Understanding acute and chronic inflammation

The right kind of inflammation is essential to your body's healing system. But chronic inflammation can be a problem.

The saying "too much of a good thing" applies to much of life, but especially to inflammation.

"People think inflammation needs to be stomped out at all times, but it plays an essential role in healing and injury repair to keep your body safe and healthy," says Dr. Robert H. Shmerling, medical editor of Understanding Inflammation from Harvard Health Publishing and an associate professor of medicine at Harvard Medical School. "Some inflammation is good. Too much is often bad. The goal is to recognize when inflammation is simply doing its job, and when it can potentially cause problems."

Signs of inflammation are like a car's dashboard engine light. It tells you that something is wrong. But your response is not to take out the bulb, because that's not the problem. Instead, you look at what caused the light to turn on. "It's the same with inflammation," says Dr. Shmerling. "It's telling you that something bigger is going on that requires attention."

Acute and chronic

There are two types of inflammation: acute and chronic. People are most familiar with acute inflammation. This is the redness, warmth, swelling, and pain around tissues and joints that occurs in response to an injury, like when you cut yourself. When the body is injured, your immune system releases white blood cells to surround and protect the area.

"Acute inflammation is how your body fights infections and helps speed up the healing process," says Dr. Shmerling. "In this way, inflammation is good because it protects the body." This process works the same if you have a virus like a cold or the flu.

In contrast, when inflammation gets turned up too high and lingers for a long time, and the immune system continues to pump out white blood cells and chemical messengers that prolong the process, that's known as chronic inflammation. "From the body's perspective, it's under consistent attack, so the immune system keeps fighting indefinitely," says Dr. Shmerling.

When this happens, white blood cells may end up attacking nearby healthy tissues and organs. For example, if you are overweight and have more visceral fat cells — the deep type of fat that surrounds your organs — the immune system may see those cells as a threat and attack them with white blood cells. The longer you are overweight, the longer your body can remain in a state of inflammation.

Research has shown that chronic inflammation is associated with heart disease, diabetes, cancer, arthritis, and bowel diseases like Crohn's disease and ulcerative colitis.

Yet, because chronic inflammation can continue for a long time, it's not easy to know its exact impact. "It's a chicken-and-egg scenario," says Dr. Shmerling. "Does chronic inflammation increase the risk of these ailments, or is it a byproduct? It is not always clear."

When to worry

Most of the time, you don't need to worry too much about acute inflammation, says Dr. Shmerling. You can take an over-the-counter pain reliever to help relieve symptoms, or apply cold compresses to reduce swelling. "Otherwise, it is usually best to let the inflammation do its work to help with healing," says Dr. Shmerling.

Of course, the cause of acute inflammation may need treatment. For example, a bacterial infection may require antibiotics, so if you have a fever or significant symptoms — such as severe pain or shortness of breath — see your doctor.

Chronic inflammation is trickier to deal with. The problem is that chronic inflammation is often "invisible," since it does not show telltale physical signs the way acute inflammation does.

So how can you prevent or reduce inflammation you cannot necessarily see or feel?

The only way to detect chronic inflammation is to have an evaluation by your doctor. He or she will review your symptoms, perform a physical exam, and perhaps check your blood for signs of inflammation. (See "A test for inflammation.")

Otherwise, the best approach is to prevent conditions related to chronic inflammation. "It goes back to the basics: maintaining a healthy weight, choosing a good diet, getting plenty of sleep, and exercising regularly," says Dr. Shmerling.

Eat right, move more

Diet and exercise have an especially strong impact on managing chronic inflammation since they both also can help control weight and improve sleep.

The evidence is not clear that a specific type of diet can prevent chronic inflammation. However, certain foods are associated with either promoting or inhibiting the inflammatory response. These foods also are linked to a lower risk of problems related to chronic inflammation, such as heart disease, weight gain, and cancer.

For instance, cut back or eliminate foods high in simple sugars like soda, fruit juices with added sugars, sports drinks, processed meat, and refined carbs like white bread and pasta. "These foods can spike blood sugar levels, which can lead to overeating and weight gain," says Dr. Shmerling.

Also, eat more foods high in the antioxidants known as polyphenols, which can lower inflammation. Examples include all types of berries, cherries, plums, red grapes, onions, turmeric, green tea, and dark green leafy vegetables like spinach and kale.

Regular exercise can help protect against conditions linked with chronic inflammation, especially heart disease and obesity. A 2017 study in Brain, Behavior, and Immunity found that just 20 minutes of moderate-intensity exercise (in this case, walking on a treadmill) can have an anti-inflammatory effect.

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