Nutrition

Inflammation

Definition

Inflammation is the immune system's coordinated response to harmful stimuli, including pathogens, damaged tissue, and chemical irritants. Acute inflammation is a short-lived, protective process that resolves once the threat is cleared. Chronic, low-grade inflammation persists when the resolution cascade fails; it maintains a systemic burden that underpins cardiovascular disease, type 2 diabetes, cancer, and neurodegenerative conditions.

How it works

Inflammation begins when pattern-recognition receptors on innate immune cells detect damage-associated or pathogen-associated molecular patterns. These receptors trigger cytokine and chemokine release within minutes, drawing neutrophils to the affected site 2. The classic cardinal signs, redness, warmth, swelling, and pain, are direct consequences of vasodilation and increased vascular permeability, which concentrate immune effectors precisely where they are needed.

What distinguishes acute from chronic inflammation is not the intensity of the initial response but the success of its resolution. Resolution is an active, orchestrated process governed by specialised pro-resolving lipid mediators; when this cascade fails, the inflammatory state persists indefinitely rather than clearing 3. In persistent low-grade inflammation, circulating interleukin-6 (IL-6) and C-reactive protein (CRP) remain sub-clinically elevated for months to years; they are accessible biomarkers of systemic inflammatory burden 2.

When low-grade inflammation persists, it couples with dyslipidaemia to drive leukocyte recruitment into arterial walls, a mechanism that initiates atheroma formation 1. This pathway from molecular immune signal to structural tissue disease illustrates why elevated CRP predicts future cardiovascular events independently of traditional lipid risk factors: inflammation is not merely a downstream marker of these conditions but a causally active driver.

In action

Example

An individual consuming a diet heavy in ultra-processed foods and refined carbohydrates shows no obvious signs of illness. Routine blood work returns CRP and IL-6 values in the upper portion of normal reference ranges. No individual marker breaches any diagnostic threshold, yet the combination reflects a sustained, sub-clinical inflammatory burden that progressively raises cardiovascular risk beyond what lipid readings alone would indicate.

Chronic inflammation's hazard is precisely its silence; the damage accumulates across years before any clinical threshold is crossed.

Why it matters

Chronic systemic inflammation is mechanistically linked to every major non-communicable condition: cardiovascular disease, type 2 diabetes, chronic kidney disease, non-alcoholic fatty liver disease, and neurodegenerative disorders across the life span 2. These links are not coincidental markers; they are causal pathways. Persistent immune activation amplifies insulin resistance, promotes atheroma formation in arterial walls, and creates a tissue environment permissive to tumour development 1.

Inflammatory burden is modifiable. Obesity, physical inactivity, poor dietary quality, environmental toxicants, and sustained psychological stress all sustain chronic inflammation 3. Dietary change towards omega-3 fatty acids, fibre, and polyphenol-rich whole foods produces measurable reductions in CRP and IL-6 within weeks 4. The implication for anyone optimising health and performance is direct: inflammation is not only a consequence of lifestyle choices but also a target for them.

Frequently asked
What is the difference between acute and chronic inflammation?+

Acute inflammation is a short-lived protective response that resolves once the triggering threat is cleared. Chronic, low-grade inflammation persists when the resolution process fails, maintaining sub-clinical immune activation for months or years. The distinction is mechanistic: a failure of resolution rather than simply a prolonged version of the acute response.

Which foods cause or reduce inflammation?+

Diets high in refined carbohydrates, saturated fats, and trans-fats activate innate immune pathways and raise CRP and IL-6. Mediterranean-style diets rich in omega-3 fatty acids, dietary fibre, and polyphenols consistently lower these markers. Randomised trial evidence shows measurable CRP reductions within weeks of switching to an anti-inflammatory dietary pattern.

What are the symptoms of chronic inflammation?+

Chronic low-grade inflammation typically produces no obvious symptoms. When signs do appear, they are diffuse and non-specific: persistent fatigue, mild joint discomfort, and slow recovery from illness or physical stress. Clinically, the condition is identified through elevated blood markers, primarily CRP and interleukin-6, rather than through any distinctive symptom pattern.

How does chronic inflammation contribute to disease?+

Chronic inflammation promotes atheroma formation in arterial walls through leukocyte recruitment and pro-inflammatory cytokine expression, linking it directly to cardiovascular disease. It also impairs insulin signalling, accelerating progression to type 2 diabetes, and creates a molecular environment permissive to tumour development. Elevated CRP predicts future cardiovascular events independently of traditional lipid markers.

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Sources
1 Libby (2002) Inflammation in atherosclerosis Nature DOI
2 Furman et al. (2019) Chronic inflammation in the etiology of disease across the life span Nature Medicine DOI
3 Cifuentes et al. (2025) Low-Grade Chronic Inflammation: a Shared Mechanism for Chronic Diseases Physiology DOI
4 Giugliano et al. (2006) The Effects of Diet on Inflammation Journal of the American College of Cardiology DOI