Explosion of dementia stunningly linked to one of America’s favorite foods
Eating too much steak and bacon may increase the risk of dementia later in life, a controversial government-funded study suggests.
Harvard researchers looked at 133,000 adults over four decades and evaluated how much processed and unprocessed red meat they ate on average per day.
They found that eating one serving of processed red meat – roughly two slices of bacon or a single sausage – was linked to a 13 percent increased risk of dementia.
The study concluded that a person could reduce their risk of dementia by 28 percent by replacing a daily serving of processed red meat with the same amount of fish.
The team’s more controversial finding was that consuming at least one serving of unprocessed meat — for example, a sirloin steak, ground beef or lamb — was linked to a 16 percent increased risk of cognitive decline, which is a precursor to dementia.
Processed red meat, eaten in excess, is known to be linked to colon cancer because preservative chemicals are added to the meat or produced during cooking.
But the team at Mass General Brigham says there is evidence that eating too much processed red meat may also contribute to dementia.
Experts have also cited flaws in recent research on unprocessed red meat, suggesting these are just observations and don’t take into account other lifestyle factors.
A new study suggests that red and processed meat may increase the risk of dementia and cognitive decline. However, red meat was associated with self-reported cognitive decline rather than actual increases in dementia diagnoses
The study also did not look at steak, one of the most common non-processed meats in America.
The study results should be treated with caution, as previous research has not always found a link between red meat consumption and dementia.
But a strength of the new research is that it analyzed people who answered detailed questions about their diet every two to four years, and were followed to see if they developed dementia for decades — up to 43 years.
Processed red meat contains nitrites, added as a preservative to keep it from spoiling, which can cause molecules called free radicals to grow out of control and damage the brain.
The high salt content of foods like bacon can also lead to high blood pressure, which damages blood vessels, reduces blood flow to the brain and causes vascular dementia – the second most common form of dementia.
The study, published in the journal Neurologylooked at data on US healthcare workers who enrolled in research studies in midlife.
Nearly 12,000 of these people developed dementia, and nearly 17,500 female volunteers received telephone assessments to assess their cognitive function, including memory, language skills and thinking speed.
People’s scores on these assessments were used to determine their ‘brain age’ for thinking skills, and people who ate too much red meat could have their brain age compared to others.
The results suggest that a person’s brain was about 20 months older, based on cognitive function, for each additional serving of processed red meat he or she ate per day.
A serving is about three ounces of meat, which is the size of a deck of cards.
People’s verbal memory – their ability to remember words and the details of stories, for example – was worse, equivalent to the equivalent of a 20-month older brain, for every additional daily serving of processed red meat.
Researchers also looked at people’s self-reported cognitive problems, based on answers to questions such as whether they had trouble remembering people or had recently become lost.
These self-reports are less reliable than an expert opinion, but people who report thinking problems are often right and are later diagnosed with cognitive decline or dementia.
People who ate at least a quarter of a serving of processed red meat per day were 14 percent more likely than those who ate an average of a tenth of a serving to self-report cognitive problems.
The results also suggest that too much unprocessed red meat, such as beef and lamb, can have an effect on thinking skills.
The graph above shows the number of cases of Alzheimer’s disease per 100,000 people, both age-standardized and at all ages. Age standardization is a method used to adjust for differences in age distribution between populations or over time, while non-age standardized is the raw percentage calculated for all age groups in the population without any adjustment.
The study found an increased prevalence of dementia in those who ate more processed meats such as bacon and sausage. However, red meat did not have the same effect
Self-reported cognitive decline was 16 percent more likely in people who ate an average of at least one daily serving of unprocessed red meat, compared with those who ate less than half a serving.
However, no increased risk of being diagnosed with dementia was found in association with unprocessed red meat.
All the study findings took into account factors that can increase people’s risk of dementia, such as their weight, physical activity and family history of dementia.
Red meat, when digested in the body, produces a substance called trimethylamine N-oxide (TMAO), which some scientists think may contribute to the buildup of proteins in the brain that occur in dementia.
However, this is only based on studies involving animals, not humans.
Dr. Wang said: ‘Reducing the amount of red meat a person eats and replacing it with other protein sources and plant-based options could be included in dietary guidelines to promote cognitive health.’
Currently, nearly 8 million Americans suffer from some form of dementia, and approximately 500,000 new cases are diagnosed each year.
The number of diagnoses is also expected to increase from 60,000 in 2020 to 179,000 per year in 2060.
Dementia also affects almost 1 million Brits, and it is estimated that one in eleven people over 65 have the condition. The numbers are expected to rise to 1.4 million by 2040, according to the Alzheimer’s Society.
Dr. Peter Attia, a surgeon and founder of Early Medical, said research on red meat often does not take into account other lifestyle factors such as smoking and sedentary lifestyles.
The findings follow recent criticism of studies into the health effects of red meat.
In a recent episode of the Triggernometry podcastDr. Peter Attia, a surgeon and founder of Early Medical, suggested that much of the research linking red meat to negative health outcomes such as dementia and colon cancer may be flawed.
He said: ‘The problem is that epidemiology, especially when the risk ratios are relatively small, is so full of errors. Epidemiology only identifies associations, but can never identify causation.
‘One of the major challenges in red meat epidemiology is that people who consume red meat and people who do not consume red meat are, on average, a proxy for very different behavior.
He noted that people who consume higher amounts of red meat are also more likely to consume more processed meats, such as beef jerky and bacon.
However, those who avoid red meat are also more likely to exercise, quit smoking, and add more fruits and vegetables to their diet.
Dr. Attia said: “I honestly think there’s more nuance to it and I think it also comes down to the type of red meat you’re going to consume. And I don’t think all red meat is created equal.”
The researchers in the new study said there are several limitations, including the reliance on observational data and the use of self-reported data to measure cognitive decline.
The study also mainly involved white professionals, making the sample size less diverse.