Short answer: Diet probably affects inflammation in the brain, but no trial has measured it directly in people. Lab, animal and observational studies link sugar, trans fats, ultra-processed food and heavy drinking to more inflammation, and omega-3s, polyphenols, fiber and olive oil to less. A Mediterranean-style diet is a reasonable, low-risk choice, not a proven treatment.

Diet may push the brain’s immune system toward or away from chronic inflammation, but the evidence is preliminary. Most of it comes from animal studies and from human studies of inflammation markers in the blood, not the brain.

A Western-style diet high in sugar, trans fats, ultra-processed food and alcohol, and low in fiber, is linked to more inflammation. A diet rich in fatty fish, polyphenols, fiber and extra virgin olive oil has anti-inflammatory effects in lab and some human studies.

Whether that pattern reduces inflammation inside the human brain has not been measured. It is a sensible way to eat for other reasons too.

What to eat to reduce inflammation

  1. Eat fatty fish at least twice a week: salmon, mackerel, sardines, anchovies or herring. If you are thinking about a fish or algal oil supplement, ask a doctor or pharmacist first. Fish oil can increase bleeding risk with anticoagulant or antiplatelet drugs. In trials, doses above about 1 g a day have been linked to a higher risk of atrial fibrillation.
  2. Use extra virgin olive oil as your main fat, about 2-4 tablespoons a day. Fresh oil with a peppery sting at the back of the throat contains oleocanthal.
  3. Aim for at least 30 grams of fiber a day from legumes, vegetables, whole grains, nuts, seeds and fruit.
  4. Eat polyphenol-rich foods daily: berries, dark leafy greens, dark chocolate (70%+ cacao), green tea, turmeric and colorful vegetables.
  5. Include fermented foods such as yogurt, kefir, sauerkraut and kimchi. In a trial (Wastyk 2021), a diet high in fermented foods reduced inflammatory markers in the blood.
  6. Cut down on ultra-processed food. Replace packaged snacks, sugary drinks, processed meats and industrial baked goods with whole foods. The aim is a real reduction, not perfection.
  7. Keep added sugar below 25 grams a day.
  8. If you drink alcohol, keep it minimal and avoid binges. Brain changes have been seen at 7–14 UK units a week.

What neuroinflammation is

The brain has its own immune cells. Microglia make up about a tenth of brain cells. At rest, they prune unneeded connections between neurons, clear debris and watch for damage. When they detect a threat, they switch on and release inflammatory signals. Astrocytes, another support cell, can amplify those signals, according to lab and mouse experiments.

Short-term inflammation after an injury, infection or stroke is useful and settles within days to weeks. The problem is chronic inflammation, when the trigger never fully goes away. Microglia stay switched on for months or years, and inflammation damages neurons, which creates more debris and more inflammation.

Chronic, low-grade brain inflammation is found in Alzheimer’s and Parkinson’s disease.

A review (Heneka 2015) described how the brain’s immune response contributes to Alzheimer’s progression and noted that body-wide inflammation and obesity probably promote it. The Whitehall II study followed 5,217 adults (Singh-Manoux 2014). Higher midlife levels of the inflammatory signal IL-6 were linked to greater decline in reasoning and on a memory screening test over the next decade. CRP, another common inflammation marker, was not.

How diet may reach the brain

The blood-brain barrier controls what passes from the blood into the brain. When it leaks, more proteins, inflammatory signals and immune cells get through. Diet may affect it in several ways:

  • High blood sugar: Chronically high blood sugar damages the cells lining blood vessels. Using contrast MRI in 10 older people with type 2 diabetes and 10 controls, Starr 2003 found a leakier barrier in the diabetes group.
  • Saturated and trans fats: In mice, a diet high in saturated fat disrupted the barrier and let plasma proteins leak into the brain. Statins or ibuprofen restored it (Pallebage-Gamarallage 2012).
  • Toxins from gut bacteria: When the gut lining is weakened, for example by a low-fiber, highly processed diet, a bacterial toxin called LPS leaks into the blood. Very little LPS crosses into the brain (about 0.025% of an injected dose in mice). Its effects seem to work mostly through receptors on the barrier and outside it (Banks & Robinson 2010).

Blood pressure, blood sugar and age also affect the barrier, so diet is one factor among several.

Foods linked to more inflammation

Sugar and refined carbohydrates

Repeated blood sugar spikes cause oxidative stress and switch on inflammatory genes. High sugar also forms compounds called AGEs, which trigger inflammation in microglia and blood vessels and have been tied to Alzheimer’s disease. Cherbuin 2012 followed 266 Australians aged 60–64 without diabetes for four years. Higher fasting blood sugar within the normal range was linked to more shrinkage of the hippocampus and amygdala, two memory-related areas.

High sugar intake may also change gut bacteria in ways that reduce short-chain fatty acids. See blood sugar and brain function.

Trans fats

Industrial trans fats, found in partially hydrogenated oils, some margarines and many processed baked goods, are among the dietary components most consistently linked to harm.

In 1,486 women aged 70 and over with type 2 diabetes (Devore 2009), higher saturated and trans fat intake since midlife was linked to worse cognitive decline over two years. Regulation has reduced trans fats in some countries, but they remain in many processed and fast foods.

Ultra-processed food

Ultra-processed foods are high in refined carbohydrates, omega-6-rich seed oils and additives such as emulsifiers that may weaken the gut lining. Gonçalves 2023 followed nearly 11,000 people in the ELSA-Brasil cohort for a median of eight years. Those whose intake was above the lowest quarter had a 28% faster rate of cognitive decline. The study was observational and did not measure inflammation. More in ultra-processed food and the brain.

Alcohol

In mice (Alfonso-Loeches 2010), chronic alcohol switched on microglia and astrocytes through TLR4 receptors; mice lacking TLR4 were protected. Alcohol can also make the gut leakier. Leclercq 2014 found a leaky gut in some, but not all, people with alcohol dependence. It was linked to altered gut bacteria and to more depression, anxiety and craving after three weeks without alcohol.

Harm seems to rise with dose. In 25,378 UK Biobank participants (Topiwala 2022), lower total gray matter volume was seen in people drinking as little as 7–14 UK units a week. This is observational.

Low fiber and the gut

Gut bacteria fed on fiber make short-chain fatty acids that keep the gut lining intact and calm inflammation. A low-fiber diet may weaken that lining and let LPS into the blood, which can trigger inflammatory signals in the brain through cells at and outside the barrier.

In mice (Cani 2007), a 4-week high-fat diet raised blood LPS two to three times. Infusing LPS at that level caused weight gain, insulin resistance and inflammation in fat tissue. The study did not look at the brain.

Foods linked to less inflammation

Omega-3s from fish

The body turns the omega-3 fats EPA and DHA into compounds called resolvins and protectins, which actively switch off inflammation (Serhan 2002; Serhan 2014). One of them, neuroprotectin D1, calmed inflammatory genes and helped stressed human brain cells survive in the lab. DHA and neuroprotectin D1 were also lower in the hippocampus of people with Alzheimer’s disease (Lukiw 2005). Our omega-3 guide covers sources and doses.

Polyphenols

Polyphenols, found in berries, dark chocolate, green tea, turmeric and colorful vegetables, reduce brain inflammation in lab and animal studies.

  • Curcumin: In cell and animal studies (Cole 2007), curcumin reduced inflammatory signals from microglia and helped them clear amyloid. It is poorly absorbed, but turmeric in cooking adds to overall polyphenol intake.
  • Berries: In the Nurses’ Health Study (Devore 2012), women who ate the most blueberries and strawberries had slower cognitive decline, equal to up to 2.5 years of delayed cognitive aging. This was observational and did not measure inflammation.
  • Green tea: A systematic review (Kakutani 2019) looked at eight observational studies. Most, but not all, reported full or partial links between green tea and lower risk of dementia or cognitive impairment.

Fiber

Fiber feeds gut bacteria that make short-chain fatty acids, including butyrate. Butyrate strengthens the gut lining. A review of mostly animal studies (Stilling 2016) found that butyrate can raise BDNF, a growth factor for brain cells, and reduce inflammatory signals from microglia.

Many Western adults eat well below the commonly recommended 25–30 grams of fiber a day. Closing that gap is good for general health; its effect on brain inflammation has not been measured.

Extra virgin olive oil

Oleocanthal, which gives fresh extra virgin olive oil its throat sting, blocks the same enzymes as ibuprofen (Beauchamp 2005). The amount in a normal diet is much smaller than a drug dose. The oil also contains hydroxytyrosol and other polyphenols with anti-inflammatory effects in the lab.

Valls-Pedret 2015 ran a PREDIMED sub-study in 447 older adults, followed for a median of 4.1 years. A Mediterranean diet with extra olive oil (1 litre a week to each household) led to better frontal and global cognition scores than a low-fat diet.

Western vs Mediterranean diet

A review (Myles 2014) concluded that the Western diet, high in sugar, red and processed meat, refined grains and ultra-processed food, activates the immune system and sustains low-grade inflammation. In the Moli-sani cohort of about 24,000 Italians (Bonaccio 2017), closer adherence to the Mediterranean diet was linked to a lower inflammation score based on CRP and blood cell counts.

For the brain, the evidence is suggestive. A meta-analysis (Loughrey 2017) of 15 cohort studies with 41,492 people and two trials found small links between the Mediterranean diet and better global cognition and memory in older adults. In the PREDIMED-NAVARRA trial (Martínez-Lapiscina 2013), 522 people followed a Mediterranean diet with extra olive oil or nuts for 6.5 years. They had slightly better scores on two cognitive screening tests than the low-fat group, though cognition was measured only at the end.

A trial of the related MIND diet (Barnes 2023) found no cognitive benefit. None of these studies measured brain inflammation. See our anti-inflammatory diet guide for the eating pattern.

Can blood tests measure it?

Not really. No blood test measures brain inflammation, and none has been shown to track changes in the brain after a diet change. Measuring microglia directly needs a research PET scan.

  • hs-CRP: The most common inflammation marker. It is not specific to the brain, and in Whitehall II it did not predict cognitive decline.
  • IL-6: Sometimes available through specialized testing. Higher IL-6 predicted cognitive decline in Whitehall II.
  • Fasting insulin and HOMA-IR: Indirect markers of insulin resistance, which goes hand in hand with body-wide inflammation.
  • Omega-3 index: The share of EPA and DHA in red blood cells. Values below 4% and above 8% are used as cut-offs for higher and lower cardiovascular risk.

Ask your doctor before ordering tests.

Frequently Asked Questions

Can diet reverse neuroinflammation, and how fast?

The brain has its own ways of ending inflammation. In healthy adults, a fermented-food diet lowered blood inflammatory markers over several weeks (Wastyk 2021), and gut bacteria shift within days of a big diet change. Effects on brain inflammation have not been measured, and diet does not reverse damage from neurodegenerative disease. The diet trials that found cognitive differences ran for years.

Are anti-inflammatory supplements a substitute for diet?

No. Curcumin, fish oil and resveratrol supplements cannot make up for an otherwise inflammatory diet, and they carry risks. Fish oil can increase bleeding risk with blood thinners. Curcumin supplements, especially high-absorption or piperine products, have been linked to liver injury. Ask a doctor or pharmacist first, especially if you are pregnant, breastfeeding, take medication or have a health condition.

Is neuroinflammation the same as brain fog?

No. Brain fog is a symptom, and inflammation is one plausible cause of some cases. Sleep loss, thyroid problems and medication side effects are others. See our brain fog diet and, if yours started after an infection, the post-COVID brain fog diet. If brain fog is severe or persistent, see a doctor.

Does the ketogenic diet reduce neuroinflammation?

In lab and animal studies, the ketone BHB blocks an inflammation switch called the NLRP3 inflammasome. Whether keto diets reduce brain inflammation in people is not established. Fat sources matter: a keto diet built on processed meat may add other inflammatory inputs. Keto is dangerous with insulin, sulfonylureas or SGLT2 inhibitors without medical supervision, and unsuitable with a history of eating disorders or during pregnancy or breastfeeding.

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