Short answer: No diet has been tested in a trial for long COVID brain fog, so the evidence is preliminary and indirect. Brain fog after COVID is linked to inflammation and gut changes. A Mediterranean-style diet with fatty fish, fermented foods and plenty of fiber is a low-risk start. Supplements are unproven; ask your doctor first.
We don’t know whether diet helps brain fog after COVID, because no trial has tested a diet in people with long COVID. What we do know is that lasting brain fog after COVID has been linked to inflammation, a leaky blood-brain barrier and changes in gut bacteria. A diet that lowers inflammation and supports gut bacteria is a sensible, low-risk bet.
Diet is not a substitute for medical assessment and care for long COVID. Supplements such as vitamin D, zinc, NAC, fish oil and curcumin are not proven for long COVID. They can have side effects or interact with medicines, so discuss them with a doctor first.
This page is about brain fog that started after a COVID-19 infection. For brain fog in general, see the brain fog diet. For brain fog during the menopause transition, see the perimenopause brain fog diet.
What to eat after COVID
None of these steps has been tested as a treatment for post-COVID brain fog. They follow general healthy-eating evidence and what is known about the condition.
- Use a Mediterranean-style pattern as the base: extra virgin olive oil, fatty fish, vegetables, legumes, nuts and whole grains.
- Eat fatty fish two to three times a week: salmon, mackerel, sardines or anchovies.
- Eat a variety of fermented foods each day: yogurt, kefir, sauerkraut, kimchi, miso, kombucha or tempeh.
- Aim for 30 grams or more of fiber a day, increasing slowly. Garlic, onions, leeks, legumes, oats and cooked-and-cooled potatoes or rice are good sources.
- Cook with turmeric and other spices. Avoid curcumin supplements unless your doctor agrees.
- Cut down hard on ultra-processed food, added sugar and alcohol.
- Be patient. Changes kept up over months are more realistic than quick fixes, though their effect on brain fog has not been measured.
Why brain fog lingers after COVID
Post-COVID brain fog means trouble concentrating, poor short-term memory, word-finding problems and mental fatigue. In a meta-analysis of 43 studies (Ceban 2022), 22% of people had cognitive impairment 12 weeks or more after a COVID-19 diagnosis.
The changes can show up on brain scans. Douaud 2022 compared scans taken before and after the pandemic in 785 UK Biobank participants aged 51–81. The 401 who had COVID-19 between scans had a greater reduction in gray matter thickness in regions linked to smell and memory. They also had a greater reduction in overall brain size and greater cognitive decline.
The changes held after excluding the 15 who had been hospitalized.
Researchers have proposed several reasons. None is yet proven to cause brain fog.
Inflammation in the brain
Microglia are the brain’s own immune cells. In a study of mice and human tissue (Fernández-Castañeda 2022), COVID-19 was followed by reactive microglia in white matter. In mice, a mild respiratory infection led to lasting problems with making new neurons and a loss of myelin, the insulation around nerve fibers. Levels of an inflammatory signal called CCL11 rose.
People with lasting cognitive symptoms after COVID also had raised CCL11. Mild flu produced some similar changes in mice.
In people with long COVID (Phetsouphanh 2022), parts of the immune system were still highly activated eight months after infection. This may feed inflammation in the brain, though how it causes brain fog is not clear. Our page on neuroinflammation and diet covers the wider topic.
A leaky blood-brain barrier
The blood-brain barrier normally keeps inflammatory molecules and toxins out of the brain. Using a specialized MRI scan, Greene 2024 found barrier disruption in people with long COVID brain fog, along with signs of ongoing inflammation in the blood. A leaky barrier may let inflammatory signals reach the brain more easily.
Changes in gut bacteria
The virus can infect cells of the gut lining, and in some people the gut bacteria stay altered after the respiratory symptoms resolve. Liu 2022 followed 106 patients in Hong Kong for six months. Those with lasting symptoms had fewer bacteria that produce butyrate, a short-chain fatty acid that helps keep the gut barrier intact and helps regulate immune responses.
Gut bacteria at hospital admission were linked to who went on to have lasting symptoms. This is observational evidence.
The diet pattern to start with
Since inflammation is thought to play a part, a sensible base is a diet linked to lower inflammation. Neither pattern below has been tested in long COVID.
Mediterranean diet
The Mediterranean diet is built on olive oil, fatty fish, vegetables, legumes, nuts, whole grains and some fermented dairy. It is the most studied healthy eating pattern.
Valls-Pedret 2015 ran a trial in 447 older Spanish adults at high cardiovascular risk. A Mediterranean diet with extra olive oil or nuts led to better scores on some cognitive measures than a low-fat diet. The pattern is also high in the fiber that feeds helpful gut bacteria.
MIND diet
The MIND diet combines the Mediterranean and DASH diets and emphasizes leafy greens, berries, nuts, olive oil, whole grains, fish, beans and poultry. In an observational study (Morris 2015), even moderate adherence was linked to a lower rate of Alzheimer’s disease. But a trial in 604 older adults (Barnes 2023) found no difference in cognitive change over three years compared with a control diet with mild calorie restriction.
Feeding your gut bacteria
Because gut changes are linked to post-COVID symptoms, foods that support varied gut bacteria are a sensible part of a recovery diet. This has not been tested in long COVID trials. See our gut-brain axis guide for more.
Fermented foods
In a 17-week trial of 36 healthy adults (Wastyk 2021), a diet high in fermented foods steadily increased the variety of gut bacteria and lowered markers of inflammation. Whether the same happens in long COVID is not known.
Participants worked up to about six servings a day. A few servings a day of different fermented foods is a reasonable goal, since each brings different microbes. Choose products with live cultures. Our fermented foods page lists options.
Fiber
Certain fibers, including inulin and resistant starch, feed the gut bacteria that make short-chain fatty acids such as butyrate. Butyrate strengthens the gut lining and has anti-inflammatory effects.
Good sources include garlic, onions, leeks, asparagus, Jerusalem artichokes, slightly green bananas, oats and legumes. Cooked-and-cooled potatoes and rice form resistant starch. Aim for 30 grams or more of fiber a day, and increase slowly so your gut can adjust.
Bone broth provides glutamine, an amino acid that gut-lining cells use for fuel. The case for it is mechanistic only. No trial shows it helps post-COVID symptoms.
What to cut back on
These foods are linked to worse brain health in general populations. None has been studied in long COVID.
- Ultra-processed food: These foods contain additives such as emulsifiers, are high in refined carbohydrates and push out nutrient-dense food. In an observational study of over 10,000 Brazilian adults (Gonçalves 2023), eating more of them was linked to faster cognitive decline.
- Added sugar: In a cross-sectional analysis of the Framingham Heart Study (Pase 2017), more sugary drinks were linked to lower brain volume and poorer memory. Keep added sugar below 25 grams a day, and start with soft drinks, fruit juice and sweetened coffee.
- Alcohol: In 36,678 UK Biobank adults (Daviet 2022), lower brain volume was already visible in people averaging one to two UK alcohol units a day, with stronger links at higher intakes. Alcohol can also impair sleep and damage the gut lining. Avoiding or minimizing it during recovery is sensible.
Nutrients and supplements
Some nutrients have a biological rationale for post-COVID recovery. None has been shown in trials to improve long COVID brain fog. Food sources are the safer route. If you are considering a supplement, discuss it with a doctor or pharmacist first, especially if you take medication, are pregnant or breastfeeding, or have a health condition.
| Nutrient | Food sources | Evidence | Cautions |
|---|---|---|---|
| Omega-3 (EPA, DHA) | Salmon, mackerel, sardines, anchovies, herring | Anti-inflammatory in lab and animal studies; no long COVID trials | Fish oil can increase bleeding risk with anticoagulant or antiplatelet drugs; above about 1 g a day linked to atrial fibrillation in trials |
| Vitamin D | Fatty fish, egg yolks, fortified foods, sunlight | Slightly reduced acute respiratory infections in trials (Jolliffe 2021); not shown for long COVID | Adult upper limit 4,000 IU a day; higher doses only under medical supervision |
| Zinc | Oysters, red meat, pumpkin seeds, lentils, chickpeas | Deficiency proposed as a risk factor for severe COVID-19 (Wessels 2022); no long COVID trials | Adults need 8–11 mg a day; upper limit 40 mg; long-term high doses can cause copper deficiency |
| NAC | Supplement only; broccoli, garlic, onions and eggs supply building blocks for glutathione | Not tested for long COVID brain fog | Can cause stomach upset; interacts with some medicines, including nitroglycerin |
| Curcumin | Turmeric in cooking | Small trial outside long COVID (see below) | Supplements linked to cases of liver injury, more often high-absorption or piperine products; avoid with liver disease; ask a doctor first if you take blood thinners |
On vitamin D, ask your doctor whether a test makes sense for you. For healthy adults, Endocrine Society guidance (2024) advises against routine testing and high doses.
On curcumin, a trial of 40 adults (Small 2018) found that a well-absorbed curcumin supplement improved some memory and attention scores over 18 months compared with placebo. The trial was small and not in people with long COVID. Turmeric in cooking, for example in curries, is fine for most people.
What we know and what we don’t
The evidence supports this much: COVID-19 is linked to brain inflammation, blood-brain barrier disruption and gut changes that persist in some people. In healthy adults, one trial found that fermented foods increased gut bacterial variety and lowered inflammatory markers.
We don’t know whether any diet or nutrient improves long COVID brain fog. No randomized trial has tested a diet in long COVID with cognition as the main outcome. We also don’t know how diet compares with exercise, sleep or medication for recovery. The evidence here comes from other populations and from lab studies. A healthy diet is low-risk; supplements are not risk-free.
Frequently Asked Questions
How long does post-COVID brain fog last?
It varies. Some people recover within weeks; others have symptoms for months or years. Whether diet speeds recovery is not known. If symptoms persist beyond three months despite lifestyle changes, see a healthcare provider experienced with long COVID for a full evaluation.
Can diet alone fix post-COVID brain fog?
Probably not on its own. Sleep, physical activity, stress and sometimes medication all play a part. A reasonable plan combines a healthy diet with enough sleep (7-9 hours), graduated exercise and stress reduction.
Do some foods make it worse?
Possibly. There are no long COVID studies, but ultra-processed food, added sugar and alcohol are most often linked to worse brain health. Some people report sensitivity to gluten, dairy or histamine-rich foods after COVID, but this evidence is anecdotal. If you suspect a trigger, a structured elimination and reintroduction can help identify it.
Should I try keto or intermittent fasting?
There are no trials of either in long COVID. Keto can cut the fiber your gut bacteria need, and many people with long COVID already face fatigue and poor nutrition, so restrictive eating may backfire. Keto and fasting are dangerous with insulin, sulfonylureas or SGLT2 inhibitors without medical supervision, and unsuitable during pregnancy, breastfeeding or with a history of eating disorders.
Sources
- Barnes, L. L., Dhana, K., Liu, X., et al. (2023). Trial of the MIND diet for prevention of cognitive decline in older persons. New England Journal of Medicine, 389(7), 602-611. doi:10.1056/NEJMoa2302368
- Ceban, F., Ling, S., Lui, L. M. W., et al. (2022). Fatigue and cognitive impairment in post-COVID-19 syndrome: a systematic review and meta-analysis. Brain, Behavior, and Immunity, 101, 93-135. doi:10.1016/j.bbi.2021.12.020
- Daviet, R., Aydogan, G., Jagannathan, K., et al. (2022). Associations between alcohol consumption and gray and white matter volumes in the UK Biobank. Nature Communications, 13, 1175. doi:10.1038/s41467-022-28735-5
- Douaud, G., Lee, S., Alfaro-Almagro, F., et al. (2022). SARS-CoV-2 is associated with changes in brain structure in UK Biobank. Nature, 604(7907), 697-707. doi:10.1038/s41586-022-04569-5
- Fernández-Castañeda, A., Lu, P., Geraghty, A. C., et al. (2022). Mild respiratory COVID can cause multi-lineage neural cell and myelin dysregulation. Cell, 185(14), 2452-2468. doi:10.1016/j.cell.2022.06.008
- Gomes Gonçalves, N., Vidal Ferreira, N., Khandpur, N., et al. (2023). Association between consumption of ultraprocessed foods and cognitive decline. JAMA Neurology, 80(2), 142-150. doi:10.1001/jamaneurol.2022.4397
- Greene, C., Connolly, R., Brennan, D., et al. (2024). Blood-brain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment. Nature Neuroscience, 27, 421-432. doi:10.1038/s41593-024-01576-9
- Jolliffe, D. A., Camargo, C. A., Sluyter, J. D., et al. (2021). Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials. The Lancet Diabetes & Endocrinology, 9(5), 276-292. doi:10.1016/S2213-8587(21)00051-6
- Liu, Q., Mak, J. W. Y., Su, Q., et al. (2022). Gut microbiota dynamics in a prospective cohort of patients with post-acute COVID-19 syndrome. Gut, 71(3), 544-552. doi:10.1136/gutjnl-2021-325989
- Morris, M. C., Tangney, C. C., Wang, Y., et al. (2015). MIND diet associated with reduced incidence of Alzheimer’s disease. Alzheimer’s & Dementia, 11(9), 1007-1014. doi:10.1016/j.jalz.2014.11.009
- Pase, M. P., Himali, J. J., Jacques, P. F., et al. (2017). Sugary beverage intake and preclinical Alzheimer’s disease in the community. Alzheimer’s & Dementia, 13(9), 955-964. doi:10.1016/j.jalz.2017.01.024
- Phetsouphanh, C., Darley, D. R., Wilson, D. B., et al. (2022). Immunological dysfunction persists for 8 months following initial mild-to-moderate SARS-CoV-2 infection. Nature Immunology, 23, 210-216. doi:10.1038/s41590-021-01113-x
- Small, G. W., Siddarth, P., Li, Z., et al. (2018). Memory and brain amyloid and tau effects of a bioavailable form of curcumin in non-demented adults: a double-blind, placebo-controlled 18-month trial. American Journal of Geriatric Psychiatry, 26(3), 266-277. doi:10.1016/j.jagp.2017.10.010
- Valls-Pedret, C., Sala-Vila, A., Serra-Mir, M., et al. (2015). Mediterranean diet and age-related cognitive decline: a randomized clinical trial. JAMA Internal Medicine, 175(7), 1094-1103. doi:10.1001/jamainternmed.2015.1668
- Wastyk, H. C., Fragiadakis, G. K., Perelman, D., et al. (2021). Gut-microbiota-targeted diets modulate human immune status. Cell, 184(16), 4137-4153. doi:10.1016/j.cell.2021.06.019
- Wessels, I., Rolles, B., Slusarenko, A. J., & Rink, L. (2022). Zinc deficiency as a possible risk factor for increased susceptibility and severe progression of Corona Virus Disease 19. British Journal of Nutrition, 127(2), 214-232. doi:10.1017/S0007114521000738