Most people know that diet affects heart health, but what we eat can also influence the brain’s long-term performance. Neurologists and nutrition experts have highlighted certain common foods that could contribute to cognitive decline if consumed frequently. These foods are linked to inflammation, poor blood sugar control, and other processes that may accelerate the risk of dementia later in life.
Understanding which foods fall into this category and why they may be harmful can help you make smarter choices for brain health over the long term.
Sugary Drinks and Snacks
Sugary beverages are often singled out because they deliver a high dose of simple sugars with minimal nutritional value. Drinks like sodas, energy drinks, and sweetened teas can spike blood glucose levels quickly, which not only affects energy and mood but also promotes inflammation throughout the body and brain. Over time, this inflammatory response has been associated with poorer cognitive performance. Similarly, sugary snacks and desserts — including cakes, cookies, and pastries — tend to destabilize blood sugar and contribute to oxidative stress, which can damage brain cells and compromise memory functions.
Processed and Red Meats
Dietary patterns high in processed meats are linked with elevated dementia risk, according to extensive research. Processed meats such as bacon, sausages, hot dogs, and deli cuts are typically rich in saturated fats and preservatives. These ingredients can lead to chronic inflammation, a known contributor to cognitive degeneration. Long-term observational studies involving tens of thousands of people have found that eating greater amounts of processed red meat over decades correlates with a significantly higher likelihood of developing dementia compared with lower intake levels. Those studies also noted that saturated fats and chemicals used in processing may harm blood vessels and accelerate plaque buildup in the brain. Replacing even a small amount of processed meat with plant-based proteins or leaner options — such as nuts, fish, or legumes — was associated in research with reduced chances of cognitive decline.
Refined Carbohydrates
Refined carbohydrates are another food group experts recommend limiting. These include white bread, pastries, sugary cereals, and other products made with highly processed flour. They break down rapidly in the body, leading to quick spikes in blood sugar and insulin. Over the long term, this cycle can promote inflammation and oxidative stress — both risk factors for neurodegenerative conditions. People who follow diets high in refined carbs may experience more episodes of brain fog, poorer memory recall, and greater mental fatigue compared with those who eat whole grains, legumes, and other high-fiber alternatives.
Ultra-Processed Foods
Ultra-processed foods, such as chips, ready-to-heat meals, and certain frozen dishes, are linked with higher dementia risk in large population studies. These foods often contain additives, excess salt, sugar, and unhealthy fats, all of which can support biological conditions unfavourable for cognitive health. Regularly consuming a very high percentage of this food category was associated with an increased risk of developing dementia. Even swapping out just a portion of these foods for fresh produce or minimally processed alternatives was linked with a lower risk in research analyses.
What This Means for Your Diet
Diet alone doesn’t determine dementia risk — genetics, physical activity, sleep quality, and other lifestyle factors also play major roles. But focusing on whole, nutrient-rich foods while limiting sugar, processed meats, and ultra-processed snacks can support overall brain health. Experts often point to dietary patterns like the Mediterranean or MIND diets, which emphasize fish, vegetables, nuts, and whole grains, as approaches associated with slower cognitive decline and lower dementia risk.
