March 12, 2012 (Boston, Massachusetts) — 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 . 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 , 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 the Health Professionals Follow-up Study (HPFS) and 83 644 women from the Nurses’ Health Study (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 MI 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 Disease; Eat More, Weigh Less; Love & Survival; and the Spectrum.