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‘Robust’ study endorses link between red/processed meats and cardiovascular disease

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Eating two servings of red meat, processed meat or poultry – but not fish – per week was linked to a 3-7% higher risk of cardiovascular disease, the study found. Eating two servings of red meat or processed meat – but not poultry or fish – per week was associated with a 3% higher risk of all causes of death.

“It’s a small difference, but it’s worth trying to reduce red meat and processed meat like pepperoni, bologna and deli meats,” said senior study author Norrina Allen, associate professor of preventive medicine at Northwestern University Feinberg School of Medicine. “Red meat consumption also is consistently linked to other health problems like cancer.”

“Modifying intake of these animal protein foods may be an important strategy to help reduce the risk of cardiovascular disease and premature death at a population level,” said lead study author Victor Zhong, assistant professor of nutritional sciences at Cornell University, who did the research when he was a postdoctoral fellow in Allen’s lab.

The findings come on the heels of a controversial meta-analysis published last November that recommended people not reduce the amount of red meat and processed meat they eat. “Everyone interpreted that it was OK to eat red meat, but I don’t think that is what the science supports,” Allen said. “Our study shows the link to cardiovascular disease and mortality was robust,” Zhong said.

“Fish, seafood and plant-based sources of protein such as nuts and legumes, including beans and peas, are excellent alternatives to meat and are under-consumed in the US,” said study co-author Linda van Horn, professor of preventive medicine at Feinberg who also is a member of the 2020 US Dietary Guidelines Advisory committee.

The study found a positive association between poultry intake and cardiovascular disease, but the evidence so far isn’t sufficient to make a clear recommendation about poultry intake, Zhong said. Still, fried chicken is not recommended.

The study pooled together a large diverse sample from six cohorts, included long follow-up data up to three decades, harmonised diet data to reduce heterogeneity, adjusted a comprehensive set of confounders and conducted multiple sensitivity analyses. The study included 29,682 participants (mean age of 53.7 years at baseline, 44.4% men and 30.7% non-white). Diet data were self-reported by participants, who were asked a long list of what they ate for the previous year or month.

Key findings: a 3 to 7% higher risk of cardiovascular disease and premature death for people who ate red meat and processed meat two servings a week; a 4% higher risk of cardiovascular disease for people who ate two servings per week of poultry, but the evidence so far is not sufficient to make a clear recommendation about poultry intake and the relationship may be related to the method of cooking the chicken and consumption of the skin rather than the chicken meat itself; and no association between eating fish and cardiovascular disease or mortality.

Limitations of the study are participants’ dietary intake was assessed once, and dietary behaviours may have changed over time. In addition, cooking methods were not considered. Fried chicken, especially deep fat-fried sources that contribute trans-fatty acids, and fried fish intake have been positively linked to chronic diseases, Zhong said.

The study was funded by National Institutes of Health/National Heart, Lung, and Blood Institute (R21 HL085375), American Heart Association Strategically Focused Research Networks and the Feinberg School of Medicine.

Abstract
Importance: Although the associations between processed meat intake and cardiovascular disease (CVD) and all-cause mortality have been established, the associations of unprocessed red meat, poultry, or fish consumption with CVD and all-cause mortality are still uncertain.
Objective: To identify the associations of processed meat, unprocessed red meat, poultry, or fish intake with incident CVD and all-cause mortality.
Design, Setting, and Participants: This cohort study analyzed individual-level data of adult participants in 6 prospective cohort studies in the United States. Baseline diet data from 1985 to 2002 were collected. Participants were followed up until August 31, 2016. Data analyses were performed from March 25, 2019, to November 17, 2019.
Exposures: Processed meat, unprocessed red meat, poultry, or fish intake as continuous variables.

Main Outcomes and Measures Hazard ratio (HR) and 30-year absolute risk difference (ARD) for incident CVD (composite end point of coronary heart disease, stroke, heart failure, and CVD deaths) and all-cause mortality, based on each additional intake of 2 servings per week for monotonic associations or 2 vs 0 servings per week for nonmonotonic associations.
Results: Among the 29 682 participants (mean [SD] age at baseline, 53.7 [15.7] years; 13 168 [44.4%] men; and 9101 [30.7%] self-identified as non-white), 6963 incident CVD events and 8875 all-cause deaths were adjudicated during a median (interquartile range) follow-up of 19.0 (14.1-23.7) years. The associations of processed meat, unprocessed red meat, poultry, or fish intake with incident CVD and all-cause mortality were monotonic (P for nonlinearity ≥ .25), except for the nonmonotonic association between processed meat intake and incident CVD (P for nonlinearity = .006). Intake of processed meat (adjusted HR, 1.07 [95% CI, 1.04-1.11]; adjusted ARD, 1.74% [95% CI, 0.85%-2.63%]), unprocessed red meat (adjusted HR, 1.03 [95% CI, 1.01-1.06]; adjusted ARD, 0.62% [95% CI, 0.07%-1.16%]), or poultry (adjusted HR, 1.04 [95% CI, 1.01-1.06]; adjusted ARD, 1.03% [95% CI, 0.36%-1.70%]) was significantly associated with incident CVD. Fish intake was not significantly associated with incident CVD (adjusted HR, 1.00 [95% CI, 0.98-1.02]; adjusted ARD, 0.12% [95% CI, −0.40% to 0.65%]). Intake of processed meat (adjusted HR, 1.03 [95% CI, 1.02-1.05]; adjusted ARD, 0.90% [95% CI, 0.43%-1.38%]) or unprocessed red meat (adjusted HR, 1.03 [95% CI, 1.01-1.05]; adjusted ARD, 0.76% [95% CI, 0.19%-1.33%]) was significantly associated with all-cause mortality. Intake of poultry (adjusted HR, 0.99 [95% CI, 0.97-1.02]; adjusted ARD, −0.28% [95% CI, −1.00% to 0.44%]) or fish (adjusted HR, 0.99 [95% CI, 0.97-1.01]; adjusted ARD, −0.34% [95% CI, −0.88% to 0.20%]) was not significantly associated with all-cause mortality.
Conclusions and Relevance: These findings suggest that, among US adults, higher intake of processed meat, unprocessed red meat, or poultry, but not fish, was significantly associated with a small increased risk of incident CVD, whereas higher intake of processed meat or unprocessed red meat, but not poultry or fish, was significantly associated with a small increased risk of all-cause mortality. These findings have important public health implications and should warrant further investigations.

Authors
Victor W Zhong, Linda van Horn, Philip Greenland, Mercedes R Carnethon, Hongyan Ning, John T Wilkins, Donald M Lloyd-Jones, Norrina B Allen

Northwestern University material

JAMA Internal Medicine abstract

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