The authors carried out a follow-up of three studies involving approximately 149,000 Americans.
As background information, the researchers explained that the consumption of red meat has been linked to an elevated risk of type 2 diabetes in several studies. However, most of them measured how much red meat participants ate at the beginning of the study (at baseline) without much follow-up information.
People's eating patterns do not always stay the same; they change over time. Measuring a person's dietary habits over a small slice of time does not take into account the variability of dietary patterns during follow-up.
An Pan, Ph.D., and team gathered and analyzed data from three studies that had been conducted at Harvard University. They followed up 48,709 women in the Nurses' Health Study, 74,077 women in the Nurses' Health Study II, and 26,357 men in the Health Professionals Follow-up Study. Participants were asked to complete food frequency questionnaires.
Over a follow-up period of more than 1.9 million person-years, the investigators identified 7,540 incident cases of type 2 diabetes.
The authors wrote:
"Increasing red meat intake during a four-year interval was associated with an elevated risk of T2DM during the subsequent four years in each cohort."
Compared to those with no change in how much meat they ate, the participants whose meat consumption rose by more than 0.50 servings per day had a 48% higher risk of developing type 2 diabetes during the subsequent four years.
Participants whose meat intake went down by more than 0.50 servings per day, from baseline to the first four years, had a 14% lower risk of developing type 2 diabetes during the whole follow-up period.
The researchers emphasized that theirs was an observational study, so readers should not infer causality.
The authors concluded:
"Our results confirm the robustness of the association between red meat and T2DM and add further evidence that limiting red meat consumption over time confers benefits for T2DM prevention."
The study was funded by the NIH (National Institutes of Health).
Oxygen-Carrying Proteins in Meat and Risk of Diabetes Mellitus - CommentaryWilliam J. Evans, Ph.D., of GlaxoSmithKline and Duke University, Durham, N.C., wrote in an invited Commentary:
"The article by Pan et al confirms previous observations that the consumption of so-called red meat is associated with an increased risk of type 2 diabetes mellitus (T2DM)." "Perhaps a better description of the characteristics of the meat consumed with the greatest effect on risk is the saturated fatty acid (SFA) content rather than the amount of oxygen-carrying proteins.
"A recommendation to consume less red meat may help to reduce the epidemic of T2DM. However, the overwhelming preponderance of molecular, cellular, clinical and epidemiological evidence suggests that public health messages should be directed toward the consumption of high-quality protein that is low in total and saturated fat. ... These public health recommendations should include cuts of red meat that are also low in fat, along with fish, poultry and low-fat dairy products. It is not the type of protein (or meat) that is the problem: it is the type of fat."
Red meat linked to several health problemsOver the last ten years, nearly all studies on red meat consumption have reported on its negative consequences for human health:
- A study led by Stanley Hazen, of the Cleveland Clinic in Ohio, found an association between red meat and a higher risk of heart problems involving gut bacteria.
Bacteria in our gut digest L-carnitine, an abundant compound in red meat, to produce TMAO (trimethylamine-N-oxide). TMAO is suspected of helping clog up the arteries. The study was published in Nature Medicine (April 2013 issue).
- Researchers from the Harvard School of Public Health found that regular red meat eaters were more likely to die prematurely from any cause, from cancer, or from a cardiovascular disease than those who either never ate red meat or consumed very little.
If you are a regular meat eater and switch to other protein sources, such as poultry, fish, soya, nuts and legumes, your risk will probably go down, they added. Their study was published in Archives of Internal Medicine (March 2012).
Lead author, An Pan, said "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."
- Dr Elaine Chong, from the Centre for Eye Research Australia, at the University of Melbourne, and team found that frequent red meat intake was associated with a higher chance of developing AMD (age-related macular degeneration), the leading cause of blindness among seniors in America and Western Europe.