Experts are aware that processed red meats can increase the risk of cardiovascular disease and death. Nor are they less toxic to unprocessed meats, fish and poultry? New inquiries are ongoing.
Many studies have identified a correlation between eating processed meat — including bacon, hot dogs, sausages and other similar foods — and an increased risk of cardiovascular disease (CVD) and death.
Such correlations may be clarified by the greater amount of saturated fats in these foods, along with a higher level of salt and preservatives. Newer research has suggested that even a small amount of these foods would be adequate to endanger health.
But what about other meats, like red meat unprocessed, poultry or fish? Do those foods have the same effect on cardiovascular risk and longevity?
The work here is more complex. The results of some research varied in part because the methods were different, and in part because there were limitations on the existing prospective cohort studies.
A group of scientists led by Victor W. Zhong, Ph.D., Cornell University, Ithaca, New York, set out to conduct a new meta-analysis of six existing studies in order to fill this gap in research.
The pooled research will appear in the JAMA Internal Medicine journal.
Studying intake of meat, poultry, and fish
Zhong and the team looked at prospective cohort studies that had been performed across the U.S., totalling 29,682 U.S. adults without baseline CVDs.
44 per cent of participants were men, and nearly 31 per cent were non-white.
Researchers had documented the dietary data of the participants from 1985–2002 and followed them clinically for 30 years, until 31 August 2016.
6,963 adverse cardiovascular events and 8,875 all-cause deaths occurred over a median follow-up period of 19 years.
Of the cardiovascular events, 38.6% were cases of coronary heart disease, 25% were events of a stroke, and 34.0% involved heart failure.
The researchers used the Willett Food Frequency Questionnaire to define what constitutes 1 serving of meat and to assess the diet of the participants.
“1 serving equals 4[ ounces] for unprocessed red meat or poultry, or 3[ ounces] of fish. Of processed meat, 1 serving consisted of 2 slices of bacon, 2 tiny sausage links or 1 hot dog,” the authors explain.
Average consumption of meat, poultry and fish servings per week was 1.5 for processed meat, 3 for unprocessed red meat, 2 for poultry and 1.6 for fish.
“Participants with a higher total intake than participants with a lower total intake of these four types of food,” the authors write, “were more likely to:
- be younger and male
- be non-Hispanic black
- be smokers, have diabetes, a higher body mass index (BMI), higher non-high-density lipoprotein (HDL) cholesterol levels, and consume more alcohol
- have lower HDL cholesterol levels and eat a lower diet quality diet
- have a higher incidence of CVD and death from any cause
The key result the scientists were looking for was the relative risk of CVD and all-cause mortality between people who ate these different foods over the 30 years, as well as the difference in absolute risk over the same period.
We measured the risks of 2 servings per week for each extra intake.
Up to 7% higher relative risk of death, CVD
Zhong and the team summarize the findings:’ The consumption of processed meat, unprocessed red meat or poultry was significantly associated with cardiovascular disease, but the intake of fish was not.’
Specifically, the increased relative risk of CVD and all-cause mortality ranged from about 3% to 7%. “Over the 30 years of follow-up, the raised absolute threats were less than 2 per cent,” the authors say.
More in-depth analysis shows that the relative risk of all-cause mortality rose by 3 percent for every 2 additional servings of processed meat per week compared to those not eating processed meat.
For every additional 2 servings of unprocessed meat the same was valid.
For every 2 servings of processed meat per week, the relative risk of CVD increased by 7 per cent. The risk was 3 per cent for untreated red meat.
An increase in 2 weekly portions of poultry correlated with a 4% higher relative risk, whereas the risk of CVD was not associated with fish.
“There would be greater risks for those who consume more portions per week,” the researchers say.
Study of ‘critical public health’ importance
The authors take the “critical public health” tests as important. We also mention the need for more work to confirm the results.
As it stands there are some disadvantages to the current study, such as the self-reported nature of dietary results. This may have resulted in the relation being over-or underestimated.
Second, the scientists lacked data on the food preparation process. Whether the meat was fried or not, the health outcomes may have been affected.
Third, at the beginning of the study, the study used only one dietary metric but the participants ‘ dietary habits may have changed over time.
Finally, the residual confounding, the study’s retrospective existence, and the fact that results may only be restricted to U.S. adults are further limitations of this analysis. But Zhong and the team conclude:
“Since dietary habits are modifiable, the findings of this study tend to have important public health consequences and most people consume these four types of food on a daily or weekly basis.”