What is inflammation?

Runner with knee pain, conceptual computer illustration.
(Image credit: Getty Images)

Inflammation is a vital part of the immune system's response to injury and infection. It is the body's way of signaling the immune system to heal and repair damaged tissue, as well as defend itself against foreign invaders, such as viruses and bacteria. 

Without inflammation as a physiological response, wounds would fester and infections could become deadly. 

There are different types of inflammation, ranging from acute to chronic. However, if the inflammatory process goes on for too long or if the inflammatory response occurs in places where it is not needed, it can become problematic. Chronic inflammation has been linked to certain diseases such as heart disease or stroke, and may also lead to autoimmune disorders, such as rheumatoid arthritis and lupus. But a healthy diet and lifestyle can help keep inflammation under control. 

Types of inflammation

Acute inflammation

Acute inflammation occurs after a cut on the knee, a sprained ankle or a sore throat. It's a short-term response with localized effects, meaning it works at the precise place where a problem exists. According to the National Library of Medicine (opens in new tab) (NLM) the telltale signs of acute inflammation include: 

  • Redness
  • Swelling
  • Heat
  • Pain
  • Loss of function

In the case of acute inflammation, blood vessels dilate, blood flow increases and white blood cells swarm the injured area to promote healing, said Dr. Scott Walker, a family practice physician at Gunnison Valley Hospital (opens in new tab) in Utah. This response is what causes the injured area to turn red and become swollen. 

During acute inflammation, chemicals known as cytokines are released by the damaged tissue. The cytokines act as "emergency signals" that bring in your body's immune cells, hormones and nutrients to fix the problem, Walker told Live Science.

In addition, hormone-like substances known as prostaglandins create blood clots to heal damaged tissue, and they also trigger pain and fever as part of the healing process. As the body heals, the acute inflammation gradually subsides. 

Dr. Scott Walker, family medicine doctor
Dr. Scott Walker

Dr. Scott Walker is a family practice doctor. He received his medical degree from the University of Utah and his Doctor of Osteopathic Medicine from Kansas City University. He completed his family medicine residency at University of Wyoming with a specialty in obstetrics. Walker is certified by the American Board of Family Medicine and the American Osteopathic Association. 

Chronic inflammation

Unlike acute inflammation, chronic inflammation can have long-term and whole-body effects. Chronic inflammation is also called persistent, low-grade inflammation because it produces a steady, low-level of inflammation throughout the body, as judged by a small rise in immune system markers found in blood or tissue. This type of systemic inflammation can contribute to the development of disease, according to the NLM (opens in new tab)

Low levels of inflammation can be triggered by a perceived internal threat, even when there isn't a disease to fight or an injury to heal, and sometimes this signals the immune system to respond. As a result, white blood cells swarm but have nothing to do and nowhere to go, and they may eventually start attacking internal organs or other healthy tissues and cells, Walker said.

Chronic inflammation, caused by allergies, smoking or drinking, may also continually simmer under the surface. And while this low-grade level of chronic inflammation often does not have symptoms, doctors can test for C-reactive protein (CRP), a marker for inflammation in the blood. 

High levels of CRP have been linked with an increased risk of heart disease. CRP levels can also indicate an infection, or a chronic inflammatory disease, such as rheumatoid arthritis or lupus, according to the Mayo Clinic (opens in new tab)

Besides looking for clues in the blood, a person's diet, lifestyle habits and environmental exposures can contribute to chronic inflammation. Therefore, it's important to maintain a healthy lifestyle to keep inflammation in check.

Disease caused by inflammation

Researchers are still working to understand the implications of chronic inflammation on the body and the mechanisms involved in the process, but it's known to play a role in the development of many diseases.

Heart disease and stroke  

One theory suggests that when inflammatory cells stay too long in blood vessels, they promote the buildup of plaque. The body perceives this plaque as a foreign substance that doesn't belong, so it tries to wall off the plaque from the blood flowing inside the arteries, according to the American Heart Association (opens in new tab) (AHA). If the plaque becomes unstable and ruptures, it forms a clot that blocks blood flow to the heart or brain, triggering a heart attack or stroke.

Cancer

Cancer is another disease linked with chronic inflammation. According to the National Cancer Institute (opens in new tab), over time, chronic inflammation can cause DNA damage and lead to some forms of cancer. For example, the institute says that those with chronic inflammatory bowel diseases, such Crohn's disease (opens in new tab), have an increased risk of colon cancer.

What is an anti-inflammatory diet?

Anti-inflammatory diets have become popular in recent years. The recommended foods are typical of a Mediterranean diet and include eating more:

  • Fish
  • Fresh fruits
  • Vegetables
  • Healthy fats
  • Eating moderate amounts of nuts
  • Eating very little red meat 

Like the Mediterranean diet, the principles of an anti-inflammatory diet are healthful ones and the approach is nutritionally sound, according to the Mayo Clinic (opens in new tab).

"Anti-inflammatory food components, such as omega-3 fats, protect the body against the possible damage caused by inflammation," said Ximena Jimenez, a Miami-based nutritionist.

Ximena Jimenez
Ximena Jimenez

Ximena Jimenez is a registered dietitian with a private practice in Miami. She proudly served as a national media spokesperson for the Academy of Nutrition and Dietetics for seven years. Ximena has appeared as a guest expert on local, national and international shows, including CNN en Español, Telemundo, Univision, AmericaTeve, Caracol, Univision Radio, and WLRN. 

An anti-inflammatory diet also means staying away from foods that can promote inflammation. It's best to minimize the amount of foods you eat that are high in saturated and trans fats, such as red meats, dairy products and foods containing partially hydrogenated oils, according to the University of Wisconsin (opens in new tab).

In addition, limit sugary foods and refined carbohydrates, such as white rice and bread. And cut back on the use of cooking oils and margarines that are high in omega-6 fatty acids, such as corn, safflower and sunflower oils. 

Anti-inflammatory drugs

To help combat unwanted inflammation, there are a range of prescription and over-the counter medications. The most common ones are the over-the-counter medications known as non-steroidal anti-inflammatory drugs (NSAIDs). They include: 

An anti-inflammatory diet also means staying away from foods that can promote inflammation. It's best to minimize the amount of foods you eat that are high in saturated and trans fats, such as red meats, dairy products and foods containing partially hydrogenated oils, according to the University of Wisconsin. In addition, limit sugary foods and refined carbohydrates, such as white rice and bread. And cut back on the use of cooking oils and margarines that are high in omega-6 fatty acids, such as corn, safflower and sunflower oils. 

  • Aspirin 
  • Naproxen (Aleve)
  • Ibuprofen (Advil and Motrin)

According to the NLM (opens in new tab), NSAIDs work by blocking the enzyme cyclooxygenase, which produces prostaglandins, a hormone-like substance that promotes inflammation. Prescription-strength NSAIDs are also available, such as Acetaminophen (which is also known as Paracetamol). This is another common pain reliever, but it does not relieve inflammation, the NLM states. 

Corticosteroids, such as cortisone and prednisone, may be prescribed for inflammatory conditions, such as asthma and arthritis. The Mayo Clinic says corticosteroids may help suppress inflammation, but these powerful drugs also carry a risk of side effects, such as weight gain and fluid retention. 

Before taking any of these drugs, it’s always best to speak to a healthcare provider. 

Anti-inflammatory supplements

Several dietary supplements are said to have anti-inflammatory properties, such as ginger, turmeric and willow bark. Although there is some limited evidence that a few natural products may provide modest benefits for acute inflammation, in general, there is insufficient evidence to support the use of many of these products for inflammatory conditions, according to the National Center for Complimentary and Integrative Health (opens in new tab).

Additional resources:

This article is for informational purposes only and is not meant to offer medical advice. 

Live Science Contributor