For immediate release: Monday, May 17, 2010
Boston, MA—In a new study, researchers from the Harvard School of
Public Health (HSPH) have found that eating processed meat, such as
bacon, sausage or processed deli meats, was associated with a 42%
higher risk of heart disease and a 19% higher risk of type 2 diabetes.
In contrast, the researchers did not find any higher risk of heart
disease or diabetes among individuals eating unprocessed red meat, such
as from beef, pork, or lamb. This work is the first systematic review
and meta-analysis of the worldwide evidence for how eating unprocessed
red meat and processed meat relates to risk of cardiovascular diseases
and diabetes.
“Although most dietary guidelines recommend reducing meat consumption,
prior individual studies have shown mixed results for relationships
between meat consumption and cardiovascular diseases and diabetes,”
said Renata Micha, a research fellow in the department of epidemiology
at HSPH and lead author of the study. “Most prior studies also did not
separately consider the health effects of eating unprocessed red versus
processed meats.”
Watch a video of Micha describing the findings:
The study appears online May 17, 2010, on the website of the journal Circulation.
The researchers, led by Micha and HSPH colleagues Dariush Mozaffarian,
assistant professor in the department of epidemiology and Sarah
Wallace, junior research fellow in the department of epidemiology,
systematically reviewed nearly 1,600 studies. Twenty relevant studies
were identified, which included a total of 1,218,380 individuals from
10 countries on four continents (North America, Europe, Australia, and
Asia).
The researchers defined unprocessed red meat as any unprocessed meat
from beef, lamb or pork, excluding poultry. Processed meat was defined
as any meat preserved by smoking, curing or salting, or with the
addition of chemical preservatives; examples include bacon, salami,
sausages, hot dogs or processed deli or luncheon meats. Vegetable or
seafood protein sources were not evaluated in these studies.
The results showed that, on average, each 50 gram (1.8 oz) daily
serving of processed meat (about 1-2 slices of deli meats or 1 hot dog)
was associated with a 42% higher risk of developing heart disease and a
19% higher risk of developing diabetes. In contrast, eating
unprocessed red meat was not associated with risk of developing heart
disease or diabetes. Too few studies evaluated the relationship between
eating meat and risk of stroke to enable the researchers to draw any
conclusions.
“Although cause-and-effect cannot be proven by these types of
long-term observational studies, all of these studies adjusted for
other risk factors, which may have been different between people who
were eating more versus less meats,” said Mozaffarian. “Also, the
lifestyle factors associated with eating unprocessed red meats and
processed meats were similar, but only processed meats were linked to
higher risk.”
“When we looked at average nutrients in unprocessed red and
processed meats eaten in the United States, we found that they
contained similar average amounts of saturated fat and cholesterol. In
contrast, processed meats contained, on average, 4 times more sodium
and 50% more nitrate preservatives,” said Micha. “This suggests that
differences in salt and preservatives, rather than fats, might explain
the higher risk of heart disease and diabetes seen with processed
meats, but not with unprocessed red meats.”
Dietary sodium (salt) is known to increase blood pressure, a strong
risk factor for heart disease. In animal experiments, nitrate
preservatives can promote atherosclerosis and reduce glucose tolerance,
effects which could increase risk of heart disease and diabetes.
Given the differences in health risks seen with eating processed
meats versus unprocessed red meats, these findings suggest that these
types of meats should be studied separately in future research for
health effects, including cancer, the authors said. For example, higher
intake of total meat and processed meat has been associated with
higher risk of colorectal cancer, but unprocessed red meat has not been
separately evaluated. They also suggest that more research is needed
into which factors (especially salt and other preservatives) in meats
are most important for health effects.
Current efforts to update the United States government’s Dietary Guidelines for Americans,
which are often a reference for other countries around the world, make
these findings particularly timely, the researchers say. They
recommend that dietary and policy efforts should especially focus on
reducing intake of processed meat.
“To lower risk of heart attacks and diabetes, people should consider
which types of meats they are eating. Processed meats such as bacon,
salami, sausages, hot dogs and processed deli meats may be the most
important to avoid,” said Micha. “Based on our findings, eating one
serving per week or less would be associated with relatively small
risk.”
This study was supported by the Bill & Melinda Gates
Foundation/World Health Organization Global Burden of Diseases, Risk
Factors, and Injuries Study; the National Heart, Lung, and Blood
Foundation, National Institutes of Health (R01 HL 085710); and the
Searle Scholars Program.
“Red and Processed Meat Consumption and Risk of Incident Coronary
Heart Disease, Stroke, and Diabetes Mellitus: A Systematic Review and
Meta-Analysis,” Renata Micha, Sarah K. Wallace, Dariush Mozaffarian, Circulation, online May 17, 2010.
For more information:
Todd Datz
617.998.8819
tdatz@hsph.harvard.edu
617.998.8819
tdatz@hsph.harvard.edu