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March 26, 2009 — Eating red and processed meat is associated with modest increases in total mortality, cancer mortality, and cardiovascular disease mortality rates, according to the results of a large, prospective study reported in the March 23 issue of the Archives of Internal Medicine.

“High intakes of red or processed meat may increase the risk of mortality,” write Rashmi Sinha, PhD, from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services in Rockville, Maryland, and colleagues. “Our objective was to determine the relations of red, white, and processed meat intakes to risk for total and cause-specific mortality.”

The National Institutes of Health–AARP Diet and Health Study enrolled approximately half a million people aged 50 to 71 years at baseline. A food frequency questionnaire administered at baseline allowed estimation of meat intake, and Cox proportional hazards regression models allowed calculation of hazard ratios (HRs) and 95% confidence intervals (CIs) within quintiles of meat intake.

Red meat included all types of beef and pork such as bacon, beef, cold cuts, hamburgers, hotdogs, steak, and meats in pizza, lasagna, and stew. White meat included chicken, turkey, and fish along with poultry cold cuts, canned tuna, and low-fat hotdogs. Processed meats could include either red or white meats in the form of sandwich meats or cold cuts as well as bacon, red meat and poultry sausages, and regular hotdogs and low-fat hotdogs made from poultry. The authors note that some of the meats may overlap in the 3 categories, but they were not duplicated or used in the same models in the study analysis.

The models considered covariates of age, education, marital status, presence or absence of family history of cancer (for cancer mortality only), race, body mass index, smoking history, physical activity, energy intake, alcohol drinking, use of vitamin supplements, fruit consumption, vegetable consumption, and use of menopausal hormone therapy in women. Primary endpoints of the study were total mortality and deaths caused by cancer, cardiovascular disease, injury and sudden deaths, and all other causes.

During 10 years of follow-up, 47,976 men and 23,276 women died. Overall mortality risks were increased for men and women in the highest vs the lowest quintile of red meat intake (HR, 1.31; 95% CI, 1.27 - 1.35; and HR, 1.36; 95% CI, 1.30-1.43, respectively) and processed meat intake (HR, 1.16; 95% CI, 1.12 - 1.20; and HR, 1.25; 95% CI, 1.20 - 1.31, respectively). Men and women with higher intake also had increased risks for cancer mortality for red meat (HR, 1.22; 95% CI, 1.16 - 1.29; and HR, 1.20; 95% CI, 1.12 - 1.30, respectively) and processed meat (HR, 1.12; 95% CI, 1.06 - 1.19; and HR, 1.11; 95% CI 1.04 - 1.19, respectively).

Cardiovascular disease risk was increased for men and women in the highest quintile of intake of red meat (HR, 1.27; 95% CI, 1.20 - 1.35; and HR, 1.50; 95% CI, 1.37 - 1.65, respectively) and processed meat (HR, 1.09; 95% CI, 1.03 - 1.15; and HR, 1.38; 95% CI, 1.26 - 1.51, respectively). For the highest vs the lowest quintile of white meat intake for both men and women, there was an inverse association for total mortality, cancer mortality, and mortality from all other causes.

“Red and processed meat intakes were associated with modest increases in total mortality, cancer mortality, and cardiovascular disease mortality,” the study authors write. “In contrast, high white meat intake and a low-risk meat diet was associated with a small decrease in total and cancer mortality.”

Limitations of this study include possible residual confounding by smoking; possible measurement error; and cohort predominantly non-Hispanic white, more educated, with less smoking, less fat and red meat intake, and more intake of fiber and fruit and vegetables than similarly aged adults in the US population, limiting generalizability.

“These results complement the recommendations by the American Institute for Cancer Research and the World Cancer Research Fund to reduce red and processed meat intake to decrease cancer incidence,” the study authors write. “Future research should investigate the relation between subtypes of meat and specific causes of mortality.”

In an accompanying editorial, Barry M. Popkin, PhD, from the University of North Carolina, Chapel Hill, discusses how the implications of reducing excessive meat intake would relate to several major global concerns.

“Of equal importance is the role of clinicians as public health advocates,” Dr. Popkin writes. “Far too few clinicians speak out on topics such as this. What the public hears is the side of the profession that is preaching vegetarian diets and not the side of the profession that is discussing moderation as a healthy option.”

The Intramural Research Program of the National Institute of Health, National Cancer Institute supported this study in part. The study authors have disclosed no relevant financial relationships. Dr. Popkin is not a vegetarian and has no financial conflict of interest related to any food product as it affects health.

Arch Intern Med. 2009;169:543-545, 562-571.

Clinical Context

Dietary patterns are changing around the globe, and an editorial by Popkin, which accompanies the current article, describes these patterns. Individuals in higher-income countries continue to consume meat and dairy products at 2 to 3 times the rate of lower-income countries. However, meat and dairy products are becoming a more common dietary staple in some developing countries, particularly India, China, and Brazil.

In part, higher consumption of meat is the result of a lower cost of beef vs several decades ago. At the same time, the cost of grains and rice has increased significantly on the world market in the last 6 years. This has important environmental consequences, as the need for water and feedstock is much higher in raising animals vs raising basic crops.

Meat consumption can have significant effects on rates of obesity and overall health as well. The current study examines a large cohort of adults to determine the effect of meat intake on mortality rates.

Study Highlights

• Study participants included adults between the ages of 50 and 71 years who lived in 6 different regions of the United States.
• Participants completed a 124-item food frequency questionnaire at baseline, which inquired regarding dietary habits during the previous 12 months.
• The main study variable was the consumption of red meats, white meats, and processed meats. Processed meats could include either red or white meats in the form of sandwich meats or cold cuts.
• The main outcome of the study was total mortality rate, and secondary outcomes included cause-specific mortality rates related to cancer and cardiovascular disease. These data were derived from national mortality databases and diagnostic codes.
• The relationship between meat consumption and mortality was adjusted to account for major confounding factors, including demographic, family history, and health habit variables.
• 322,263 men and 223,390 women were included in the study analysis. During 10 years of follow-up, there were 47,796 and 23,276 deaths among men and women, respectively.
• Men and women in the lowest quintile of red meat intake consumed approximately 9 g per 1000 kcal of diet per day. Men and women in the highest quintile of red meat intake consumed 68.1 and 65.9 g per 1000 kcal of diet daily, respectively.
• The median processed meat consumption in the first and fifth quintiles were 1.6 g per 1000 kcal/day and 22.6 g per 1000 kcal/day, respectively.
• Participants who consumed more red meat tended to be married, of non-Hispanic white ethnicity, and have worse health habits and a higher body mass index.
• The adjusted HRs for all-cause mortality in comparing the highest vs the lowest quintiles of red meat consumption were 1.31 for men and 1.36 for women. This same comparison for processed meats yielded adjusted HRs of 1.16 and 1.25, respectively. All of these values were statistically significant.
• The risk for death increased gradually with increasing red and processed meat consumption.
• The risk for cancer mortality was increased by a factor of 1.2 in comparing the highest vs the lowest quintiles of red meat intake. The risk for cardiovascular death was increased by 1.27 among men and 1.50 among women in comparing these same quintiles.
• The consumption of processed meat also increased the specific risks for cancer and cardiovascular mortality.
• Red meat consumption increased the risk for death from injury or sudden death among men but not women, and the risk for deaths from other causes was increased with higher red meat consumption in both sexes.
• Consumption of white meat had the opposite effect on the risk for mortality. The risk for death among both women and men in the highest vs the lowest quintile of white meat consumption was 0.92.
• Subgroup analysis based on smoking status did not change the main study findings.
• Overall, the researchers concluded that 11% of deaths among men and 16% of deaths among women might be prevented if all adults consumed red meat at levels commensurate with the first study quintile.

Pearls for Practice

• Although some lower-income countries have increasing levels of meat and dairy consumption, the rate of consumption of these products is still 2 to 3 times higher among individuals in higher-income countries. The cost of beef has decreased worldwide in the last several decades, whereas the cost of grains and rice has increased during the last 6 years.
• In the current study, red meat and processed meat consumption were associated with higher rates of all-cause, cardiovascular, and cancer mortality. However, white meat consumption was associated with a lower risk for mortality.