How funding affects cardiac red meat study conclusions

How funding affects cardiac red meat study conclusions

A new review shows how financial conflicts of interest and strategic study design are influencing the narrative about the real effects of red meat on cardiovascular health, prompting calls for more transparent and independent nutritional research.

Study: Industry Study Sponsorship and Conflicts of Interest on the Impact of Unprocessed Red Meat on the Risk of Cardiovascular Disease: A Systematic Review of Clinical Trials. Photo credit: Sergey Ryzhov/Shutterstock.com

A study published inThe American Journal of Clinical Nutrition demonstrated that red meat industry financial sponsorship and conflicts of interest may be associated with differences in scientific conclusions regarding the effects of red meat intake on cardiovascular health.

background

Excessive intake of processed red meat is a known risk factor for cardiovascular disease and related mortality. This increased risk could be due to high levels of salt, polycyclic aromatic hydrocarbons, nitrates and nitrites in processed meats.

A healthy diet that emphasizes consuming plant-based foods and limiting animal foods is considered beneficial for cardiovascular health. When it comes to unprocessed meat intake, the evidence is inconclusive, with some studies reporting negative effects, some showing neutral effects, and some even showing positive effects on cardiovascular health.

While parallels have been drawn with research funded by the tobacco and alcohol industries, which are known to influence scientific conclusions, nutrition research has also shown patterns in which industries' funding aligns with sponsoring interests. For example, studies funded by the red meat industry have sometimes been linked to efforts to downplay the environmental impact of livestock on climate change and planetary health.

However, prior to this study, evidence did not conclusively show that funding of the red meat industry drives favorable or inconclusive findings on the association between unprocessed red meat consumption and cardiovascular health.

Given the growing attention on unprocessed red meat intake for health and environmental reasons, this systematic review aimed to assess whether red meat industry sponsorship or conflicts of interest influence study results on the effects of unprocessed red meat intake on cardiovascular disease risk.

Review design

The researchers examined various electronic databases to identify randomized and non-randomized controlled trials that examined the effects of unaddressed cardiovascular disease risk factors. Unprocessed red meat refers to beef, veal, pork, lamb, mutton, horse and goat meat that has not been preserved other than refrigeration or freezing.

The selected studies were classified as “red meat industry-related” if authors declared an affiliation or financial disclosure indicating a connection to the red meat industry or “red meat industry-independent” if no authors declared an affiliation or financial disclosure indicating a connection with the red meat industry.

Studies were also assessed using the Cochrane risk of bias tool and the degree approach to assess the quality of evidence, which was largely rated as low or very low. Additionally, they were grouped by comparator type: animal protein, plant protein, refined carbohydrates, or a mixture.

Study results

The researchers systematically analyzed 44 studies, 29 involving the red meat industry. Most selected studies compared unprocessed red meat with animal protein, plant protein, refined carbohydrates, and a combination of animal and plant protein.

Approximately 21% and 79% of red meat industry studies reported favorable and neutral cardiovascular outcomes following unprocessed red meat intake. In contrast, 73% and 27% of industry-independent red meat studies reported unfavorable and neutral results, respectively. None of the independent studies reported favorable cardiovascular outcomes.

Studies with financial conflicts of interest were almost four times more likely to report favorable or neutral results than independent studies.

Investigate significance

This systematic review shows that most studies not associated with the red meat industry indicate adverse cardiovascular outcomes for those consuming red meat. On the other hand, studies funded by the red meat industry are more likely to report neutral or favorable cardiovascular outcomes.

In the red meat industry, studies are more likely to report neutral or favorable results, which can be explained by their experimental design comparing unprocessed red meat to animal protein or refined carbohydrates.

However, accident-independent red meat studies primarily compared unprocessed red meat with plant protein, leading to the conclusion of unfavorable cardiovascular outcomes. These observations highlight the importance of selecting an appropriate comparator while assessing the impact of diet on health outcomes.

Processed meat or refined carbohydrates are known risk factors for cardiovascular disease. Comparing these food products to unprocessed meat increases the likelihood of favorable or neutral results. This methodological choice has been frequently observed in industry-related studies.

Studies not associated with the red meat industry have found that unprocessed red meat should be replaced with high-quality plant proteins to improve heart health.

The study emphasizes that nutritional effects must be interpreted in context, as dietary components are not consumed in isolation. This is called the “isocaloric principle,” meaning that the health effects of food often depend on what it replaces.

Almost all of the studies included in the review were conducted in high-income countries, raising questions about the global applicability of the results

Plant proteins may increase the abundance of anti-inflammatory bacteria and decrease the abundance of inflammatory bacteria in the gut, potentially justifying their cardiovascular health benefits. On the other hand, animal proteins can adversely affect gut microbiota composition and diversity, highlighting their potential adverse cardiovascular effects.

However, the study notes that these mechanisms are still being investigated, and the benefits of replacing red meat with plant proteins may be due in part to beneficial compounds in plant foods as well as the removal of potentially harmful components in red meat.

Given the observations made in this review, researchers advise carefully interpreting the results of industry-funded studies to ensure public health where potential conflicts of interest exist. However, they agreed that industrial funding is essential to supporting major nutrition research.

Although the review highlights the significant influence of conflicts of interest on study results, the researchers mentioned that such influence does not necessarily imply intentional misconduct, and the researchers should not be assumed without clear evidence.

The authors also emphasized that the industry-funded studies did not differ in overall quality compared to independent studies, suggesting that the choice of comparator, rather than study quality itself, may play a more crucial role in shaping conclusions.

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