Processed meats don’t just affect the heart. They could increase your risk of dementia

A large new study suggests that regularly eating processed red meats such as bacon, sausages and salami could increase your likelihood of developing dementia and cognitive decline as you age.

Health authorities have long urged people to reduce their intake of processed red meat because of its association with cardiovascular disease, cancer and type 2 diabetes. But the new study, published on Wednesday in the journal Neurology, is among the first to suggest a link between cured meats and higher rates of dementia and worse cognition.

The researchers said they believe that high levels of sodium, saturated fat and chemical additives such as nitrates and nitrites in processed red meat could help explain their findings.

There are a number of reasons bacon, salami, sausages and other processed red meats could be detrimental to brain health, experts say.Credit: Getty Images

The study also found that replacing one daily serving of processed red meat with plant proteins such as nuts and legumes was associated with a 19 per cent lower risk of dementia and 1.37 fewer years of cognitive ageing. Replacing processed red meat with chicken and fish also lowered the risk of dementia and reduced cognitive ageing.

Daniel Wang, a senior author of the new study and an assistant professor in the Department of Nutrition at the Harvard T.H. Chan School of Public Health, says replacing processed red meat with other sources of protein accomplishes two things at the same time: “You decrease your intake of harmful ingredients while also increasing your intake of all these beneficial nutrients.”

The facts

• The researchers analysed data on more than 133,000 men and women in the US who were tracked for more than 40 years. The participants were part of two different cohorts of nurses, doctors, dentists and other health professionals who regularly answered questions about their diets, weight, physical activity and other lifestyle habits. 
• The participants were administered tests that evaluated their memory, recall and cognitive function at various points throughout the study. They filled out questionnaires that investigated whether they had any self-reported issues with memory and mental abilities – a measure known as “subjective cognitive decline” that can detect early stages of worsening cognitive function. The researchers also tracked diagnoses of dementia and deaths from the disease.
• The researchers found that people who ate a quarter of a serving of processed red meat or more a day had a 13 per cent higher risk of developing dementia compared with people who ate little or no processed red meat. They also had a 14 per cent higher risk of subjective cognitive decline. Each additional serving of processed red meat daily was linked to an extra 1.69 years of cognitive ageing in a participant’s ability to understand and remember words and sentences.
• Researchers also looked at unprocessed red meats, such as beef, pork, lamb and steak, and did not find that a higher intake of these types of red meat were associated with higher odds of developing dementia or worse cognitive function.

The study’s limitations

The authors of the new study cautioned that their study was observational, meaning it showed an association between eating processed red meats and poorer cognitive function but could not prove causation. It’s possible that other lifestyle habits or factors that weren’t accounted for in the study could explain the findings.

Other research, however, has pointed in a similar direction. One study, for example, that tracked half a million adults in Britain over roughly eight years found that eating the equivalent of about an ounce (or 28 grams) of processed meat or more a day was associated with a 44 per cent higher likelihood of developing dementia and a 52 per cent higher risk of developing Alzheimer’s disease. But eating unprocessed red meat, in contrast, was found to be protective against dementia and Alzheimer’s disease.

What other experts are saying

One expert who was not involved in the new research, Yian Gu, an associate professor of neurological sciences at the Columbia University Irving Medical Centre, says the study and its findings are “very important”.

She says that it’s often difficult for people to change their longtime dietary habits. But encouraging people to make slight changes – like cutting back on their intake of processed red meat – could lead to significant health benefits. In her own studies, Gu has found that eating more fruits, vegetables, fish, nuts, whole grains and legumes is associated with less brain atrophy as people get older.

Why processed meats may affect brain health

There are a number of reasons why bacon, salami, sausages and other processed red meats could be detrimental to brain health, Wang says.

He pointed out that cured meats typically contain a lot of sodium, which can increase blood pressure and cause vascular problems that have an impact on the brain. They contain nitrites, nitrates and other preservatives and chemical additives that can cause oxidative stress.

They contain a lot of saturated fat, which can increase cholesterol levels and disrupt the function of neurons in the brain and nervous system. Some research suggests that diets high in saturated fat might also reduce levels of brain-derived neurotrophic factor, a protein that can trigger the growth of new brain cells.

Eating for better brain health

Wang says he recommends that people try to reduce the amount of processed red meat in their diets and replace it with other proteins. “There’s quite a range of healthier options for you,” he says. “You can replace it with chicken, fish, nuts, low-fat dairy and legumes.”

The benefits of making these substitutions are well documented, Wang says. Studies show that people who eat seafood regularly are less likely to develop Alzheimer’s disease and dementia, likely because seafood is high in omega-3 fatty acids, which promote brain and cardiovascular health. Nuts and seeds are rich sources of unsaturated fats. Like beans, lentils and legumes, they are also high in fibre and polyphenols. Studies show that nuts and seeds can improve blood sugar metabolism and protect against type 2 diabetes, a risk factor for dementia.

The Washington Post

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