Reconciling contrasting guideline recommendations on red and processed meat for health outcomes

Saturated fat and human health: a protocol for a methodologically innovative systematic review and meta-analysis to inform public health nutrition guidelines

BACKGROUND

The health effects of dietary fats are a controversial issue on which experts and authoritative organizations have often disagreed. Care providers, guideline developers, policy-makers, and researchers use systematic reviews to advise patients and members of the public on optimal dietary habits, and to formulate public health recommendations and policies. Existing reviews, however, have serious limitations that impede optimal dietary fat recommendations, such as a lack of focus on outcomes important to people, substantial risk of bias (RoB) issues, ignoring absolute estimates of effects together with comprehensive assessments of the certainty of the estimates for all outcomes.

OBJECTIVE

We therefore propose a methodologically innovative systematic review using direct and indirect evidence on diet and food-based fats (i.e., reduction or replacement of saturated fat with monounsaturated or polyunsaturated fat, or carbohydrates or protein) and the risk of important health outcomes.

METHODS

We will collaborate with an experienced research librarian to search MEDLINE, EMBASE, CINAHL, and the Cochrane Database of Systematic Reviews (CDSR) for randomized clinical trials (RCTs) addressing saturated fat and our health outcomes of interest. In duplicate, we will screen, extract results from primary studies, assess their RoB, conduct de novo meta-analyses and/or network meta-analysis, assess the impact of missing outcome data on meta-analyses, present absolute effect estimates, and assess the certainty of evidence for each outcome using the GRADE contextualized approach. Our work will inform recommendations on saturated fat based on international standards for reporting systematic reviews and guidelines.

CONCLUSION

Our systematic review and meta-analysis will provide the most comprehensive and rigorous summary of the evidence addressing the relationship between saturated fat modification for people-important health outcomes. The evidence from this review will be used to inform public health nutrition guidelines.

TRIAL REGISTRATION

PROSPERO Registration: CRD42023387377 .

One person's meat is another's poison: representations of the meat-health nexus in UK news media

Mainstream media play a central role in shaping the ways diet and nutrition are discussed in the public sphere, yet few studies have explored its depictions of the meat-health nexus. Focusing on eight of the most popular news online sites consumed by lower-income groups in the UK—the demographic most likely to eat meat, according to a survey conducted for this study—we carried out content analysis of 128 articles. We found, first, a multiplicity of pro- and anti-meat narratives across all news outlets; second, that the dominant recommendation, found in 40% of our sample, was to eat less or no red meat; and third, that a balanced or neutral sentiment was present in over half of our sample, with a ratio of 3:2 (anti-versus pro-meat) in remaining articles. We found that the editorial leaning of a news outlet was not closely correlated with its overall sentiment towards meat consumption; all were neutral or slightly anti-meat, with the exception of LAD Bible, the only clearly pro-meat outlet. Qualitative analysis uncovered three key themes: the risk of red meat on colorectal cancer, uncertainty around plant-based options, and individual dietary choice. We use case studies guided by these themes to highlight some of the shortcomings of health communication and provide recommendations, with a focus on improved dialogue between journalists and researchers.

Similarities, reliability and gaps in assessing the quality of conduct of systematic reviews using AMSTAR-2 and ROBIS: systematic survey of nutrition reviews

BACKGROUND

AMSTAR-2 ('A Measurement Tool to Assess Systematic Reviews, version 2') and ROBIS ('Risk of Bias in Systematic Reviews') are independent instruments used to assess the quality of conduct of systematic reviews/meta-analyses (SR/MAs). The degree of overlap in methodological constructs together with the reliability and any methodological gaps have not been systematically assessed and summarized in the field of nutrition.

METHODS

We performed a systematic survey of MEDLINE, EMBASE, and the Cochrane Library for SR/MAs published between January 2010 and November 2018 that examined the effects of any nutritional intervention/exposure for cancer prevention. We followed a systematic review approach including two independent reviewers at each step of the process. For AMSTAR-2 (16 items) and ROBIS (21 items), we assessed the similarities, the inter-rater reliability (IRR) and any methodological limitations of the instruments. Our protocol for the survey was registered in PROSPERO (CRD42019121116).

RESULTS

We found 4 similar domain constructs based on 11 comparisons from a total of 12 AMSTAR-2 and 14 ROBIS items. Ten comparisons were considered fully overlapping. Based on Gwet's agreement coefficients, six comparisons provided almost perfect (> 0.8), three substantial (> 0.6), and one a moderate level of agreement (> 0.4). While there is considerable overlap in constructs, AMSTAR-2 uniquely addresses explaining the selection of study designs for inclusion, reporting on excluded studies with justification, sources of funding of primary studies, and reviewers' conflict of interest. By contrast, ROBIS uniquely addresses appropriateness and restrictions within eligibility criteria, reducing risk of error in risk of bias (RoB) assessments, completeness of data extracted for analyses, the inclusion of all necessary studies for analyses, and adherence to predefined analysis plan.

CONCLUSIONS

Among the questions on AMSTAR-2 and ROBIS, 70.3% (26/37 items) address the same or similar methodological constructs. While the IRR of these constructs was moderate to perfect, there are unique methodological constructs that each instrument independently addresses. Notably, both instruments do not address the reporting of absolute estimates of effect or the overall certainty of the evidence, items that are crucial for users' wishing to interpret the importance of SR/MA results.

Toward more rigorous and informative nutritional epidemiology: The rational space between dismissal and defense of the status quo

To date, nutritional epidemiology has relied heavily on relatively weak methods including simple observational designs and substandard measurements. Despite low internal validity and other sources of bias, claims of causality are made commonly in this literature. Nutritional epidemiology investigations can be improved through greater scientific rigor and adherence to scientific reporting commensurate with research methods used. Some commentators advocate jettisoning nutritional epidemiology entirely, perhaps believing improvements are impossible. Still others support only normative refinements. But neither abolition nor minor tweaks are appropriate. Nutritional epidemiology, in its present state, offers utility, yet also needs marked, reformational renovation. Changing the status quo will require ongoing, unflinching scrutiny of research questions, practices, and reporting-and a willingness to admit that "good enough" is no longer good enough. As such, a workshop entitled "Toward more rigorous and informative nutritional epidemiology: the rational space between dismissal and defense of the status quo" was held from July 15 to August 14, 2020. This virtual symposium focused on: (1) Stronger Designs, (2) Stronger Measurement, (3) Stronger Analyses, and (4) Stronger Execution and Reporting. Participants from several leading academic institutions explored existing, evolving, and new better practices, tools, and techniques to collaboratively advance specific recommendations for strengthening nutritional epidemiology.

Perspective: Unpacking the Wicked Challenges for Alternative Proteins in the United States: Can Highly Processed Plant-Based and Cell-Cultured Food and Beverage Products Support Healthy and Sustainable Diets and Food Systems?

Over the past decade, a plethora of alternative protein (AP) products has entered the US food system as plant-based food and beverage products. These AP products, which include plant-based meat and dairy alternatives and cell-cultured meat and seafood products, are being developed for the marketplace to simulate the appearance, texture, taste, and flavor and nutritional profiles of animal products. The new generation of AP plant-based and cell-cultured food and beverage products are part of a market-driven narrative that has embraced technology to address future human health, environmental, ethical, and planetary health challenges. This perspective article synthesizes evidence about the benefits of adopting minimally processed plant-based diets that support sustainable food systems and human and planetary health. Thereafter, it examines 4 wicked challenges related to AP products in the US context that include 1) a confusing marketing landscape for the public; 2) diverse views and varying acceptance among consumers about the health and environmental benefits of these products; 3) inadequate education and labeling provided by federal agencies to enable consumers to understand how these may support healthy sustainable diets; and 4) slow federal policy and regulatory actions to address the range of AP products and provide industry guidance. The article concludes with suggested policies and actions for government agencies and food system actors to address these challenges. Future research and actions are needed to balance the human health, equity, animal welfare, and economic viability goals and to clarify how AP products may support safe, healthy, sustainable diets and food systems.