Scientists Studied Americans for Eight Years to Find Out How Red Meat Affected Their Health
Scientists who found a link between eating red meat and a higher risk of death believe cutting down on foods like burgers and bacon could lead to a longer life.
Over a period of eight years, eating 3.5 more servings of red meat per week on average was linked to a 10 percent higher risk of dying in the following eight years. That percentage rose to 13 percent for processed meat, falling to 9 percent for unprocessed, according to the study published in the journal BMJ.
But a decrease of one serving per day of red meat and an increase of one serving per day of fish over eight years was linked to a 17 percent lower risk of death in the subsequent eight years.
The servings sizes depended on the food, with 85g counting as one portion of beef, pork, and lamb as a main dish.
The authors concluded that short, medium and long-term changes in how much red, processed and unprocessed meat the participants ate was "directly associated" with the risk of death, regardless of their starting level.
The study is the latest in a pile of evidence which suggests eating red meat can heighten the risk of developing conditions including heart disease, type 2 diabetes, as well as types of cancer including colorectal. Processed meat, meanwhile, is also associated with heart failure, chronic obstructive pulmonary disease—which includes breathing problems like emphysema and bronchitis—and high blood pressure. Scientists think this could be explained by the combination of saturated fats, cholesterol, potential carcinogens, salt, and preservatives which foods like beef, bacon, hot dogs, and sausages contain.
This could be of particular concern for Americans, who eat more than double the amount of meat than the rest of the world, on average.
For the latest study, scientists wanted to look at whether eating more or less meat over eight years would affect health in the following eight years.
A total of 53,553 women aged between 30 to 55 at the start of the study, and 27,916 men aged between 40 to 75, took part in the research. The participants had worked as healthcare professionals and were free from cancer and heart disease when the study launched.
Every four years between 1986 and 1994, the participants filled out questionnaires about their lifestyle, medical history, and what they would normally eat. That included how often they consumed a standard portion of different foods in the past year, such as beef, pork, lamb, hamburgers, bacon, hot dogs, salami, and other processed red meats.
This gave the researchers an idea of how their health and habits changed over time. Researchers followed up with the participants in 2010, and divided them into five categories according to how their consumption of red meat changed over time.
When researchers followed-up with participants after eight years, they found 14,019 people had died. Between 1986 to 1994, more participants ate less meat than added it to their diet.
The figures revealed a pattern: those who ate increasing levels of red meat over the eight years had a higher risk of death. That means they were more likely to die than the other participants in the study, on average.
The risks remained even when the authors accounted for variables like age, exercise levels, the quality of the diet and whether they smoked or drank alcohol.
But the authors acknowledged several limitations to their study, including that the participants were health professional, so the results might not be applicable to others, and that they didn't know exactly what caused the changes in diet.
"Because this is an observational study, the observed association does not necessarily imply causality. Dietary information was based on self-reports by the participants and thus some inaccuracies are inevitable," study co-author Frank B. Hu, professor and chair of the Department of Nutrition at Harvard T.H. Chan School of Public Health, told Newsweek.
Still, both Hu and experts not involved agreed this works provides further evidence that it is wise to cut down on how much red meat we eat.
Hu said: "it is desirable to cut back on overall red meat consumption, but it does not mean that everyone has to become a vegetarian or vegan.
"It's better to minimize processed meats as much as possible. It's also important to choose healthy sources of protein such as fish, nuts, whole grains, and legumes."
He continued that reducing red meat in the diet can also help with environmental sustainability.
Ian Johnson, nutrition researcher at the Quadram Institute Bioscience, who was not involved in the work, commented that although the study was observational—where researchers look at a population which they have no control over and can't confirm causation—the results come from a large, well established cohort study and are consistent with current public health advice.
"The important new point is that adults seem to be able to significantly improve their chances of a longer healthier life by adjusting their diets toward what can be broadly described as a more 'Mediterranean' pattern," he said.
Professor Tom Sanders, professor emeritus of nutrition and dietetics at King's College London who also didn't work on the research, said: "This report comes hot on the heels of another big study of 409,885 men and women in nine European countries that found red and processed meat consumption was associated with a 19 percent increased risk of ischemic heart disease, which is a leading cause of premature mortality.
"That study also found milk, fish, eggs and poultry were not associated with risk.
"These findings taken together challenge the popular myth that high protein diets containing lots of red meat are good for health, but support current dietary guidelines that advocate a shift to a Mediterranean style diet, which contains plenty of vegetables, nuts, wholegrain, some fish, poultry and milk but very small amounts of red and processed meat."
Gunter Kuhnle, associate professor in nutrition and health at the U.K.'s University of Reading, highlighted that the benefits were modest and only when meat was replaced with certain foods: in particular nuts, fish, whole grains and vegetables, without legumes.
"The study is mainly of interest for long-term dietary recommendations, as it shows that on a population scale, even small increases in meat intake were associated with increased mortality, although only slightly—and that replacing meat with nuts, fish, whole grains or vegetables was associated with reduced mortality."
He continued that meat is an important source of essential nutrients like iron and vitamin B12.
"This highlights the difficulties of nutritional research and the development of dietary recommendations: many foods are 'healthy' when consumed in the right amounts and it is excessive (or insufficient) consumption that has an adverse effect on health," Kuhnle said