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Study Claims Red Meat Increases Death Risk

13 March 2012, at 8:58am

US - A new study from Harvard School of Public Health (HSPH) researchers has found that red meat consumption is associated with an increased risk of total, cardiovascular, and cancer mortality.

The results also showed that substituting other healthy protein sources, such as fish, poultry, nuts and legumes, was associated with a lower risk of mortality.

The study is published online in Archives of Internal Medicine.

“Our study adds more evidence to the health risks of eating high amounts of red meat, which has been associated with type 2 diabetes, coronary heart disease, stroke, and certain cancers in other studies,” said lead author An Pan, research fellow in the Department of Nutrition at HSPH.

However, the study has brought a swift response from the American Meat Institute Foundation that says the research relies on "on notoriously unreliable self-reporting about what was eaten and obtuse methods to apply statistical analysis to the data".

The AMI Foundation added: "This imprecise approach is like relying on consumers’ personal characterization of their driving habits in prior years in determining their likelihood of having an accident that kills them in the future. It has a high likelihood of giving erroneous conclusions."

Betsy Booren, AMI Foundation Director of Scientific Affairs said: “Red and processed meat continues to be a healthy part of a balanced diet and nutrition decisions should be based on the total body of evidence, not on single studies that include weak and inconsistent evidence and stand in contrast to other research and to the Dietary Guidelines for Americans, 2010."

The AMI Foundation said that beyond the major weakness of this being an epidemiological study which uses survey data – not test tubes, microscopes or lab measurements--the researchers method of collecting and analyzing their data is highly inaccurate.

It said that the information in the report indicates that estimates of red and processed meat intake were only 27 - 35 per cent accurate versus actual measurements. The researchers also inserted estimated data where an actual survey measurement was missing and also stopped updating the dietary information once participants reported a diagnosis. All of these factors could have significant impacts on the results.

“Too often, epidemiological findings are reported as ‘case closed’ findings, as if a researcher has discovered the definitive cause of a disease or illness. But epidemiological studies look at a multitude of diet and lifestyle factors in specific volunteer human populations and use sophisticated statistical methods to try and tease out relationships or associations between these factors and certain forms of disease. This method of comparing relationships has many limitations which are widely recognised by researchers in this field. More often than not, epidemiological studies, over time, provide more contradictions than conclusions,” Ms Booren said.

“All of these studies struggle to disentangle other lifestyle and dietary habits from meat and processed meat and admit that they can't do it well enough to use their conclusions to accurately recommend people change their dietary habits. What the total evidence has shown, and what common sense suggests, is that a balanced diet and a healthy body weight are the keys to good health.”

Dr Carrie Ruxton from the Meat Advisory Panel (MAP) in the UK said: "This US study looked at associations between high intakes of red meat and risk of mortality, finding a positive association between the two. However, the study was observational, not controlled, and so cannot be used to determine cause and effect.

"The authors' conclusion that swapping a portion of red meat for poultry or fish each week may lower mortality risk was based only on a theoretical model. This conflicts with evidence from controlled trials.

"In a recent intervention study, which compared a healthy, low meat diet (28g/day) with a healthy, high meat diet (156g/day), both groups experienced improvements in heart health indicators such as LDL blood cholesterol levels.

"In two other studies meat diets were switched for fish diets and markers of colorectal cancer risk, (e.g. apoptosis in colon cells, toxicity of faecal water) were studied. Neither study showed a significant reduction in risk, even after six months.

"This suggests that a simple switch from red meat to white meat or fish doesn’t provide the benefits anticipated by the theoretical model. Clearly, other factors, such as body weight, fat intakes, physical activity and fruit/vegetable consumption, are also important.” The researchers, including senior author Frank Hu, professor of nutrition and epidemiology at HSPH, and colleagues, prospectively observed 37,698 men from the Health Professionals Follow-up Study for up to 22 years and 83,644 women in the Nurses’ Health Study for up to 28 years who were free of cardiovascular disease (CVD) and cancer at baseline. Diets were assessed through questionnaires every four years.

A combined 23,926 deaths were documented in the two studies, of which 5,910 were from CVD and 9,464 from cancer.

Regular consumption of red meat, particularly processed red meat, was associated with increased mortality risk.

One daily serving of unprocessed red meat (about the size of a deck of cards) was associated with a 13 per cent increased risk of mortality, and one daily serving of processed red meat (one hot dog or two slices of bacon) was associated with a 20 per cent increased risk.

Among specific causes, the corresponding increases in risk were 18 per cent and 21 per cent for cardiovascular mortality, and 10 per cent and 16 per cent for cancer mortality. These analyses took into account chronic disease risk factors such as age, body mass index, physical activity, family history of heart disease or major cancers.

Red meat, especially processed meat, contains ingredients that have been linked to increased risk of chronic diseases, such as cardiovascular disease and cancer. These include heme iron, saturated fat, sodium, nitrites and certain carcinogens that are formed during cooking.

Replacing one serving of total red meat with one serving of a healthy protein source was associated with a lower mortality risk: seven per cent for fish, 14 per cent for poultry, 19 per cent for nuts, 10 per cent for legumes, 10 per cent for low-fat dairy products and 14 per cent for whole grains. The researchers estimated that 9.3 per cent of deaths in men and 7.6 per cent in women could have been prevented at the end of the follow-up if all the participants had consumed less than 0.5 servings per day of red meat.

“This study provides clear evidence that regular consumption of red meat, especially processed meat, contributes substantially to premature death,” said Hu.

“On the other hand, choosing more healthful sources of protein in place of red meat can confer significant health benefits by reducing chronic disease morbidity and mortality.”

Support for the study was provided by the National Heart, Lung, and Blood Institute and the National Cancer Institute.

Other HSPH authors include Qi Sun, Adam Bernstein, JoAnn Manson, Meir Stampfer and Walter Willett.