Can Your Diet Cause Brain Fog?

Ever walk into a room and forget why you’re there? Or re-read the same email three times before it finally sinks in? That frustrating lack of focus, sometimes a result of brain fog, can leave you feeling mentally stuck, even when you’re trying your best to power through the day. While it’s easy to blame stress, sleep, or just being “off,” new research suggests that what you eat could also be part of the picture. 

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

Let’s dig into how nutrition can impact your mental sharpness and share realistic strategies to help you feel more clear-headed and focused.

Understanding Brain Fog

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

Common signs of brain fog include:

• Difficulty concentrating or staying on task
• Short-term memory lapses (e.g., forgetting why you walked into 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 point to an underlying cause that could be improved with lifestyle changes.

Possible contributors to brain fog include:

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

The Diet-Brain Connection

The choices we make about food today could shape how our brains function decades from now. Feeling foggy after a meal might seem harmless, but over time, those moments of mental fuzziness could be your body’s way of signaling something deeper. More and more research is connecting the dots between what we eat and how our brains function in the long run.

One possible contributor? Blood sugar fluctuations. Eating foods high in refined carbohydrates or added sugar, may lead to a quick blood sugar spike —followed by a crash that can leave you feeling tired, irritable, or unable to concentrate. These rollercoaster patterns don’t just affect your energy levels—they can also wear on your brain over time. Poor blood sugar regulation may be associated with long-term risks like cognitive deficits and even dementia (9).

Researchers are now calling dementia “Type 3 diabetes” to illustrate just how significant the blood sugar-brain connection is. This term has emerged in response to findings that insulin resistance and poor glucose metabolism can damage brain cells and contribute to neurodegeneration (10). 

Another major factor is inflammation caused by consuming high amounts of ultra-processed foods, added sugars, and unhealthy fats. Chronic, low-grade inflammation may interfere with communication between brain cells and disrupt neurotransmitter balance, two components of our metabolism that are essential for clear thinking and memory (1). 

About the Experts

Caroline Thomason, RD is a dietitian and diabetes educator combining her love of nutrition with the power of making better health easy to understand. With 12 years in the industry, her work has appeared in more than 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 bachelors and masters at San Diego State University and completed her dietetic internship at Sodexo. Her areas of focus 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 obtained her culinary arts degree from Johnson and Wales University.

Melissa Jaeger RD, LD is the Head of Nutrition for MyFitnessPal. Melissa 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 recognized as the Registered Young Dietitian of the Year awarded by the Minnesota Academy of Nutrition and Dietetics.

Nutritional Factors Contributing to Brain Fog

Your brain relies on key nutrients to function at its best. A diet low in certain nutrients or high in sugar and processed foods may make it harder to stay energized, focused, and mentally sharp. 

One diet that can help you get the nutrition you need for brain health is the MIND diet. “The MIND Diet encourages you to eat more of very specific foods and food groups rich in key nutrients and reduce your intake of a few less nutrient dense food groups. Plus, there is data to suggest that modest adherence to the MIND diet may help support brain health and potentially lower the risk of Alzheimer’s disease,” says Melissa Jaeger, RD, LD Head of Nutrition for MyFitnessPal (12).

The MIND diet encourages:

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

The MIND diet suggests being more mindful about:

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

Here are some common nutrients that you may want to consider when understanding what may contribute to brain fog symptoms:

Vitamin B12

Vitamin B12 plays a major role in supporting brain function and the nervous system. When you’re low in B12, some people may experience symptoms like forgetfulness, mental fog, fatigue, or even tingling in your hands and feet. If a deficiency is not addressed over time, it could potentially lead to nerve issues and challenges with cognitive function . Older adults and people following plant-based diets may be at higher risk, since B12 is found mostly in animal products. (2).

Eat more: eggs, dairy, fish, chicken, beef, or fortified nutritional yeast and plant milks.

Iron

Iron helps your red blood cells carry oxygen—so when you’re low, your brain may not get the fuel it needs. Over time, iron deficiency can lead to anemia, which may impact mental and physical performance (4). “Infants, young kids, teenage girls, pregnant women and premenopausal women are at highest risk for iron deficiencies. Iron deficient anemia is the most common result of iron deficiency. Iron deficient anemia can be linked to GI issues, weakness, fatigue, difficulty concentrating, impaired immune function and challenges with body temperature regulation,” says Emily Sullivan, a MyFitnessPal dietitian. 

Eat more: lean red meat, poultry, lentils, beans, spinach, and iron-fortified cereals. Pair iron-rich foods with vitamin C (like citrus or bell peppers) to boost absorption.

Vitamin D

Often called the “sunshine vitamin,” vitamin D does more than support bones—it also impacts mood and memory. Because vitamin D is hard to get from food alone, many people fall short—especially those who spend most of their time indoors or live in less sunny climates. Low levels have been linked to depression, trouble focusing, and long-term cognitive function (7).

“Getting enough vitamin D through the diet is difficult for all groups. For most people, sunlight and fortified sources are needed to get sufficient amounts. Infants who are partially or fully breastfed need supplementation to meet their needs because of low levels of sun exposure and insufficient amounts from mothers milk. Older adults may be at higher risk because of a decline in the skin’s ability to synthesize it diminishes as we age. Plus, people with limited sun exposure, dark pigmentation, fat malabsorption issues, and people who have had gastric bypass may be at a higher risk of deficiency,” advises Brookell White, a MyFitnessPal dietitian.

Eat more: salmon, sardines, egg yolks, and fortified dairy or plant-based milks. A supplement may be needed to meet your needs.

Omega-3 fatty acids

“Many people do not consume enough omega-3’s so focusing on getting more in the diet is important for your health,” White offers. These powerful fats are essential for brain health, helping your neurons communicate and keeping inflammation in check. Not getting enough omega-3s may lead to memory lapses, mental fatigue, and trouble concentrating. Over time, a deficiency may raise your risk for depression and changes in cognitive function (8).

Eat more: fatty fish like salmon, mackerel, or sardines; walnuts, chia seeds, flaxseeds, or a high-quality fish or algae oil supplement.

How to Fight Brain Fog With Food

While there’s no single “brain fog diet,” your daily food choices can make a big difference in how clearly you think and feel. 

Here are some simple, science-backed tips to help sharpen your focus through nutrition:

• Balance your meals: Build meals with a mix of protein, healthy fats, and fiber-rich carbs to help support stable blood sugar and support steady energy levels throughout the day.
• Limit ultra-processed foods: Foods high in added sugars and refined carbs can cause blood sugar spikes and drops, which may contribute to mental fatigue and irritability. Try swapping packaged snacks for whole foods like fruit, nuts, or hard-boiled eggs.
• Get enough omega-3s: These healthy fats are important for brain function. Aim for fatty fish twice a week or add chia seeds, walnuts, or flaxseeds to your meals.
• Watch for hidden deficiencies: Low levels of B12, vitamin D, or iron can all contribute to brain fog. Consider getting lab work done if symptoms persist, and include more nutrient-rich foods in your diet.
• Eat for your gut: Fermented foods like yogurt, kefir, kimchi, and fiber-rich veggies help support a healthy gut microbiome—which is closely tied to mood, focus, and memory.
• Stay hydrated: Even mild dehydration can impact focus and concentration. Aim for at least 8 cups of water per day, more if you’re active or live in a warm climate.
• Track your intake: Using an app like MyFitnessPal can help you identify patterns—like skipping protein at breakfast or not getting enough fiber—that may be contributing to sluggish thinking. Logging your meals for even a few days can be eye-opening.

Frequently Asked Questions (FAQs)

The Bottom Line

If you’ve been struggling to concentrate, forgetting things more often, or feeling mentally foggy after meals, your food choices might be worth a closer look. Brain fog isn’t always about stress or lack of sleep—what you eat (or don’t eat) plays a major role too.

By focusing on blood sugar stability, gut health, and nutrient-rich meals, you can fuel your brain to feel sharper, more energized, and focused. Start small: balance your plate, hydrate, and consider tracking your meals to spot trends that could be holding you back.

Use MyFitnessPal to log your food for a few days—it’s a simple way to gain insight into what’s really going on with your diet and mental clarity. Your brain will thank you.

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