, greater exposure to ultra-processed foods, whether measured as higher versus lower consumption, additional servings per day, or a 10% increment, was consistently associated with a higher risk of adverse health outcomes (71% of outcomes).

Considering the evidence classification criteria assessments, we graded 9% of the pooled analyses as providing convincing evidence (class I), including those measuring risks of cardiovascular disease related mortality, common mental disorder outcomes, and type 2 diabetes (dose-response) ( fig 4). We graded 16% of pooled analyses (all non-dose-response) as providing highly suggestive evidence (class II), encompassing risks of all cause mortality, heart disease related mortality, adverse sleep related outcomes, wheezing, obesity, and type 2 diabetes. We graded approximately 29% of the pooled analyses as providing suggestive evidence (class III), covering a range of conditions from risks of abdominal obesity to overweight, with 18% graded as weak evidence (class IV), encompassing outcomes such as risks of colorectal cancer and overweight and obesity (evaluated together as single outcome). We graded the remaining 29% of pooled analyses as lacking evidence (class V), spanning conditions from asthma to ulcerative colitis. As previously noted, moderate to high levels of heterogeneity were observed across 45% of pooled analyses. Using GRADE assessments, which initially assign observational epidemiological studies as "low" quality evidence, 38 approximately 29% of the pooled analyses remained unchanged, indicating that no additional concerns were identified based on GRADE criteria, with a further 9% upgraded to a "moderate" rating owing to a dose-response gradient ( fig 4). Dose-response pooled analyses upgraded to "moderate" quality evidence related to all cause mortality, prostate cancer, overweight and obesity (assessed together), and type 2 diabetes. Associations were downgraded largely owing to inconsistencies or heterogeneity in the effect estimates found across the original research articles or owing to imprecision (that is, wide confidence intervals).

The heterogeneity and imprecision noted across several of the pooled analyses, as shown by both the evidence classification criteria and GRADE assessments, may be partly explained by the treatment of different effect estimates derived from original research articles (hazard ratios, odds ratios, and risk ratios) as approximately equivalent in various meta-analysis studies. 40 42 43 45 47 Such variations in scales may introduce heterogeneity and reduce precision in pooled estimates, even if the original research articles share conceptual similarities in exposures and outcomes. 52 Moreover, the synthesis of results based on three or fewer original research articles may contribute to heterogeneity and imprecision, 53 affecting outcomes assessed in our review such as certain cancers, asthma, and intermediate cardiometabolic risk factors. Although the pooled analyses relating to these outcomes were rated as having no or low quality evidence based on the evidence classification criteria and GRADE assessments, this does not necessarily negate the potential for an association, particularly as more data may become available in the future. Furthermore, considering the overall body of evidence, 93% of pooled analyses indicated point estimates in the same direction (greater than one) ( fig 2 and fig 3). The presence of 95% confidence intervals that included the null value in 24% of these pooled analyses signifies some uncertainty in the data, which may be partly due to insufficient sample size, particularly in analyses with a small number of original research articles and results showing wide confidence intervals. 54 This underscores the importance of conducting additional original research and subsequent meta-analyses in the respective disease areas.

Potential mechanisms of action

Understanding the aspects of ultra-processed dietary patterns that link them to poor health and early death requires more research. 12 55 The available evidence indicates that ultra-processed foods differ from unprocessed and minimally processed foods in several aspects, potentially explaining their plausible links with adverse health outcomes. These differences include poorer nutrient profiles, the displacement of non-ultra-processed foods from the diet, and alterations to the physical structure of consumables through intensive ultra-processing. More specifically, diets rich in ultra-processed foods are associated with markers of poor diet quality, with higher levels of added sugars, saturated fat, and sodium; higher energy density; and lower fibre, protein, and micronutrients. 6 56 Ultra-processed foods displace more nutritious foods in diets, such as fruits, vegetables, legumes, nuts, and seeds, 6 resulting in reduced intakes of beneficial bioactive compounds that are present in these foods, including polyphenols or phytoestrogens such as enterodiol. 57 58 Such nutrient-poor dietary profiles have been implicated in the prevalence and incidence of chronic diseases through various pathways, including inflammatory mechanisms. 13 14 16

The adverse health outcomes associated with ultra-processed foods may not be fully explained by their nutrient composition and energy density alone but also by physical and chemical properties associated with industrial processing methods, ingredients, and by-products. Firstly, alterations in the food matrix during intensive processing, also known as dietary reconstitution, may affect digestion, nutrient absorption, and feelings of satiety. 59 Secondly, emerging evidence in humans shows links between exposure to additives, including non-sugar sweeteners, emulsifiers, colorants, and nitrates/nitrites, and detrimental health outcomes. 60 61 62 63 64 65 A recent review of experimental research found that ultra-processed weight loss formulations composed of ostensibly balanced nutrient profiles but containing different additives, including non-sugar sweeteners, may have adverse effects on the gut microbiome-which is thought to play an important function in many of the diseases studied here-and related inflammation. 66 The World Health Organization recently warned against the ongoing use of sugar substitutes for weight control or non-communicable illnesses, 67 and, according to its new report, non-sugar sweeteners may also elevate the risk of cardiometabolic diseases and mortality. 67 In addition, citing "limited evidence" in humans, the International Agency for Research on Cancer recently classified the non-sugar sweetener aspartame as "possibly carcinogenic to humans" (group 2B). 68 A growing body of data shows instances of exposure to combinations of multiple additives, which may have potential "cocktail effects" with greater implications for human health than exposure to a single additive. 69 Thirdly, the intensive industrial processing of food may produce potentially harmful substances that have been linked to higher risks of chronic inflammatory diseases, including acrolein, acrylamide, advanced glycation end products, furans, heterocyclic amines, industrial trans-fatty acids, and polycyclic aromatic hydrocarbons. 12 70 Finally, ultra-processed foods can contain contaminants with health implications that migrate from packaging materials, such as bisphenols, microplastics, mineral oils, and phthalates. 12

Experimental evidence indicates a robust causal relation between ultra-processed diets and increased energy intake and weight gain (approximately 500 kcal (2000 kJ) per day and 0.9 kg during the ultra-processed diet). 71 Other experimental evidence has also shown that using the Nova food classification system for nutritional counselling and adjunctive to physical activity effectively prevents excessive weight gain in pregnant women with high body mass index. 72 The mechanisms contributing to the excess consumption effect of diets rich in ultra-processed foods seem to involve the nature of the energy source-specifically, whether it comes from solid foods or beverages. 71 Furthermore, the greater energy density, faster eating rate, and hyper-palatability attributed to ultra-processed foods are regarded as important factors influencing this effect. 73 The extensive marketing strategies used by ultra-processed food manufacturers, which involve visually captivating packaging with eye catching designs and health related assertions, have also been suggested as a potential contributing factor to excessive consumption. 74

Strengths and limitations of study and comparisons with other studies

Recognising the importance of establishing causality, we acknowledge that further randomised controlled trials are needed, particularly for outcomes for which strong meta-analytic epidemiological evidence exists, such as cardiometabolic disorder and common mental disorder outcomes. However, only short term trials testing the effect of ultra-processed food exposure on intermediate outcomes (such as alterations to body weight, insulin resistance, depressive and anxiety symptoms, gut microbiome, and inflammation) would be feasible. Setting up trials testing the effect of long term exposure to interventions with suspected deleterious properties (that is, diets rich in ultra-processed foods) on hard disease endpoints such as cardiovascular disease or cancer will not be possible, for obvious ethical reasons. In this context, our umbrella review of extant observational epidemiological research provides complementary insights and has implications for public health, especially in light of the current debate about tackling (or not) exposure to ultra-processed foods through public health measures. It stands as the first comprehensive synthesis of current evidence derived from meta-analyses of epidemiological studies, exploring the associations between dietary exposure to ultra-processed foods and various adverse health outcomes. We used rigorous systematic methods, including duplicate study selection and data extraction, alongside the evidence classification criteria and GRADE assessments, to evaluate the credibility and quality of the pooled analyses. An additional strength of our review is that we reviewed the competing interests and funding disclosures of the included meta-analysis studies, with none being funded by companies involved in the production of ultra-processed foods.

One limitation of umbrella reviews in general is their high level overview. As a result, we did not consider specific confounder or mediator adjustments and sensitivity analyses as part of our review, but these may be important factors, particularly in the context of ultra-processed foods. The consumption of ultra-processed foods is linked to a lower intake of unprocessed or minimally processed fruits, vegetables, legumes, and seafood. 6 This raises the question of whether the associations between exposure to ultra-processed foods and poorer health are due to an overall unhealthy dietary pattern. Although such analyses were beyond the scope of our review, which focused on evaluating overall associations between exposure to ultra-processed foods and adverse health outcomes, we note that a recent meta-analysis found that adjusting for diet quality or patterns does not change the consistent evidence for direct associations between greater ultra-processed food exposure and a higher risk of adverse health outcomes (as per inference criteria and sizes of effect estimates). 75 Furthermore, the inclusion of original research articles with different methods of assessing ultra-processed food intake, such as dietary history, food frequency questionnaires, food records, and 24 hour dietary recalls, introduces an inevitable measurement bias regardless of whether validated methods were applied. 76 Considering that observational epidemiological studies have inherent limitations is also important, with residual confounding being perhaps most pertinent. 77 However, the consistent findings across most pooled analyses in our review support the notion that residual confounding does not fully explain the observed associations.

Although our umbrella review provides a systematic synthesis of the role of ultra-processed dietary patterns in chronic disease outcomes, a related consideration is the possible heterogeneity of associations between subgroups and subcategories of ultra-processed foods and chronic disease outcomes. A meta-analysis by Chen and colleagues (2023), included in our review, established a clear link between overall consumption of ultra-processed foods and a higher risk of type 2 diabetes, consistently observed across multiple cohorts. 47 However, while certain subcategories of ultra-processed foods further showed higher risk, others were inversely associated, such as ultra-processed cereals, dark/wholegrain bread, packaged sweet and savoury snacks, fruit based products and yoghurt, and dairy based desserts. 47 These findings underscore the complexity of the relation between ultra-processed foods and adverse health. Nevertheless, although some subcategories of ultra-processed items may have better nutrient and ingredient profiles, the overall consumption of ultra-processed foods remains consistently associated with a higher risk of chronic diseases, as evidenced by our review. Some people have argued that understanding the differences within subcategories of ultra-processed foods may aid consumers in adopting a healthier dietary pattern compared with maximally reducing their consumption on the whole. 78 However, others propose that the focus should be on the overall quality of the diet, including all ultra-processed foods, and its link to higher disease risk, rather than specific subcategories or individual products. 79

When considering the above and examining subcategories of ultra-processed foods, composite interactions between various consumables within broader dietary patterns are unaccounted for. This limitation may partially account for differences in the strength of evidence observed in our review compared with another recent umbrella review focusing on dietary sugar consumption, including sugar sweetened beverages, a commonly consumed subcategory of ultra-processed foods. 25 That review found no convincing (class I) evidence for adverse health outcomes linked to dietary sugar or sugar sweetened beverage consumption. 25 In contrast, our umbrella review shows compelling evidence (class I) that supports direct associations between greater dietary exposure to ultra-processed foods and higher risks of adverse health outcomes spanning cardiometabolic diseases, common mental disorders, and mortality. These findings support recommendations to consider overall diet quality in nutritional epidemiology, 79 and they suggest that higher consumption of ultra-processed foods within broader dietary patterns may have synergistic or compounded consequences compared with lower intakes, as hypothesised elsewhere. 12 13 14 15

Policy implications

Organisations such as the American Heart Association have cautiously advised people to choose unprocessed and minimally processed foods over ultra-processed foods, noting the absence of a widely accepted definition for ultra-processed foods. 80 Although various food classification systems have been developed to classify foods on the basis of processing related criteria, 81 82 83 84 85 the most commonly used classification system worldwide is the Nova food classification system. 86 Furthermore, Nova has received recognition from authoritative reports by the Food and Agricultural Organisation of the United Nations and the Pan American Health Organization of the WHO. 87 88 89 90 91 A recent statement from the UK's Scientific Advisory Committee on Nutrition (SACN) evaluated the Nova classification system among others and concluded that Nova is the only suitable classification for potential use in the country. 92 However, SACN expressed concerns about various key points. For example, it highlighted that the available studies applying the Nova system are primarily epidemiological in nature and may lack adequate consideration of confounding factors or covariates 92. Criticisms of Nova as a classification system also exist, with concerns raised about its possible imprecision and inconsistency among evaluators. 93 94 95 96 In contrast, more recent assessments show acceptable construct validity and strong agreement among coders, 97 98 with the definitions and examples provided by the Nova system deemed adequate in classifying more than 70% of the food items reported in food frequency questionnaires from various cohorts from the US, 99 as well as more than 90% of the food items reported in 24 hour dietary recalls from participants in a national Brazilian dietary survey. 100 Recent efforts including best practice guidelines have further focused on improving the efficiency and transparency of the categorisation process for Nova food groups, which ultimately aim to enhance the accuracy of effect estimates. 101

Public health measures promoting a reduction or avoidance of ultra-processed products have already been implemented most comprehensively in Latin American countries. These strategies include octagonal front-of-pack warning labels, taxes on sugar sweetened beverages and ultra-processed foods, marketing restrictions, and bans in schools. 102 103 104 Since the introduction of the recommendation to avoid ultra-processed foods in the 2014 Dietary Guidelines for the Brazilian Population, 105 seven additional countries have adopted the term and similar recommendations. 106 Furthermore, similar strategies for paediatric development and prevention of liver disease have also been recommended by the UK's First Steps Nutrition Trust and the European Association for the Study of the Liver-Lancet Commission, respectively. 107 108 We also note that WHO and the International Agency for Research on Cancer endorse public health strategies to limit the intake of components commonly present in ultra-processed foods, including high levels of added sugar and non-sugar sweeteners. 67 68 109 Importantly, sustained progress in implementing these strategies and the exploration of novel approaches mean that stakeholders need to be responsive and sensitive to factors that influence access to fresh produce and food choices, including the relatively greater time, effort, and (in some contexts) cost of preparing non-ultra-processed food. 95

Conclusions

This umbrella review reports a higher risk of adverse health outcomes associated with ultra-processed food exposure. The strongest available evidence pertained to direct associations between greater exposure to ultra-processed foods and higher risks of all cause mortality, cardiovascular disease related mortality, common mental disorder outcomes, overweight and obesity, and type 2 diabetes. Evidence for the associations of ultra-processed food exposure with asthma, gastrointestinal health, some cancers, and intermediate cardiometabolic risk factors remains limited and warrants further investigation. Coupled with existing population based strategies, we recommend urgent mechanistic research and the development and evaluation of comprehensive population based and public health strategies, including government led policy frameworks and dietary guidelines, aimed at targeting and reducing dietary exposure to ultra-processed foods for improved human health.

Ethical approval

Not required.

# data[].attributes.attachment_link.title
Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses

# data[].attributes.attachment_link.description
Objective To evaluate the existing meta-analytic evidence of associations between exposure to ultra-processed foods, as defined by the Nova food classification system, and adverse health outcomes. Design Systematic umbrella review of existing meta-analyses. Data sources MEDLINE, PsycINFO, Embase, and the Cochrane Database of Systematic Reviews, as well as manual searches of reference lists from 2009 to June 2023.

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blog post 1: processed foods are also recognized for containing substances of deliberate use in food production, such as pesticides and additives

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blog post 1: processed foods are also recognized for containing substances of deliberate use in food production, such as pesticides and additives

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According to the article it made a claim that processed foods contain many substances. And in those substances it said that pesticides and additive were just some of those. And after reading that I honestly feel that eating processed foods is nasty. not only because sometimes you don't even know if the work place is clean but you don't even know what is being put inside your food. I think that people should really take the time to buy and cook their foods at home because at least there you know what its being made with and you know that everything is clean well.

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Blog post 2: current pandemic of obesity and other diseases related to the populations eating habits pose a serious threat to future well being and economics prosperity worldwide

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Blog post 2: current pandemic of obesity and other diseases related to the populations eating habits pose a serious threat to future well being and economics prosperity worldwide

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when reading this article it made many claims that eating processed foods may bring you many serious diseases. And many of those diseases would be obesity, heart problems, diabetes and etc. and I think that people should really be careful on what they are consuming and hoe much of it they are eating. because I think that if you eat lets say in n out once a week its fine but there are many people that eat processed foods everyday and that's when it starts to become a problems. because not only are they just eating fatty foods but they aren't doing anything to help prevent these diseases. And eventually these diseases may led to taking peoples lives because they never cared to put their health first.

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Blog post 3: greater exposure to ultra-processed food is associated with higher risk of adverse health outcomes especially with mental health and mortality outcomes

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Blog post 3: greater exposure to ultra-processed food is associated with higher risk of adverse health outcomes especially with mental health and mortality outcomes

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This article states that while eating processed foods sounds and taste good it can bring people mental and health complications. it can cause Cardiometabolic conditions like diseases of obesity, diabetes and heart diseases. while also giving people mental heath disorders like depression and anxiety. It also increases the mortality rates in people that's why there's a high number of people dying now and days because almost all of them are related to them not taking care themselves.

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Blog post 4: public health measures to target and reduce dietary exposure to ultra-processed foods for improved human health

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Blog post 4: public health measures to target and reduce dietary exposure to ultra-processed foods for improved human health

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this quote is basically explaining that people need to take action in helping with limiting the risk of people catching deadly diseases from eating processed foods. the article states that the government and health organizations should make strategies to help reduce their consumptions in these type of foods. Those possible strategies should be having stricter food regulations, better Nutritional labeling, or just by simply promoting ways healthier alternatives to people. The article states that by them doing these things it should really help improve with the mortality rates and with people not having to deal with many of those deadly diseases.

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public health measures on exposure on processed foods

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a new skill that I was able to learn from this project was learning how to read an article and make annotations. and also learning how to summarize the article in a few words and just getting the main ideas. this can be applied in future projects by reading thoroughly . I learned that processed foods can lead to multiple health problems but they can also lead to people have mental health issues.