Inflammation gets talked about constantly in health circles, usually as something to fight or suppress. But inflammation is also what keeps you alive. It's the immune response your body triggers when it detects injury, infection, or threat. Understanding the difference between helpful and harmful inflammation is one of the most useful things you can do for your long-term health.
What inflammation actually is
Inflammation is your immune system's rapid-response mechanism. When tissue is damaged or an invader is detected, the body sends a surge of blood and immune cells to the affected area. That's why a cut finger swells, reddens, and feels warm. Those four signs (redness, swelling, heat, and pain) are the textbook markers of acute inflammation, first described by the Roman physician Celsus around 30 BCE.
Acute inflammation is protective. It creates an environment hostile to bacteria, clears out damaged cells, and begins the repair process. It typically resolves within a few days. The problem starts when it doesn't.
Acute vs chronic inflammation
Acute inflammation is short, targeted, and necessary. Chronic inflammation is the opposite: low-grade, persistent, and often invisible. It can continue for months or years without obvious symptoms, quietly damaging healthy tissue in the process.
Chronic inflammation is now linked to a wide range of serious conditions, including type 2 diabetes, cardiovascular disease, certain cancers, Alzheimer's disease, and autoimmune disorders such as rheumatoid arthritis and lupus. It's not the only driver of these conditions, but the evidence connecting them has become hard to ignore over the past two decades.
The tricky part is that chronic inflammation doesn't always announce itself. You won't feel a burn or see a swollen joint. Instead, you might feel persistently tired, mentally foggy, or just vaguely unwell, symptoms that are easy to attribute to stress or poor sleep.
What causes chronic inflammation?
Several factors are well-established triggers. A diet high in ultra-processed foods is one of the clearest. Refined sugars, seed oils, and heavily processed meat products have been shown in multiple studies to elevate inflammatory markers like C-reactive protein (CRP) and interleukin-6 in the bloodstream.
Chronic stress is another driver. When the body stays in a prolonged stress state, it produces elevated cortisol. Over time, cells become resistant to cortisol's anti-inflammatory signalling, leaving the immune system in a state of low-level activation. If you want to understand exactly how cortisol shapes this process, our piece on what cortisol does to your body explains the mechanism in detail.
Other established contributors include:
- Poor sleep (less than 6 hours per night consistently raises inflammatory markers)
- Sedentary behaviour
- Smoking and excess alcohol consumption
- Gut microbiome imbalance
- Obesity, particularly visceral fat stored around the organs
Visceral fat is particularly relevant. It isn't metabolically inert. It actively secretes inflammatory chemicals called adipokines, which means excess abdominal weight isn't just a side effect of inflammation, it also causes it.
How gut health connects to inflammation
The gut plays a central role in regulating immune responses throughout the body. About 70 per cent of the immune system resides in or around the gut wall, and the health of the gut lining determines how much of what's inside the intestine stays there. When the gut lining becomes permeable (often called "leaky gut"), bacterial fragments and food particles can cross into the bloodstream, triggering a sustained immune response.
Diet is the most direct way to influence gut health. Fibre-rich foods feed beneficial bacteria. Ultra-processed foods feed harmful ones. The connection between what you eat and how inflamed your body is runs directly through the gut microbiome, which is why gut health and inflammation are so frequently discussed together.
What blood tests measure inflammation?
Doctors use several markers to assess systemic inflammation. C-reactive protein (CRP) is the most common. A high-sensitivity CRP (hs-CRP) test is more precise and can detect low-grade chronic inflammation even when nothing obviously feels wrong. An hs-CRP level below 1 mg/L is considered low risk; 1–3 mg/L is moderate; above 3 mg/L is elevated.
Other markers include erythrocyte sedimentation rate (ESR), ferritin, and specific interleukins. These tests don't diagnose a specific condition, but they give a clinician a picture of whether the immune system is running hot. A GP can order these as part of a routine blood panel.
What reduces chronic inflammation?
The evidence points strongly to lifestyle, not supplements. Anti-inflammatory eating patterns, particularly Mediterranean-style diets rich in vegetables, legumes, olive oil, and oily fish, have shown consistent benefits in reducing CRP and other inflammatory markers. A 2020 review published in the journal Frontiers in Nutrition found the Mediterranean diet reduced hs-CRP by an average of 0.58 mg/L across included trials.
Regular moderate exercise also has a well-documented anti-inflammatory effect. Exercise temporarily increases acute inflammatory signals, but the body adapts over time, producing a net reduction in baseline inflammation. The key word is moderate: very high-intensity training without adequate recovery can have the opposite effect.
Sleep is non-negotiable. Poor sleep quality consistently elevates inflammatory markers, and improving sleep hygiene is one of the fastest ways to bring them down. If you're not sure where to start, the principles behind good sleep hygiene are practical and evidence-backed.
Anti-inflammatory supplements get enormous attention, particularly omega-3 fatty acids, turmeric/curcumin, and vitamin D. The evidence for omega-3s is reasonably strong, especially at therapeutic doses above 2 grams per day of EPA and DHA combined. Curcumin shows promise but has poor bioavailability in standard supplement form. The real leverage, though, still sits with diet, sleep, and movement.
When to see a doctor
If you're experiencing persistent fatigue, joint pain, unexplained weight changes, or recurrent infections, it's worth asking your GP to check inflammatory markers alongside a standard blood panel. Chronic inflammation caught early is far easier to address than inflammation that's already contributed to structural damage.
Autoimmune conditions, in particular, often go undiagnosed for years while symptoms are attributed to stress or lifestyle. An hs-CRP result above 3 mg/L without an obvious acute cause is a reasonable prompt to investigate further.
Inflammation is not the enemy. Chronic, unchecked inflammation is. The distinction matters, because the goal isn't to suppress your immune system. It's to stop triggering it unnecessarily.