Hypothyroidism is a hormone imbalance with strong effects in most organs of the body. “Brain fog” is not a medical condition. It’s a term used for a group of symptoms that can affect your cognition, mood, and energy. Read on to learn more about the possible link between hypothyroidism and “brain fog.”
What Is Hypothyroidism?
Hypothyroidism is a deficiency in thyroid hormone production by the thyroid gland. Its main symptoms include [1, 2]:
- Fatigue and weakness
- Reduced memory and concentration
- Cold intolerance
- Weight gain
- Dry skin and hair loss
- Painful joints and muscles
Hypothyroidism can be caused by defects in the thyroid gland (primary hypothyroidism) or the hypothalamus or pituitary gland (secondary hypothyroidism) [1, 2].
What Is “Brain Fog”?
“Brain fog”, also known as ‘mental fog’, ‘clouding of consciousness’, and ‘cognitive dysfunction’, is an unofficial term used to describe a constellation of cognitive symptoms such as [3, 4]:
- Reduced mental clarity and cognitive function
- Difficulty focusing and multitasking
- Loss of short- and long-term memory
- Slow thinking
Because these symptoms are generally subjective, doctors can consider them too mild or unspecific to diagnose cognitive impairment.
For more about how hypothyroidism progresses and how it may cause “brain fog” symptoms, check out this post.
Complementary Strategies that May Help “Brain Fog” Symptoms and Hypothyroidism
You may try the complementary approaches for “brain fog” associated with hypothyroidism listed below if you and your doctor determine that they could be appropriate in your case after discussing them. Remember that none of them should ever be done in place of what your doctor recommends or prescribes.
1) Physical Exercise
Always remember to speak with your physician before starting any new exercise regimen or drastic changes in diet.
Doing more exercise may improve how your thyroid gland works. In 2 small trials on 20 adults and 36 adolescents, exercise increased T3 and T4 while decreasing TSH levels [5, 6].
What’s more, exercise may be beneficial for cognitive function, especially if it combines aerobic and strength training. In 4 small trials on almost 100 people with cognitive problems, it improved learning, processing speed, attention, executive function, and movement coordination [7, 8, 9, 10, 11].
Exercise may increase cognitive function by stimulating the birth of new cells, increasing synaptic plasticity, reducing inflammation and oxidative damage, and improving blood flow in the brain [12, 13, 14, 15, 7].
However, extenuating exercise may do more harm than good. It may reduce T3 levels, increase inflammation (Th17 immune response), and cause fatigue, a typical “brain fog” trigger [16, 17, 18, 19].
Experts recommend moderate exercises such as walking, yoga, tai chi, or water aerobics.
2) Improve your Sleep
Poor sleep quality is a common cause of “brain fog” symptoms. Lack of sleep reduced attention, memory, creativity, language and numerical skills, and executive function in multiple studies [20, 21, 22, 23, 24, 25].
Sleep loss may increase free radical damage in the hypothalamus by reducing the production of the antioxidant glutathione. It also increases the production of pro-inflammatory cytokines (such as TNF-alpha, IL-6, IL-17, and CRP) [26, 27, 28, 29, 30, 31].
If you have “brain fog” from hypothyroidism, improving the quality of your sleep may help. Read this post to learn how to fix your sleep.
People with interrupted breathing during sleep (sleep apnea) are at an increased risk of “brain fog”. In addition to worsening sleep quality, apnea reduces oxygen intake. The lack of oxygen produces free radicals, which cause oxidative damage and trigger inflammation .
Importantly, sleep apnea increases the risk of developing Hashimoto’s hypothyroidism. The risk is especially high in women and those with severe apnea. Similarly, apnea increases thyroid antibody levels in people with Hashimoto’s, suggesting the development of the symptoms may be faster .
3) Reduce Stress
Stress decreases thyroid function. Repeated stress increases glucocorticoid production, which in turn reduces the levels of T3, T4, and TSH [34, 35+].
Both chronic stress and the hormones produced in these conditions may impair memory and learning. While the effects are reversible in adults, they may be permanent in young children [36, 37].
Stress may reduce the birth and branching of brain cells in the hippocampus and the function of the messenger glutamate in the prefrontal cortex [36, 38, 39].
Alternatively, the stress hormone CRH may contribute to “brain fog” by increasing inflammation. CRH increases Th1 dominance and activates the inflammatory hub NF-kB. However, it also leads to the production of the anti-inflammatory hormone cortisol [40, 41, 42, 43].
Read here how to reduce your stress response.
4) Check if You Have Gluten Intolerance
In addition to its well-known effects on the gut, celiac disease damages the brain by causing inflammation and producing antibodies that target its proteins .
People with celiac disease often experience “brain fog” symptoms with reduced memory, attention, executive function, and processing speed after eating. In a small trial on 11 people recently diagnosed with celiac disease, going gluten-free improved “brain fog” symptoms [45, 46].
The frequency of celiac disease is higher in people with hypothyroidism, especially in those with autoimmune types such as Hashimoto’s [47, 48, 49].
Speak with your physician to see if you suffer from gluten intolerance to determine if it could be a possible cause for your “brain fog” symptoms.
5) Prevent Insulin Resistance
Diets rich in high-glycemic sugars and fats (a combination typically found in fast food) cause obesity and insulin resistance. This means that the body’s cells don’t take up sugar from the blood in response to insulin [50, 51].
Insulin resistance causes acute fluctuations in blood sugar levels, which increases oxidative damage and inflammation. This damages the brain and may result in “brain fog” symptoms [52, 53].
Obesity triggers insulin production in the hypothalamus at lower blood sugar concentrations, resulting in higher insulin levels .
High blood sugar and insulin lower NAD+ levels. This reduces the ability of the mitochondria to produce the energy molecule ATP, resulting in increased fatigue [55, 56].
Reducing dietary carbohydrates may be especially beneficial in people with autoimmune hypothyroidism. In a clinical trial on almost 200 people with Hashimoto’s, a low-carbohydrate diet reduced thyroid antibody production .
Read here what causes insulin resistance and possible ways to combat it.
6) Reduce Goitrogenic Foods
Goitrogens are substances that reduce iodine uptake by the thyroid gland, resulting in reduced production of thyroid hormones [58, 59].
Foods rich in goitrogens include [60+]:
- Cruciferous vegetables (cabbage, broccoli, cauliflower)
- Root vegetables (cassava, turnip)
- Cereals (sorghum, millet, maize)
- Legumes (soybean, Lima bean)
People with hypothyroidism may want to reduce their intake of these foods to decrease their “brain fog” symptoms. Note, however, that most of them will only interfere with your thyroid function if you have iodine deficiency or eat high amounts (an exception being millet) and cooking these vegetables may inactivate the goitrogenic compounds [61, 62, 63].
7) Gut Health
Gut inflammation produces cytokines that are currently being investigated to determine if they can result in cognitive problems and behavioral changes. Although it’s important to remember the link between mental fatigue and gut inflammation remains unclear, people with chronic fatigue syndrome often have IBS as well [64, 65, 66].
Some foods may increase gut inflammation and worsen IBS symptoms, although more research is needed to confirm their potential effects on cognitive function. These include those rich in [67, 68, 69, 70, 71, 72, 73]:
- Lectins (such as beans, peanuts, lentils, tomatoes, and eggplants)
- Casein (dairy products)
- FODMAPs (such as many fruits, vegetables, cereals, and dairies)
- Salicylates (such as apricots, oranges, pineapples, dates, and raspberries)
- Amines (such as chocolate, cheese, wine, beer, and fish)
- Tannins (such as bananas, chocolate, tea, nuts, and whole spices)
- Trypsin inhibitors (such as legumes, cereals, potatoes, and eggs)
- Oxalates (such as leafy vegetables, dark chocolate, legumes, and nuts)
- Yeast (such as gluten-free bread)
- Food additives like carrageenan and carboxymethylcellulose (such as ice cream, almond milk, candy bars, and some cheeses)
- Caffeine (such as coffee, tea, and cocoa)
To find out if any of these food groups might be worsening your “brain fog” symptoms from hypothyroidism, you can try to follow an elementary diet for 2 weeks and then add one at a time back in. Because elementary diets can lead to deficiencies, follow your doctor’s instructions carefully.
Some scientists believe that gut microbiota plays a role in cognitive function and behavior. The communication between these two organs is often called the ‘brain-gut axis’ .
In animal studies, a Western diet rich in saturated fats and added sugars reduced beneficial bacteria in the gut. These changes are associated with obesity and cognitive impairment [75+, 76, 77].
While the full link and efficacy remains unclear, recent studies have shown that probiotics improved cognitive function and the gut microbiome composition in some small clinical trials. They improved visual memory in 22 healthy people, attention and memory in 50 people with mild cognitive impairment, and visual learning, attention, and general fatigue in 44 people with chronic fatigue syndrome [78, 79, 80].
They also improved learning and memory in mice and rats. Conversely, changes in the gut microbiota (from infections and antibiotics) were associated with cognitive problems and behavioral changes in mice [81, 82, 83, 84, 85, 86].
Interestingly, hypothyroidism is associated with bacterial overgrowth in the small bowel. It would be interesting for future research to determine if this overgrowth may worsen “brain fog” symptoms by disturbing the normal microbiome .
The following supplements might be of benefit in restoring normal thyroid hormone levels:
- Selenium [88, 89, 90, 91]
- Iron [92, 93, 94]
- Iodine 
- Zinc 
- Copper 
- Taurine 
- N-acetylcysteine (NAC) 
- Vitamin D [98, 94]
- Vitamin B12 
- Vitamin A 
In the case of vitamin D, it’s important to combine dietary sources and supplements with sun exposure [101, 102].
Additionally, vitamin B1 increases energy by stimulating carbohydrate breakdown. Supplementation with this vitamin reduced fatigue in 3 people with Hashimoto’s hypothyroidism [103, 104], though it’s very important to remember much further work needs to be done to determine how useful vitamin B1 is in people with this disease.
Remember, it’s preferable to take certain vitamin and mineral supplements only in cases of deficiency. Some of them may be toxic at excessive doses and even worsen hypothyroidism or brain fog. Hence, remember to speak with your doctor before taking any supplements.
This is especially the case of iodine. Although it’s required to make thyroid hormones, high doses may trigger inflammation by increasing T cells (Th1 and Th17) and cytokines (such as IL-6, IL-17, and TGF-beta). This may worsen both “brain fog” symptoms and autoimmune hypothyroidism [105, 106].
Limitations and Caveats
Most studies investigating an association between hypothyroidism and brain fog symptoms were cohort studies. These studies can’t establish a cause-effect relationship.
Additional limitations to most studies included evaluating subjective symptoms, using different methods of measurement, studying heterogeneous populations, and establishing different TSH thresholds to distinguish between overt and subclinical hypothyroidism. This creates a bias that makes it difficult to compare studies.
All the studies on overt hypothyroidism and a lot of those on subclinical hypothyroidism were done on a small number of people. More studies on larger populations are required to confirm their findings.
In the case of subclinical hypothyroidism, the studies on both its association with “brain fog” and possible improvement with thyroid hormone replacement therapies showed contradictory results.
Hypothyroidism is when your thyroid gland doesn’t make enough thyroid hormones. “Brain fog” is not a medical condition but a term used for a group of symptoms that can affect your cognition, mood, and energy.
Some of the ways to get symptomatic relief from “brain fog” as a result of hypothyroidism include getting moderate exercise, improving sleep, and lowering stress. These steps are theorized to stimulate the thyroid to make more thyroid hormones improving brain health.
Additionally, gluten intolerance, insulin resistance, microbiome imbalances, and gut inflammation are all being investigated to determine their role in these symptoms. These factors may worsen autoimmune hypothyroidism and exacerbate “brain fog”.
Eating a nutritious diet (or supplements to prevent nutrient deficiency) and avoiding eating iodine-binding foods like cabbage in large amounts may help.