6 Foods Brain Experts Urge You to Avoid for Optimal Cognitive Health

Swapping processed items with nutrient-rich alternatives enhances memory and clarity.

By Medha deb

Created on Sep 24, 2025

Swapping processed items with nutrient-rich alternatives enhances memory and clarity.

Food and nutrition experts have long highlighted the best things to eat for a sharper mind and resilient memory, from blueberries to salmon. But what about foods that harm your brain? Leading neurologists, neuropsychologists, and psychiatrists say there are specific items they avoid to safeguard their own cognitive health—and you should consider doing the same. Here’s an in-depth look at six foods brain experts urge you to avoid, why they pose risks, and what to try instead for better memory, focus, and long-term brain vitality.

Why What You Don’t Eat Matters

While you may already fill your diet with brain-boosters, it’s just as crucial to steer clear of certain foods linked to brain fog, faster cognitive decline, inflammation, and even elevated risk for diseases like Alzheimer’s. According to expert insight, these common foods and ingredients can:

Slow processing speed and memory
Promote brain shrinkage and nerve damage
Increase your risk of neurodegenerative diseases
Crowd out the nutrients your brain needs

With that in mind, here’s what top brain docs keep off their plates:

1. High-Mercury Fish

Mercury is a known neurotoxin, and certain types of fish build up this heavy metal over time. According to Dr. Gail Saltz, MD, big, long-lived species like shark, swordfish, king mackerel, and tilefish accumulate the highest mercury levels. Mercury disrupts cognitive functions and particularly targets the cerebellum—the brain region responsible for balance, coordination, and visual processing. Chronic exposure has been linked to problems ranging from brain fog to coordination impairment and—in pregnant women—developmental issues for babies.

The Environmental Protection Agency (EPA) offers these guidelines to minimize mercury risk:

Avoid high-mercury fish: Shark, swordfish, king mackerel, and tilefish
Stick to lower-mercury options: Shrimp, canned light tuna, salmon, pollock, catfish (up to 12 oz per week)
Limit white (albacore) tuna: No more than 6 oz per week

Tip: When eating sushi or tuna salad, watch your portion sizes and frequency to keep cumulative mercury exposure in check.

2. Prepared Biscuits and ‘Flaky’ Baked Goods

That perfectly flaky biscuit or golden croissant may have a dangerous secret: trans fats. Dr. Susan Albers, PsyD, warns that manufacturers have long used trans fats to create that signature layered texture. Despite major efforts to eliminate them from the food supply, trace amounts below 0.5 grams per serving can still be labeled as “trans fat–free.” Even tiny doses add up—especially in processed biscuits, pizza crusts, margarine, and microwave popcorn.

Trans fats increase brain inflammation and interfere with nerve transmission.
Chronic intake has been linked to reduced brain volume and worse memory.
They also raise “bad” LDL cholesterol, compounding cardiovascular risk (which is closely tied to brain health).

Check ingredient lists for words like “partially hydrogenated oil”—a red flag for hidden trans fats.

3. Processed Foods and Fast Food

Heavily processed foods, including fast food, snacks, and sodas, are a minefield of trouble for the brain. Dr. Dianna Purvis Jaffin, PhD, points out that:

They often contain a combination of unhealthy fats (including trans fats), artificial additives, and added sugars.
They’re low in fiber, antioxidants, and essential nutrients your brain needs for repair and optimal function.
A diet dominated by processed foods favors inflammation and can promote obesity, both of which increase the risk of memory loss and cognitive decline.
Excess sugar in soda and packaged snacks can add to the risk by spiking insulin resistance in the brain.

Research suggests that limiting processed foods while increasing real, whole foods is one of the single best defenses against dementia and age-related cognitive decline.

4. Sugary Drinks

Sugary beverages—from regular soda to some sweetened coffees, teas, and even energy drinks—deliver a concentrated dose of added sugar with few or no nutrients. Studies in both humans and animals have shown that sugar-sweetened beverages:

Promote inflammation in the brain
Impair memory and learning, especially when consumed frequently
Are associated with shrunken brain volume in older adults
Increase your risk of diabetes and obesity, which double the risk for brain diseases

Some experts recommend steering clear entirely, while others advocate for reserving sweet drinks as rare treats. Swap sugary sodas for sparkling water or unsweetened iced tea for maximum brain benefit.

5. Artificial Sweeteners

Many people reach for artificial sweeteners like aspartame, sucralose, or saccharin to curb sugar cravings. However, these sugar substitutes are also flagged by neuropsychologists and nutrition-focused psychiatrists:

While calorie-free, research suggests some sweeteners alter the gut microbiome in ways that may indirectly affect mood and cognitive function.
Certain sweeteners, especially in high doses, may produce headaches or even neurobehavioral changes in sensitive individuals.
Some observational studies have hinted at links between routine artificial sweetener intake and poorer memory or higher risk of stroke, but evidence is still emerging.

When reducing your sugar intake, try to favor naturally sweet whole fruits or low-glycemic alternatives like stevia or monk fruit in moderation.

6. Gluten (in Sensitive Individuals)

While gluten is not inherently dangerous for most people, some brain experts recommend that those with celiac disease or non-celiac gluten sensitivity avoid gluten-containing foods. In these individuals:

Consumption may trigger brain symptoms like headache, “brain fog,” mood swings, and poor concentration.
Over time, chronic inflammation caused by a gluten reaction can affect memory and cognitive processing.

Gluten is found in wheat, barley, and rye. If you suspect gluten sensitivity, speak with your doctor about testing and exploring a temporary elimination diet. For those without diagnosed gluten sensitivity, whole grains—including those with gluten—often benefit rather than harm brain health.

Summary Table: Foods to Avoid and Their Cognitive Risks

Food	Main Brain Risk	Expert Tip
High-mercury fish	Neurotoxicity, impaired coordination	Limit to < 1x/week; choose lower-mercury seafood
Prepared biscuits/’flaky’ baked goods	Trans fats: Brain shrinkage, memory loss	Avoid foods with ‘flaky’ texture or partially hydrogenated oils
Processed foods/fast food	Inflammation, nutrient deficiencies	Focus on whole, unprocessed foods instead
Sugary drinks	Brain shrinkage, memory impairment	Opt for water, tea, or unsweetened beverages
Artificial sweeteners	Possible gut/brain axis disruption	Use naturally sweet or low-glycemic sweeteners in moderation
Gluten (sensitive people)	Brain fog, concentration issues	Test for gluten intolerance before eliminating

What to Eat Instead: Brain-Boosting Alternatives

If you want to build a brain-beneficial diet while eliminating these six problematic foods, experts recommend incorporating more of the following:

Dark, leafy greens (spinach, kale)
Berries (blueberries, strawberries)
Omega-3 rich nuts (walnuts, almonds)
Beans and legumes (excellent for fiber and minerals)
Whole grains (oats, brown rice, quinoa—unless gluten-sensitive)
Low-mercury seafood (salmon, sardines)
Herbs and spices (turmeric, rosemary, parsley)

Both the Mediterranean and MIND diets have been shown to protect long-term memory, mental clarity, and brain resilience through their whole-food focus and restriction of processed, fried, and sugary foods.

Frequently Asked Questions (FAQs)

Why is mercury in fish a problem for the brain?

Mercury is a neurotoxin that accumulates in the brain and impairs its development and function—particularly the cerebellum, which handles movement and vision. Chronic exposure can negatively impact memory, balance, and overall cognitive processing.

Is it okay to eat tuna?

Tuna (especially albacore) contains more mercury than other fish. Experts suggest limiting albacore tuna to 6 oz per week, and choosing lower-mercury options like salmon and canned light tuna for the rest of your seafood intake.

What are trans fats and why are they so bad for the brain?

Trans fats are artificial fats used to increase shelf life and create flaky textures in baked goods. They boost inflammation, disrupt nerve signaling, shrink brain tissue, and are linked to memory loss. Even small amounts in processed foods can add up, so reading labels is critical.

Are all processed foods bad?

Not all processed foods are equal, but heavily processed options (think fast food, soda, snack cakes) are low in nutrients and high in unhealthy fats and sugars. The more processed a food is, the more it tends to harm your brain in the long run.

Should everyone avoid gluten?

No. Only those with celiac disease or non-celiac gluten sensitivity need to avoid gluten. Whole grains containing gluten can actually benefit brain and body health for most people.

Does sugar really cause memory loss?

High intake of added and refined sugar is linked to brain inflammation, impaired learning, and memory problems—especially when consumed as sugar-sweetened beverages.

What’s wrong with artificial sweeteners?

The research is mixed, but some artificial sweeteners may negatively impact the gut-brain axis and, in large amounts, have been associated with headaches or mood disturbances. Moderation is advised and natural alternatives are preferred.

Keeping Your Brain Healthy: The Expert Prescription

To guard against cognitive decline, consider these science-backed strategies:

Limit or avoid: High-mercury fish, foods with trans fats, sugary drinks, artificial sweeteners, most heavily processed foods, and (if appropriate) gluten
Prioritize: Fresh vegetables, whole fruits (especially berries), nuts, seeds, whole grains, healthy oils, and low-mercury fish
Read labels: Watch for hidden trans fats and added sugars, even in foods advertised as “healthy”
Adopt eating patterns: Consider Mediterranean or MIND diet templates for optimal cognitive protection

Making these changes doesn’t just support your memory and daily focus—it also builds resilience against age-linked diseases so your brain stays vibrant for life.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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