An epidemiological study published August 10, 2011, in The American Journal of Clinical Nutrition, suggests that eating as little as one serving a day of red meat increases the risk of type 2 diabetes, i.e., “maturity-onset diabetes,” which typically affects adults. Type 2 diabetes develops when not enough insulin hormone is produced by the body to maintain a normal blood glucose level, or when cells stop responding to insulin or are unable to effectively use the insulin that is being produced, a condition known as “insulin resistance.” Type 2 diabetes is much more common than type 1 diabetes, which occurs when the body does not produce any insulin at all.
The authors of the study, researchers affiliated with Harvard University, examined the relation between the consumption of different types of red meat, unprocessed and processed, and the risk of type 2 diabetes in American adults. They concluded that consumption of red meat and processed foods like bacon, hot dogs, or sausage, is correlated with a significant increase in the risk of type 2 diabetes. However, the risk may be lowered if a person substitutes nuts, low-fat dairy food, and whole grains on a daily basis for each serving of meat. For an individual who eats one daily serving of red meat, substituting one serving of nuts per day was associated with a 21 percent lower risk of type 2 diabetes; substituting low-fat dairy, a 17 percent lower risk; and substituting whole grains, a 23 percent lower risk.
This study, the largest of its kind in terms of sample size and follow-up years, included a broad analysis of approximately 210,000 male and female health professionals, 25 to 75 years of age [37,083 men in the Health Professionals Follow-Up Study (1986–2006), 79,570 women in the Nurses’ Health Study I (1980–2008), and 87,504 women in the Nurses’ Health Study II (1991–2005)] who were divided into three cohorts (groups). Diet was assessed by validated food-frequency questionnaires, and data were updated every four years. The incidence of type 2 diabetes was confirmed by a validated supplementary questionnaire. The study included data collected between 1980 and 2008.
Subjects who ate a four-ounce serving of unprocessed red meat, including steak, hamburgers, and pork chops daily increased their risk of type 2 diabetes by 20 percent, compared with those who ate that amount only once a week. A daily serving of processed meat, such as one hot dog or sausage or two slices of bacon (about 50 grams), increased the risk by 51 percent, compared with people who ate processed meat less than once a month, according to study co-author Dr. Frank Hu, Professor of Nutrition and Epidemiology at the Harvard School of Public Health.
The analysis used mathematical models to determine the benefits of replacing one serving of meat with nuts, and found that doing so could lower the risk of developing type 2 diabetes by 21 percent. When yogurt or another low-fat dairy product was substituted for the meat, the risk was decreased by 17 percent. The risk of diabetes was also lower when fish or poultry was eaten in place of the meat.
Much science already exists to support the researchers’ conclusion derived from the validated food-frequency questionnaires of the study participants. Dr. Hu and his colleagues suggest that the results could be due to the high iron content of red meat. Previous research has shown that high levels of iron can increase inflammatory chemicals which destroy insulin-producing beta cells. Abnormally low levels of insulin cause an unhealthy glucose build-up in the blood, which is essentially the basis of diabetes.
The nitrates in processed meats may also be toxic to beta cells, which could explain why processed meats contributed even more to the risk than unprocessed meats. Whether the high saturated fat content typical of red meat also contributes to an increase in inflammation remains unknown.
The researchers also noted that study subjects who ate the most red meat also tended to eat fewer fruits and vegetables and were more likely to smoke and be obese. Smoking itself is a risk factor associated with increased irritation and inflammation of the lining of blood vessels. Although the study used statistical methods to account for these and additional lifestyle factors – which may also contribute to type 2 diabetes risk – the researchers themselves admitted at the end of the study, “observed associations do not necessarily mean causation.’’
The study findings should be taken seriously, however, especially since diabetes has reached epidemic levels worldwide, affecting nearly 350 million adults. According to the Centers for Disease Control and Prevention (CDC), diabetes is the seventh leading cause of death in the US. More than 11 percent of US adults over age 20, approximately 25.6 million, have the disease. The majority are affected by type 2 diabetes, which is associated with obesity, physical inactivity, and an unhealthy diet.
Dr. Hu states that “the findings send a clear message that Americans should be emphasizing more of a plant-based diet and looking for other sources of protein such as nuts, fish, low-fat dairy, and poultry. I think we should change our mindset in terms of protein sources in our diet…red meat consumption, particularly processed red meat, is associated with an increased risk of type 2 diabetes.”
References:
- Pan, An; Sun, Qi; Bernstein, Adam M.; Schulze, Matthias B.; Manson, JoAnn E.; Willett, Walter C.; Hu, Frank B. “Red Meat Consumption and Risk of Type 2 Diabetes: 3 Cohorts of US Adults and an Updated Meta-Analysis.” The American Journal of Clinical Nutrition. August 10, 2011. [Author Affiliations: From the Departments of Nutrition (AP, QS, AMB, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; Channing Laboratory (QS, WCW, and FBH) and the Division of Preventive Medicine (JEM), Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA; and the Department of Molecular Epidemiology (MBS), German Institute of Human Nutrition, Nuthetal, Germany.]
- “Red Meat Linked to Increased Risk of Type 2 Diabetes: Processed Red Meats Especially Boost the Risk.” Harvard School of Public Health: Press Release. August 19, 2011.
- “Risks: Replacing Red Meat, Staving off Diabetes.” The New York Times: Science Times. August 16, 2011. p. D6.
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