While the health effects of red meat on health have been heavily researched, most of these studies are observational, meaning that they’re designed to detect associations but cannot prove causation (cause and effect).
Observational studies tend to have confounding variables — factors other than the ones being studied that might be influencing the outcome variable (13).
It’s impossible to control for all of these factors and determine if red meat is a “cause” of any health outcome. That limitation is important to keep in mind when reviewing the research and determining if red meat is something you’d like to incorporate into your regular diet.
Red meat and heart disease
Several observational studies show that red meat is associated with a greater risk of death, including heart disease (14, 15).
One study in 43,272 males showed that consuming a higher amount of red meat — including both processed and unprocessed varieties — was associated with a higher risk of heart disease (16).
Furthermore, the same study concluded that substituting red meat with plant-based proteins such as legumes, nuts, or soy could possibly reduce the risk of developing heart disease (16).
Other research indicates the risk may vary between processed or unprocessed meat.
Another large study including 134,297 individuals found that consuming at least 5.3 oz. (150 gm) of processed meat per week was significantly associated with an increased risk of death and heart disease (17).
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One of the reasons processed meats may be more strongly associated with heart disease risk is the high salt content. Excessive sodium intake has been linked to high blood pressure (19).
Conversely, the study of more than 130,000 participants found no association between unprocessed red meat consumption, even in amounts of 8.8 oz. (250 gm) or more per week (17).
Another review of controlled studies concluded that eating half a serving (1.25 oz. or 35.4 gm) or more of unprocessed red meat daily doesn’t adversely affect heart disease risk factors, such as blood lipids and blood pressure levels (18).
Randomized controlled trials — which are considered to be of higher quality than observational studies — appear to support these results.
It’s still important to keep in mind that both processed and unprocessed types of red meat are high in saturated fat, which can increase LDL (bad) cholesterol levels, a risk factor for heart disease (8).
For this reason, the American Heart Association (AHA) recommends limiting saturated fat intake to less than 6% of total daily calories, choosing lean cuts of meat when possible, and limiting consumption of processed meats (15, 20).
Red meat and cancer
Observational studies show that both processed and unprocessed red meat consumption is associated with an increased risk of certain cancers, especially colorectal and breast cancers (21, 22, 23).
In fact, in 2015, the World Health Organization (WHO) cancer agency classified red meat as “probably carcinogenic to humans.” They also classified processed meat as “carcinogenic to humans,” noting that processed meat has been shown to cause colorectal cancer (24).
A review of studies also found that people who consumed high amounts of processed and unprocessed meats had a 9% and 6% greater risk of developing breast cancer, respectively, compared to those who consumed the lowest amount (21).
While it’s not fully understood how red and processed meats increase the risk of certain cancers, it’s thought that using nitrites to cure meat and smoking meats can produce carcinogenic (cancer-causing) compounds. High heat cooking, such as grilling, may also create cancer-promoting compounds (25, 26).
That being said, more research is needed to understand the effects of processed and unprocessed red meat intake on cancer development.
Red meat and type 2 diabetes
Some research suggests that red meat consumption may be linked to an increased risk of type 2 diabetes.
For example, one study found that replacing one serving of red meat per day with a serving of eggs was linked to a decreased risk of developing type 2 diabetes, even after adjusting for other factors like body mass index and belly fat (27).
Similarly, another study showed that swapping red meat with other sources of protein was tied to a lower risk of type 2 diabetes. This association was found for processed and unprocessed meat varieties but was more significant with processed red meat (28).
Furthermore, according to a review of 15 studies, people who consumed the highest amounts of processed and unprocessed red meats were 27% and 15% more likely to develop type 2 diabetes, respectively, compared to those who consumed the lowest amounts (29).
Still, more high quality studies are needed to evaluate the relationship between red meat intake and type 2 diabetes and to understand whether other factors may also be involved.