Characterized by symptoms like confusion, forgetfulness, and difficulty concentrating, brain fog can be a complex and frustrating issue.

What’s more, brain fog can be caused by a wide range of conditions, making it challenging to diagnose and treat.

In addition to hormone changes, chronic stress, and lack of sleep, many people may wonder whether diet might also affect brain fog.

This article will take a closer look at some of the common causes of brain fog and whether or not certain nutrient deficiencies can contribute.

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Brain fog” is a term used to describe a group of symptoms that can affect your ability to think clearly (1).

It’s typically characterized by issues like:

  • difficulty concentrating
  • forgetfulness
  • confusion
  • lack of mental clarity
  • slow or sluggish thinking
  • feeling easily distracted
  • finding it difficult to put your thoughts into words

In some cases, brain fog may interfere with your performance at work or school and can make it more difficult to complete tasks.

Brain fog is believed to occur as a result of low-level chronic inflammation in the brain, which can be caused by a variety of different factors (1).

Fortunately, treating the underlying cause of brain fog can help ease symptoms and improve mental clarity.


Brain fog is a term used to describe a group of symptoms that can affect concentration, focus, and memory. Treating the underlying cause can decrease symptoms and improve mental clarity.

Some research suggests that undereating (not eating enough) could negatively affect cognitive function, resulting in symptoms like brain fog.

That’s partly because not eating enough can increase your risk of nutritional deficiencies, some of which could cause or worsen brain fog (2).

For instance, one review noted that a lack of certain nutrients in the diet could contribute to memory loss (3).

Similarly, the review noted that increased intake of antioxidant-rich fruits and vegetables could reduce oxidative stress and inflammation, which may actually help prevent cognitive decline (3).

Not eating enough may also be associated with depression and anxiety. For example, one study found that people with cancer who were malnourished were nearly twice as likely to experience symptoms of anxiety and more than six times as likely to have symptoms of depression (4).

Both anxiety and depression can negatively affect cognitive function and may potentially worsen brain fog (5, 6).

However, more research is needed.


Not eating enough can increase the risk of nutritional deficiencies, some of which may cause brain fog. It could also contribute to anxiety and depression, both of which can negatively affect brain function. However, more research is needed.

Heads up

Routinely and intentionally undereating can indicate a disordered relationship with food or an eating disorder.

If you are preoccupied with food or your weight, feel guilt surrounding your food choices, or often engage in restrictive diets, consider reaching out for support.

Disordered eating and eating disorders can affect anyone, regardless of gender identity, race, age, socioeconomic status, or other identities.

They can be caused by any combination of biological, social, cultural, and environmental factors — not just by exposure to diet culture.

Feel empowered to talk with a qualified healthcare professional, such as a registered dietitian, if you’re struggling.

You can also chat, call, or text anonymously with trained volunteers at the National Eating Disorders Association helpline for free or explore the organization’s free and low cost resources.

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Several nutrient deficiencies could contribute to brain fog, including vitamin D, vitamin B-12, iron, and omega-3 fatty acids.

Vitamin D

Vitamin D plays a key role in several aspects of health, including brain function (7).

Interestingly, some research has found that low levels of vitamin D may also be linked to a higher risk of depression (8, 9).

Depression can cause a range of symptoms, including brain fog and memory problems (10, 11).

If you are deficient in vitamin D, you may be able to correct your levels by taking a supplement, eating more fortified foods, or getting regular sun exposure. That may be beneficial for depression, cognitive decline, and brain fog (12, 13, 14, 15).

In fact, one study in 42 older women with low levels of vitamin D found that those who supplemented with 2,000 IU per day of vitamin D for one year performed better in learning and memory tests compared with those who took 600 IU or 4,000 IU per day (16).

Vitamin B-12

Vitamin B-12 is an important micronutrient involved in DNA synthesis, red blood cell production, and the function of the central nervous system (17).

A deficiency in this key vitamin can negatively affect brain function, which can cause issues with memory, thinking, and judgement (18, 19).

Fortunately, increasing your intake of vitamin B-12 through food sources or supplements can be beneficial.

For instance, one study in 202 people with cognitive impairment and low levels of vitamin B-12 found that supplementing enhanced cognition in 84% of participants and improved scores on a test evaluating memory, language, and attention in 78% of participants (19).


Though iron may be best known for its role in promoting the formation of healthy red blood cells, it’s also involved in cognitive function and brain development (20, 21).

Some research has found that both high and low levels of iron in the blood could disrupt the function of the nervous system, which may lead to alterations in memory, attention, and behavior — all of which are associated with brain fog (22).

Interestingly, one study even showed that iron status was significantly associated with cognitive performance in children, meaning that those with iron deficiency anemia were more likely to score lower on a test measuring mental function (23).

Because iron is found mostly in animal products, vegans and vegetarians may want to increase their intake of fortified foods to meet their needs or consider talking with a medical professional like a registered dietitian (RD) or doctor to determine if supplementation may help (20).

Learn about Healthline’s picks of the best iron supplements here.

Accessing affordable medical care

Worried about costs? Many health professionals, including RDs, accept health insurance and Medicare or can adjust fees based on a sliding scale as needed to help make their services more affordable.

Learn more about finding affordable medical care in your community here or explore some telemedicine options here.

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Omega-3 fatty acids

Omega-3 fatty acids are a type of healthy fat found naturally in many varieties of fish (24).

In addition to reducing inflammation and promoting heart health, some research shows that omega-3 fatty acids may also support brain function (25, 26).

In fact, low levels of omega-3 fatty acids could be linked to a higher risk of depression, which may cause brain fog (27, 28).

What’s more, one review noted that docosahexaenoic acid (DHA), a specific type of omega-3 fatty acid, plays a central role in brain function throughout the lifespan and may be associated with significant improvements in learning and memory (29).

If you don’t regularly eat fish, an omega-3 supplement may be worth considering to ensure you’re getting enough of this heart-healthy fat in your diet, which can help prevent brain fog.

Studies show that omega-3 fatty acid supplementation may help improve several measures of cognitive function in older adults, including short-term memory and perceptual speed (the ability to accurately complete tasks involving visual perception) (30).

Other nutrients

Several other nutrient deficiencies could contribute to brain fog, including:

  • Magnesium. In addition to increasing your body’s susceptibility to stress — a possible contributor to brain fog — a deficiency in this key mineral may also be linked to decreased cognitive function (31, 32, 33, 34).
  • Vitamin C. One study found that having adequate blood levels of vitamin C was associated with improved concentration, memory, focus, and attention. Low levels of vitamin C may also cause symptoms like depression, which could contribute to brain fog (35, 36).
  • Choline. This micronutrient is essential for brain function and could help protect against cognitive decline. Though more research is needed, one small study found that supplementing with choline improved memory, learning, and processing speed (37, 38).

A deficiency in several nutrients could potentially contribute to brain fog, including vitamin D, vitamin B12, iron, and omega-3 fatty acids. Low levels of magnesium, vitamin C, and choline may also cause brain fog, but more research is needed.

In addition to the nutrient deficiencies detailed above, several other factors can contribute to brain fog.

For example, some of the hormone changes that occur during pregnancy or menopause can affect memory and concentration, leading to brain fog (39, 40).

Not getting enough sleep can also impair concentration and make it more difficult to focus during the day (41).

Chronic stress may also cause mental fatigue, resulting in issues with memory and decision-making (42, 43).

Plus, several medications can lead to brain fog, including cancer treatments like chemotherapy (1, 44).

Other health conditions that might contribute to brain fog include (10, 45, 46, 47, 48, 49):

  • fibromyalgia
  • depression
  • anxiety
  • hypothyroidism
  • dehydration
  • COVID-19
  • neurodegenerative disorders like dementia and Alzheimer’s disease

If you are experiencing chronic or persistent brain fog, a doctor can help you pinpoint the cause and determine the best course of treatment.


There are many other factors that could cause brain fog, including hormone changes caused by pregnancy or menopause, sleep deprivation, chronic stress, and certain medications or health conditions.

Can malnutrition cause brain fog?

Malnutrition (getting too little or too much of certain nutrients) can increase the risk of brain fog. It could also contribute to anxiety and depression, which may negatively impact cognitive function (4, 5, 6).

What is brain fog a symptom of?

Many different factors can contribute to brain fog, including hormone changes, sleep deprivation, vitamin deficiencies, and chronic stress. Certain medications and health conditions can also cause brain fog, such as fibromyalgia, depression, dementia, dehydration, and hypothyroidism (1).

What vitamins are best for brain fog?

If your brain fog is caused by low levels of a certain nutrient — such as vitamin B-12, vitamin D, iron, or omega-3 fatty acids — supplementation may be beneficial. For a closer look at a few of the best vitamins for brain fog, check out this article.

Diet plays an important role in brain function and could contribute to brain fog.

In particular, not eating enough makes it harder to meet your nutritional needs and could contribute to issues like depression and anxiety, both of which may affect brain function.

Several specific nutrient deficiencies could worsen brain fog, including vitamin D, vitamin B12, iron, omega-3 fatty acids, vitamin C, magnesium, and choline.

However, there are many other potential causes of brain fog, including lifestyle factors and health conditions.

For this reason, it’s best to talk with a doctor if you are experiencing chronic or persistent brain fog. They can help you determine the underlying cause and best course of treatment.

Just one thing

Try this today: In addition to combatting brain fog, certain nutrients may also be beneficial for brain health. Check out this article for a few of the best supplements to boost brain power.

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