The word inflammation gets used a lot. It appears on supplement labels, in newspaper health columns, and increasingly in conversations about food. Most of the time it is used loosely, as a catch-all for something bad that diet can either cause or fix. The science is more precise — and more useful — than that.
This series is about what inflammation actually is, what the research says about the foods that affect it, and what any of that means for you if you live with a food allergy, intolerance, or digestive condition. By the end of four posts you will have a clear, evidence-based picture of the relationship between diet and inflammation, and you will be better placed to make sense of the health claims you see online and in shops.
We start with the biology.
Two very different things with the same name
Inflammation is not one thing. It is two very different processes that share a name, and confusing them leads to a lot of muddled thinking about food and health.
The first kind is acute inflammation. This is your immune system doing exactly what it is supposed to do. When you cut your finger, stub your toe, or catch a cold, your immune system spots the damage or the invader and launches a rapid local response. Blood flow increases. White blood cells flood in. The tissue swells, reddens, warms, and hurts. These are not side effects — they are features. The swelling brings immune cells to the injury. The heat makes conditions hostile for bacteria. The pain tells you to rest the damaged area. Acute inflammation is fast, targeted, purposeful, and — when things go well — it switches itself off once the job is done [1].
The second kind is chronic inflammation. This is your immune system stuck in a low-grade, persistent state of alert that it cannot switch off. There is no obvious injury to repair, no clear bug to fight. Instead, the inflammatory response smoulders on for months or years, producing a slow drip of inflammatory chemicals — called cytokines — that circulate through your body and, over time, cause damage to tissues and organs. Chronic inflammation does not produce dramatic symptoms. It shows up in blood tests as raised markers — particularly a protein called C-reactive protein (CRP) — and its effects build up gradually [1].
The link between chronic inflammation and serious disease is now one of the most solid findings in modern medicine. Chronic, low-grade inflammation is connected to cardiovascular disease, type 2 diabetes, certain cancers, and a range of digestive conditions including inflammatory bowel disease [2].
And what you eat has a real influence on whether that slow fire burns or stays quiet.
How food gets involved
Your gut is the largest immune organ in your body. Around 70% of your immune cells are found in or around the digestive system, positioned to deal with the enormous and constant flow of foreign material — food, bacteria, toxins — passing through it [2].
This means what you eat, and what it does to your gut environment, has a direct line to your immune system. Food does not just give you energy and nutrients. It shapes your gut microbiome — the community of bacteria living in your digestive system — and those bacteria produce compounds that influence whether your immune system sits in a more inflammatory or more regulated state. Food also affects the gut lining itself, which is only one cell thick in places and needs to stay intact to stop bacterial fragments leaking into the bloodstream and triggering inflammation throughout the body.
When your diet consistently gives the gut microbiome what it needs — mainly fibre, which gut bacteria ferment into anti-inflammatory compounds called short-chain fatty acids — your immune system tends toward a more regulated, less inflammatory state. When the diet is consistently low in fibre and high in processed ingredients, the microbiome becomes less diverse, the gut lining becomes less robust, and the inflammatory tone of your immune system shifts upward [3].
This is not a switch that flips with a single meal. It is a gradient that shifts over time with consistent patterns of eating.
Why this matters if you live with a food condition
If you manage a food allergy, intolerance, or digestive condition, the inflammation story is directly relevant to you in at least two ways.
First, many of the conditions covered in this blog involve inflammation as part of their mechanism. Coeliac disease, inflammatory bowel disease, and some food allergy pathways all involve immune-mediated inflammatory responses. Understanding what inflammation is — and what makes it worse or better — gives you a more complete picture of what is happening in your body.
Second, the relationship between diet and chronic inflammation runs through the gut microbiome, which is also central to many of the digestive conditions people manage when eating out. The food you eat shapes the bacterial community in your gut, which in turn affects the inflammatory tone of your immune system and the health of your gut lining. If you have IBS, Crohn's, or another condition that affects your digestive system, the science in this series is part of the background to your experience.
The posts that follow give you the evidence base. Part 2 looks at what the research says about foods and dietary patterns consistently linked to lower inflammatory markers. Part 3 examines the Mediterranean diet — the best-studied dietary pattern in this area. Part 4 covers ultra-processed foods, what the science says about their effects on the gut and immune system, and why that matters for digestive conditions.
References
Pahwa R, Goyal A, Jialal I. Chronic Inflammation. StatPearls. Treasure Island (FL): StatPearls Publishing; 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493173/
Furman D, Campisi J, Verdin E, et al. Chronic inflammation in the etiology of disease across the life span. Nat Med. 2019;25(12):1822–1832. DOI: 10.1038/s41591-019-0675-0
Reyneke GL, Lambert K, Beck EJ. Dietary patterns associated with anti-inflammatory effects: an umbrella review of systematic reviews and meta-analyses. Nutr Rev. 2025;nuaf104. DOI: 10.1093/nutrit/nuaf104
