Consumption of red meat, however, did not significantly increase the risk for CHD and diabetes.
"Although most dietary guidelines recommend reducing meat consumption, prior individual studies have shown mixed results for relationships between meat consumption and cardiovascular diseases and diabetes," said lead author Renata Micha, from Harvard University in Boston, Massachusetts, USA.
She added: "Most prior studies also did not separately consider the health effects of eating unprocessed red versus processed meats."
Micha and colleagues selected 20 studies for inclusion in the analysis, 17 prospective cohort studies and three case-control studies. These included 1,218,380 participants altogether, of whom 23,889 had CHD, 10,797 had diabetes, and 2280 had stroke.
Red meat intake of 100 g/day or more was not associated with increased risk for CHD or diabetes.
However, a 50 g/day intake of processed meat significantly increased the relative risk for CHD by 42% and for diabetes by 19%.
Neither red nor processed meat consumption was associated with stroke, but as only three studies assessed stroke, the data available may be too limited to demonstrate an association.
"When we looked at average nutrients in unprocessed red and processed meats eaten in the United States, we found that they contained similar average amounts of saturated fat and cholesterol," said Micha. "In contrast, processed meats contained, on average, four times more sodium and 50% more nitrate preservatives."
She added: "This suggests that differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats."
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