Carnivores and Cognition: How the Type of Meat You Eat Impacts Dementia Risk
With over 10 million new cases diagnosed each year, dementia is a significant global contributor to morbidity, mortality, and high financial and societal burdens. Although the causes of dementia are multifactorial, one aspect of its development that researchers come back to again and again is diet. It can be difficult to connect that what we eat in our 30s and 40s affects how well our brains will function in our 60s and beyond, but research has shown that early signs of dementia can be detected in the brains of adults several decades before an Alzheimer’s disease diagnosis occurs.
Some aspects of diet and nutrition are pretty well-established for their roles in impacting cognition — for example, trans fats increase the risk of dementia, while leafy green vegetables decrease it. However, what researchers don’t yet know for sure is whether or not eating meat is helpful or harmful to brain health in the long run.
A recent study published in the American Journal of Clinical Nutrition supplies evidence that it’s not as simple as eating meat or not — there are plenty of differences in the types of meat we eat and how they affect the risk of dementia. From bacon or beef to sausage or steak, this UK-based research team looked at data from almost half of a million adults to tease out the relationship between carnivores and cognition — and the answer lies in the differences between processed and unprocessed meat.
Detailing the Differences of Dementia Development
In this large study of adults in the United Kingdom, 493,888 participants between the ages of 40 and 69 were tracked for about eight years. Zhang and colleagues assessed dietary intake, lifestyle habits, and the incidence of developing Alzheimer’s disease or vascular dementia — a form of cognitive impairment caused by a lack of blood flow to the brain — during that time. They also looked at genetic factors, like carrying the APOE ε4 gene, which is known to increase the risk of both types of dementia substantially.
After the 8-year follow-up period, there were 2,896 new cases of all-cause dementia, 1,006 cases of Alzheimer’s disease, and 490 cases of vascular dementia. These individuals were more likely to be APOE ε4 carriers, of older age, smokers, less educated, less physically active, and of lower socioeconomic status. In contrast to other research, which finds women outnumbering men 2-to-1 in global dementia cases, this UK-based population had more men than women developing dementia.
Bad News For Bacon Lovers
Next, Zhang and colleagues looked at the dietary differences between those who developed dementia and those who didn’t — specifically, with the types and quantity of meat they consumed. For all-cause dementia, there was a 44% increased risk of developing the disease with each additional 25 grams of processed red meat, like ham, sausage, hot dogs, and burgers, that were consumed per day — for reference, this would equate to about one or two slices of bacon, depending on the size. Similarly, the risk of developing Alzheimer’s disease — the most common form of dementia — increased by 52% with each additional 25 grams per day of processed meat consumed. After uncovering this data, Zhang states, “Our research adds to the growing body of evidence linking processed meat consumption to increased risk of a range of non-transmissible diseases.”
On the other hand, higher consumption of unprocessed red meat (beef, lamb, and pork) was protective against dementia. For each additional 50 grams consumed (almost 2 ounces of meat, or about half of a quarter-pound burger patty), the risk of all-cause dementia and Alzheimer’s disease was reduced by 19% and 30%, respectively.
The Brain-Related Differences of Bacon Versus Beef
Finding such vast differences in dementia rates with the types of meat consumed was unexpected, leading Zhang and colleagues to speculate about why this variability occurred. While the high amounts of protein, zinc, and iron found in meat products are thought to be favorable to brain health, there are three components of processed red meat that may negate these brain-boosting benefits: nitrites, advanced glycation endproducts (AGEs), and sodium.
First, the nitrites found in processed meats, like ham or hot dogs, are added to prevent the growth of harmful bacteria, extend shelf life, add a pink coloring, or preserve the meat. These nitrites lead to the production of nitrosamines in the body, which are harmful compounds linked to DNA damage, activation of inflammatory molecules called cytokines, and increased levels of oxidative stress — a buildup of reactive oxygen species that damage cells and proteins. As inflammation and oxidative stress are highly detrimental to brain health, the dietary nitrites in processed meats are a likely culprit for the development of dementia.
The accumulation of advanced glycation endproducts in older adults — “AGEing” — is also involved in neurodegenerative disorders. These compounds develop when foods are cooked at high heat (like grilling, barbecuing, or frying), causing the proteins or fats in the food to “stick” to sugars in the bloodstream — also known as glycation. AGEs are considered toxic to the brain, as they create high amounts of oxidative stress and neuroinflammation by altering the structure and function of proteins. Although AGEs can develop from high-heat cooking of all meats, processed red meats are particularly susceptible to developing these harmful compounds — one study found that fried bacon had 20 times more AGEs than fried pork chops.
Lastly, the high sodium content may be another reason why these foods increase dementia risk, as salt is added to processed meats for preservation and curing. High salt intake increases the risk of high blood pressure, which also plays a role in neurodegenerative diseases. One study with animals found that long-term high-salt consumption led to reduced blood flow in the brain, memory and learning deficits, and cognitive impairment.
Does This Mean Sayonara to Sausage Forever?
With this study comes a greater understanding of the differences between the meat we eat and our risk of dementia in the future. However, this research has some limitations, such as the lack of diversity (95% of the participants were white) and the notorious unreliability of self-reported dietary data — after all, think about how accurately you could detail the quantities and types of foods you recently ate. Plus, it’s important to note that correlation does not equal causation — as stated by Professor Paul Matthews at the UK Dementia Research Institute, “Risk as defined in this study means association, but does not provide evidence that eating processed meat causes dementia.” Despite these drawbacks, this research adds to the evidence of the health-harming effects of processed red meats, while uncovering new data on how unprocessed meats may protect cognition with age.
Although it doesn’t necessarily mean that you can never eat bacon or sausage again, this study implies that it would be wise to limit your consumption of meats from the processed section — especially not eating them on a daily basis. As summarized by one author of this study, Professor Cade, “Anything we can do to explore potential risk factors for dementia may help us to reduce rates of this debilitating condition. This analysis is a first step towards understanding whether what we eat could influence that risk."
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