In an extensive re-analysis of data from three large observational trials, Dr. An Pan and colleagues from the National University of Singapore and the Harvard School of Public Health, reported that increased intake of red meat (beef, lamb, or pork) over time increased the risk of type 2 diabetes, while decreasing intake slightly decreased the risk.
The researchers examined data from the Nurses Health Study I and II, as well as the Health Professionals Followup Study all from the Harvard School of Public Health. Using food frequency questionnaires, they estimated initial red meat intake, and then repeated the estimations every four years thereafter.
Complex statistical analyses suggested that increasing red meat consumption over four years by at least half a serving per day resulted in a 48 percent increased risk of type 2 diabetes; a figure that was statistically significant. When these data were controlled for coincident weight gain, the risk was attenuated but not eliminated.
So one might conclude that decreasing consumption of red meat might thus similarly decrease the risk of diabetes over the same time period, right? This wasn t the result, however. Decreasing red meat intake by at least half a serving per day was associated with only a ten percent decrease in risk of diabetes. Neither the increased risk or decreased risk would be considered large by epidemiologists.
In an invited commentary, Dr. William J. Evans of GlaxoSmithKline noted that the description of red meat used in Dr. Pan s study was not particularly appropriate. Evans commented that some types of fish and poultry flesh actually contain as much or more saturated fat than these types of meat, and that the saturated fat content would be a better marker of diabetes risk.
ACSH s Dr. Ruth Kava suggested, While this is a very large study that certainly deserves our attention, there are problems with concluding that red meat intake increases the risk of diabetes as the authors indeed noted. It s important to remember that observational studies, no matter how large, cannot establish causation. The suggestion that the categorization of red meat was inaccurate may well invalidate the results of the current study. Stay tuned for more information on this topic.