Post by Enchantress on Oct 6, 2004 13:10:25 GMT -5
Study: Red Meat Consumption and Type 2 Diabetes in Middle-Aged/Elderly Women
A Prospective Study of Red Meat Consumption and Type 2 Diabetes in Middle-Aged and Elderly Women
The Women's Health Study
Posted 09/21/2004
Yiqing Song, MD; JoAnn E. Manson, MD, DRPH; Julie E. Buring, SCD; Simin Liu, MD, SCD
Conclusions
In this large prospective study, we found that a higher consumption of red meat, especially total processed meat, was associated with an increased risk of developing type 2 diabetes in middle-aged and older U.S. women, independent of known diabetes risk factors.
The prospective design and high follow-up rates in our study minimized the possibility of selection bias or recall bias. As any measurement errors from baseline SFFQ were unlikely to be related to subsequent diabetes end points, misclassification of dietary assessment would most likely be nondifferential and would have attenuated the true associations. Thus, our observed associations may not be explained by such errors and were, on the contrary, somewhat conservative. Our results were also less likely to be influenced by misclassification of type 2 diabetes because of a high accuracy of self-reported diabetes as assessed by our validation study. Moreover, because we adjusted for age, BMI, and other important risk factors for type 2 diabetes, the residual confounding due to these known factors was probably modest.
Our findings are consistent with recent evidence from both the Health Professionals Follow-Up Study of male health professionals and the Nurses' Health Study II of younger and middle-aged U.S. women.[8,9] Processed meat appeared entirely responsible for the elevated diabetes risk associated with total red meat in these two large cohort studies.[8,9]
Red meat, especially processed meat, contains certain types of preservatives, additives, or other chemicals arising from meat preparation, including preservation, packaging, and cooking. These compounds include nitrates and nitrites added in meat processing as well as a variety of heterocyclic amines and polycyclic aromatic hydrocarbons formed in red meat, especially when cooked well done.[17] These compounds can be converted to N-nitrosamines,[17] which were found to be toxic to pancreatic รข-cell.[18] Consumption of foods with a high content of nitrites and nitrosamines has been associated with type 1 diabetes.[19-21] Also, advanced glycation and lipoxidation end products produced during the cooking or processing of meat have been associated with insulin resistance and diabetes-related complications in animal models[22] and human subjects.[23,24] Therefore, such specific compounds mainly present in processed meat might largely explain the observed significant association between processed meat intake and type 2 diabetes.
Nevertheless, red meat is also a major source for saturated fat, cholesterol, animal protein, and heme iron. It has been shown that certain types of fat from red meat may play a major role in the development of type 2 diabetes.[9,25] As noted in a recent review, epidemiological evidence for the relevance of dietary fats and risk of type 2 diabetes seem to be inconsistent.[25] The present study did not show any positive associations between intakes of saturated fat or trans fatty acid and risk of type 2 diabetes. Likewise, we found no evidence of decreased risk of diabetes with increased intake of monounsaturated or polyunsaturated fatty acids or vegetable fat. However, cholesterol intake tended to be positively related to an elevated risk of diabetes. Cholesterol intake from red meat may thus explain, at least in part, the observed association between red meat intake and type 2 diabetes.
Recently, body iron overload has been postulated to promote insulin resistance and increase type 2 diabetes risk.[26-30] However, the positive association between heme iron intake and type 2 diabetes should be interpreted with caution because the high correlation between red meat intake and heme iron intake substantially limited our statistical capability to separate the independent effect of heme iron from other components of red meat. The lack of association between total iron intake and risk of type 2 diabetes might reflect the fact that body iron status is not well regulated by intakes of total dietary iron or heme iron.
Our study has several limitations. First, we cannot completely exclude the possibilities of residual confounding from unmeasured or incompletely measured underlying lifestyle factors even though we have adjusted for many major risk factors for type 2 diabetes. Second, participants might change their diets after developing some diseases. However, these associations persisted when we carried out secondary analyses after excluding participants who had a history of hypertension or high cholesterol levels, which allows for elimination of dietary change related to these diagnoses. Third, because of a high degree of statistical collinearity, our ability to reliably distinguish the effect of red meat from intakes of its major components such as animal fat, animal protein, and heme iron was limited. Fourth, limited variation of intakes for each subtype of total red meat or other processed meat in our cohort could lead to insufficient statistical power to detect significant association. Finally, we were also unable to assess levels of specific chemicals added or produced in different food preparation methods and thus could not address the relationship between these specific chemicals and diabetic risk.
In conclusion, our study indicates that higher consumption of total red meat, especially various processed meats, may increase risk of developing type 2 diabetes in women. However, the underlying mechanisms by which consumption of red meat or processed meat influence type 2 diabetes risk are still not well understood and require further investigation.
Acknowledgements
We are indebted to the 39,876 dedicated and committed participants of the WHS.
Funding Information
This study was supported by the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases Grant DK-02767.
Reprint Address
Simin Liu, MD, ScD, Division of Preventive Medicine, Brigham and Women's Hospital, 900 Commonwealth Ave. East, Boston, MA 02215. E-mail: simin.liu~channing.harvard.edu
A Prospective Study of Red Meat Consumption and Type 2 Diabetes in Middle-Aged and Elderly Women
The Women's Health Study
Posted 09/21/2004
Yiqing Song, MD; JoAnn E. Manson, MD, DRPH; Julie E. Buring, SCD; Simin Liu, MD, SCD
Conclusions
In this large prospective study, we found that a higher consumption of red meat, especially total processed meat, was associated with an increased risk of developing type 2 diabetes in middle-aged and older U.S. women, independent of known diabetes risk factors.
The prospective design and high follow-up rates in our study minimized the possibility of selection bias or recall bias. As any measurement errors from baseline SFFQ were unlikely to be related to subsequent diabetes end points, misclassification of dietary assessment would most likely be nondifferential and would have attenuated the true associations. Thus, our observed associations may not be explained by such errors and were, on the contrary, somewhat conservative. Our results were also less likely to be influenced by misclassification of type 2 diabetes because of a high accuracy of self-reported diabetes as assessed by our validation study. Moreover, because we adjusted for age, BMI, and other important risk factors for type 2 diabetes, the residual confounding due to these known factors was probably modest.
Our findings are consistent with recent evidence from both the Health Professionals Follow-Up Study of male health professionals and the Nurses' Health Study II of younger and middle-aged U.S. women.[8,9] Processed meat appeared entirely responsible for the elevated diabetes risk associated with total red meat in these two large cohort studies.[8,9]
Red meat, especially processed meat, contains certain types of preservatives, additives, or other chemicals arising from meat preparation, including preservation, packaging, and cooking. These compounds include nitrates and nitrites added in meat processing as well as a variety of heterocyclic amines and polycyclic aromatic hydrocarbons formed in red meat, especially when cooked well done.[17] These compounds can be converted to N-nitrosamines,[17] which were found to be toxic to pancreatic รข-cell.[18] Consumption of foods with a high content of nitrites and nitrosamines has been associated with type 1 diabetes.[19-21] Also, advanced glycation and lipoxidation end products produced during the cooking or processing of meat have been associated with insulin resistance and diabetes-related complications in animal models[22] and human subjects.[23,24] Therefore, such specific compounds mainly present in processed meat might largely explain the observed significant association between processed meat intake and type 2 diabetes.
Nevertheless, red meat is also a major source for saturated fat, cholesterol, animal protein, and heme iron. It has been shown that certain types of fat from red meat may play a major role in the development of type 2 diabetes.[9,25] As noted in a recent review, epidemiological evidence for the relevance of dietary fats and risk of type 2 diabetes seem to be inconsistent.[25] The present study did not show any positive associations between intakes of saturated fat or trans fatty acid and risk of type 2 diabetes. Likewise, we found no evidence of decreased risk of diabetes with increased intake of monounsaturated or polyunsaturated fatty acids or vegetable fat. However, cholesterol intake tended to be positively related to an elevated risk of diabetes. Cholesterol intake from red meat may thus explain, at least in part, the observed association between red meat intake and type 2 diabetes.
Recently, body iron overload has been postulated to promote insulin resistance and increase type 2 diabetes risk.[26-30] However, the positive association between heme iron intake and type 2 diabetes should be interpreted with caution because the high correlation between red meat intake and heme iron intake substantially limited our statistical capability to separate the independent effect of heme iron from other components of red meat. The lack of association between total iron intake and risk of type 2 diabetes might reflect the fact that body iron status is not well regulated by intakes of total dietary iron or heme iron.
Our study has several limitations. First, we cannot completely exclude the possibilities of residual confounding from unmeasured or incompletely measured underlying lifestyle factors even though we have adjusted for many major risk factors for type 2 diabetes. Second, participants might change their diets after developing some diseases. However, these associations persisted when we carried out secondary analyses after excluding participants who had a history of hypertension or high cholesterol levels, which allows for elimination of dietary change related to these diagnoses. Third, because of a high degree of statistical collinearity, our ability to reliably distinguish the effect of red meat from intakes of its major components such as animal fat, animal protein, and heme iron was limited. Fourth, limited variation of intakes for each subtype of total red meat or other processed meat in our cohort could lead to insufficient statistical power to detect significant association. Finally, we were also unable to assess levels of specific chemicals added or produced in different food preparation methods and thus could not address the relationship between these specific chemicals and diabetic risk.
In conclusion, our study indicates that higher consumption of total red meat, especially various processed meats, may increase risk of developing type 2 diabetes in women. However, the underlying mechanisms by which consumption of red meat or processed meat influence type 2 diabetes risk are still not well understood and require further investigation.
Acknowledgements
We are indebted to the 39,876 dedicated and committed participants of the WHS.
Funding Information
This study was supported by the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases Grant DK-02767.
Reprint Address
Simin Liu, MD, ScD, Division of Preventive Medicine, Brigham and Women's Hospital, 900 Commonwealth Ave. East, Boston, MA 02215. E-mail: simin.liu~channing.harvard.edu