NEW YORK (Realist English). According to the Alzheimer’s Association, more than 7 million American adults are living with Alzheimer’s disease, and that number is projected to reach 13 million by 2050. At the same time, nearly 45% of dementia cases may be preventable or delayed through lifestyle changes, and diet plays a key role.
Four dietitians surveyed by Yahoo Life have compiled a list of five foods that are most harmful to the brain.
Author Kelli McGrane (Senior Wellness Writer) summarized expert opinions on what should be eliminated or strictly limited to preserve cognitive function.
Sweetened beverages
Gretchen Terry-Leonard, host of the Your Second Prime Podcast, puts soda, energy drinks and sweetened coffee drinks at the top of her list. In her words, “liquid sugar hits the bloodstream fast, and the brain takes that hit harder than most organs.” Sharp blood sugar spikes cause “brain fog,” impair attention and slow information processing speed.
Chronically high fructose intake is linked to impaired memory formation and changes in the hippocampus — the brain’s primary memory center. Additionally, excess sugar triggers inflammation and increases the risk of obesity and type 2 diabetes, known risk factors for Alzheimer’s disease.
Deli meats (cold cuts, salami, hot dogs)
Terry-Leonard notes that back in 2015, the World Health Organization classified processed meat as a Group 1 carcinogen. “The brain research has been catching up,” she says. “Processed meat has been associated with faster declines in executive function and global cognition in older adults.
A 2024 French dementia study found that deli meats were one of the main dietary vehicles for neurotoxic chemical contaminants linked to higher dementia risk.”
The dietitian advises following a Mediterranean approach: let olives, marinated vegetables, fruits and nuts carry the dish, with meat as a flavor accent rather than the main event.
Jennifer Ventrelle, assistant professor at Rush University Medical Center, adds that the MIND diet (designed to protect the brain) recommends limiting processed meat portions to 85–140 grams no more than once per week.
Ultra-processed foods (chips, cookies, instant noodles)
Dietitian Johannah Katz explains: “Ultra-processed foods tend to be low in fiber and micronutrients while being high in refined carbohydrates, unhealthy fats and additives. That combination is pro-inflammatory and can contribute to blood sugar dysregulation — both of which impact cognitive function and mental health.”
A 2022 study in JAMA Neurology followed 10,775 individuals over eight years and found that those who ate the most ultra-processed foods had a 25% faster rate of executive function decline and a 28% faster rate of overall cognitive decline compared with those who ate the least.
Furthermore, an analysis of 31,000 women in 2023 found that those who consumed nine or more servings of ultra-processed foods per day were 50% more likely to develop depression. Ventrelle recommends swapping chips for nuts, sweets for fresh fruit, and instant noodles for whole grains.
Fried foods
The connection begins with oils: many fried foods are cooked in oils high in saturated fat or even partially hydrogenated oils containing industrial trans fats. These raise LDL cholesterol, contribute to arterial inflammation and reduce blood flow — and when blood flow to the brain is compromised, so is cognitive function.
Additionally, deep-frying creates acrylamide — a chemical that contributes to neuroinflammation and weakens the blood-brain barrier.
A UK Biobank study of more than 140,000 people found that eating just one serving of fried food per day was associated with a 12% higher risk of anxiety and a 7% higher risk of depression. The MIND diet recommends eating fried foods less than once per week.
Alcohol
The question of alcohol remains controversial. Both the MIND diet and the Mediterranean diet allow up to one 5-ounce (150 ml) glass of wine per day, but recent research has prompted a rethink. Ventrelle notes: “Some studies suggest that certain individuals should not consume any alcohol at all — neither for heart health nor for brain health.”
Any amount of alcohol affects the central nervous system by suppressing glutamate (key for memory and cognition) and boosting GABA (which slows brain activity). Regular consumption has been linked to reduced brain volume. A 2022 study of 36,678 adults found that those who drank four or more drinks per day had brain volumes that appeared roughly 10 years older than those of non-drinkers.
What to eat instead?
Ashley Koff, a registered dietitian and author of Your Best Show, recommends “a wide range of colorful foods — the whole rainbow — and low-mercury fatty fish.” Ventrelle and Terry-Leonard point to the MIND diet: people with the highest adherence to it had cognitive decline rates equivalent to being seven and a half years younger. The diet specifically promotes:
- Leafy green vegetables
- Other colorful vegetables
- Berries
- Extra-virgin olive oil
- Nuts and seeds
- Fish and seafood
- Poultry
- Whole grains
- Beans and legumes
Terry-Leonard adds fermented foods (yogurt, kefir, sauerkraut) to support the gut microbiome, which is directly linked to the brain.