Nearly 90 percent of Americans who’ve been hospitalized with COVID-19 had underlying health conditions, including hypertension, diabetes and chronic lung disease. Most chronic disease is linked in some way to inflammation in the body. But what is inflammation exactly? It might be hard to tell based on recent (pre-coronavirus) headlines. On one hand, a study showed widespread brain inflammation in veterans with Gulf War Syndrome. On the other hand, you can find articles touting anti-inflammatory foods as a way to “melt” belly fat. Are they talking about the same phenomenon?
In general terms, inflammation is a defense mechanism. You might think of a sore throat or a sprained ankle that’s swollen and tender. Those are examples of acute inflammation, a short-term response to bodily harm with five hallmark symptoms: pain, redness, swelling, loss of function and heat. Essentially, it’s your body’s way of protecting you, by sending white blood cells to injured tissue to begin the healing process.
Chronic inflammation, on the other hand, is slow-moving and destructive. Instead of using these mechanisms for healing, the body targets healthy tissue, essentially attacking itself.
“An acute inflammatory response is healthy,” says Donna Arnett, an epidemiologist and the current dean of the University of Kentucky’s College of Public Health. “When someone develops an infection, part of the inflammatory response is to turn on our immune system to fight the infection.”
During chronic inflammation, the body remains in a prolonged, low-grade state of emergency, sometimes for years. It often emerges in response to an autoimmune disease or exposure to environmental toxins like air pollution. It’s also been associated with obesity, smoking and a diet rich in saturated fat, trans fats or refined sugar.
We would do well to understand it better: Chronic inflammation plays a role in almost every major disease. Studies have linked it to cancer, heart disease, diabetes, dementia and mental health disorders. The World Health Organization says chronic inflammatory diseases are the leading cause of death worldwide. Six in 10 adults in the US live with a chronic disease, such as diabetes or chronic lung disease. Four in 10 have two or more chronic diseases.
“It was only recently that scientists fully appreciate the extent to which inflammation might be a common process underlying risk for several different types of health problems — everything from depression to anxiety disorders to cardiovascular disease and cancer,” says George Slavich, director of the UCLA Laboratory for Stress Assessment and Research.
Some studies suggest the roots of chronic inflammation could begin in utero. A recent paper in the journal Nature Medicine examined maternal lifestyle and environmental exposures, including diet, stress, smoking and air pollution, which can influence the way the baby’s immune system is programmed, setting them on a possible course for increased inflammation later in life.
What’s especially tricky about chronic inflammation is that you might not know you have it. There are no accepted biomarkers. But levels of C-reactive protein in the body increase when inflammation is present, and they can be measured with a simple blood test. Doctors often use CRP tests to detect flare-ups of autoimmune diseases, like lupus and rheumatoid arthritis, but anyone can ask their primary care doctor to perform one. A CRP test can’t reveal the cause of inflammation, though. Arnett points to a study that showed the flu vaccine raised CRP levels acutely, making the test inconclusive. The American Heart Association only recommends the test for patients with an increased risk for having a heart attack.
“We know that autoimmune disease is associated with increased heart disease risk,” says Arnett, an AHA past president. “However, a very large randomized clinical trial using a drug to reduce inflammation did not find benefit for reducing CRP or reducing the risk of cardiovascular events.”
While Slavich doesn’t see any harm in doing the test (which can cost around $12 to $16) if you’re curious about your CRP levels, he says chronic inflammation may also be managed through lifestyle changes — the same habits recommended for general health: Don’t smoke, exercise regularly and get a good night’s sleep.
Diet matters too, as certain foods influence chronic inflammation for better or worse. Research has shown that trans fatty acids and high salt intake lead to increased inflammation. Refined sugars and ultra-processed foods can contribute to the activation of inflammatory genes. On the other hand, foods rich in omega-3 fatty acids, like mackerel, salmon and chia seeds, have shown inflammation-reducing effects; leafy greens and fruits are high in inflammation-fighting antioxidants and polyphenols. Many doctors also recommend a Mediterranean diet as an overall anti-inflammatory diet. Coffee makes the cut too, according to Harvard researchers.
But if a person can make only one lifestyle change to reduce inflammation and improve immune health, according to Slavich, it should be cutting down on stress.
“Unlike genetic factors, which are impossible to change, and access to healthy foods, which can be difficult to change, the ability to change how we perceive the world lies in the hands of all of us,” he says. “Stress is the silent killer that everyone knows about but few tackle.”
Arnett agrees, and points to yoga as an effective stress-reducer. Stress has been linked to a shorter lifespan in mice. Research also suggests that certain psychological stressors in the workplace disrupt inflammation-reducing hormones.
On a brighter note, we are inching toward more actionable data. In a study published in February in the journal Cell Metabolism, researchers at the University of California, Berkeley, identified what they describe as a “molecular switch.” It’s a collection of immune system proteins that can be turned off to stop a hyperinflammatory response. Overactivation of this particular collection of proteins has been linked to cancer, multiple sclerosis and dementia. Developing future drugs that target this switch has potential to treat or even prevent some of these conditions, researchers suggest.
“It’s really not enough to just know that inflammation is bad,” says Slavich. “We need to actually begin changing the factors that increase inflammation and damage health. The silver lining is that we all have the ability to change these risk factors.”