Inflammation: How to eat to regulate immune responses
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Eat this because it’s anti-inflammatory. Avoid that because it’s pro-inflammatory. Most of us have heard this advice but do we know what inflammation is?
Luke O’Neill, from the School of Biochemistry and Immunology at Trinity College Dublin, says it’s a normal process that happens when you’re infected with bacteria or a virus or injured yourself, such as spraining an ankle: “It’s designed to bring immune cells to the affected area to fight the infection and repair the damage.”
Five key signs indicate inflammation is present.
“There’s redness and heat due to blood rushing to the area,” says O’Neill. “Swelling happens because white blood cells travel to the affected area too, bringing blood plasma with them. There’s pain because nerves are firing, in part to stop you using the body part so it has a chance to heal. And there’s loss of function because the ongoing inflammation stops the affected area from working properly.”
“We need inflammation to deal with pathogens and we also need it to clear up cellular damage and debris after we experience injury or trauma,” says Daniel McCartney, professor of human nutrition and dietetics at Technological University Dublin. “But it must be triggered at the correct time and in the correct amount. If it goes on for too long or there’s too much of it, inflammation can cause problems.”
O’Neill points out that chronic inflammation — inflammation that persists for a long time or recurs constantly — is a factor in diseases such as rheumatoid arthritis, inflammatory bowel disease and multiple sclerosis.
One in three people in Ireland is affected by a chronic inflammatory condition.
“It’s a major cause of suffering as it’s so painful,” says O’Neill. “And the attack on the part of the body it affects can cause damage. With arthritis for example, you can have sore joints that you can’t use properly.”
McCartney adds that if left untreated, chronic inflammation can also increase our risk of serious health issues like cancer, cardiovascular disease and type 2 diabetes.
The emerging medical consensus is that obesity has a role in this.
“Obesity, particularly visceral fat around the waistline, appears to be associated with persistent low-grade inflammation,” says McCartney. “Inflammation seems to originate in the fat that’s stored around the organs and in people with longstanding abdominal obesity, there can be a cumulative effect where inflammation damages the body over time.”
We can take steps to control our inflammation, including being careful about what we eat.
“The saturated fat found in processed meats like sausages and ham, and in rich dairy foods like butter and cream, are pro-inflammatory as are trans fats — which are found in deep-fried foods and in pastries, biscuits and processed foods that contain hydrogenated oils,” says McCartney.
If we are to cut back on saturated and trans fats, a 2015 American study suggests we should increase our consumption of omega 3s.
“These seem to lower inflammation levels and are found in oily fish such as mackerel, herring, trout, tuna, pilchards, sardines and salmon as well as in eggs, nuts and seeds,” says McCartney.
Rachel Crossan, a registered dietitian at the Dublin Nutrition Centre, says we should be mindful of our sugar intake.
“A high intake of added sugar may contribute to inflammation by promoting obesity, type 2 diabetes and digestion problems,” she says.
McCartney adds: “Steer particularly well clear of sugar-sweetened drinks.”
Fruit and vegetables should be regarded as some of our most potent weapons in the fight against inflammation, says McCartney.
“When inflammation is triggered, white blood cells produce free radicals to wipe out bacteria,” he says. “But when inflammation persists, so does the production of free radicals and over time, they can damage our cells, tissues, and organs and eventually lead to disease. Antioxidants mop up free radicals and there are lots of antioxidants in fruit and vegetables.”
Vitamin C is a potent antioxidant, which is why McCartney advises us to eat citrus fruits, pineapples, and berries. The more varieties of fruit and vegetables we eat in as many different colours, the better.
“The colour of a fruit or vegetable is determined by compounds called phytochemicals which are a type of antioxidant,” says Crossan. “Phytochemicals along with the fibre and folate content of fruit and vegetables bring many health benefits.”
According to the National Adult Nutrition Survey 2024, Irish people aren’t eating enough fruit and vegetables. Only 21% of 18 to 64-year-olds meet the recommended daily 400gm intake.
Crossan has tips on how we can all incorporate more into our diets.
“Aim for two portions at each meal plus one portion as a snack,” she says. “Blend vegetables into sauces for stews and curries. Include berries and grapes with breakfast every day. Have a piece of fruit with lunch and snack on things like carrot sticks between meals.”
Beans, lentils, tofu, and other legume-based foods, rich in fibre and antioxidants, also help fight against inflammation.
“They support a healthy gut,” says Crossan. “I’d recommend adding them to stews, curries and soups. And if you’re new to these foods, why not start with the classic beans on toast?”
Spices are another powerful tool in our arsenal in the fight against inflammation, so much so that Crossan recommends that we season our meals with turmeric, ginger, cinnamon, garlic, chilli, and black pepper.
An international study published in 2020 found that the curcumin compound in turmeric was associated with anti-inflammatory, anticancer, antimicrobial, antiviral, and antioxidant properties.
A Stanford University study published in 2021 suggested that fermented foods can also play a role in reducing inflammation. Half the study participants were instructed to eat a diet rich in fermented foods such as yoghurt, kimchi, and sauerkraut, and saw decreased levels of inflammation as a result.
Crossan believes this could be the result of the probiotics in fermented food.
“Our gut is home to a microbiome of trillions of bacteria that influence our immune system,” she says. “The probiotics in fermented foods help improve the diversity of that microbiome.”
McCartney reminds us all of the importance of taking a vitamin D supplement.
“It’s a major player in our immune function,” he says. “Many of those who were badly hit by covid-19 were deficient in vitamin D. This meant they already had low-grade inflammation and as a result, their immune system struggled to deal with the virus. Every one of us should be supplementing with vitamin D, particularly in the winter months when our levels are likely to be low and viruses, including respiratory viruses like covid-19, are prevalent.”
According to Crossan, the best way to combat inflammation through diet is by eating a wide variety of foods. Different foods contain different nutrients, each of which counters inflammation in a different way.
“So rather than specific foods, dietary patterns are what play the most specific role in promoting or reducing chronic inflammation,” she says.
“A varied diet that is rich in whole foods and that includes lots of colourful fruits and vegetables, lean proteins, fibre, and healthy fats is what best supports our body’s immune system.”
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