Abstract
Growing evidence suggests that effects of red meat consumption on coronary heart disease (CHD) and type 2 diabetes could vary depending on processing. We reviewed the evidence for effects of unprocessed (fresh/frozen) red and processed (using sodium/other preservatives) meat consumption on CHD and diabetes. In meta-analyses of prospective cohorts, higher risk of CHD is seen with processed meat consumption (RR per 50 g: 1.42, 95 %CI = 1.07-1.89), but a smaller increase or no risk is seen with unprocessed meat consumption. Differences in sodium content (~400 % higher in processed meat) appear to account for about two-thirds of this risk difference. In similar analyses, both unprocessed red and processed meat consumption are associated with incident diabetes, with higher risk per g of processed (RR per 50 g: 1.51, 95%CI = 1.25–1.83) versus unprocessed (RR per 100 g: 1.19, 95% CI = 1.04–1.37) meats. Contents of heme iron and dietary cholesterol may partly account for these associations. The overall findings suggest that neither unprocessed red nor processed meat consumption is beneficial for cardiometabolic health, and that clinical and public health guidance should especially prioritize reducing processed meat consumption.
Generated Summary
This review article presents an updated analysis of the evidence on the effects of unprocessed (fresh/frozen) and processed meats on the risk of coronary artery disease (CHD) and type 2 diabetes. The study primarily uses meta-analyses of prospective cohort studies to assess the associations between meat consumption and these cardiometabolic diseases. The research considers the characterizations and definitions of different meat types, the evidence for effects on clinical endpoints, potential mechanisms for associations, potential biases, and implications for clinical and public health priorities. The analysis focuses on total unprocessed red meat consumption, including beef, pork, and lamb, and total processed meat consumption, including bacon, hot dogs, sausage, salami, and processed deli or luncheon meats. The core methodology involves pooling findings from multiple studies to derive the best available evidence, with careful consideration of factors such as temporality, consistency, magnitude, and dose-response.
Key Findings & Statistics
- In meta-analyses of prospective cohorts, higher risk of CHD is seen with processed meat consumption (RR per 50 g: 1.42, 95 %CI = 1.07-1.89), but a smaller increase or no risk is seen with unprocessed meat consumption.
- Differences in sodium content (~400 % higher in processed meat) appear to account for about two-thirds of this risk difference.
- In similar analyses, both unprocessed red and processed meat consumption are associated with incident diabetes, with higher risk per g of processed (RR per 50 g: 1.51, 95%CI = 1.25–1.83) versus unprocessed (RR per 100 g: 1.19, 95% CI = 1.04–1.37) meats.
- The pooled dose-response, including 56,311 participants and 769 events, found no significant association between unprocessed red meat consumption and CHD risk (RR = 1.00 per 100 g serving/day, 95% CI = 0.81-1.23).
- Each 50 g serving/day of processed meats was associated with 42 % higher risk (RR = 1.42, 95 % CI = 1.07-1.89) of CHD.
- Matching the serving sizes, each 100 g serving/day of processed meats was associated with 2-fold higher risk of CHD (RR = 2.02, 95 % CI = 1.14–3.57).
- Each 100 g serving/day of unprocessed red meats was associated with 19 % higher risk of CHD (RR = 1.19, 95 % CI = 1.07–1.32), and each 50 g serving/day of processed meats was associated with 20% higher risk (RR = 1.20, 95 % CI = 1.03–1.40).
- Each serving/day of unprocessed red meats was associated with 18 % higher risk of CVD mortality (RR = 1.18, 95 % CI = 1.13-1.23), and each serving/day of processed meats was associated with 21% higher risk of CVD mortality (RR = 1.21, 95 % CI = 1.13–1.31).
- In a pooled analysis, each daily 100 g serving of unprocessed red meats was associated with 19% higher risk (RR = 1.19, 95 % CI = 1.04–1.37) of type 2 diabetes.
- Each 50 g daily serving of processed meats was associated with 51% higher risk (RR = 1.51,95 % CI = 1.25-1.83) of diabetes.
- Each daily 100 g serving of processed meats was associated with a more than 2-fold higher risk of diabetes (RR = 2.28, 95 % CI = 1.56–3.35).
Other Important Findings
- The overall findings suggest that neither unprocessed red nor processed meat consumption is beneficial for cardiometabolic health.
- Differences in sodium content are a major factor, with processed meats containing significantly more sodium than unprocessed meats.
- Heme iron and dietary cholesterol may partly account for the associations with incident diabetes.
- Associations appeared relatively similar for subtypes of unprocessed red meats, as well as for most subtypes of processed meats (including deli meats that would often be processed chicken or turkey), except that bacon and hot dogs appeared associated with relatively higher CHD risk compared with other processed meat subtypes.
- The recommendation to select lean meats was partly based on saturated fat and dietary cholesterol content and consequent effects on blood LDL-cholesterol. Interestingly, our analysis suggests that other constituents may be more relevant.
- Processed meats were predominantly red meats but also included some processed poultry meats (e.g., chicken or turkey deli meats and hot dogs) that were not separately evaluated.
Limitations Noted in the Document
- The dietary assessment methods in studies generally do not permit reliable quantification of every possible subtype of meat, potentially leading to misclassification.
- Reliance on observational studies introduces the possibility of residual confounding due to imprecisely measured or unmeasured factors.
- Bias can also reduce observed associations, due to random errors in measurement of self-reported diet, or overadjustment for factors which could be potential intermediates in the causal pathway.
- Relatively few studies have reported on subcategories of unprocessed and processed meats, raising concerns about publication bias and generalizability.
- The study acknowledges that in observational studies, residual confounding due to imprecisely measured or unmeasured confounders can never be fully excluded.
Conclusion
The study’s primary conclusion is that clinical and public health guidance should prioritize reducing processed meat consumption to reduce the risk of CHD and DM, and it suggests reducing sodium and other preservatives in processed meats. The research emphasizes that neither unprocessed red nor processed meat consumption is beneficial for cardiometabolic health, while also pointing out that there is no evidence of cardiometabolic benefits from unprocessed red meat. The study suggests that the focus should be on reducing processed meat consumption due to its strong associations with cardiovascular events and diabetes, as supported by the evidence from both the 2010 meta-analysis and the updated publications. The article highlights the need to reduce processed meat consumption and other harmful dietary factors. The findings suggest that other constituents of meats, like sodium and other preservatives, may be more relevant than total fat or saturated fat for cardiometabolic effects, which is contrary to the prior recommendations. The study also notes that cattle farming has significant environmental impacts and suggests that healthier alternatives, like fish, nuts, fruits, whole grains, and vegetables, are vastly preferable dietary choices compared to unprocessed red meats. The study emphasizes that while unprocessed red meat consumption has smaller effects on DM and little or no effect on CHD, there is no evidence to suggest it has any cardiometabolic benefits. The study suggests that future research should investigate if subcategories of processed meats have different effects on cardiometabolic risk.