Red Meat Intake Increases Mortality Risk

CLINICAL CONTEXT

According to the current study by Pan and colleagues,

meat is a major source of protein and fat in most diets,

but red meat consumption has been linked to

cardiovascular disease (CVD) and certain cancers.

Although red meat is also associated with increased mortality risk, studies have not examined the role of unprocessed vs processed red meat, and no study has examined the role of substitution of red meat with other foods on mortality risk.

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This analysis of 2 prospective cohorts — the Health Professionals Follow-up Study (HPFS) and the Nurses’ Health Study (NHS) — compares mortality risk associated with unprocessed and processed red meat consumption among men and women and determines the risk reduction associated with substitution with other food types.

STUDY SYNOPSIS AND PERSPECTIVE

Long-term data from two large studies might have more people considering a switch to vegetarianism, with investigators reporting results showing that processed and unprocessed meat consumption is associated with a significantly increased risk of all-cause and cardiovascular mortality, as well as increased risk of death from cancer [1]. After adjustment for multiple risk factors, eating one additional serving of meat daily was associated with a 16% increase in the risk of cardiovascular mortality and a 10% increased risk of death from cancer.

“I think the overall message is that we should reduce our meat consumption and for processed meats we should definitely try to avoid or eliminate these from the diet,” lead investigator Dr An Pan (Harvard School of Public Health, Boston, MA) told heartwire . “For unprocessed red meat, most people should reduce the amount consumed to less than three servings per week and to replace these servings with fish, poultry, and healthy whole grains. The problem with the US diet is that a lot of people eat more than one and sometimes more than two servings of red meat per day. That’s a lot.”

To Dr Dean Ornish (Preventive Medicine Research Institute, Sausalito, CA), who wrote an accompanying comment on the study [2], there is an emerging consensus among nutritionists as to what constitutes a healthy diet. Individuals should aim to eat little to no red meat, more good carbohydrates such as vegetables, fruits, whole grains, legumes, and soy and fewer simple and refined carbohydrates, and more healthy fatty acids. In other words, “more quality, less quantity,” he writes. Such a diet would go a long way toward treating the health crisis in the US, as well as reducing global warming and energy consumption.

“At a time when 20% of people in the US go to bed hungry each night and almost 50% of the world’s population is malnourished, choosing to eat more plant-based foods and less red meat is better for all of us — ourselves, our loved ones, and our planet,” writes Ornish. “In short, don’t have a cow!”

The study and editorial are published online March 12, 2012 in the Archives of Internal Medicine.

Long-term follow-up from HPFS and NHS

Previous epidemiological studies have shown that eating meat, particularly red meat, is associated with an increased risk of diabetes, coronary heart disease, stroke, and some types of cancers, including colorectal cancer. With these risks, the researchers sought to determine whether eating red meat was associated with an increased risk of death from cardiovascular causes or cancer using data from 37 698 men from HPFS and 83 644 women from NHS.

In total, 8926 deaths, including 2716 deaths from cardiovascular causes and 3073 cancer deaths, were reported in follow-up of 22 years in the HPFS. In the NHS, with 28 years of follow-up, there were 15 000 deaths, including 3194 from cardiovascular causes and 6391 deaths from cancer. Overall, men and women who ate more red meat were less likely to be physically active and more likely to be current smokers as well as more likely to drink alcohol and have a higher body-mass index (BMI). Higher intake of red meat was also associated with eating more calories but with reduced intakes of grains, fruits, and vegetables, as well as lower intakes of fish and poultry.

Overall, eating processed and unprocessed red meat was associated with an increased risk of all-cause mortality, cardiovascular mortality, and cancer mortality in men and women in risk models that adjusted for age and multiple risk factors, including physical activity, BMI, and smoking status, among others. When red-meat intake was treated as a continuous variable, each additional serving of red meat was associated with a significant 12%, 16%, and 10% increased risk of all-cause, cardiovascular, and cancer mortality.

Mortality according to red-meat intake* in HPFS and NHS

Variable Quintile (Q) 1 Q2, HR (95% CI) Q3, HR (95% CI) Q4, HR (95% CI) Q5, HR (95% CI) p for trend HR (95% CI) for each 1-serving/day increase
All-cause mortality, total red meat 1 (reference) 1.10 (1.05) 1.15 (1.06–1.26) 1.21 (1.14–1.28) 1.30 (1.18–1.43) < 0.001 1.12 (1.09–1.15)
All-cause mortality, unprocessed red meat 1 (reference) 1.08 (1.05–1.12) 1.10 (1.03–1.17) 1.15 (1.05–1.25) 1.23 (1.14–1.34) < 0.001 1.13 (1.07–1.20)
All-cause mortality, processed red meat 1 (reference) 1.05 (1.00–1.09) 1.11 (1.04–1.18) 1.15 (1.11–1.20) 1.32 (1.16–1.30) < 0.001 1.20 (1.15–1.24)
Cardiovascular mortality, total red meat 1 (reference) 1.12 (1.03–1.22) 1.13 (1.04–1.24) 1.23 (1.13–1.34) 1.40 (1.29–1.53) < 0.001 1.16 (1.12–1.20)
Cancer mortality 1 (reference) 1.05 (0.98–1.12) 1.09 (1.02–1.16) 1.16 (1.08–1.24) 1.19 (1.11–1.28) < 0.001 1.10 (1.07–1.13)

*Red meat consumption in Q1, Q2, Q3, Q4, and Q4 was 0.22, 0.62, 1.01, 1.47, and 2.36 servings per day in the HPFS and 0.53, 1.04, 1.52, 2.01, and 3.10 servings per day in NHS

The researchers also performed a “replacement analysis,” reporting on the reduction in mortality risk if one serving of red meat was replaced with healthier options. Replacing one serving of red meat with fish, poultry, nuts, legumes, low-fat dairy products, or whole grains was associated with a 7%, 14%, 19%, 10%, 10%, and 14% lower risk of total mortality, respectively. The group estimated that nearly one in 10 deaths in men and 7.6% of deaths in women could be prevented if the population consumed fewer than 0.5 servings of red meat per day.

“We are not telling people to totally eliminate red meat,” Pan told heartwire . “That’s not possible for a lot of people. Instead, we’d like them to try to replace red meat with other healthier options. We don’t want everybody to be a vegetarian.”

For Ornish, the substitution analysis also confirms the relative importance of what is included in the diet. Plant-based foods, he notes, are high in phytochemicals, bioflavonoids, and other protective substances, and individuals have a whole range of healthy food options available to them when reducing or eliminating red meat from their diets.

To heartwire , Pan said there are several possible reasons for the increased risk of death with red-meat consumption, most notably that red meat contains saturated fat and cholesterol. Adjusting for saturated fat and cholesterol attenuated the risk of mortality in their analysis but did not eliminate it, suggesting other factors might mediate the increased risk. Heme iron, primarily from red meat, has previously been associated with an increased risk of myocardial infarction and fatal coronary heart disease. Adjusting for heme iron in this analysis moderately attenuated the risk of death, suggesting heme-iron intake might partially explain the association between red meat and cardiovascular mortality. High cooking temperatures might also create possible carcinogens, which might partially explain the cancer risk, say researchers.

The authors reported no conflicts of interest. Ornish is author of several diet books, including Dr Dean Ornish’s Program for Reversing Heart DiseaseEat More, Weigh LessLove & Survival; and the Spectrum.

References

  1. Pan A, Sun Q, Bernstein AM, et al. Red meat consumption and mortality. Arch Intern Med 2012; DOI:10.1001/archinternmed.2011.2287. Available at: http://www.archinternmed.com.
  2. Ornish D. Holy cow! What’s good for you is good for our planet. Arch Intern Med 2012; available at:http://www.archinternmed.com.

STUDY HIGHLIGHTS

 

  • The HPFS was initiated in 1986 and involved 51,529 men 40 to 75 years old. These men were male health professionals who completed biennial mailed questions about lifestyle, food consumption, and health status.
  • The NHS was initiated in 1976 and involved 121,700 female nurses 30 to 55 years old who also completed mailed biennial questionnaires.
  • In each 2-year cycle, the response rate was more than 90% in both cohorts.
  • The baseline for this study was 1986 for the HPFS cohort and 1980 for the NHS cohort when a food frequency questionnaire was used to determine energy intake from food sources.
  • In each food frequency questionnaire, participants were asked about frequency of consumption of up to 166 items (early food frequency questionnaires contained 61 items) in a standard portion size.
  • There were 9 possible responses from “never or less than once per month” to “6 or more times per day.”
  • Unprocessed red meat included beef, pork, and lamb as a main dish. The standard portion size was 3 ounces.
  • Processed red meat included hamburger, sausage, bacon, hot dogs, and other unprocessed meats.
  • Ascertainment of death was by postal authorities, from next of kin or by search of the National Death Index.
  • Causes of death were verified by examination of death certificates. The International Classification of Diseases, Eighth Revision, criteria were used for causes of death.
  • Analysis controlled for other variables such as physical activity, smoking, medication, and diagnosis of diabetes. For women, menopausal status was an additional variable.
  • For this analysis, exclusion criteria were CVD or cancer at baseline or missing or implausible data on the food frequency questionnaire.
  • The HPFS (n = 37,698) had up to 22 years of follow-up (758,524 person-years), and 896 deaths were documented (2716 CVD deaths and 3073 cancer deaths).
  • The NHS (n = 83,644) had up to 28 years of follow-up (2,199,892 person-years), and 15000 deaths were documented (3194 CVD deaths and 6391 cancer deaths).
  • For both cohorts combined, there were 23,926 deaths (5910 CVD deaths and 9464 cancer deaths) during 2.96 million person-years of follow-up.
  • Men and women with higher red meat intake were likely to have a higher BMI, be less physically active, were more likely to smoke, and were more likely to drink alcohol.
  • Higher red meat intake was associated with higher energy intake and lower intake of whole grains, fruits, and vegetables.
  • During follow-up, red meat consumption declined in men and women.
  • For example, the mean daily intake of unprocessed red meat decreased from 0.75 to 0.63 servings between 1986 and 2006 in men, and from 1.10 to 0.55 servings between 1980 and 2006 in women.
  • In the adjusted model, unprocessed and processed red meat consumption was associated with increased risks for total, CVD, and cancer deaths among both men and women.
  • The hazard ratio (HR) for 1 additional serving per day for total mortality was 1.12 for total red meat, 1.13 for unprocessed red meat, and 1.20 for processed red meat.
  • The respective HRs for CVD death were 1.16, 1.18, and 1.21 for total red meat, unprocessed red meat, and processed red meat.
  • The respective HRs for cancer mortality were 1.10, 1.10, and 1.16 for total red meat, unprocessed red meat, and processed red meat.
  • There were no differences in the risk for mortality for different types of unprocessed meat or processed meat.
  • However, bacon and hot dog were associated with a higher risk than other meat items.
  • There was no interaction of physical activity or BMI with the association between meat intake and mortality risk.
  • Adjustment for intake of other nutrients such as fish, grains, and dairy products did not alter the associations.
  • Results were not changed by adjustment for chronic diseases.
  • In substitution analyses, 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 for total mortality.
  • For replacement of total red meat, the mortality rates were 7% lower for fish, 14% lower for poultry, 19% lower for nuts, 10% lower for legumes, 10% lower for low-fat dairy products, and 14% lower for whole grains.
  • The corresponding reductions for replacement of unprocessed red meat were 5%, 13%, 18%, 8%, 9%, and 13%.
  • The corresponding reductions for replacement of processed red meat were 10%, 17%, 22%, 13%, 13%, and 16%.
  • The authors estimated that 9.3% of deaths in men and 7.6% of deaths in women could have been prevented if all participants consumed fewer than 0.5 servings of total red meat daily. Estimates were 8.6% in men and 12.2% in women for deaths from CVD.
  • The authors concluded that total red meat consumption for both processed and unprocessed red meats was associated with an increased risk for mortality and that substitution with other, healthier foods reduced the risk.

 

CLINICAL IMPLICATIONS

 

  • In both men and women, consumption of total red meat, unprocessed red meat, and processed red meat is associated with increased risks for total mortality, CVD mortality, and cancer mortality.
  • Substitution of red meat with fish, poultry, nuts, legumes, low-fat dairy products, or whole grains is associated with a reduced risk for mortality from red meat consumption.

 

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