
Why all the buzz about inflammation — and just how bad is it?
Quick health quiz: how bad is inflammation for your body?
You’re forgiven if you think inflammation is very bad. News sources everywhere will tell you it contributes to the top causes of death worldwide. Heart disease, stroke, dementia, and cancer all have been linked to chronic inflammation. And that’s just the short list. So, what can you do to reduce inflammation in your body?
Good question! Before we get to the answers, though, let’s review what inflammation is — and isn’t.
Inflammation 101
Misconceptions abound about inflammation. One standard definition describes inflammation as the body’s response to an injury, allergy, or infection, causing redness, warmth, pain, swelling, and limitation of function. That’s right if we’re talking about a splinter in your finger, bacterial pneumonia, or the rash of poison ivy. But it’s only part of the story, because there’s more than one type of inflammation:
- Acute inflammation rears up suddenly, lasts days to weeks, and then settles down once the cause, such as an injury or infection, is under control. Generally, acute inflammation is a reaction that attempts to restore the health of the affected area. That’s the type described in the definition above.
- Chronic inflammation is quite different. It can develop for no medically apparent reason, last a lifetime, and cause harm rather than healing. This type of inflammation is often linked with chronic disease, such as:
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- excess weight
- diabetes
- cardiovascular disease, including heart attacks and stroke
- certain infections, such as hepatitis C
- autoimmune disease
- cancer
- stress, whether psychological or physical.
Which cells are involved in inflammation?
The cells involved with both types of inflammation are part of the body’s immune system. That makes sense, because the immune system defends the body from attacks of all kinds.
Depending on the duration, location, and cause of trouble, a variety of immune cells, such as neutrophils, lymphocytes, and macrophages, rush in to create inflammation. Each type of cell has its own particular role to play, including attacking foreign invaders, creating antibodies, and removing dead cells.
4 inflammation myths and misconceptions
Inflammation is the root cause of most modern illness.
Not so fast. Yes, a number of chronic diseases are accompanied by inflammation. In many cases, controlling that inflammation is an important part of treatment. And it’s true that unchecked inflammation contributes to long-term health problems.
But inflammation is not the direct cause of most chronic diseases. For example, blood vessel inflammation occurs with atherosclerosis. Yet we don’t know whether chronic inflammation caused this, or whether the key contributors were standard risk factors (such as high cholesterol, diabetes, and smoking — all of which cause inflammation).
You know when you’re inflamed.
True for some conditions. People with rheumatoid arthritis, for example, know when their joints are inflamed because they experience more pain, swelling, and stiffness. But the type of inflammation seen in obesity, diabetes, or cardiovascular disease, for example, causes no specific symptoms. Sure, fatigue, brain fog, headaches, and other symptoms are sometimes attributed to inflammation. But plenty of people have those symptoms without inflammation.
Controlling chronic inflammation would eliminate most chronic disease.
Not so. Effective treatments typically target the cause of inflammation, rather than just suppressing inflammation itself. For example, a person with rheumatoid arthritis may take steroids or other anti-inflammatory medicines to reduce their symptoms. But to avoid permanent joint damage, they also take a medicine like methotrexate to treat the underlying condition that’s causing inflammation.
Anti-inflammatory diets or certain foods (blueberries! kale! garlic!) prevent disease by suppressing inflammation.
While it’s true that some foods and diets are healthier than others, it’s not clear their benefits are due to reducing inflammation. Switching from a typical Western diet to an “anti-inflammatory diet” (such as the Mediterranean diet) improves health in multiple ways. Reducing inflammation is just one of many possible mechanisms.
The bottom line
Inflammation isn’t a lone villain cutting short millions of lives each year. The truth is, even if you could completely eliminate inflammation — sorry, not possible — you wouldn’t want to. Among other problems, quashing inflammation would leave you unable to mount an effective response to infections, allergens, toxins or injuries.
Inflammation is complicated. Acute inflammation is your body’s natural, usually helpful response to injury, infection, or other dangers. But it sometimes sparks problems of its own or spins out of control. We need to better understand what causes inflammation and what prompts it to become chronic. Then we can treat an underlying cause, instead of assigning the blame for every illness to inflammation or hoping that eating individual foods will reduce it.
There’s no quick or simple fix for unhealthy inflammation. To reduce it, we need to detect, prevent, and treat its underlying causes. Yet there is good news. Most often, inflammation exists in your body for good reason and does what it’s supposed to do. And when it is causing trouble, you can take steps to improve the situation.
About the Author
Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

A liquid biopsy for metastatic prostate cancer
Metastatic prostate cancer can progress in different ways. In some men the disease advances rapidly, while other men have slower-growing cancer and a better prognosis. Researchers are developing various tools for predicting how fast prostate cancer might progress. Among the most promising are assays that count circulating tumor cells (CTCs) in blood samples.
Prostate cancer spreads by shedding CTCs into the bloodstream, so higher counts in blood generally reflect worse disease. Sometimes referred to as a liquid biopsy, the CTC assay can help doctors decide if patients should get standard or more aggressive treatment. Just one CTC assay is currently on the market for prostate cancer. Called CellSearch, its use is so far limited to men with late-stage metastatic cancer for whom hormonal therapies are no longer effective.
Using CTC data
Hormonal therapies block testosterone, a hormone that drives prostate tumors to grow. Research shows that high CTC counts predict poorer survival and faster disease progression among patients with metastatic prostate cancer who become resistant to this form of treatment. But new research shows CTC counts are also predictive for early-stage metastatic prostate cancer that still responds to hormonal therapy.
Why is that important? Because the earlier doctors can predict a cancer’s trajectory, the better their ability to select patients who could benefit from more powerful (and potentially more aggressive) drug combinations or a clinical trial. Conversely, men who are older or frail might be treated less aggressively if doctors had better insights into their prognosis.
How the study was done
The investigators collected blood samples from 503 newly-diagnosed patients with hormonally-sensitive metastatic prostate cancer who had enrolled in a clinical trial with experimental hormonal therapies. The team collected baseline samples at trial registration, and then another set of samples after the treatments were no longer working. CTC counts were divided in three categories:
- more than 5 CTCs per 7.5 milliliters (mLs) of blood
- between 1 and 4 CTCs per 7.5 mLs of blood
- zero CTCs per 7.5 mLs of blood.
What the research showed
Results showed that men with higher baseline CTC counts fared worse regardless of which cancer drugs they were taking. Median survival for men with 5 or more CTCs per sample was 27.9 months compared to 56.2 months in men with 1 to 4 CTCs. There weren’t enough patient deaths among those with 0 CTCs to calculate a survival rate.
Similarly, higher CTC counts predicted faster onset of resistance to hormonal therapy: 11.3 months for men in the highest CTC category, compared to 20.7 months and 59 months for men with 1 to 4 and zero CTCs respectively. Importantly, higher CTC counts correlated with measures of prostate cancer severity, including PSA levels, numbers of metastases in bone, and other indicators.
Observations and comments
“This research emphasizes the continued emergence of CTCs in helping to determine outcomes and potentially treatment options for men with metastatic prostate cancer,” said Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of the Harvard Medical School Guide to Prostate Diseases.
“Still to be determined is how this type of testing compares with more traditional evaluations of disease advancement, such as x-rays, bone scans, and other types of imaging. Ready access to cancer cells in blood that, in turn, eliminate the need for more invasive biopsy procedures of metastatic deposits will be a welcome addition — especially if future studies show that CTCs inform more precise treatment choices.”
Dr. David Einstein, a medical oncologist specializing in genitourinary cancers at Beth Israel Deaconess Medical Center and assistant professor at Harvard Medical School, agreed with that assessment. “But the Holy Grail is finding predictive biomarkers [like CTCs] that tell you if patients will or will not benefit from particular treatments,” he added. “Answering these types of questions requires randomized clinical trials.”
About the Author
Charlie Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases
Charlie Schmidt is an award-winning freelance science writer based in Portland, Maine. In addition to writing for Harvard Health Publishing, Charlie has written for Science magazine, the Journal of the National Cancer Institute, Environmental Health Perspectives, … See Full Bio View all posts by Charlie Schmidt
About the Reviewer
Marc B. Garnick, MD, Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing
Dr. Marc B. Garnick is an internationally renowned expert in medical oncology and urologic cancer. A clinical professor of medicine at Harvard Medical School, he also maintains an active clinical practice at Beth Israel Deaconess Medical … See Full Bio View all posts by Marc B. Garnick, MD