Can Your Diet Cause Brain Fog?

Ever walked into a room and forgotten why you’re there? Or re-read the same email multiple times before it sinks in? This frustrating lack of focus, often referred to as brain fog, can leave you feeling mentally stuck, even when you’re trying to power through the day. While it’s easy to blame stress or lack of sleep, new research suggests that your diet could also play a significant role.

One study published in the journal Nutrients found that those who consumed a higher proportion of ultra-processed foods (UPFs) had significantly poorer cognitive performance. This link remained even when accounting for overall diet quality, suggesting that processed foods alone may negatively impact brain health (1).

Let’s explore how nutrition affects mental sharpness and share practical strategies to help you feel more clear-headed and focused.

Understanding Brain Fog

Brain fog isn’t a medical diagnosis, but it’s a real experience. It describes a range of cognitive symptoms that can leave you feeling mentally sluggish, unfocused, or just off.

Common signs of brain fog include:

• Difficulty concentrating or staying on task
• Short-term memory lapses (e.g., forgetting why you entered a room)
• Slower thinking or trouble processing information
• Mental fatigue, especially after meals or long work sessions
• Struggling to find the right words in conversation

While occasional brain fog can happen to anyone, persistent symptoms might indicate an underlying cause that could be improved through lifestyle changes.

Potential contributors to brain fog include:

• Diet: Nutrient deficiencies, blood sugar fluctuations, dehydration, or ultra-processed foods. For example, B12 deficiencies are linked to reduced cognitive function (2).
• Medical conditions: Thyroid issues, anemia, and inflammatory diseases can contribute to brain fog symptoms (3, 4, 5).
• Gut-brain axis dysfunction: Imbalances in the gut microbiome may affect cognitive function and mood (6).

The Diet-Brain Connection

Your food choices today can shape your brain’s function in the future. Feeling foggy after eating may seem harmless, but over time, it could signal deeper issues. Research increasingly connects diet to brain health, especially when it comes to blood sugar regulation and inflammation.

For example, consuming foods high in refined carbohydrates or added sugar can cause blood sugar spikes followed by crashes, leaving you tired, irritable, or unable to concentrate. Poor blood sugar control is linked to long-term risks like cognitive decline and even dementia (9).

Researchers have coined the term “Type 3 diabetes” to describe dementia, emphasizing the significant link between insulin resistance, poor glucose metabolism, and brain cell damage (10).

Chronic inflammation from excessive consumption of ultra-processed foods, added sugars, and unhealthy fats can also interfere with brain cell communication and disrupt neurotransmitter balance, both essential for clear thinking and memory (1).

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About the Experts

Caroline Thomason, RD is a dietitian and diabetes educator who combines her passion for nutrition with making health easy to understand. With 12 years of experience, her work has appeared in over 40 publications. She’s also a speaker, broadcast spokesperson, and recipe developer.

Brookell White, MS, RD is a Food Data Curator at MyFitnessPal. She earned her bachelor’s and master’s degrees at San Diego State University and completed her dietetic internship at Sodexo. Her focus areas include metabolism, gut health, obesity, and weight management.

Emily Sullivan, RD is a food data curator at MyFitnessPal. She earned her bachelor’s degree and completed her dietetic internship at The Ohio State University and holds a culinary arts degree from Johnson and Wales University.

Melissa Jaeger RD, LD is the Head of Nutrition for MyFitnessPal. She received a Bachelor of Arts in Nutrition (DPD) from the College of Saint Benedict and completed her dietetic internship through Iowa State University. In May 2024, she was named Registered Young Dietitian of the Year by the Minnesota Academy of Nutrition and Dietetics.

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Nutritional Factors Contributing to Brain Fog

Your brain relies on key nutrients to function optimally. A diet lacking in essential nutrients or high in sugar and processed foods can make it harder to stay energized and focused.

One diet that supports brain health is the MIND diet. “The MIND Diet encourages eating specific nutrient-rich foods and reducing less nutrient-dense options. Research suggests that even modest adherence may support brain health and lower Alzheimer’s risk,” says Melissa Jaeger, RD, LD (12).

The MIND diet recommends:

• Berries
• Beans
• Fish
• Whole grains
• Green leafy vegetables
• Olive oil
• Nuts

It suggests limiting:

• Red meats
• Butter and stick margarine
• Cheese
• Pastries and sweets
• Fried food

Here are some key nutrients that may help reduce brain fog:

Vitamin B12

Vitamin B12 supports brain function and the nervous system. Deficiency can cause forgetfulness, mental fog, fatigue, or tingling in the hands and feet. Older adults and those on plant-based diets are at higher risk since B12 is mainly found in animal products (2).

Sources: Eggs, dairy, fish, chicken, beef, or fortified nutritional yeast and plant milks.

Iron

Iron helps red blood cells carry oxygen. Low iron can lead to anemia, impacting mental and physical performance (4). “Infants, young kids, teenage girls, pregnant women, and premenopausal women are at the highest risk,” says Emily Sullivan, RD.

Sources: Lean red meat, poultry, lentils, beans, spinach, and iron-fortified cereals. Pair with vitamin C for better absorption.

Vitamin D

Vitamin D impacts mood and memory. Low levels are linked to depression, trouble focusing, and cognitive decline. Sunlight and fortified foods are key sources (7).

Sources: Salmon, sardines, egg yolks, fortified dairy or plant-based milks. Supplements may be necessary.

Omega-3 Fatty Acids

Omega-3s are essential for brain health, aiding communication between neurons and reducing inflammation. Deficiency may lead to memory lapses and mental fatigue (8).

Sources: Fatty fish like salmon, mackerel, or sardines; walnuts, chia seeds, flaxseeds, or fish oil supplements.

How to Fight Brain Fog With Food

While there’s no single “brain fog diet,” your food choices can significantly impact your mental clarity.

Here are some science-backed tips:

• Balance your meals: Include protein, healthy fats, and fiber-rich carbs to stabilize blood sugar and energy levels.
• Limit ultra-processed foods: Swap packaged snacks for whole foods like fruit, nuts, or eggs.
• Get enough omega-3s: Essential for brain function. Aim for fatty fish twice a week or add seeds and nuts to meals.
• Watch for nutrient deficiencies: Low B12, vitamin D, or iron can contribute to brain fog. Consider lab work and increase nutrient-rich foods.
• Support gut health: Include fermented foods like yogurt, kefir, and fiber-rich vegetables.
• Stay hydrated: Dehydration can impair focus. Aim for at least 8 cups of water daily.
• Track your intake: Use apps like MyFitnessPal to identify patterns affecting mental clarity.

Frequently Asked Questions

The Bottom Line

If you’re struggling with mental fog, your diet could be a key factor. Brain fog isn’t just about stress or sleep—nutrition plays a significant role. By focusing on balanced meals, hydration, and nutrient-rich foods, you can improve mental clarity and energy. Start small: track your meals, stay hydrated, and prioritize whole foods. Use MyFitnessPal to gain insights into your diet and optimize your brain health.

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