You’ve heard time and again that it’s not wise to eat too much red meat, especially if processed, since higher intakes are linked with increased risks of obesity, cardiovascular disease, type 2 diabetes and several cancers. A growing number of studies suggest dietary patterns high in meat may promote cognitive decline, too.
When Japan made the nutrition transition from the traditional Japanese diet to the Western diet, AD rates rose from 1% in 1985 to 7% in 2008. The most important dietary link to AD appears to be meat consumption, with eggs and high-fat dairy also contributing. The mechanisms linking dietary risk factors to AD are fairly well known and include increased oxidative stress from metal ions such as copper as well as from advanced glycation end products associated with high-temperature cooking, increased homocysteine concentrations, and cholesterol and its effects on amyloid beta, insulin resistance, and obesity.
Pork parasite caution (ewww!).
This study of 2,621 people who were an average age of 25 showed that maintaining good dietary practices throughout adulthood can help to preserve brain health at midlife. Good dietary practices were defined as being close to three heart-healthy diets: The Mediterranean diet, the DASH diet, and the APDQS diet. All are low-meat diets.
From the Adventist Health Study: matched subjects who ate meat (including poultry and fish) were more than twice as likely to become demented as their vegetarian counterparts and the discrepancy was further widened when past meat consumption was taken into account.
Advanced Glycation End Product (AGEs)
Glycation affects physiological aging and neurodegenerative diseases such as Alzheimer’s disease and amyotrophic lateral sclerosis. Modulation of the AGE-RAGE axis is now considered promising in the prevention of neurodegenerative diseases. Dietary advanced gycation end products are associated with a decline in memory including Alzheimer’s. AGEs explain many of the neuropathological and biochemical features of AD such as extensive protein crosslinking, glial induction of oxidative stress and neuronal cell death. Oxidative stress and AGEs initiate a positive feedback loop, where normal age-related changes develop into a pathophysiological cascade. AGEs may contribute to eventual neuronal dysfunction and death as an important factor in the progression of various neurodegenerative diseases, including Alzheimer’s disease.
Glycotoxins in our food, also known as advanced glycation end products, or AGE’s, suppress sirtuin activity, promote insulin resistance and chronic inflammation which are cognitive threats. Glycotoxins also promote premature ageing – another cognitive threat.
. The Western diet includes excessive AGE’s, which can be neurotoxic. High levels in the blood may predict cognitive decline over time. If you measure the urine levels of glycotoxins flowing through the bodies of older adults, those with the highest levels went on to suffer the greatest cognitive decline over the subsequent nine years.
When meat is heated, it can produce advanced glycation end products (AGEs), sometimes called glycotoxins, which form when protein or fat reacts with sugar. The research found a link between high blood levels of these and cognitive decline in adults over 60, as well as reduced insulin sensitivity (a precursor to type 2 diabetes), the BBC reported. Mice fed a diet high in AGEs also accumulated a defective protein in their brains and performed worse on mental and physical tests.
AGEs are naturally present in uncooked animal-derived foods, and cooking results in the formation of new AGEs within these foods. In particular, grilling, broiling, roasting, searing, and frying propagate and accelerate new AGE formation.
Most processed meats, such as sausages and bacon, are cooked at high temperatures until brown. This browning is an indicator that toxic compounds, called advanced glycation end-products (AGEs), have formed on the surface of the meat. AGEs cause neuro-inflammation in the brain.
The idea is that a diet rich in AGEs can change the brain’s chemistry, at least in mice, according to the BBC: It leads to a build-up of defective beta amyloid protein–a hallmark of Alzheimer’s disease. The mice eating a low-AGEs diet were able to prevent the production of damaged amyloid. The mice performed less well in physical and thinking tasks after their AGEs-rich diet.
Glycotoxin fed mice developed brain SIRT1 deficiency, amyloid-β deposits, cognitive and motor deficits, and MS. These findings were validated in older healthy humans with high baseline circulating glycotoxin levels by a time-dependent decline in cognition and insulin sensitivity. The data suggest that food-derived AGEs, an environmental factor, contribute to both AD and MS by causing chronic SIRT1 suppression.
Food-derived AGEs, an environmental factor, contribute to both AD and MS by causing chronic SIRT1 suppression. Importantly, reduction of food-derived AGEs is feasible and may provide an effective treatment strategy for both these epidemics.
In contrast, plant-based foods, such as vegetables, fruits, legumes and whole grains, contain relatively few AGEs, even after cooking. These are the same types of foods that are linked with lower risk of Alzheimer’s disease and that are more environmentally friendly than meat, making them good choices.
Red meat made headlines recently as a food that may raise Alzheimer’s disease risk. These news stories were based on a study published in the Journal of the American College of Nutrition. The analysis included 10 countries: the United States, Brazil, Chile, Cuba, Egypt, India, Mongolia, Nigeria, Republic of Korea and Sri Lanka.
This study of 204 healthy adults (aged 20–55) showed that red meat and animal fat consumption were negatively correlated with cognitive performance, and this relation was dependent on the age of our participants.
In this cross-sectional analysis of the adult UK population (n = 496, 695), higher intake of red meat was associated with poorer cognitive function including reaction and reasoning ability, short-term and prospective memory especially among men.
This study 16,948 participants in the Singapore Chinese Health Study found that a higher intake of red meat in midlife was associated with increased likelihood of cognitive impairment in later life.
Research shows that saturated and trans fats found in dairy products, meats, pastries, and fried foods can increase the risk for cognitive decline. Instead, eat a plant-based diet, which helps protect brain health.
Diets high in saturated fat, such as from meat, may promote insulin resistance, which is a risk factor for Alzheimer’s disease.
Among 6,183 older participants in the Women’s Health Study it was demonstrated that higher saturated fat intake was associated with worse global cognitive and verbal memory trajectories, while higher mono-unsaturated intake was related to better trajectories.
This study of 1,233 nondemented persons showed that a high mono-plus polyunsaturated fatty acid to saturated fatty acid ratio reduced the risk of cognitive decline.
The hypothalamus is susceptible to developing neuroinflammation following the onset of HFD-feeding that precedes peripheral inflammation and weight gain. Palmitate (dietary saturated fat) altered inflammatory gene expression in hypothalamic neurons in mice.
Increased consumption of fat is a main contributing factor to obesity, leading to elevated levels of saturated fatty acids (SFA) both in serum and the hypothalamus. Elevated SFA in the hypothalamus results in deleterious effects marked by the induction of neuroinflammation, oxidative stress, endoplasmic reticulum (ER) stress, and circadian disruption, all of which can lead to hormonal resistance and neuropeptide dysregulation.
Critically, NAMPT mRNA and protein expression is decreased in the adipose tissue of high fat diet (HFD)-fed mice. Moreover, NAMPT expression is modulated by palmitate (a saturated fat) in the heart and the liver.
The hypothalamus is susceptible to developing neuroinflammation following the onset of HFD-feeding that precedes peripheral inflammation and weight gain. Hypothalamic neuroinflammation involves the secretion of inflammatory cytokines.
Part of the problem is that processed meats are often accompanied by other unhealthy foods. Data from 500,000 people showed that consuming a 25g serving of processed meat a day, the equivalent to one rasher of bacon, is associated with a 44% increased risk of developing dementia.
In this cohort study of 493,888 participants, each additional 25 grams (approximately a single serving) of processed meat per day was associated with a 44% increased risk for all dementias and a 52% increased risk for Alzheimer’s disease. Processed meat contains preservatives that are not present in fresh meat, such as nitrite which can turn into harmful compounds, increasing oxidative stress and inflammation. Also, processed meat is often high in sodium levels, which could lead to high blood pressure, a risk factor for dementia.
This study of 1,500 volunteers found that diets high in processed meats and snack foods may be associated with the risk of dementia.
A study of 2982 participants in the Seniors-ENRICA cohort, who were aged ≥60 years showed that a higher consumption of processed meat was associated with a higher risk of impairment in agility and lower-extremity function. Replacing processed meat by other protein sources may slow the decline in physical functioning in older adults.