Limitations of the study
As with all epidemiolgical studies looking at diet and health, it’s possible that something else about red and processed meat eaters in the NIH-AARP study raised their risk of dying.
However, the researchers did all they could to adjust the results to account for known death-risk factors.
Among other possible “confounding” factors, they accounted for the effects of people's weight, education, smoking habits, and for alcohol, vitamin, and vegetable and fruit consumption.
They could have missed—or incompletely accounted for—something other than meat that raises a meat eater’s risk of dying.
Still, this is the biggest study to look for associations between meat eating and mortality, and it was done by expert NCI researchers.
When the one-fifth of men and women who ate the most red meat were compared to the one-fifth who ate the least red meat, the heavy meat eaters were about 33 percent more likely to have died before the end of the 10-year study.
The men and women who ate the most processed red meat were about 20 percent more likely to have died.
And the risk of dying from cancer was 21 percent higher among those who ate the most red meat, and about 12 percent higher among those who ate the most processed meat.
(The people who consumed at least 2,000 calories a day ate also about five ounces of red meat a day… the equivalent of eating just over one and one-half Quarter Pounders or Big Macs a day.)
As the researchers concluded, “Red and processed meat intakes were associated with modest increases in total mortality, cancer mortality, and cardiovascular disease mortality” (Sinha R et al. 2009).
Fish and white meat exonerated by findings
Unlike the risks linked to red and processed meats, heavy consumption of chicken, turkey, and fish did not appear to raise cancer or death risk.
In fact, those who ate the most chicken, turkey, and fish had slightly lower odds of dying than those who ate the least.
The new meat-and-health findings add weight to recommendations issued in a 2008 report by the World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR).
In Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective, the WCRF/AICR recommended that people limit their consumption of red meat to no more than 300 g (11 oz) per week, and limit total meat consumption to less than 500 g (18 oz) per week.
Grain-fed vs. grass-fed: A choice with warming implications
As we've reported previously, several peer-reviewed studies suggest that clearing land—either for farming of livestock or bio-fuels—results in deforestation, which contributes to rising carbon dioxide levels.
(See “Biofuels Doubts Deepened by US Study.”)
However, as we described in “Cows' Climate-Warming Gases Cut by Grassy Diet,” raising cattle, hogs, poultry, and farmed fish without grain-soy feeds could cut carbon emissions related to petrochemical fertilizers and fuels, nitrous oxide release from petrochemical fertilizers, and methane emissions from the animals themselves.
It’s not possible to cut livestock-related emissions without switching to pasture-feeding on existing fields rather than on carbon-sequestering, water-retaining forest lands cleared to grow grasses.
Placing limits on the number of livestock fed grain and soy would place strict limits on the numbers produced for meat.
And such limitations would butt up against the pressure to produce ever more meat for fast-developing nations like India, China, and Brazil.
Importantly, the WCRF/AICR added that very little of this meat should be processed (Wiseman M 2009).
The WCIF/AICR report defines red meat as beef, pork, lamb, and goat and processed meat as meat preserved by smoking, curing or salting, or addition of chemical preservatives.
Top cardiologist links meat, health, and climate change
Speaking at the European Society of Cardiology’s August 2009 conference, professor emeritus Ole Faergeman told journalists that release of the new study affirms his conviction that eating lots of red meat promotes cancer and heart disease.
And he noted that production of conventional, grain-fed livestock is estimated to account for about 18 percent of greenhouse gas emissions.
Faergeman called on the European Society of Cardiology to recommend reducing the average intake of red meat to 300 grams per week (This equals 10.7 ounces, or about three standard, palm-sized servings).
And as he told reporters last month, “We'd then be helping prevent heart disease and global warming.”
Linking global warming and coronary artery disease, Faergeman noted that people who use fossil fuels frequently—such as to drive to work and blow or mow leaves with gas engines—are less active and produce more greenhouse gasses.
Conventional livestock raising results in release of three greenhouse gases:
- Nitrogen oxide released from standard petrochemical fertilizers on fields.
- Methane released from both ends of cattle and pigs.
- Carbon released from trees and other plants when forests are cleared to grow grass, soy, or grains for animal feed.
We think that other physicians and scientists who understand the climate issue should use their positions to publicize diet-climate-health connections.
- Sinha R, Cross AJ, Graubard BI, et al. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med 2009;169:562–571.
- Wiseman M. The second World Cancer Research Fund/American Institute for Cancer Research expert report. Food, nutrition, physical activity, and the prevention of cancer: a global perspective. Proc Nutr Soc. 2008 Aug;67(3):253-6. Epub 2008 May 1. Review.
- Fricker J. Cardiologists in Pole Position to Fight Climate change. ESC Congress News. August 29, 2009. Accessed at http://www.escardio.org/congresses/esc-2009/news/Pages/Perils-climate.aspx
- Cross AJ, Leitzmann MF, Gail MH, Hollenbeck AR, Schatzkin A, Sinha R. A prospective study of red and processed meat intake in relation to cancer risk. PLoS Med. 2007 Dec;4(12):e325.
- Larsson SC, Bergkvist L, Wolk A. Processed meat consumption, dietary nitrosamines and stomach cancer risk in a cohort of Swedish women. Int J Cancer. 2006 Aug 15;119(4):915-9.