By Craig Weatherby
Earlier this week, we covered the latest study that seems to damn processed red meats … see “Processed Meat May Speed Death”.
Frankly, we wish we’d read the full study first, because there’s surprisingly little substance to it (Rohrmann S et al. 2013).
We were too ready to accept the authors’ summary at face value, given the similar results of other epidemiological studies comparing people’s self-reported diets to their health outcomes.
(See “New Cancer-Risk Findings Rank Seafood and Poultry Far Safer than Processed Meats” and other reports in the Meats & Health section of our news archive.)
The authors analyzed data from a study that involved 448,568 men and women from ten countries, who were followed for an average of 13 years … called the European Prospective Investigation into Cancer and Nutrition or EPIC (Rohrmann S et al. 2013).
The EPIC participants – who were between 35 and 69 years old – had no history of cancer, stroke, or heart attacks.
The study authors had access to the volunteers’ body mass indices and self-reported diets and lifestyles. As we wrote, “[as] an epidemiological study, this data analysis cannot prove a cause-effect relationship between dietary habits and health outcomes.”
While the authors calculated that people who ate more than 5.7 ounces (160 grams) of processed meat a day were 44 percent more likely to die within 13 years, they detected no risk from high consumption of unprocessed red meat.
The EU researchers blamed the higher death risk among the heavy eaters of processed red meats on these foods’ salt, fat, and potential carcinogens like nitrite … which are absent from un-processed meat. But not all “processed meat” is made the modern, chemical way.
A naturally cured Italian prosciutto bears little relationship to the processed meats in popular products like Lunchables.
Italians live longer than Americans, despite eating lots of processed red meats, which are mostly naturally made by traditional methods.
Study’s conclusions don’t bear scrutiny
The combined results of higher-quality epidemiological studies can provide strong indications … but still cannot prove a cause-effect relationship between foods and health.
And some studies find no risk from unprocessed red meat.
For example, Harvard researchers published similar large study last year, which found that adding an extra portion of unprocessed red meat daily appeared to increase the risk of death by 13 percent. Adding an extra portion of processed meat daily seemed worse, raising the risk of death by 20 percent (Pan A et al. 2012).
But the Harvard study also showed that those who ate moderate amounts of unprocessed red meat fared better than those who ate little or no red meat.
And a large study in Japan found no increase in heart disease deaths from eating up to 100 gram (3.5 oz) of meat (beef, pork, poultry, liver and processed meat) per day … the amount generally considered “moderate”.
The weak reliability of these and similar epidemiological studies stems from the fact that people who eat lots of processed meats – hot dogs, salami, pepperoni, ham, and baloney – are often unhealthy in many ways.
Conversely, people who eat relatively little red meat typically have healthier diets and lifestyle habits than their meat-loving peers.
These bundles of habits make it impossible for typical epidemiological studies to pin people’s health problems or benefits on a single food or food category.
EPIC study suffered from tangle of habits
The people in the EPIC study who reported eating a lot of processed meats were also more likely to be older, smoke, eat few fruits and vegetables, have lower levels of education, and be heavier and less active than the other participants. The men in this group also drank heavily.
And the people who ate the most processed meat also died of lots of “other causes” … including accidents and other non-dietary causes. (Those who ate lots of seafood or chicken didn't smoke much, ate more fruits and vegetables, exercised, and attended college.)
The researchers tried to adjust for the effects of low produce consumption, drinking, smoking, education, and sugar consumption.
But they couldn't completely factor those things out, or there would have been very few people left in the study.
For example, out of 127,000 or so male participants, only 619 were heavy processed-meat eaters who'd never smoked.
In fact, so few non-smokers reported heavy consumption of processed meat that only former or current smokers fit that category … a finding they acknowledged is “compatible with residual confounding [muddying of results] by smoking.”
Further, less than one percent of those who died during the 12 years of the study were among those who ate the most processed meat.
Finally, the number of people in the high-processed-meat consumption category was very small, while the link between processed meats and early death didn’t hold true for women.
What does all this mean?
Take the associations detected in epidemiological studies with a big grain of salt, unkless they make sense in the context of lab and clinical studies (if any exist).
And by itself, enjoying red meats – especially grass-fed beef and holistically raised pork – in moderation isn't likely to hasten death, and may well be healthy for many.
Bernstein AM, Sun Q, Hu FB, Stampfer MJ, Manson JE, Willett WC. Major dietary protein sources and risk of coronary heart disease in women. Circulation. 2010 Aug 31;122(9):876-83. doi: 10.1161/CIRCULATIONAHA.109.915165. Epub 2010 Aug 16. BioMed Central Limited (BCL).
Processed meat linked to premature death. March 5, 2013. Accessed at http://www.alphagalileo.org/ViewItem.aspx?ItemId=129056&CultureCode=en
Chan DS, Lau R, Aune D, Vieira R, Greenwood DC, Kampman E, Norat T. Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PLoS One. 2011;6(6):e20456. doi: 10.1371/journal.pone.0020456. Epub 2011 Jun 6.
Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, Willett WC, Hu FB. Red meat consumption and mortality: results from 2 prospective cohort studies. Arch Intern Med. 2012 Apr 9;172(7):555-63. doi: 10.1001/archinternmed.2011.2287. Epub 2012 Mar 12.
Rohrmann S et al. Meat consumption and mortality - results from the European Prospective Investigation into Cancer and Nutrition. BMC Medicine, 2013; 11 (1): 63 DOI: 10.1186/1741-7015-11-63
Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin A. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med. 2009 Mar 23;169(6):562-71. doi: 10.1001/archinternmed.2009.6.