Introduction
Pork is a red meat that is consumed frequently across the globe. Cross-sectional analyses of the 2006–2016 United States National Health and Nutrition Examination Survey data sets showed that approximately 19.4%, 16.5%, and 16.1% of adults in the U.S. consume pork, fresh pork, and fresh lean pork, respectively (An et al., 2019). Both pork tenderloin and pork sirloin meet the American Heart Association (2021) Heart Health Checkmark criteria, which means that they contain ≤5 g of fat, ≤2 g of saturated fat, and ≤480 mg of sodium per label serving. A 4-ounce raw, boneless, lean pork chop (top loin) provides approximately 144 kcal of energy, 25.3 g of protein, 3.86 g of fat (1.36 g of saturated fat), and substantial amounts of iron, zinc, selenium, magnesium, phosphorus, potassium, thiamin, riboflavin, niacin, pantothenic acid, choline, and vitamins B6 and B12 to the diet (FoodData Central identifier 168251) (U.S. Department of Agriculture Agricultural Research Service, 2019). Increased lean pork rather than total pork intake was recently associated with improved nutrient intakes of protein, magnesium, potassium, selenium, zinc, phosphorus, thiamin, riboflavin, niacin, and vitamin B6 and with lesser increases in daily total energy, saturated fat, and sodium intakes among U.S. adults (An et al., 2019). Aside from the effects of pork on nutrient intakes, there is a plethora of scientific evidence regarding the effects of pork intake on human nutrition and health. Recent randomized controlled trials have shown that the addition of lean pork to both the Mediterranean diet and the Dietary Approaches to Stop Hypertension diet does not affect the demonstrated benefits of these diets on established biomarkers of cardiovascular disease (Sayer et al., 2015; Wade et al., 2019). The addition of an average of 3 servings of lean pork to a Mediterranean-style diet pattern in older adults has been suggested to improve cognitive outcomes (Wade et al., 2019). However, evidence on the health effects of pork is heterogenous and in many cases conflicting.
The use of systematic methodologies for reviewing evidence continues to increase in the nutrition science field. Scoping reviews (otherwise known as evidence mapping) are a relatively new and important tool used to systematically characterize the range of research activity in broad topic areas and are used to guide research priority setting and whether evidence is sufficient for systematic reviews and meta-analyses. They are less exhaustive but utilize rigorous systematic and replicable methodologies that allow for a better understanding of the extent and distribution of evidence in a broad area, highlighting where evidence and evidence gaps exist (Hetrick et al., 2010; Althuis and Weed, 2013; Wang et al., 2016). Although scoping reviews are conducted for different purposes compared with systematic reviews, they are still rigorous and transparent in their methodology to ensure trustworthy results (Munn et al., 2018). Purposes for conducting a scoping review may include the following: (1) to identify the types of available evidence in a given field, (2) to clarify concepts and definitions in the scientific literature, (3) to examine how research is conducted on a certain topic or in a certain field, (4) to identify key characteristics or factors related to a concept, (5) to serve as a precursor to systematic review, and/or (6) to pinpoint and analyze knowledge gaps (Arksey and O’Malley, 2005; Anderson et al., 2008; Levac et al., 2010; Peters et al., 2015; Wang et al., 2016; Munn et al., 2018). Scoping reviews are also extremely useful in helping groups prioritize research agendas, particularly when resources are limited and a plethora of heterogenous evidence exists.
Therefore, our research objective was to conduct a scoping review of clinical and population-based studies assessing the effects of pork consumption in relation to human nutrition and health.
Materials and Methods
We created a literature database and performed evidence mapping following methods described elsewhere (Wang et al., 2016). We reported the results according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (Tricco et al., 2018).
Definitions of fresh, processed, and mixed pork
The American Meat Science Association (AMSA) Lexicon for the standardization of various terms used in meat sciences was adopted for these analyses (Seman et al., 2018). Fresh pork was defined as products that met the AMSA standards for “minimal processing,” wherein raw, uncooked meat products have not been significantly altered compositionally and contain no added ingredients but may have been reduced in size by fabrication, mincing, grinding, and/or a meat recovery system (Seman et al., 2018). Processed pork was defined as products that met the AMSA standards for “further processing,” which entails any process wherein meat products undergo a transformation, beyond minimal processing, containing approved ingredients and may be subjected to a preservation or processing step(s) through the application of salting, curing, fermentation, thermal processing (smoking and/or cooking), batter/breading, or other processes to enhance sensory, quality, and safety attributes. These products may include ready-to-cook and ready-to-eat products (Seman et al., 2018). Mixed pork was defined as a combination of fresh and processed pork.
Literature search and selection
We developed search strategies with the help of university librarians. We searched Ovid Medline from 1946 to present, Embase from 1974 to present, and Cochrane Central from 1910 to present (Appendix A). No restrictions were set regarding languages or outcome terms. Additional articles were found via reference mining.
After duplicated citations were removed in Endnote, we uploaded titles and abstracts to Rayyan (https://rayyan.qcri.org) for double independent abstract screening. Two independent reviewers screened all abstracts to exclude irrelevant abstracts such as narrative reviews, systematic reviews, case studies, letters to the editor, ecological studies, and conference proceedings or abstracts. We included studies conducted in participants of all ages looking at pork consumption compared with any comparator. Because many study population details were not described in the abstracts, we only excluded those abstracts that clearly stated nonpork primary exposures and outcomes not related to health or nutrition. We then retrieved the full-text articles of all potentially relevant abstracts and performed full-text screening according to our inclusion and exclusion criteria (Table 1). Two reviewers discussed all discrepancies and disagreements during both abstract and full-text screening phases and resolved discrepancies via consensus. If no consensus could be reached, a third reviewer or the entire research team resolved the remaining discrepancies. We recorded the primary reason for exclusion of all full-text articles (Appendix B). Studies in Appendix B were “set aside due to processed meat” if they did not specify whether the processed meat was pork or other meat.
Study eligibility criteria for full-text screening
| Parameter | Inclusion Criteria | Exclusion Criteria |
|---|---|---|
| Populations of interest | Any human participants | None |
| Interventions or exposures of interest | Consumption of pork products alone or in combination with other foods/dietary patterns | Articles assessing foods other than pork or dietary patterns not including pork |
| Articles that only specify red meat or sausage without identifying pork as a component | ||
| Studies that do not include dietary assessment (i.e., studies using self-report only) | ||
| Comparators of interest | Any or no comparator | None |
| Outcomes of interest | Any health-related outcomes including nutrition deficiency/insufficiency | Food safety outcomesFood allergy outcomes irrespective of measure |
| Articles looking singularly at the effect of pork on overall nutrient status | ||
| Hunger and satiety outcomes | ||
| Study designs of interest | Any interventional and observational study design | Narrative reviews |
| Systematic reviews | ||
| Meta-analyses | ||
| Letters to the editor | ||
| Case studies | ||
| Ecological studies | ||
| Conference proceedings or abstracts |
Data extraction
We performed data extraction on all included full-text articles. We extracted information on study characteristics (i.e., study design and sample size), study participant characteristics (i.e., age, health status, and gender), intervention characteristics (i.e., pork source, dose, and form of administration), and a list of analyzed outcomes. Data were extracted by one reviewer and spot checked by a second team member.
We did not perform a risk-of-bias assessment of included studies in the scoping review.
Data analysis and charting
We used one study as our unit of analysis. We treated multiple studies reported in one publication as separate studies in the analysis. To allow for frequency analysis and identification of research gaps, outcomes were classified into categories based on biomarkers and indicators for health outcomes. The outcome categories were cancer, cardiovascular disease risk, diabetes risk, cognitive function, weight status and body composition, nutrient status, inflammation, oxidative stress, and other (Table 2). All other health outcomes that could not be grouped into these predefined outcome categories were grouped into an “other” outcome category.
List of outcome categories
| Outcome Category | Definition |
|---|---|
| Cancer | Bladder cancer; breast cancer; colorectal cancer; esophageal cancer; gastric cancer; larynx cancer; lung cancer; malignant lymphoma; non-cardia gastric cancer; oral cancer; pancreatic cancer; prostate carcinoma; renal cell carcinoma; thyroid cancer; urinary system cancer; urothelial cancer |
| Cardiovascular disease risk | Arterial compliance; blood lipids profile; blood pressure; hypercholesterolemia; hypertension |
| Diabetes risk | Blood/plasma/serum glucose; GDM; insulin status; metabolic syndromes; type 2 diabetes |
| Cognitive function | Appetite; cognitive function scores; mood |
| Weight status and body composition | Anthropometrics; body composition; BMI; bone mineral density; muscle mass; obesity; weight |
| Nutrient status | Iron absorption or status; nitrogen balance; protein metabolites; serum folate; vitamin B12 status; zinc status |
| Inflammation and oxidative stress | Inflammatory status; monocyte activation markers; muscle inflammation markers; oxidative stress markers |
| Other | Alcoholic liver diseases; blood urine nitrogen; blood cadmium concentration; blood nitrosamine concentration; body strength; carboxymethyl-lysine; cholesterol gallstones; energy expenditure; Epstein-Barr virus; forearm fracture; gout; glomerular filtration rate; health-related quality of life; hemoglobin; homocysteine; life satisfaction; N-nitrosodimethylamine; pigment gallstones; polymorphisms of vitamin D metabolism genes; urinary PhIP |
BMI = body mass index; GDM = gestational diabetes mellitus; PhIP = 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.
To summarize the characteristics of the included studies, we conducted descriptive analyses on study design, country, sample size, study population characteristics, health outcome categories assessed in the studies, and funding source.
To visualize gaps in research, we created bubble plots (a type of weighted scatterplot) grouping studies by health outcome, study design, and pork category (fresh pork, processed pork, and mixed sources).
Results
We screened a total of 1,967 abstracts identified through literature searches in the Medline, Cochrane, and Embase databases. A total of 318 full-text articles were retrieved for full-text screening. After excluding 194 articles (see Appendix B for exclusion reasons), we included 126 studies (published in 124 articles) for data extraction. Of these 126 articles, we set aside 40 (see Appendix B for exclusion reasons).
We included 85 studies (in 83 publications) in the final scoping review (Lubin et al., 1981; Lakritz et al., 1982; Miller et al., 1983; Hislop et al., 1986; Kaul et al., 1986; Kune et al., 1987; Steineck et al., 1988; Olsen et al., 1989; Kneller et al., 1991; Richardson et al., 1991; Swanson et al., 1992; Abe et al., 1993; Yu et al., 1993; Goldbohm et al., 1994; Lohsoonthorn and Danvivat, 1995; Wilkens et al., 1996; Ambrosone et al., 1998; Bode et al., 1998; Takashima et al., 1998; Kidd et al., 1999; Smit et al., 1999; Sung et al., 1999; Breslow et al., 2000; Matsuo et al., 2001; Baech et al., 2003; Hu et al., 2003; Markaki et al., 2003; Nomura et al., 2003; Chiu and Gapstur, 2004; Toporcov et al., 2004; Brink et al., 2005; Radosavljević et al., 2005; Sakauchi et al., 2005; Milias et al., 2006; Pitsavos et al., 2006; Rubio et al., 2006; Sato et al., 2006; Xu et al., 2006; Dosil-Díaz et al., 2007; Hu et al., 2007a; 2007b; Leidy et al., 2007; Li et al., 2007; Brunt et al., 2008; Borawska et al., 2009; Campbell and Tang, 2010; Gilsing et al., 2012; McArthur et al., 2012; Murphy et al., 2012; Semba et al., 2012; Celada et al., 2013; Egeberg et al., 2013; Nolan-Clark et al., 2013; Pierre et al., 2013; Murphy et al., 2014; Poomphakwaen et al., 2014; Samman et al., 2014; Wang et al., 2014; Yazawa et al., 2014; Gong et al., 2015; Zou et al., 2015; Angelo et al., 2016; Charlton et al., 2016; Khorosh et al., 2016; Beals et al., 2017; Gong et al., 2017; Harrold et al., 2017; Hu et al., 2017; Kehlet et al., 2017; Martínez-Sánchez et al., 2017; Park et al., 2017; Song et al., 2017; Vulcan et al., 2017; Bartáková et al., 2018; Torres-Sánchez et al., 2018; Tricco et al., 2018; Xu et al., 2018; Gacek and Wojtowicz, 2019; Saliba et al., 2019; Sheng et al., 2019; Sneyd and Cox, 2020; Wedekind et al., 2020; American Heart Association, 2021). These included 16 randomized controlled trials, 1 uncontrolled trial, 7 cohort studies, 4 nonrandomized controlled trials, 4 case-cohort and nested case-control studies, 33 case-control studies, and 20 cross-sectional studies. Figure 1 outlines each stage of the literature search and selection process.
Literature search and study selection process. RCT = randomized controlled trial.
Study characteristics
Many studies investigated the effects of pork consumption on various outcome categories. Figure 2 shows the cumulative frequency of studies published every 5 y from 1988 to 2020. As shown in Figure 2, there was a significant increasing trend in the number of publications reporting cancer outcomes from 1988 to 2020. Meanwhile, the number of publications reporting cardiovascular disease risk and nutrient status outcomes experienced a steady increase. The research published in other outcome categories, including diabetes mellitus risk factors, weight status and body composition, cognitive function, and inflammation and oxidative stress, emerged at the beginning of the 21st century and has increased since then.
Cumulative frequency of published studies by outcome categories. CVD = cardiovascular disease; DM = diabetes mellitus.
Interventional studies
Among the 85 included studies, 21 were interventional studies (Table 3). Of these, 76.19% were randomized control trials, 19.05% were nonrandomized control trials, and 4.76% were uncontrolled trials. Of the included interventional studies, the average participant’s mean age was 39.51 y (range, 1.49 to 82.69 y). Most studies had a duration of 1 to 6 mo (52.38%); 28.57% of studies were >1 mo in duration, whereas only 3 studies were longer than 6 mo. Within the 4 pork intervention categories, 28.57% were exclusive fresh meat, 14.29% provided only processed meat, 38.10% were mixed pork sources, and the other studies (19.05%) did not specify pork category. The majority of funding sources came from industry (33.33%) and mixed sources (38.10%). One-third of the interventional studies were conducted in Europe, 28.57% in North America, and 23.81% in Oceania. Only a few articles were from China (9.52%) and other Asian countries (4.76%). Nutrition status was the most frequently studied outcome among interventional studies, followed by weight status and body composition (28.57%) and cardiovascular heart disease risk (28.57%). Some studies focused on inflammation (14.29%), cancer (4.76%), and cognitive function (4.76%), whereas 38.1% studied other outcomes. Only 3 interventional studies isolated effects of processed pork intake.
Summary of study characteristics of interventional studies
| Characteristic | Interventional Study (N = 21) |
|---|---|
| Design | |
| Randomized controlled trial | 16 (76.19) |
| Non–randomized controlled trial | 4 (19.05) |
| Uncontrolled trial | 1 (4.76) |
| Sample size, n (range) | 42.86 (1–180) |
| Mean age, y (range)a | 39.51 (1.49–82.69) |
| Intervention duration | |
| <1 mo | 7 (33.33) |
| 1–6 mo | 11 (52.38) |
| 6–12 mo | 2 (9.52) |
| ≥1 y | 1 (4.76) |
| Pork category | |
| Fresh meat only | 6 (28.57) |
| Mixed | 8 (38.10) |
| Processed meat only | 3 (14.29) |
| Not specified | 4 (19.05) |
| Baseline health status | |
| 100% healthy | 19 (90.48) |
| Generally healthyb | 0 (0.00) |
| With disease conditionc | 2 (9.52) |
| Not reported | 0 (0.00) |
| Funding source | |
| Academic | 0 (0.00) |
| Government | 0 (0.00) |
| Industry | 7 (33.33) |
| Nonprofit | 1 (4.76) |
| Mixed sources | 8 (38.10) |
| Not reported | 5 (23.81) |
| Region | |
| North America | 6 (28.57) |
| South America | 0 (0.00) |
| China | 2 (9.52) |
| Other Asia | 1 (4.76) |
| Oceania | 5 (23.81) |
| Europe | 7 (33.33) |
| Outcome categoriesd | |
| Cancer | 1 (4.76) |
| Cardiovascular disease risk factors | 7 (33.33) |
| Diabetes mellitus risk factors | 6 (28.57) |
| Nutrient status | 10 (47.62) |
| Weight status and body composition | 9 (42.86) |
| Cognitive function | 3 (14.29) |
| Inflammation and oxidative stress | 4 (19.05) |
| Other | 6 (28.57) |
Data are presented as n (%) unless indicated otherwise.
Mean age represents the average of the reported mean age for each included study. The median age was used if the mean age was not reported. The midpoint of the reported age range was used if neither mean age nor median age was reported. One study did not report mean age, median age, or age range.
Generally healthy: ≤20% of the population have diseases.
With disease conditions: >20% of the population have diseases.
Some studies examined multiple outcomes, which generates percentages that sum to >100%.
Observational studies
A total number of 64 observational studies were included. Most were cross-sectional studies and case-control studies (82.81%). Cohort studies (17.19%) include prospective and retrospective cohort studies, case-cohort studies, and nested case-control studies (Table 4). The average participant’s mean age was 53.7 y. About half of the included studies specified the type of pork exposure. For instance, 15.62% reported fresh pork as the only exposure, 9.38% reported processed pork exposure only (i.e., bacon, ham, and other processed pork product), and 25% reported mixed exposure of fresh and processed pork. More than half of the included studies reported the funding source. Of these, 7.81% were supported by multiple funding resources. As for studies reporting a single funding source, government funding was the most common (29.69%), followed by nonprofit (9.38%) and industry (6.25%) funding. Included studies were conducted across the globe, with 32.81% conducted in North American countries, 26.56% in European countries, and 20.31% in China. No cohort studies were identified as being conducted in the South America region or the Oceania region. The most commonly reported outcome was cancer (60.9%), followed by cardiovascular disease risk factors (10.93%) and weight status and body composition outcome (7.81%). Cancer and weight status and body composition were the only 2 outcomes reported in cohort studies. Only 6 case-control and 6 cross-sectional studies isolated effects of processed pork intake, with the large majority focusing on cancer incidence.
Summary of study characteristics of observational studies
| Characteristic | Combined (N = 64) | Cross-Sectional and Case-Control Studies (n = 53) | Cohort Studiesa (n = 11) |
|---|---|---|---|
| Number of studies | 64 (100) | 53 (82.81) | 11 (17.19) |
| Sample size, mean (range) | 7,851 (46–64,539) | 4,456 (46–56,237) | 24,205 (3,500–64,539) |
| Mean age, yb | 53.71 | 53.44 | 54.92 |
| Follow-up duration, y | |||
| 2–5 | NA | NA | 1 (9.09) |
| 5–10 | NA | NA | 3 (27.27) |
| 10–15 | NA | NA | 4 (36.36) |
| ≥15 | NA | NA | 3 (27.27) |
| Pork category | |||
| Fresh meat only | 10 (15.62) | 8 (15.09) | 2 (18.18) |
| Mixed | 16 (25.00) | 13 (24.53) | 3 (27.27) |
| Processed meat only | 6 (9.38) | 6 (11.32) | 0 (0.00) |
| Not specified | 32 (50.00) | 26 (49.06) | 6 (54.55) |
| Baseline health status | |||
| 100% healthy | NA | NA | 3 (27.27) |
| Generally healthyc | NA | NA | 2 (18.18) |
| With disease conditionsd | NA | NA | 3 (27.27) |
| Not reported | NA | NA | 3 (27.27) |
| Funding source | |||
| Academic | 1 (1.56) | 1 (1.89) | 0 (0.00) |
| Government | 19 (29.69) | 15 (28.30) | 4 (36.36) |
| Industry | 4 (6.25) | 4 (7.55) | 0 (0.00) |
| Nonprofit | 6 (9.38) | 4 (7.55) | 2 (18.18) |
| Mixed sources | 5 (7.81) | 4 (7.55) | 1 (9.09) |
| Not reported | 29 (45.31) | 25 (47.17) | 4 (36.36) |
| Region | |||
| North America | 21 (32.81) | 19 (35.83) | 2 (18.18) |
| South America | 2 (3.12) | 2 (3.77) | 0 (0.00) |
| China | 13 (20.31) | 12 (22.64) | 1 (9.09) |
| Other Asia | 8 (12.50) | 6 (11.32) | 2 (18.18) |
| Oceania | 3 (4.69) | 3 (5.66) | 0 (0.00) |
| Europe | 17 (26.56) | 11 (20.75) | 6 (54.55) |
| Outcome categoriese | |||
| Cancer | 39 (60.94) | 29 (54.72) | 10 (90.91) |
| Cardiovascular disease risk factors | 7 (10.94) | 7 (13.21) | 0 (0.00) |
| Diabetes mellitus risk factors | 3 (4.96) | 3 (5.66) | 0 (0.00) |
| Nutrient status | 1 (1.56) | 1 (1.56) | 0 (0.00) |
| Weight status and body composition | 5 (7.81) | 4 (7.55) | 1 (9.09) |
| Cognitive function | 0 (0.00) | 0 (0.00) | 0 (0.00) |
| Inflammation and oxidative stress | 0 (0.00) | 0 (0.00) | 0 (0.00) |
| Other | 12 (18.5) | 12 (22.64) | 0 (0.00) |
Data are presented as n (%) unless indicated otherwise.
Cohort studies include prospective cohort study, retrospective cohort study, case-cohort study, and nested case-control study.
Mean age represents the average of reported mean age for each included study. The median age was used if the mean age was not reported. The midpoint of the reported age range was used if neither mean age nor median age was reported. Fifteen studies did not report mean age, median age, or age range.
Generally healthy: ≤20% of the population have diseases.
With disease conditions: >20% of the population have diseases.
Some studies examined multiple outcomes, which generates percentages that sum to >100%.
NA = not applicable.
Identifying research gaps related to study design and pork categorization
Figure 3 shows the differences in outcome categories explored by interventional studies and observational studies. Nutrient status outcomes were the most frequently explored in interventional studies. These included nutrient status biomarkers for protein/amino acids, folate iron, vitamin B6, vitamin B12, and zinc. We did not find studies assessing pork’s contribution to selenium or thiamin status. Cancer outcomes were the most frequently explored in observational studies. Very few observational studies explored inflammation, oxidative stress, or cognitive function associated with pork consumption. Only one interventional study assessed the role of pork intake with cancer outcomes. As expected, sample sizes were much larger for observational studies compared with interventional studies.
Bubble plot of health outcome categories by study design. Each bubble in the figure represents one study, and the size of the bubble is proportional to the study sample size. CVD = cardiovascular disease; DM = diabetes mellitus.
Figure 4 shows the differences in health outcomes reported by categorization of pork as fresh pork, processed pork, and mixed pork sources. Studies that included fresh pork as the main exposure of interest reported on almost all outcome categories, with the largest number of fresh pork studies reporting on cancer risk. Studies that included processed pork as the main exposure of interest primarily reported on cancer risk, with 1 study reporting on weight status and body composition and 1 study reporting on cardiovascular disease risk. Studies that included mixed pork sources as the main exposure of interest reported on all outcomes, and cancer was the most frequently investigated outcome. Figure 5 shows differences in cancer outcome sites reported by categorization of pork as fresh pork, processed pork, and mixed pork sources. Cancers of the gastrointestinal tract were frequent sites to be assessed across observational studies.
Bubble plot of health outcome categories by pork categorization. Each bubble in the figure represents one study, and the size of the bubble is proportional to the study sample size. Categories specified as “other” were not included in this bubble plot. CVD = cardiovascular disease; DM = diabetes mellitus.
Bubble plot of cancer outcome sites by pork categorization. Each bubble in the figure represents one study, and the size of the bubble is proportional to the study sample size.
Discussion
Scoping reviews are a replicable, systematic, and evidence-based approach used to identify, collect, and evaluate the characteristics of the existing peer-reviewed literature. Here, we highlight research gaps and opportunities for systematic reviews in relation to the effects of pork consumption on human nutrition and health. The scientific literature contains mostly observational studies, a large majority being case-controlled and cross-sectional analyses. To date, there are a dearth of high-quality randomized controlled trials assessing effects of pork intake on disease risk factors and outcomes. The effect of pork intake on patients’ nutrient status was the most assessed outcome. No interventional studies explored diabetes mellitus risk, and only 1 study assessed cancer risk associated with pork consumption. The single “cancer risk” intervention sought to investigate whether cured meat modulates biomarkers of cancer risk and whether specific agents can suppress cured meat–induced preneoplastic lesions in rats and associated biomarkers in rats and humans. Data from this study suggest that the addition of calcium carbonate to the diet or α-tocopherol to cured meat may reduce colorectal cancer risk associated with cured meat intake among observational studies (Pierre et al., 2013). Along the same lines, regular consumption of biopeptides contained in dry-cured ham but absent in cooked ham were shown to impair platelet and monocyte activation and levels of plasmatic P-selected, monocyte chemoattractant protein-1 and interleukin-6 in healthy subjects (Martínez-Sánchez et al., 2017). Surprisingly, there was a dearth of observational studies and absence of prospective cohort studies that examined the role of processed pork on cancer incidence and other health outcomes. Many food frequency questionnaires (FFQ) used in observational analyses are currently not able to quantify intake of fresh and processed pork. This is an important research gap that needs to be addressed among FFQ and when designing future observational research.
Although rural Chinese toddlers consuming fortified cereal had higher vitamin B12 levels in one study, those receiving 50 g of pork per day had higher cognitive scores (Sheng et al., 2019). However, a separate quasi-experimental study did not find any advantages of pork versus chicken on cognitive function in healthy older adults, suggesting that the type of dietary protein during aging may not impact cognitive function (Charlton et al., 2016). The inclusion of 2 to 3 weekly servings of fresh, lean pork in the Mediterranean diet was shown to lead to improved cognitive performance over a 24-wk period, as indicated by higher processing speed performance and emotional role functioning. The Mediterranean diet, which is rich in high-selenium foods such as seafood and nuts, has been associated with a lower risk of age-related cognitive decline (Scarmeas et al., 2006; Hardman et al., 2016). Several micronutrients in pork, including zinc, iron, selenium, choline, thiamin, and vitamins B6 and vitamin B12, are thought to influence cognitive function and may prove to be an exciting emerging area of research. Future prospective cohort investigations could greatly help in the design of larger, long-duration randomized clinical trials that assess outcomes (e.g., Alzheimer’s dementia incidence).
Most observational studies assessed the effect of pork on cancer incidence, followed by cardiovascular disease, weight status and body composition, type 2 diabetes, and nutrient status. No prospective cohort studies assessed the effects of pork on cardiovascular disease, type 2 diabetes, cognition, inflammation/oxidative stress, or nutrient status.
Our study has several strengths and weaknesses. The main strength of this review is the thorough, systematic search strategy and detailed analysis of characteristics reported in the included studies. This review is limited by the availability of manuscripts to online searches in the English language. Another limitation important to note is that scoping reviews do not typically include quality (risk of bias) appraisal of included studies, and therefore there can be substantial amounts of poor-quality research. Observational studies failed to indicate whether the AMSA lexicon for “minimal processing and “further processing” was adopted, in the same way we categorized products as “fresh” or “processed” pork. The inability of current FFQ to distinguish between fresh and processed pork poses additional major limitations to our analyses.
Conclusions
Few conclusions can be drawn from studies evaluating the effects of pork on human nutrition and health. Several micronutrients in pork, including zinc, iron, selenium, choline, thiamin, and vitamins B6 and vitamin B12, are thought to influence cognitive function, and this may prove to be an exciting area of emerging research. To date, there is a dearth of high-quality randomized controlled trials assessing the effects of pork intake on disease risk factors and outcomes. The scientific literature contains mostly observational studies, a large majority being case-controlled and cross-sectional analyses. Of note, there is a lack of studies examining isolated effects of processed pork intake on human health. Future clinical trials should address the role of pork consumption in health outcomes, intermediate outcomes, and validated biomarkers.
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Wedekind, R., A. Kiss, P. Keski-Rahkonen, V. Viallon, J. A. Rothwell, A. J. Cross, A. L. Rostgaard-Hansen, T. M. Sandanger, P. Jakszyn, and J. A. Schmidt. 2020. A metabolomic study of red and processed meat intake and acylcarnitine concentrations in human urine and blood. Am. J. Clin. Nutr. 112:381–388. doi: https://doi.org/10.1093/ajcn/nqaa140.
Wilkens, L. R., M. M. Kadir, L. N. Kolonel, A. Nomura, and J. H. Hankin. 1996. Risk factors for lower urinary tract cancer: The role of total fluid consumption, nitrites and nitrosamines, and selected foods. Cancer Epidem. Biomar. 5:161–166.
Xu, L., M. Phillips, C. D’Este, M. Dibley, J. Porteous, and J. Attia. 2006. Diet, activity, and other lifestyle risk factors for forearm fracture in postmenopausal women in China: A case-control study. Menopause. 13:102–110. doi: https://doi.org/10.1097/01.gme.0000191206.20738.da.
Xu, X., X. Wu, Y. Deng, K. Ji, Y. Li, X. Liang, X. Chen, J. Zeng, Z. Wang, and G. Yi. 2018. The influence of diet and behaviour on metabolic syndrome and the prevalence of metabolic syndrome according to different definitions in west China. Asia Pac. J. Clin. Nutr. 27:1040–1047. doi: https://doi.org/10.6133/apjcn.122017.06.
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Appendix A. Search Strategies
A1.
Database: Ovid MEDLINE(R) <1946 to December Week 5 2020>
Search Strategy:
---------------------
1 exp Pork Meat/ (172)
2 (“Boston butt” or Loin or Pancetta or Collops or Gammon or Bacon or Sausage or Charcuterie or Terrines or Galantines or Pates or Confit or Jamon or Feijoada or Bakkwa or Charsiu or Lechan).af. (10575)
3 pork.af. (8253)
4 2 or 3 (17988)
5 diet.mp. or exp Diet/ (486323)
6 4 and 5 (1902)
7 1 or 6 (2051)
8 limit 7 to (english language and humans) (1022)
A2.
Embase
Session Results
………………………………….
No.,Query,Results
#10, #8 NOT #9, 905
#9, #8 AND [medline]/lim, 1445
#8,"#7 AND [english]/lim AND [humans]/lim”,2350
#7,"#1 OR #6",5405
#6,"#4 AND #5",2544
#5,"'diet'/exp OR diet”,776986
#4,"#2 OR #3",25289
#3,"pork”,11334
#2,"'boston butt’ OR loin OR pancetta OR collops OR gammon OR bacon OR sausage OR charcuterie OR terrines OR galantines OR pates OR confit OR jamon OR feijoada OR bakkwa OR charsiu OR lechan”,15043
#1,"'pork'/exp”,3373
A3.
Database: EBM Reviews - Cochrane Central Register of Controlled Trials <December 2020>, Global Health <1910 to 2021 Week 04>
Search Strategy:
1 exp Pork Meat/ (0)
2 (“Boston butt” or Loin or Pancetta or Collops or Gammon or Bacon or Sausage or Charcuterie or Terrines or Galantines or Pates or Confit or Jamon or Feijoada or Bakkwa or Charsiu or Lechan).af. (10058)
3 pork.af. (22967)
4 2 or 3 (29840)
5 diet.mp. or exp Diet/ (363335)
6 4 and 5 (2885)
7 1 or 6 (2885)
8 limit 7 to (english language and humans) [Limit not valid in CCTR,Global Health; records were retained] (2166)
9 limit 8 to (“review” or “review literature” or “review of reported cases” or review, academic or review, multicase or review, tutorial) [Limit not valid in Global Health; records were retained] (2001)
10 8 not 9 (165)
Appendix B. Excluded articles with reasons for exclusion
| First Author (Year) | Title | Reason for Exclusion |
|---|---|---|
| Alves-Santos (2018) | Dietary patterns and their association with adiponectin and leptin concentrations throughout pregnancy: a prospective cohort | Pork cannot be isolated |
| Anonymous (1994) | Dietary and other risk factors of ulcerative colitis. A case-control study in Japan. Epidemiology Group of the Research Committee of Inflammatory Bowel Disease in Japan | Set aside due to processed meat |
| Armstrong (1998) | Nasopharyngeal carcinoma in Malaysian Chinese: salted fish and other dietary exposures | Pork cannot be isolated |
| Aro (1994) | Factors affecting the selenium intake of people in Transbaikalian Russia | No human subjects |
| Asakura (2014) | Estimation of food portion sizes frequently consumed by children 3-6 y old in Japan | No health outcome |
| Baker (1986 | Urine mutagenicity as an indicator of exposure to dietary mutagens formed during cooking of foods | No exposure of interest |
| Balder (2005) | Dietary patterns associated with male lung cancer risk in the Netherlands Cohort Study | Pork cannot be isolated |
| Barth (2001) | Food intake of patients with atopic dermatitis | No outcome of interest |
| Beals (2016) | Anabolic sensitivity of postprandial muscle protein synthesis to the ingestion of a protein-dense food is reduced in overweight and obese young adults | No exposure of interest |
| Bingham (1996) | Does increased endogenous formation of N-nitroso compounds in the human colon explain the association between red meat and colon cancer? | Pork cannot be isolated |
| Bingham (1996) | Does increased endogenous formation of N-nitroso compounds in the human colon explain the association between red meat and colon cancer? | Duplicate |
| Butler (2006) | Prospective study of dietary patterns and persistent cough with phlegm among Chinese Singaporeans | Pork cannot be isolated |
| Campbell (1999) | Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training-induced changes in body composition and skeletal muscle in older men | Pork cannot be isolated |
| Caselli (2014) | Test-based exclusion diets in gastro-esophageal reflux disease patients: a randomized controlled pilot trial | Pork cannot be isolated |
| Celada (2014) | Omega-3 enriched frankfurters and pâtés intake decrease TXA2 level and N-6/N-3 in volunteers at increased cardiovascular risk: a placebo-controlled study | Abstract only |
| Cempaka (2019) | Dysregulated iron metabolism-associated dietary pattern predicts an altered body composition and metabolic syndrome | Pork cannot be isolated |
| Chan (2004) | Postprandial glucose response to Chinese foods in patients with type 2 diabetes | Pork cannot be isolated |
| Charlton (2011) | Pork, beef and chicken have similar effects on acute satiety and hormonal markers of appetite | No outcome of interest |
| Chatzivagia (2019) | Nutrition transition in the post-economic crisis Greece: assessing the nutritional gap of food insecure individuals. A case-control study | Pork cannot be isolated |
| Chen (2020) | The risk of urinary tract infection in vegetarians and non-vegetarians: a prospective study | Pork cannot be isolated |
| Coates (2009) | Regular consumption of n-3 fatty acid-enriched pork modifies cardiovascular risk factors | Pork cannot be isolated |
| Coelho Nde (2015) | Dietary patterns in pregnancy and birth weight | Pork cannot be isolated |
| Cui (2007) | Dietary patterns and breast cancer risk in the Shanghai Breast Cancer Study | Pork cannot be isolated |
| Cuparencu (2020) | The anserine to carnosine ratio: an excellent discriminator between white and red meats consumed by free-living overweight participants of the PREVIEW study | PDF not found |
| Davidson (1999) | Comparison of the effects of lean red meat vs lean white meat on serum lipid levels among free-living persons with hypercholesterolemia: a long-term, randomized clinical trial | Pork cannot be isolated |
| de Gavelle (2018) | Patterns of protein food intake are associated with nutrient adequacy in the general French adult population | No outcome of interest |
| Deneo-Pellegrini (2015) | Meat consumption and risk of squamous cell carcinoma of the lung: a case-control study in Uruguayan men | Pork cannot be isolated |
| Di Pietro (2007) | Breast cancer in southern Brazil: association with past dietary intake | Pork cannot be isolated |
| Dixon (2004) | Dietary patterns associated with colon and rectal cancer: results from the Dietary Patterns and Cancer (DIETSCAN) Project | Pork cannot be isolated |
| Dolara (1984) | Urinary mutagens in humans after fried pork and bacon meals | No exposure of interest |
| Endoh (2015) | Interactions between psychological stress and drinking status in relation to diet among middle-aged men and women: a large-scale cross-sectional study in Japan | Pork cannot be isolated |
| Erhardt (2002) | Alcohol, cigarette smoking, dietary factors and the risk of colorectal adenomas and hyperplastic polyps--a case control study | No exposure of interest |
| Erkkila (2014) | Effect of fatty and lean fish intake on lipoprotein subclasses in subjects with coronary heart disease: a controlled trial | Pork cannot be isolated |
| Etemadi (2017) | Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study | Pork cannot be isolated |
| Favero (1998) | Diet and risk of breast cancer: major findings from an Italian case-control study | Set aside due to processed meat |
| Flynn (1982) | Dietary “meats” and serum lipids | PDF not found |
| Franceschi (1999) | The role of energy and fat in cancers of the breast and colon-rectum in a southern European population | Set aside due to processed meat |
| Franceschi (1995) | Influence of food groups and food diversity on breast cancer risk in Italy | Set aside due to processed meat |
| French (1994) | Food intake and physical activity: a comparison of three measures of dieting | No exposure of interest |
| Friedenberg (2010) | Population-based survey: body mass index at age 18 is strongly predictive of adulthood obesity | Abstract only |
| Fung (2004) | Dietary patterns, meat intake, and the risk of type 2 diabetes in women | Pork cannot be isolated |
| Gacek (2014) | Individual differences as predictors of dietary patterns among menopausal women with arterial hypertension | Set aside due to processed meat |
| Giles (1994) | Dietary factors and the risk of glioma in adults: results of a case-control study in Melbourne, Australia | Pork cannot be isolated |
| Giovannucci (1994) | Intake of fat, meat, and fiber in relation to risk of colon cancer in men | Pork cannot be isolated |
| Gorder (1986) | Dietary intake in the Multiple Risk Factor Intervention Trial (MRFIT): nutrient and food group changes over 6 y | Pork cannot be isolated |
| Guallar-Castillon (2013) | The Southern European Atlantic Diet is associated with lower concentrations of markers of coronary risk | Pork cannot be isolated |
| Gunasekeera (2016) | Treatment of Crohn’s disease with an IgG4-guided exclusion diet: a randomized controlled trial | No outcome of interest |
| Hansen (2015) | A long-term fatty fish intervention improved executive function in inpatients with antisocial traits and a history of alcohol and drug abuse | Pork cannot be isolated |
| Hansen (2014) | Fish consumption, sleep, daily functioning, and heart rate variability | Pork cannot be isolated |
| Hansen (2014) | Reduced anxiety in forensic inpatients after a long-term intervention with Atlantic salmon | Pork cannot be isolated |
| Hartung (1980) | Relation of diet to high-density-lipoprotein cholesterol in middle-aged marathon runners, joggers, and inactive men | PDF not found |
| Harvala (2019) | Hepatitis E virus in blood donors in England, 2016 to 2017: from selective to universal screening | No outcome of interest |
| Hebert (1998) | The effect of dietary exposures on recurrence and mortality in early stage breast cancer | Pork cannot be isolated |
| Heningburg (2015) | Nutritional intake assessment in patients with urolithiasis: a decision impact analysis | Pork cannot be isolated |
| Henry (2002) | Brief communication: energy and protein intake in a sample of hospitalized elderly in Hong Kong | No outcome of interest |
| Hernandez (2015) | An estimation of the carcinogenic risk associated with the intake of multiple relevant carcinogens found in meat and charcuterie products | No human subjects |
| Hobbs (2018) | Associations between red and processed meat consumption and cardiometabolic risk markers among British adults | Pork cannot be isolated |
| Hogan (2012) | Effects of protein quantity and source (animal versus plant) on indices of mood and fed-state large neutral amino acids and tryptophan profile | PDF not found |
| Houston (1997) | Lifestyle and dietary practices influencing iron status in university women | Pork cannot be isolated |
| Hunninghake (2000) | Incorporation of lean red meat into a National Cholesterol Education Program Step I diet: a long-term, randomized clinical trial in free-living persons with hypercholesterolemia | Pork cannot be isolated |
| Ifejika (2016) | Swipe out Stroke: Feasibility and efficacy of using a smart-phone based mobile application to improve compliance with weight loss in obese minority stroke patients and their carers | Study protocol |
| Ishizuka (1993) | Influence of meals and night shifts on health | Pork cannot be isolated |
| Jacobson (1983) | Increased excretion of malonaldehyde equivalents in the urine after consumption of cooked, stored meats | PDF not found |
| Jacques (1992) | Effects on plasma lipoproteins and endogenous sex hormones of substituting lean white fish for other animal-protein sources in diets of postmenopausal women | Pork cannot be isolated |
| Jakic (2010) | Are lipoprotein disturbances in chronic hemodialyzed patients only renal failure related? | Abstract only |
| Jonsson (2016) | Diet in 1-year-old farm and control children and allergy development: results from the FARMFLORA birth cohort | No outcome of interest |
| Jung (2010) | The influence of dietary patterns on acne vulgaris in Koreans | No outcome of interest |
| Kassier (2016) | Colon cancer and the consumption of red and processed meat: An association that is medium, rare or well done? | an review article |
| Kato (1987) | Per capita foods/nutrients intake and mortality from gastrointestinal cancers in Japan | Set aside due to processed meat |
| Kato (1987) | Relationship between westernization of dietary habits and mortality from breast and ovarian cancers in Japan | Set aside due to processed meat |
| Kiefer (2005) | Eating and dieting differences in men and women | No outcome of interest |
| Kim (2017) | Red meat and chicken consumption and its association with high blood pressure and obesity in South Korean children and adolescents: a cross-sectional analysis of KSHES, 2011-2015 | Pork cannot be isolated |
| Kimura (2007) | Meat, fish and fat intake in relation to subsite-specific risk of colorectal cancer: the Fukuoka Colorectal Cancer Study | Pork cannot be isolated |
| Kjaerheim (1998) | The role of alcohol, tobacco, and dietary factors in upper aerogastric tract cancers: a prospective study of 10,900 Norwegian men | Pork cannot be isolated |
| Kocic (1997) | Diet and breast cancer | PDF not found |
| Komorniak (2019) | What are the diets of patients before bariatric surgery? | Pork cannot be isolated |
| Lacaille (2000) | Responses of plasma lipoproteins and sex hormones to the consumption of lean fish incorporated in a prudent-type diet in normolipidemic men | Pork cannot be isolated |
| Landi (2019) | Daily meat consumption and variation with aging in community-dwellers: Results from Longevity Check-Up 7 + project | Pork cannot be isolated |
| Lang (2018) | Impact of individual traits, saturated fat, and protein source on the gut microbiome | Pork cannot be isolated |
| Langsetmo (2010) | Dietary patterns in Canadian men and women ages 25 and older: relationship to demographics, body mass index, and bone mineral density | Pork cannot be isolated |
| Lankinen (2009) | Fatty fish intake decreases lipids related to inflammation and insulin signaling--a lipidomics approach | Pork cannot be isolated |
| Larsson (2006) | Processed meat consumption, dietary nitrosamines and stomach cancer risk in a cohort of Swedish women | Pork cannot be isolated |
| Lee (2005) | Breast cancer and dietary factors in Taiwanese women | Pork cannot be isolated |
| Levi (1998) | Food groups and risk of oral and pharyngeal cancer | Pork cannot be isolated |
| Levi (2000) | Food groups and oesophageal cancer risk in Vaud, Switzerland | Set aside due to processed meat |
| Levi (1999) | Food groups and colorectal cancer risk | Set aside due to processed meat |
| Li (2016) | Effects of dietary protein source and quantity during weight loss on appetite, energy expenditure, and cardio-metabolic responses | Pork cannot be isolated |
| Li (2015) | Prospective cohort study of cured meat intake and asthma symptom score in the EGEA study | PDF not found |
| Li (2007) | Dietary mutagen exposure and risk of pancreatic cancer | Pork cannot be isolated |
| Li (2016) | Effects of dietary protein source and quantity on glycemic control in energy-restricted overweight and obese adults | PDF not found |
| Lin (2010) | Red meat and heterocyclic amine intake, metabolic pathway genes, and bladder cancer risk | Abstract only |
| Lindqvist (2009) | Herring (Clupea harengus) intake influences lipoproteins but not inflammatory and oxidation markers in overweight men | Pork cannot be isolated |
| Lindqvist (2007) | Herring (Clupea harengus) supplemented diet influences risk factors for CVD in overweight subjects | Pork cannot be isolated |
| Linseisen (2002) | Meat consumption in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts: results from 24-hour dietary recalls | No outcome of interest |
| Liu (2019) | Fat from dairy foods and ‘meat’ consumed within recommended levels is associated with favourable serum cholesterol levels in institutionalised older adults | Pork cannot be isolated |
| Lizcano (2020) | The impact of lean pork meat consumption on cardiovascular risk | Non-English study |
| Lyon (1993) | Dietary intake as a risk factor for cancer of the exocrine pancreas | Pork cannot be isolated |
| Ma (2000) | Zinc and copper intakes and their major food sources for older adults in the 1994-96 Continuing Survey of Food Intakes by Individuals (CSFII) | No outcome of interest |
| Magee (2005) | Associations between diet and disease activity in ulcerative colitis patients using a novel method of data analysis | No outcome of interest |
| Manara (2013) | Is gout still the rich and dissolute men’s disease? Results from the KING study of the Italian Society for Rheumatology (SIR) | Abstract only |
| Mannisto (2005) | Dietary patterns and breast cancer risk: results from three cohort studies in the DIETSCAN project | Pork cannot be isolated |
| Martin (2016) | Maternal dietary patterns are associated with lower levels of cardiometabolic markers during pregnancy | Pork cannot be isolated |
| McArthur (2011) | Inclusion of pork meat in the diets of young women reduces snack food consumption and increases fruit and vegetable intakes | No outcome of interest |
| McKay (2015) | Whole eggs enhance antioxidant activity when combined with energy dense, cooked breakfast foods | PDF not found |
| McNaughton (2011) | An energy-dense, nutrient-poor dietary pattern is inversely associated with bone health in women | Pork cannot be isolated |
| Minami (1993) | Female systemic lupus erythematosus in Miyagi Prefecture, Japan: a case-control study of dietary and reproductive factors | Pork cannot be isolated |
| Miyake (2018) | Dietary patterns and depressive symptoms during pregnancy in Japan: baseline data from the Kyushu Okinawa Maternal and Child Health Study | Pork cannot be isolated |
| Miyake (2011) | Maternal dietary patterns during pregnancy and risk of wheeze and eczema in Japanese infants aged 16–24 mo: the Osaka Maternal and Child Health Study | Pork cannot be isolated |
| Montoro Garcia (2016) | Dry-cured ham, its effects on human blood pressure and cardiovascular risk: a clinical study | Abstract only |
| Moon (2015) | Application of instrumental neutron activation analysis to assess dietary intake of selenium in Korean adults from meat and eggs | No human subjects |
| Mozaffarian (2006) | Dietary fish and n-3 fatty acid intake and cardiac electrocardiographic parameters in humans | No outcome of interest |
| Mrazova (2020) | The effect of consumption of pork enriched by organic selenium on selenium status and lipid profile in blood serum of consumers | No exposure of interest |
| Mubiru (2017) | Exposure assessment of epoxy fatty acids through consumption of specific foods available in Belgium | No outcome of interest |
| Nagao (2012) | Meat consumption in relation to mortality from cardiovascular disease among Japanese men and women | Pork cannot be isolated |
| Narasaki (2020) | Phosphatemic index is a novel evaluation tool for dietary phosphorus load: a whole-foods approach | PDF not found |
| Nestel (1976) | Effect of dietary polyunsaturated pork on plasma lipids and sterol excretion in man | PDF not found |
| Nielsen (2018) | Protein from meat or vegetable sources in meals matched for fiber content has similar effects on subjective appetite sensations and energy intake-a randomized acute cross-over meal test study | No outcome of interest |
| Nicklas et al. (1995) | Impact of meat consumption on nutritional quality and cardiovascular risk factors in young adults: the Bogalusa Heart Study | Pork cannot be isolated |
| No author (2017) | Foodomics application: analysis of dietary components of the DASH diet pre and post consumption | PDF not found |
| Norrish (1999) | Heterocyclic amine content of cooked meat and risk of prostate cancer | No outcome of interest |
| O’Connor (2018) | Adopting a Mediterranean-style eating pattern with different amounts of lean unprocessed red meat does not influence short-term subjective personal well-being in adults with overweight or obesity | Pork cannot be isolated |
| O’Connor (2018) | A Mediterranean-style eating pattern with lean, unprocessed red meat has cardiometabolic benefits for adults who are overweight or obese in a randomized, crossover, controlled feeding trial | Pork cannot be isolated |
| Okubo (2019) | Hardness of the habitual diet and its relationship with cognitive function among 70-year-old Japanese elderly: findings from the SONIC Study | No outcome of interest |
| Oliveira (2010) | Adherence to the Southern European Atlantic Diet and occurrence of nonfatal acute myocardial infarction | Pork cannot be isolated |
| Olsen (2020) | Nutritional status in patients with inflammatory rheumatic diseases (IRD) | Pork cannot be isolated |
| Omura (1987) | Geographical distribution of cerebrovascular disease mortality and food intakes in Japan | Ecological study |
| Ouellet (2008) | Dietary cod protein reduces plasma C-reactive protein in insulin-resistant men and women | Pork cannot be isolated |
| Ouellet (2007) | Dietary cod protein improves insulin sensitivity in insulin-resistant men and women: a randomized controlled trial | Pork cannot be isolated |
| Palacios (2018) | A lean pork-containing breakfast reduces hunger and glycemic response compared with a refined carbohydrate-containing breakfast in adults with prediabetes | Pork cannot be isolated |
| Parada (2017 | Grilled, barbecued, and smoked meat intake and survival following breast cancer | Pork cannot be isolated |
| Park (2017) | Unprocessed meat consumption and incident cardiovascular diseases in Korean adults: the Korean Genome and Epidemiology Study (KoGES) | Pork cannot be isolated |
| Patterson (1988) | Food choices and the cancer guidelines | Pork cannot be isolated |
| Pestitschek (2013) | Selenium intake and selenium blood levels: a novel food frequency questionnaire | Pork cannot be isolated |
| Petermann-Rocha (2020) | Diet-quality and its association with cardiovascular diseases and cancer incidence and all-cause mortality: a prospective cohort study from UK Biobank | Pork cannot be isolated |
| Plagens-Rotman (2016) | Odds ratio analysis in women with endometrial cancer | Pork cannot be isolated |
| Porter Starr (2019) | Impact on cardiometabolic risk of a weight loss intervention with higher protein from lean red meat: combined results of 2 randomized controlled trials in obese middle-aged and older adults | Pork cannot be isolated |
| Pu (2000) | Prostate cancer in Taiwan: epidemiology and risk factors | Set aside due to processed meat |
| Pupillo (2018) | Amyotrophic lateral sclerosis and food intake | Set aside due to processed meat |
| Pupillo (2017) | Amyotrophic lateral sclerosis and food intake in Italy | Set aside due to processed meat |
| Radosavljevic (2004) | Non-occupational risk factors for bladder cancer: a case-control study | PDF not found |
| Rahman (2007) | Dietary factors and cognitive impairment in community-dwelling elderly | Pork cannot be isolated |
| Ramadass (2017) | Faecal microbiota of healthy adults in south India: comparison of a tribal & a rural population | Pork cannot be isolated |
| Ramel (2012) | Effects of two different types of fast food on postprandial metabolism in normal and overweight subjects | Pork cannot be isolated |
| Reeves (2017) | A service evaluation of adult patients given advice to reduce intake of dietary vasoactive amines | Pork cannot be isolated |
| Robbins (2014 | Association of egg consumption and calcified atherosclerotic plaque in the coronary arteries: the NHLBI Family Heart Study | No exposure of interest |
| Rodriguez (2006) | Meat consumption among Black and White men and risk of prostate cancer in the Cancer Prevention Study II Nutrition Cohort | Pork cannot be isolated |
| Rothman (2019) | Nutritional status and food intake of women residing in rural and urban areas of Lesotho | Pork cannot be isolated |
| Salgado (2011) | Association of dietary factors and development of inflammatory bowel disease (IBD) in Rio de Janeiro, Brazil | Abstract only |
| Sarcinelli (2003) | Dietary and reproductive determinants of plasma organochlorine levels in pregnant women in Rio de Janeiro | No outcome of interest |
| Schlegel-Zawadzka (2002) | Comparative analysis of zinc status, food products’ frequency intake and food habits of 11-year-old healthy children | No outcome of interest |
| Seely (1985) | Relation between pork consumption and cirrhosis | PDF not found |
| Sharma (2013) | Contribution of meat to vitamin B12, iron and zinc intakes in five ethnic groups in the USA: implications for developing food-based dietary guidelines | Pork cannot be isolated |
| Shi (2018) | Association between dietary patterns, cadmium intake and chronic kidney disease among adults | Pork cannot be isolated |
| Shi (2011) | Dietary pattern and weight change in a 5-year follow-up among Chinese adults: results from the Jiangsu Nutrition Study | Pork cannot be isolated |
| Shin (2018) | Identifying dietary patterns associated with mild cognitive impairment in older Korean adults using reduced rank regression | Pork cannot be isolated |
| Shin (2007) | Empirically derived major dietary patterns and their associations with overweight in Korean preschool children | Pork cannot be isolated |
| Shulten (2009) | The role of diet in the management of gout: a comparison of knowledge and attitudes to current evidence | Pork cannot be isolated |
| Smigielski (2013) | The effect of selected lifestyle factors and diet on mortality of men with documented physical fitness in the city of Lodz | Pork cannot be isolated |
| Sone (1998) | Comparison of diets among elderly female residents in two suburban districts in Chiang Mai Province, Thailand, in dry season--survey on high- and low-risk districts of lung cancer incidence | Pork cannot be isolated |
| Song (2004) | A prospective study of red meat consumption and type 2 diabetes in middle-aged and elderly women: the women’s health study | Pork cannot be isolated |
| Stajic (2016) | Impact of dietary habits and mental health on nutritional status of adolescents | PDF not found |
| Stefańska (2016) | The effectiveness of a weight loss diet in a group of overweight and obese women with recurrent depressive disorders | Pork cannot be isolated |
| Sturtzel (2018) | Effects of an enhanced iron dense foods offering in the daily meals served in geriatric institutions on measures of iron deficiency anemia | Pork cannot be isolated |
| Su (2015) | Trends in dietary cholesterol intake among Chinese adults: a longitudinal study from the China Health and Nutrition Survey, 1991-2011 | No outcome of interest |
| Tamae (2018) | The associations of reactive oxygen metabolites and biological antioxidant potentials with related factors among youth | Pork cannot be isolated |
| Tan (2010) | Energy expenditure does not differ, but protein oxidation rates appear lower in meals containing predominantly meat versus soy sources of protein | Pork cannot be isolated |
| Teng (2014) | Food sources of protein and risk of incident gout in the Singapore Chinese health study | Pork cannot be isolated |
| Varraso (2007) | Prospective study of cured meats consumption and risk of chronic obstructive pulmonary disease in men | Pork cannot be isolated |
| Velie (2005) | Empirically derived dietary patterns and risk of postmenopausal breast cancer in a large prospective cohort study | Pork cannot be isolated |
| Villar (2017) | Sodium consumption patterns according to sociodemographic characteristics in an Ecuadorian population: results from the Latin American study of nutrition and health (ELANS) | No exposure of interest |
| Vincent (2017) | Herring and chicken/pork meals lead to differences in plasma levels of TCA intermediates and arginine metabolites in overweight and obese men and women | Pork cannot be isolated |
| Vitariusova (2010) | Food intake, leisure time activities and the prevalence of obesity in schoolchildren in Slovakia | No outcome of interest |
| Voon (2011) | Is there an influence of dietary habits on breast density as seen on digital mammograms? | Pork cannot be isolated |
| Vulcan (2017) | Intake of different types of red meat, poultry, and fish and incident colorectal cancer in women and men: results from the Malmö diet and cancer study | Abstract only |
| Wade (2020) | Can we modify the Mediterranean diet for non-Mediterranean populations Results from two randomised controlled trials | Abstract only |
| Wang (2013) | Joint association of dietary pattern and physical activity level with cardiovascular disease risk factors among Chinese men: a cross-sectional study | Pork cannot be isolated |
| Willett (1990) | Relation of meat, fat, and fiber intake to the risk of colon cancer in a prospective study among women | Pork cannot be isolated |
| Wu (1999) | Food sources of weight, calories, and three macro-nutrients - NAHSIT 1993-1996 | No outcome of interest |
| Wytiaz (2015) | Foods provoking and alleviating symptoms in gastroparesis: patient experiences | No outcome of interest |
| Xu (2018) | Dietary patterns, dietary lead exposure and hypertension in the older Chinese population | Pork cannot be isolated |
| Xu (2017) | Dietary pattern, serum magnesium, ferritin, C-reactive protein and anaemia among older people | Pork cannot be isolated |
| Yan (1989) | Epidemiological studies of nasopharyngeal cancer in the Guangzhou area, China. Preliminary report | Pork cannot be isolated |
| Yaw (2014) | Diet and physical activity in relation to weight change among breast cancer patients | Abstract only |
| Yu (2016) | Food groups consumed by infants and toddlers in urban areas of China | No outcome of interest |
| Zhang (2019) | The Japanese dietary pattern is associated with longer disability-free survival time in the general elderly population in the Ohsaki Cohort 2006 Study | Pork cannot be isolated |
| Zhang (2016) | Association between dietary patterns and blood lipid profiles among Chinese women | Pork cannot be isolated |
| Zhang (2015) | Dietary patterns and their associations with general obesity and abdominal obesity among young Chinese women | Pork cannot be isolated |
| Zhang (2015) | Dietary patterns and their associations with childhood obesity in China | Pork cannot be isolated |
| Zhang (2012) | Dietary inclusion of salmon, herring and pompano as oily fish reduces CVD risk markers in dyslipidaemic middle-aged and elderly Chinese women | Pork cannot be isolated |
| Zhang (2010) | Inclusion of Atlantic salmon in the Chinese diet reduces cardiovascular disease risk markers in dyslipidemic adult men | Pork cannot be isolated |
| Zhang (2000) | Intakes of fruits, vegetables, and related nutrients and the risk of non-Hodgkin’s lymphoma among women | Pork cannot be isolated |
| Zhang (1999) | Dietary fat and protein in relation to risk of non-Hodgkin’s lymphoma among women | Pork cannot be isolated |
| Zhen (2018) | Dietary pattern is associated with obesity in Chinese children and adolescents: data from China Health and Nutrition Survey (CHNS) | Pork cannot be isolated |
| Zheng (1998) | Well-done meat intake and the risk of breast cancer | No outcome of interest |
| Zhou (2016) | Higher-protein diets improve indexes of sleep in energy-restricted overweight and obese adults: results from 2 randomized controlled trials | Pork cannot be isolated |