Suffering from brain fog, stress or persistent low mood? It could be down to inflammation: a process which it’s become clear is part of the problem in many diseases of the body and, as scientists are now discovering, our minds.
Inflammation is the body’s first line of defence against infection and injury, but this acute immune response can damage the body if switched on long term. According to neurologists who are studying the area, neuroinflammation is being linked to everything from anxiety and brain fog to depression and dementia.
Emerging science, however, is also uncovering ways that we can combat inflammation in everyday life to slow or prevent the conditions associated with it and protect our cognitive function and mental health.
“Inflammation and its association with brain health is definitely one of the hot topics in the field at the moment,” says Dr Susan Kohlhaas, director of research at Alzheimer’s UK. In June a BMJ Mental Health analysis of 1.5 million people in the UK’s Our Future Health cohort revealed that people with diseases caused by chronic inflammation such as such as multiple sclerosis, inflammatory bowel disease and rheumatoid arthritis are almost twice as likely to suffer anxiety and depression, even after adjusting for factors such as chronic pain and income.
This followed analysis by researchers at King’s College London in 2021 which found that low-grade inflammation plays a “core role” in depression — and reducing it through drugs, diet and exercise could help people for whom antidepressants do not work.
Elsewhere, in 2019, researchers from the University of Birmingham and the University of Amsterdam reported in the journal Neuroimage that inflammation has a negative impact on the brain’s ability to stay alert and could be to blame for brain fog and “cognitive sluggishness”.
Midlifers displaying signs of chronic inflammation are more likely to develop problems with thinking and memory as they reach old age according to a 2019 study by neurologists at Johns Hopkins University. They followed 12,366 people in their fifties for 20 years and found that those with the highest levels of inflammation biomarkers, as measured in intermittent blood samples, had an 8 per cent sharper drop in thinking and memory skills over the two decades than the group with the lowest levels of inflammation.
A further study last year suggested that the impact of inflammation on cognitive ageing may begin in our 20s and 30s — much earlier than previously thought. The University of California, San Francisco study, published in Neurology, the medical journal of the American Academy of Neurology, followed 2,364 men and women aged 24 to 58 for nearly two decades, and found that high levels of persistent, low-grade inflammation in early adulthood set the stage for deficits in memory, brain processing speeds and executive function in middle age and an increased risk of dementia later in life.
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“Inflammation is important for cognitive ageing and may begin much earlier than previously known,” said Dr Kristine Yaffe, the study’s author. “Although current prevention efforts mainly focus on late life, our study provides evidence for the need to also target brain health in middle age.”
Another large study, of half a million people in the UK Biobank, published in PLOS One journal in 2023, found that those with the highest levels of inflammation in their blood were about 35 per cent more likely to be diagnosed with dementia several years later than those with the lowest levels.
Work is under way to develop drugs that might slow the rise of inflammation in the body. “Since 2012 there has been a lot of work looking at inflammation, understanding the link with Alzheimer’s disease and whether we can develop treatments that tackle it,” Kohlhaas says. “We have an annual review of treatments going through clinical trials for Alzheimer’s disease and at the moment about 20 per cent of that portfolio is drugs that target this neuroinflammation.”
Some drivers for inflammation are genetic, others arise due to infection and disease. But lifestyle also plays a key role in keeping chronic inflammation at bay. “Eating healthily, staying active and making sure you are not smoking or drinking too much will be helpful in terms of brain health and healthy ageing,” Kohlhaas says. “Making some adjustments in midlife or even earlier will help to reduce your risks of poor brain health later on.” Here’s what the experts advise:
Take a brisk 20-minute walk every day
“Physical activity is very important for the brain and general health,” Kohlhaas says. “Stay as active as you can through midlife and beyond.” Reporting in the Journal of Neuroscience in 2022, one group of scientists from Rush University in Chicago proved that exercise alters the activity of immune cells called microglia in the brain, which results in lower brain inflammation. A daily 20-minute walk is enough to make a difference according to researchers from the University of California in the journal Brain, Behaviour and Immunity. They showed that walking briskly (a pace of 100 steps a minute) or jogging slowly on a treadmill resulted in a beneficial reduction of immune cells that produce tumour necrosis factor, high levels of which lead to chronic inflammation.
Eat a Mediterranean-style diet
Your overall diet has a far greater effect on reducing inflammation than individual foods or ingredients, says Alex Ruani, a nutrition researcher at University College London and chief science educator at the Health Sciences Academy. She says that “many robust studies” have shown the Mediterranean-style approach containing plenty of omega-3-rich oily fish, nuts and seeds, olive oil and fruit and vegetables is the most effective for reducing inflammation that affects the brain.
In the landmark Predimed trial that was published in the Proceedings of the Nutrition Society in 2010, Spanish scientists found older adults at risk of vascular disease who were asked to follow Mediterranean-style diets enriched with either extra virgin olive oil or with nuts had significantly lower markers of inflammation after three months than people on a standard low-fat diet plan. “Levels of C-reactive protein (CRP), IL-6, and other inflammatory molecules were lower in the Mediterranean diet groups,” Ruani says. “This added weight to the idea that anti-inflammatory effects may underlie the brain-preserving benefits seen in the trial.”
Since then, many other studies have confirmed similar benefits with the so-called Mind diet (Mediterranean-dietary approaches to stop hypertension intervention for neurodegeneration delay), which focuses on plant-based foods in addition to oily fish, poultry and whole grains, emerging as a strong antidote to cognitive decline. Last month a paper in the Journal of Nutrition revealed that, in a study of 3,077 retired people, eating the Mind diet reduced several circulating inflammatory markers involved in neurodegeneration.
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Eat more oily fish, nuts and seeds
Even if you don’t follow the full Mediterranean diet, it is worth increasing your intake of healthy omega-3 fatty acids that need to be included in our diets to keep us healthy and ward off inflammatory molecules in our bodies.
Neuroinflammation is a suspected trigger of migraine headaches, according to a paper in Nature Reviews Neurology. In that study, 182 people who suffered frequent migraines were asked to consume more omega-3 fats from oily fish and other wholesome food sources such as chia seeds, walnuts and flaxseed while cutting back on too many omega-6 fats from highly processed and refined foods.
“Those consuming the omega-3 fats from wholefoods saw the biggest drop in both the number of headache days and the hours spent in pain,” Ruani says. “The findings tell us that shifting the balance of fats in what we eat could make a real difference to migraine sufferers.”
Reduce your salt intake
“There is firm evidence that too much salt in the diet contributes to low-grade inflammation that impacts brain health,” Ruani says.
One 2020 paper published in the Journal of Alzheimer’s Disease suggested that excessive salt intake causes brain inflammation linked to cognitive dysfunction in mice and last month a study by scientists from McGill University showed how a high-salt diet triggers brain inflammation that drives up blood pressure. The McGill researchers used rats in their investigation because the animals regulate salt and water in a similar way to humans, which makes the findings relevant to all of us.
Diets containing 2 per cent salt — easily accumulated if you eat processed meats and cheeses, instant noodles and ready meals — were found to induce the damaging brain inflammation. Most adults in the UK consume more than 8g of salt daily although the NHS recommends an intake of no more than 6g of salt a day.
Make sure you get enough fibre
A good fibre intake not only helps with appetite and cholesterol control and encouraging the growth of beneficial bacteria in our guts, but is also essential for lowering inflammation.
“Multiple studies have shown that dietary fibre is important for improving mental health, mood and brain function,” Ruani says. “The fibre we eat helps to keep the gut healthy by feeding bacteria in the gut, and via a connection called the gut-brain axis it might also help to reduce neuroinflammation.”
A 2021 study in the Gut Microbiome journal showed that dietary fibre intake is important for a range of beneficial cognitive processes. Most adults don’t get enough fibre: women in the UK consume a daily average of 17.2g and men 20.1g, far less than the recommended daily amount of 30g. Eating as diverse a range of plant foods as possible will help to boost your fibre intake, but good sources include avocados and other fruit, wholegrains, pulses and vegetables.
Even short meditation sessions help
Mindfulness meditation can lower anxiety and inflammation levels in the brain
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Chronic stress is a major trigger for inflammation in the body and, over time, circulating inflammatory proteins can make their way into the brain with potentially harmful consequences. As many as 27 per cent of patients with major depression have neuroinflammation, according to researchers from California and Canada.
Along with exercise, mindfulness meditation is one of the approaches shown to lower anxiety and inflammation levels in the brain. Just ten minutes of meditating a day brings stress and anxiety-relieving benefits, according to psychologists from Yale and Emory Universities.
A study at Carnegie Mellon University, published in Biological Psychiatry, has provided the strongest evidence so far that meditation leads to measurable changes in the brain. It looked at the effects of meditation on stressed-out adults who underwent brain scans and blood tests during a three-day meditation retreat. David Creswell, associate professor of psychology, found that the meditation programme resulted in lower levels of an inflammatory health biomarker called Interleukin-6, or IL-6, suggesting regular daily meditation could help to ward off stress-related illness and improve inflammatory health.
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Aim for seven to nine hours of sleep a night
“People who get too much or too little sleep tend to be more prone to brain health issues,” Kohlhaas says. “Aiming for around eight hours a night is generally accepted as a good target.”
A single night of sleep deprivation was shown by Finnish researchers to trigger an inflammatory response in the body while others have shown that regularly getting too little sleep can raise levels of inflammatory molecules including cytokines, IL-6 and C-reactive protein, all of which can have a damaging effect on brain health.
“One of the theories is that while you sleep your system is removing a build-up of proteins in your brain that are linked to inflammation,” Kohlhaas says. “But sleep does need to be consistent to be beneficial, so it is no good getting two hours one night and ten hours the next.”
Use lots of herbs and spices in your cooking
Plenty of herbs and spices have anti-inflammatory benefits
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Most herbs and spices have anti-inflammatory benefits and the more of them you include in your diet the better. Scientists at Penn State University reporting in the Journal of Nutrition asked people to add 6g of a herb-and-spice blend including basil, bay leaf, black pepper, cinnamon, coriander, cumin, ginger, oregano, parsley, red pepper, rosemary, thyme and turmeric to a processed high-fat meal. It is known that, even short term, very high-fat diets drive low-grade neuroinflammation, but the study found that markers of acute inflammation were higher when the same meal was eaten without adding the spice blend.
“Turmeric, ginger, rosemary, garlic and other herbs and spices all score favourably on the Empirical Dietary Inflammatory Index, or EDII, a ranking list of foods compiled by Harvard scientists that tells us how different foods correlate with levels of inflammatory markers in the blood,” Ruani says. “We know that people with higher EDII scores tend to have more systemic inflammation and a higher risk of poor brain and general health.”
Drink two to four cups of tea or coffee a day
Tea and coffee have potent anti-inflammatory properties
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“In moderation, a bit of tea and coffee can be part of anti-inflammatory diet,” Ruani says. “Both have favourable scores in the EDII rankings with most studies showing that two to four cups a day offers the most benefits.”
Green and black tea contain phenolic compounds such as epigallocatechin-3-gallate that have potent anti-inflammatory properties. Ginger, fennel, nettle and rosehip teas are also associated with the lowering of inflammatory markers. Coffee also has anti-inflammatory compounds including chlorogenic acid, caffeic acid, kahweol and cafestol, according to a study published by Italian scientists in Neural Regeneration Research last year. “Coffee and its bioactive compounds show neuroprotective impacts that lower the risk of cognitive decline and other neurodegenerative diseases,” the researchers said.
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Cut down on alcohol
Some studies, including research by the University of Texas Health Center, have suggested that a glass of wine or two a day helps to suppress inflammation, others that even that amount negatively impacts the brain. Certainly, heavy drinking triggers inflammation that is harmful to the brain and might increase the risk of neurodegenerative diseases. The 2024 Lancet Commission study, part-funded by the Alzheimer’s Society, says that excessive alcohol intake — above the recommended limit of 14 units per week — was “one of the lifestyle risk factors that can increase a person’s chances of developing dementia”.