Red Meat Consumption May Increase the Risk of Cognitive Decline and Dementia

A large number of epidemiological studies have examined the impact of consuming red meat and its processed derivatives (sausages, ham, bacon, etc.) on health. These studies generally use questionnaires to categorize individuals based on their usual meat consumption and estimate the relative risk of developing a given disease by comparing those who consume the most meat to those who consume the least.

In most studies, these comparisons have revealed that a high intake of red and processed meats is associated with a significant increase—around 10–15%—in the risk of cardiovascular disease, type 2 diabetes, and premature death from all causes. Conversely, reducing the consumption of red and processed meat in favour of a higher intake of plant-based proteins is associated with a reduced risk of cardiovascular disease (see our article on this topic) and premature mortality.

From Heart to Brain

Several observations suggest that the increased risk of cardiovascular disease and type 2 diabetes seen in heavy consumers of red meat may also have longer-term effects on brain health. For example, it has been reported that in young adults (ages 18–30), the presence of multiple cardiovascular risk factors such as high cholesterol, hypertension, and hyperglycemia is associated with a decline in several cognitive functions in middle age. People with type 2 diabetes are also at greater risk of experiencing cognitive decline and developing dementia in later decades.

This association between cardiovascular health and cognitive function is biologically plausible, as optimal brain function heavily depends on an adequate blood supply (the brain alone receives 15% of the cardiac output and consumes about 20% of all the body’s oxygen). Damage to blood vessels caused by cardiovascular disease and type 2 diabetes can disrupt this blood flow and, over time, lead to neuronal dysfunction.

Other factors associated with red and processed meat consumption may also influence cognitive function. For instance, the high saturated fat content of such meats raises cholesterol levels and generates chronic inflammation that promotes insulin resistance—two factors that may contribute to cognitive decline (see here and here, for example). Red meats also contain significant amounts of L-carnitine, an unusual amino acid that is metabolized by the gut microbiota into trimethylamine N-oxide (TMAO). In addition to its role in the formation of atherosclerotic plaques, this metabolite appears to contribute to the development of dementia and Alzheimer’s disease in animal models by promoting the aggregation of beta-amyloid and tau proteins in the brain. Finally, nitrites and N-nitroso compounds found in processed meats can cause DNA damage and oxidative stress, while their high sodium content may increase blood pressure, reduce cerebral perfusion, and potentially lead to vascular dementia.

Associations With Cognitive Function

A large-scale study conducted by a team of researchers from Harvard University provides new insights into the potential role of red and processed meats in the risk of cognitive decline and dementia. For the dementia component of the study (including Alzheimer’s and other types), the researchers examined the incidence of these diseases among 133,771 individuals who participated in the Nurses’ Health Study (since 1976) and the Health Professionals Follow-Up Study (since 1986).

Taking into account the potential influence of various external factors (such as smoking, hypertension, physical inactivity, education level, etc.), the long-term follow-up of participants (over 40 years in some cases) revealed that those who consumed ≥ 0.25 servings per day (about 2 servings per week—e.g. one sausage or one slice of ham) of processed red meat had a 13% higher risk of developing dementia compared to those who consumed < 0.10 servings per day (about 1 serving per week) (see Figure 1).

However, consumption of unprocessed red meat (1 serving of 113–170 g vs. <0.5 serving per day) was not associated with an increased risk of dementia.

In the other part of the study focusing on cognitive decline, the cognitive functions of 43,966 participants were assessed using questionnaires measuring general memory, executive functions (e.g. problem solving), attention, and visuospatial abilities (analyzing objects in space). Here again, the results show that processed meats are associated with a 14% increased risk of cognitive decline in the highest consumers (≥ 0.25 servings per day) compared to the lowest consumers, suggesting a detrimental effect on cognitive functions. A similar increase (16%) in the risk of cognitive decline was also associated with the consumption of unprocessed red meats (1 serving per day). Overall, these results suggest that regular consumption of red meat slightly increases the risk of cognitive decline and dementia, with stronger associations for processed meats.

Replacing Processed Meats

The unfavourable association between processed meats and brain functions is further highlighted by substitution analyses, which model the potential impact of replacing one daily serving of processed meat with equivalent amounts from other protein sources (Figure 2).

This approach showed that the increased risk of dementia or cognitive decline can be mitigated by replacing 1 serving per day of processed red meat with any of the tested alternative protein sources, including:

• Nuts and legumes: 19% reduction in dementia risk and 21% reduction in cognitive decline risk
• Fish: 28% reduction in dementia risk and 51% reduction in cognitive decline risk
• Poultry: 16% reduction in dementia risk
• Eggs: 23% reduction in dementia risk and 31% reduction in cognitive decline risk
• Low-fat dairy products: 13% reduction in dementia risk and 28% reduction in cognitive decline risk

One limitation of this study is that it was conducted in a relatively homogeneous population (health professionals) and relied on participants’ ability to accurately report their dietary intake. This intake can vary considerably over time and may be under- or overestimated. Additionally, other external factors not accounted for in the data analysis could influence the results. Nevertheless, studies conducted over the past decades have consistently shown that high consumption of red meats—especially processed meats—has negative health effects. Replacing these foods with healthier protein sources, such as legumes, nuts, and fish, can help improve diet quality and reduce the risk of developing several chronic diseases.