Too much red meat in diet can shorten lifespan: Study

By Dr. Ananya Mandal, MDMar 13 2012

According to Harvard researchers, publishing this week in the Archives of Internal Medicine, the risk of dying at an early age - from heart disease, cancer, or any other cause, rises in step with red-meat consumption. Eating too much red meat, which is high in saturated fat and cholesterol, has long been seen as unhealthy, especially for the heart. The new study, however, is the first to estimate the effect of red meat in diet on a person's lifespan.

The researchers used data from two long-running studies of health professionals, researchers tracked the diets of more than 121,000 middle-aged men and women for up to 28 years. Every four years, people in the study were asked detailed questions about their eating habits. They were also asked about other health determinants like smoking and drinking, exercise, and body weight. Men were in their early 50s, on average, when the study started. Women were in their mid-40s.

Roughly 20% of the participants died during that period. On average, each additional serving of red meat the participants ate per day was associated with a 13% higher risk of dying during the study. Additionally processed red meat products -- such as hot dogs, bacon, and salami -- appeared to be even more dangerous: Each additional daily serving was associated with a 20% higher risk of dying.

Researchers estimated that substituting one daily serving of red meat with fish, poultry, nuts, legumes, whole grains, or low-fat dairy products would reduce the risk of dying in this stage of life by 7% to 19%. If everyone in the study had slashed their average red-meat intake to less than half a serving per day, the researchers say, 9% of deaths among men and 8% of deaths among women could have been prevented.

Pan and his colleagues found that the men and women in the study who ate the most red meat also tended to be heavier, less physically active, and more likely to smoke and drink alcohol than their peers. However, the researchers did take those and other factors into account in their analysis.

“Our message is to try to reduce the red meat consumption to less than two to three servings per week,” said lead author An Pan, a research fellow at the Harvard School of Public Health, in Boston. “We don't want everyone to be a vegetarian,” Pan said, though he added that avoiding processed red meat altogether may be a good idea. “It's better to go with unprocessed products and plant-based foods.”

Dean Ornish, the founder and president of the Preventive Medicine Research Institute, in Sausalito, California, said a plant-based diet provides a “double benefit” in that it reduces a person's exposure to the harmful substances in meat while also providing valuable nutrients. “There are literally hundreds of thousands of protective substances that you find in fruits and vegetables and whole grains and legumes and soy products that prevent disease,” said Ornish, who wrote an editorial accompanying the study.

Pan explained that the reason red meat is harmful is because in addition to the high saturated fat content, which can contribute to heart disease, charring red meat at high temperatures can produce carcinogens on the surface. And processed meats contain certain additives that in high quantities are believed to promote cancer as well.

Robert Ostfeld, a cardiologist and associate professor of clinical medicine at Montefiore Medical Center, in the Bronx, N.Y. said, “If you eat more red meat, on average, you may be eating fewer fruits and vegetables, so you're getting the bad things from the red meat and you're not getting the good things from the fruits and vegetables… My preference is for people to have as little red meat as they can, and I think it's ideal to avoid red meat.” He was not a part of the study.

“Substituting almost any other food for red meat reduces risk, sometimes substantially,” Marion Nestle, a professor of nutrition, food studies, and public health at New York University, told WebMD. “This is a call for a more varied diet that substitutes other foods for red meats, especially nuts,” said Nestle, who was not involved in the research.

The study echoes previous research which has also linked diets high in red meat to a shorter life span. In 2009, a study by the National Cancer Institute found that people who ate the equivalent of a quarter-pound burger or small steak each day had about a 30% greater risk of dying over 10 years than people who only ate red meat occasionally. High red meat consumption has also been linked to obesity and type 2 diabetes.

Staffan Lindeberg, an associate professor of medicine at the University of Lund, in Sweden, said singling out red meat may be counterproductive. A bigger threat to health is the sugar- and starch-heavy Western diet as a whole, says Lund, who studies heart disease and diabetes and advocates a version of the so-called Paleolithic diet, which emphasizes lean meats, fruits, and vegetables. “We need to focus more on common foods, like grains, dairy foods, refined fats, and refined sugar,” Lindeberg said.

Beef producers point out that this is a specific type of research called an observational study, which can’t prove cause and effect. They say other studies have shown that eating lean beef can be part of a healthful diet.

“If there is one thing scientists agree on, it is that responsible dietary advice must be drawn from a look at the entire body of evidence, including rigorous, gold-standard randomized control trials when they are available,” Shalene McNeill, executive director of Human Nutrition Research for the National Cattlemen’s Beef Association, said in a written statement. “In the case of beef, there are several randomized control trials which have convincingly shown that lean beef, when included as part of a healthy, balanced diet, improves heart health by lowering cholesterol,” she said. “Most recently, the BOLD (Beef in an Optimal Lean Diet) study showed that eating lean beef every day, as part of a heart-healthy diet, could reduce [unhealthy] LDL cholesterol...” McNeill said.

Robert Eckel, a past president of the American Heart Association, says the group does not set a limit on consumption of lean red meat but promotes an overall heart-healthy diet. “A small serving (about 3 ounces) of lean red meat several times a week can be added to an overall heart-healthy dietary pattern without concern. This amount is substantially below the level of risk reported by the Harvard group.”

Marji McCullough, a nutrition epidemiologist for the American Cancer Society, says, “We've known for a long time that eating high amounts of red meat or processed meat increases the risk of colorectal cancer and possibly other cancers. This study is important because it shows that consuming red meat and processed meat increases the risk of death from all causes.” She says there is no magic number in terms of amount of red meat that you can safely consume, but “eating it no more than a few times a week would be a place to start.”