Nutritionists known for issuing warnings about the health risks of eating red meat reiterated their message this week, confirming a link between red meat consumption and Type 2 diabetes -- and showing, in a new follow-up study, that the association persists over time.
The team, which included Harvard School of Public Health epidemiologist Dr. Walter Willett, reported that people who said they increased their intake of red meat -- beef, pork or lamb -- over a four-year period had a higher chance of developing Type 2 diabetes in the subsequent four-year period than people who said the amount of red meat they ate stayed stable or went down.
In recent years, the researchers have written various observational studies demonstrating associations between eating red meat and health risks. Most previous studies of red meat consumption and diabetes risk had only looked at red meat intake at a single point in time and incorporated limited information during follow-up, the team wrote in JAMA Internal Medicine on Monday.
For this report (abstract available here), they analyzed data collected from nearly 150,000 adults who took part in three long-term studies coordinated by Harvard University: the Health Professionals Follow-up Study (which followed 51,529 male health workers starting in 1986), the Nurses' Health Study (which tracked 121,700 female registered nurses stating in 1976) and the Nurses' Health Study II (which looked at health data from 116,671 women nurses starting in 1989).
Examining years of surveys that detailed diet and lifestyle factors, as well as participant health, the scientists determined that increasing the amount of red meat a person ate in one four-year period by more than half a serving a day resulted in a 48% increased risk of diabetes in the following four-year period. People who reduced the amount of red meat they ate by at least half a serving a day during the first four years of follow-up had a 14% lower risk of diabetes over the entire follow-up period.
"Our results confirm the robustness of the association between red meat and Type 2 diabetes and add further evidence that limiting red meat consumption over time confers benefits for Type 2 diabetes consumption," the team wrote.
Plenty of people have questioned the researchers' past reports on red meat consumption, and it's likely the team will come in for some criticism this time around, as well. Many critics, for instance, would prefer to see research that set up a randomized trial to test the effects of eating red meat directly.
In the JAMA Internal Medicine study, the co-authors acknowledged that their analysis could not establish definitively that eating red meat caused the diabetes cases, but defended their study design. "Randomized clinical trials may better address the causal relationship between red meat and Type 2 diabetes but may not be feasible," they wrote.
Whatever may come of this latest report, confusion is unlikely to subside anytime soon. In a commentary article that accompanied the new study, William J. Evans, a researcher on aging for the Duke University Department of Medicine and GlaxoSmithKline wrote that "the description of red meat as a category of food ... has little value and may be misleading," and wrote that looking at the type of fats in meats -- rather than the proteins that make it red -- is an approach that makes more sense. At the same time, researchers have homed in on other ingredients in meat, including proteins and the nutrient carnitine, that may play a role in health problems.
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