Following controversial guideline, another study connects meat consumption to CVD

Another study has surfaced suggesting that meat—both processed and unprocessed—can have deleterious effects on heart health.

According to Victor W. Zhong, PhD, and colleagues, who published their research in JAMA Internal Medicine Feb. 3, processed meats, unprocessed red meats, poultry and fish are “major” components of the American diet, comprising some 40% of the nation’s protein intake, 42% of its dietary cholesterol intake and 26% of its total energy intake. The cardiovascular consequences of meat consumption are hotly debated in the U.S., with countless studies both supporting and refuting the idea that a protein-heavy diet can be healthy.

“The positive associations between processed meat intake and CVD and mortality have been established, but the associations of unprocessed red meat, poultry or fish intake with CVD and mortality remain uncertain, partly owing to heterogeneity across studies, methodological limitation and limited data from long-term prospective cohort studies,” Zhong, of Cornell University, and co-authors wrote in JAMA.

Certain studies have suggested that eating fish—or even omega-3-enriched chicken—can improve a person’s heart health, since higher omega-3 indexes have been linked to lower odds of heart attack, stroke, diabetes and cancer. The best-ranked diets of the past several years, including the Mediterranean diet, promote fish and poultry consumption, while others, including the Paleo diet, have been criticized for championing red meat.

Last October, a panel of 14 international scientists published a nutritional guideline in the Annals of Internal Medicine advising adults to continue consuming both red meat and processed meats. The recommendation, which one editorialist said was “sure to be controversial,” conflicted with many existing nutritional guidelines and received immediate pushback from the medical community. It was revealed within days of publication that one of the guideline’s authors had ties to the meat industry; Annals issued a correction to the paper just last month.

For their work, Zhong and his team focused individual-level data of 29,682 adults who participated in six prospective cohort studies in the U.S. between 1985 and 2002. Participants were on average in their early fifties and were followed until 2016.

The researchers reported 6,963 incident CVD events and 8,875 all-cause deaths during 19 years of follow-up. They said the associations of processed meat, unprocessed red meat, poultry and fish intake with CVD and all-cause mortality were monotonic, but there was a nonmonotonic relationship between processed meat intake and incident CVD.

All proteins except for fish raised individuals’ risk of heart events:

  • Processed meat: 7% increased risk of incident CVD
  • Unprocessed red meat: 3% increased risk of incident CVD
  • Poultry: 4% increased risk of incident CVD

Intake of processed meats was linked to a 3% increase in all-cause mortality, as was intake of unprocessed red meat. Poultry and fish consumption weren’t significantly associated with death.

“The significant positive associations of processed meat or unprocessed red meat intake with incident CVD and all-cause mortality remained after adjusting for a comprehensive list of covariates,” Zhong and colleagues wrote. “This study’s findings suggest that among U.S. 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. 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.”