A new study by scientists at Harvard and the Cleveland Clinic has found that the more red meat one eats, the higher the risk of death from cardiovascular disease, cancer, and all causes, while substituting fish, poultry and other healthy protein foods for red meat lowers the risk of death.
“These results indicate that replacement of red meat with alternative healthy dietary components may lower the mortality risk,” the researchers commented.
Previous studies have associated eating red meat with increased risk for diabetes, cardiovascular disease (CVD) and certain cancers, the authors write in their study background and commentary. But, they say, this is one of the first large studies to go further and examine the relationship between eating unprocessed versus processed red meats and the risk of death from these and all causes.
The new study, which included 37,698 men and 83,644 women, was conducted by An Pan, Ph.D., of the Harvard School of Public Health in Boston, and colleagues from Harvard, the Wellness Institute of the Cleveland Clinic in Ohio, and the German Institute of Human Nutrition in Nuthetal, Germany. It was supported by grants from the National Institutes of Health and an award from the National Heart, Lung and Blood Institute.
The new study was published in the March 12, 2012 issue of the Archives of Internal Medicine, a journal of the American Medical Association.
The Study; Methodology
The researchers analyzed data from two large prospective cohort studies, which included 37,698 men, aged 40 through 75 years, from the Health Professionals Follow-up study (which began in 1986 and included 22 years of follow-up) and 83,644 women, aged 30 through 55 years, from the Nurses Health Study (from which the researchers examined data starting from 1980 and including 28 years of follow-up). All participants were free of cardiovascular disease and cancer at the beginning of the studies.
The participants’ diets were measured by validated food frequency questionnaires, administered at the beginning and every 4 years during the studies. The participants were asked how often, on average (on a scale of 9, ranging from “never or less than once per month” to “6 or more times per day”) they consumed each food of a given portion size.
To measure their unprocessed red meat consumption, the participants were asked how often (on the scale of 9) they consumed an average 3 oz. portion of:
- “beef, pork, or lamb as a main dish,”
- “hamburger,” or
- “beef, pork, or lamb as a sandwich or mixed dish.”
They were also asked how often (on the above scale of 9) they consumed the below portions of processed red meat:
- “bacon” (2 slices, 13g),
- “hot dogs” (one, 45g), or
- “sausage, salami, bologna, and other processed red meats” (1 piece, 28g)
The questionnaires similarly measured intake of other foods, including other healthy protein foods, such as fish, poultry, nuts, and legumes, as well as all dairy products, whole grains, fruits, vegetables, and other foods.
In biennial follow-up questionnaires, updated information was also collected from participants on medical, lifestyle, and other health-related factors, such as their body weight, cigarette smoking, alcohol intake, physical activity level, medication or supplement use, family history of diabetes, heart attack, high blood pressure, cholesterol, and cancer history, as well as menopausal status and postmenopausal hormone use for the women.
Deaths During Study Follow-Up Period.
The researchers documented 23,926 deaths, including 5,910 from cardiovascular disease and 9,464 from cancer during the study follow-up periods (22 years for the men and 28 years for the women).
The researchers analyzed the data to determine the association, if any, between consumption of red meat and risk of death during the study period, from cardiovascular disease (CDV), cancer, and all causes. They also analyzed the association, when 1 serving of an alternative healthy protein food (such as fish, poultry, nuts, legumes, low-fat dairy products or whole grains) was substituted for red meat.
In performing their analysis, the researchers controlled and adjusted for intakes of total energy and major dietary variables, such as intakes of whole grains, fruits and vegetables, fish, poultry, nuts, legumes, and dairy products (all in quintiles); for certain dietary nutrients measured independently of foods, including glycemic load, cereal fiber, magnesium, and polyunsaturated and trans fatty acids (all in quintiles); as well as for other potential nondietary confounding variables, including age, body mass index, race, smoking status, alcohol intake, physical activity level, multivitamin use, aspirin use, family history of diabetes, heart attack or cancer, and baseline history of diabetes, high blood pressure, high cholesterol, and, in women, postmenopausal status and menopausal hormone use.
Findings & Conclusions
“In these 2 large prospective cohorts of US men and women, we found that a higher intake of red meat was associated with a significantly elevated risk of total, CVD and cancer mortality, and this association was observed for unprocessed and processed red meat, with a relatively greater risk for processed red meat,” the study authors wrote in their study report. “Substitution of fish, poultry, nuts, legumes, low-fat dairy products and whole grains for red meat was associated with a significantly lower risk of mortality,” they wrote.
Increase in Red Meat Intake Associated with Higher Risk of Death.
Their analysis showed that for each 1-serving per day increase in the intake of unprocessed red meat (approximately 3oz. of beef, pork or lamb), the participants had an 18% higher risk of death from cardiovascular disease during the 22 to 28 year follow-up period of the studies, a 10% higher risk of death during such period from cancer, and a 13% higher risk of death during that period from all causes.
The results were even more pronounced for consumption of processed red meats. For each 1-serving per day increase in the intake of processed red meats (2 slices of bacon, one hot dog, or 1 piece of sausage, salami, bologna, or other processed red meats) the participants had a 21% higher risk of death from cardiovascular disease during the 22 to 28 year follow-up period of the studies, a 16% higher risk of death during such period from cancer, and a 20% higher risk of death during that period from all causes.
The researchers found no statistically significant differences between consuming different types of unprocessed red meat, or between consuming different types of processed red meats, however, “bacon and hot dogs tended to be associated with a higher risk than other items,” they wrote.
The study authors noted that “Men and women with higher intake of red meat were less likely to be physically active and were more likely to be current smokers, to drink alcohol, and to have a higher body mass index.” “In addition,” they noted, “a higher red meat intake was associated with a higher intake of total energy but lower intakes of whole grains, fruits, and vegetables.” The researchers, however, indicate that they controlled and adjusted for these factors in their analysis.
Substituting Healthy Protein Foods for Red Meat Lowered Risk of Death.
The study analysis also found that “replacing 1 serving of total red meat with 1 serving of fish, poultry, nuts, legumes, low-fat dairy products, or whole grains daily was associated with a lower risk of total mortality.”
Specifically, the risk of death from all causes (total mortality risk) was lowered by the following overall percentages by substituting 1 serving per day of the following healthy protein foods for 1 serving per day of red meats of any kind (processed or unprocessed):
- Fish — 7% lower risk of mortality;
- Poultry — 14% lower risk of mortality;
- Nuts — 19% lower risk of mortality;
- Legumes — 10% lower risk of mortality;
- Low-fat dairy products — 10% lower risk of mortality;
- Whole Grains — 14% lower risk of mortality.
When broken down by whether unprocessed or processed red meats were replaced by healthy proteins, the results showed an even greater reduction in risk of death (from all causes) when processed red meats in the diet (like bacon, hot dog, sausage, salami, bologna, or other processed red meats) were replaced by healthy proteins. Replacing 1 serving per day of unprocessed vs. processed red meats with 1 serving per day of healthy protein foods reduced the risk of death (from all causes) by the following percentages, stated per healthy replacement food:
- Fish — 5% lower risk of mortality replacing unprocessed red meat, but 10% lower risk of mortality replacing processed red meat;
- Poultry — 13% lower risk of mortality replacing unprocessed red meat, but 17% lower risk of mortality replacing processed red meat;
- Nuts — 18% lower risk of mortality replacing unprocessed red meat, but 22% lower risk of mortality replacing processed red meat;
- Legumes — 8% lower risk of mortality replacing unprocessed red meat, but 13% lower risk of mortality replacing processed red meat;
- Low-fat dairy products — 9% lower risk of mortality replacing unprocessed red meat, but 13% lower risk of mortality replacing processed red meat;
- Whole Grains — 13% lower risk of mortality replacing unprocessed red meat, but 16% lower risk of mortality replacing processed red meat.
“We estimated that 9.3 percent in men and 7.6 percent in women of total deaths [from all causes] during follow-up could be prevented if all the participants consumed fewer than 0.5 servings per day of total red meat in these cohorts,” the authors commented.
The analysis further showed that 12.2% of the deaths of women from cardiovascular disease and 8.6% of the deaths of men from cardiovascular disease could have been prevented if all participants ate fewer than 0.5 servings per day of red meat.
In fact, however, only 22.8% of the men and 9.6% of the women in the study actually ate fewer than 0.5 servings per day of red meat, the authors said.
The authors note that “measurement errors inherent in dietary [self-]assessments were inevitable,” but they observe that the chances of confounding error were minimized in this study by the facts that all of the study participants were health professionals, the study size was large (including a combined 121,342 participants), and the follow-up response rates were high (exceeding 90%) over a long follow-up period (up to 28 years).
“In conclusion,” the study authors wrote, “we found that greater consumption of unprocessed and processed red meats is associated with higher mortality risk. Compared with red meat, other dietary components, such as fish, poultry, nuts, legumes, low-fat dairy products, and whole grains, were associated with lower risk. These results indicate that replacement of red meat with alternative healthy dietary components may lower the mortality risk.”
In an invited commentary on the new study, also published in the March 12, 2012 issue of the Archives of Internal Medicine, Dean Ornish, M.D., of the University of California, San Francisco, writes: “In addition to their health benefits, the food choices we make each day affect other important areas as well. What is personally sustainable is globally sustainable. What is good for you is good for our planet.”
Further, he comments, “More than 75 percent of the $2.6 trillion in annual U.S. health care costs are from chronic disease. Eating less red meat is likely to reduce morbidity from these illnesses, thereby reducing health care costs.”
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