Inflammation – Harvard Health

What is inflammation?

Our bodies are equipped with a built-in defense system—a complex army of infection-fighting cells and proteins that warn other cells of invaders, fight them off when they arrive, and heal any damage the resulting conflict produces. Inflammation is an important part of this defensive system and one that is essential for our survival. 

You’ve seen the effects of inflammation in real time if you’ve ever gotten a paper cut, sprained your ankle, or been stung by a bee. Redness and heat, along with pain and swelling that result from an injury or infection, are evidence of the inflammatory process underway beneath the skin’s surface. 

Not visible but similar in process is the inflammation that results when you come down with an infection like the flu or pneumonia. In both cases, the immune system is waging a battle inside your body against invading microbes. Without its defenses, a minor cut or illness could quickly turn deadly. 

There are two types of inflammation: acute and chronic. 

Acute inflammation is the body’s immediate response to an injury or infection. When the body is damaged, the immune system sends white blood cells to destroy any damaging substances, heal the tissues, and return the affected area to a state of balance. This rapid response causes familiar symptoms like redness, pain, warmth, and swelling. Acute inflammation usually resolves within a few hours to days. 

Chronic inflammation can begin via the same process as acute inflammation but becomes persistent. It can happen in several ways. One possibility is that the threat remains because the body can’t rid itself of the offending substance. Another scenario is that the immune system goes into “threat mode” when no actual threat exists. As a result, rather than healing tissues, the body breaks them down. Unhealthful lifestyle choices, such as smoking, a poor diet, excessive alcohol consumption, sedentary behavior, stress, and weight gain also can contribute to chronic inflammation.

Is inflammation helpful or harmful?

It turns out inflammation is both good and bad. On the one hand, acute inflammation helps the body to repair tissue damage and fight infections. Yet there is another side of inflammation that can be harmful rather than helpful to human health. A growing body of evidence suggests that low-grade, chronic inflammation contributes to some of the nation’s leading killers, including cardiovascular disease, cancer, and type 2 diabetes as well as Alzheimer’s disease, allergies and asthma, arthritis, anxiety and depression, and some skin conditions.

What causes inflammation?

There are many causes of inflammation.

Acute inflammation is the body’s protective response to an injury or infection. For example, when you cut your finger, your body dispatches white blood cells to protect the area. You may see and feel swelling, redness, and pain, but this process is critical to fighting infection.

Chronic inflammation may occur when the body tries to rid itself of harmful substances such as an infectious organism, an irritant, or a chemical toxin. Increased levels of chronic inflammation are also associated with an unhealthy lifestyle, including a poor diet, alcohol consumption, sedentary behavior, stress, and weight gain. Most autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, lupus, psoriasis, inflammatory bowel disease, and multiple sclerosis, also cause chronic inflammation.

It’s also possible that diet can cause chronic inflammation. Research has shown that pro-inflammatory diets are associated with a higher risk of chronic diseases that are fueled by inflammation, such as heart disease and diabetes. High-inflammatory foods include red meat and processed meat, refined carbohydrates such as white bread, white rice, snack foods, desserts, and sweetened beverages, like soft drinks.

Where does inflammation occur?

Chronic inflammation can attack the entire body and, in the process, raise the risk for certain types of diseases and disorders in specific areas like the heart, brain, joints, and gastrointestinal tract.

Heart. Inflammation can raise the risk of heart attacks, and the link is believed to be related to cholesterol. Cholesterol can cause plaque build-up in the arteries, potentially blocking blood flow and leading to a heart attack. As cholesterol invades the wall of an artery, the immune system treats it like any other invader and releases inflammation-producing chemicals to help remove it. A fibrous cap is formed over the plaque. Inflammation inside the plaque can eventually eat away at the cap, and if it ruptures, the cholesterol, inflammatory cells, and chemicals in the plaque spill into the artery causing a blood clot to form which blocks blood flow.

Brain. Research has found that high amounts of inflammation in the body are associated with brain aging, increased cognitive decline, and “brain fog,” which can impair thinking and cause memory lapses and confusion. Inflammation also may play a role in the production of an abnormal protein called tau, which is associated with Alzheimer’s disease.

Joints. Chronic inflammation can lead to pain, swelling, stiffness, and joint damage, known as inflammatory arthritis. This can damage cartilage, bones, tendons (which attach muscle to bones), or ligaments (which hold joints together) and irritate nerves. Common types of inflammatory arthritis include rheumatoid arthritis, gout, and psoriatic arthritis.

Gastrointestinal tract. Inflammation is a driver of inflammatory bowel disease (IBD), a chronic inflammation of the gastrointestinal (GI) tract, including the stomach, gallbladder, and small and large intestines. Two types of IBD are ulcerative colitis, marked by continuous inflammation of the large intestine, and Crohn’s disease, which causes inflammation anywhere in the GI tract. People with IBD can experience various symptoms, such as abdominal pain, diarrhea, blood in their stool, bloating, and weight loss.

Liver inflammation. Nonalcoholic fatty liver disease is fatty liver not caused by alcohol intake. There are two types: simple fatty liver and nonalcoholic steatohepatitis (NASH). Simple fatty liver doesn’t cause inflammation. However, NASH is more severe and occurs when fattened cells become inflamed. This inflammation can damage liver cells, resulting in cirrhosis (permanent scarring of the liver), and increase the risk of liver cancer. Chronic liver inflammation can also be caused by a hepatitis C infection and lead to cirrhosis.

How do you reduce inflammation?

Although inflammation is vital to the body’s defense and repair systems, chronic inflammation can cause more harm than good. That may make you wonder: what can I do about it? There are actually several ways to treat and reduce chronic inflammation. For example:

Follow a healthy, anti-inflammatory diet. Eating foods that have an anti-inflammatory effect may reduce inflammation and lower the risk of chronic illnesses associated with inflammation. Foods that reduce inflammation include:

  • tomatoes
  • olive oil
  • green leafy vegetables, such as spinach, kale, and collards
  • nuts like almonds and walnuts
  • fatty fish like salmon, mackerel, tuna, and sardines
  • whole grains such as quinoa, whole-grain bread, and oatmeal
  • fruits such as strawberries, blueberries, and oranges

These foods contain high amounts of anti-inflammatory compounds and antioxidants like carotenoids, polyphenols, and omega-3 fatty acids.

An easy way to eat more anti-inflammatory foods is to follow an eating plan like the Mediterranean and MIND diets, which emphasize these foods. Following an anti-inflammatory diet also helps you avoid unhealthy foods that can cause inflammation, such as refined carbohydrates, such as white bread and pastries, processed foods, sugar-sweetened beverages, and red meat. High amounts of these foods also contribute to weight gain, another risk factor for inflammation.

Other ways you can reduce inflammation include:

Regular exercise. Moderate-intensity exercise can help prevent excess weight gain and manage cytokine levels. Cytokines are small proteins that play an essential role in normal immune responses, but large amounts can lead to inflammation.

Manage stress. Repeated bouts of stress can expose the body to high levels of cortisol (the stress hormone) and lead to chronic inflammation. Yoga, deep breathing, meditation, and other forms of relaxation can help calm your nervous system.

Medications. Anti-inflammatory medicines can help treat inflammatory conditions. Examples include corticosteroids and over-the-counter nonsteroidal anti-inflammatory drugs, such as Ibuprofen and naproxen. Speak with your doctor about whether medication is an option because they could cause side effects.

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