How Diet & Nutrition affects Inflammation​

Why the modern diet may be working against immune balance, and what that means for eczema.
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Last edited: 19.02.26

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The Role of Inflammation in the Body

Inflammation is not inherently harmful. It is one of the body’s most important protective responses. When the skin is injured or exposed to a pathogen, the immune system activates a coordinated process designed to eliminate the threat and repair tissue. Blood flow increases, immune cells migrate to the site of injury, and chemical messengers signal healing. This is acute inflammation, and it is both necessary and beneficial.

The problem arises when inflammation becomes chronic. Instead of switching off once a threat has passed, the immune system remains in a low-level state of activation. This form of persistent, systemic inflammation does not always produce dramatic symptoms, but it alters immune tone throughout the body. Over time, it can contribute to conditions such as cardiovascular disease, metabolic syndrome, autoimmune disorders, and inflammatory skin conditions like eczema.

For individuals with eczema, this chronic inflammatory background matters deeply. Eczema is characterised by an exaggerated type 2 immune response and a weakened skin barrier. If the immune system is already primed toward reactivity, the threshold for triggering a flare may be lower. And research increasingly suggests that diet is one of the most powerful influences on this baseline inflammatory state.

Our Biology and the Modern Diet

For most of human history, diets were composed of minimally processed foods: fibrous plants, seasonal fruits, nuts, seeds, and modest amounts of animal protein. Meals were nutrient-dense and varied. Fibre intake was substantially higher than it is today, and food additives and preservatives did not exist.

By contrast, modern dietary patterns differ dramatically. Refined carbohydrates, added sugars, industrially processed fats, and ultra-processed foods dominate the supermarket shelves. Fibre intake has declined, plant diversity has narrowed, and caloric density has increased. These changes have occurred over a relatively short evolutionary timescale – much far faster than our immune and metabolic systems can keep up.

The immune system evolved in the context of fibre fermentation, microbial diversity, and intermittent caloric stress. It did not evolve under conditions of constant glucose spikes, food additives, and sustained caloric excess. While this mismatch does not directly “cause” conditions like eczema, it may create an internal environment in which inflammatory pathways are more easily activated and less efficiently resolved. For someone already vulnerable to barrier dysfunction, this background shift may increase the likelihood of persistent skin inflammation.

Blood Sugar Regulation and Immune Signalling

Carbohydrates are essential nutrients, and whole-food sources such as fruits, legumes, and whole grains provide fibre, vitamins, and phytonutrients. The issue is not carbohydrates themselves, but the structure and processing of modern carbohydrate-rich foods.

Refined carbohydrates, including white flour products, sugary drinks, and many processed snacks, are rapidly digested and absorbed. This leads to sharp increases in blood glucose and corresponding spikes in insulin. When these fluctuations occur repeatedly, cells may become less responsive to insulin, a state known as insulin resistance.

Persistently elevated blood glucose increases the production of molecules known as reactive oxygen species (ROS). These are unstable oxygen-containing molecules that are naturally produced inside our cells as a by-product of turning food into energy. In small amounts, ROS are normal and even useful. Immune cells use them to kill invading microbes and they also help regulate certain cellular signalling processes. 

The problem arises when too many are produced. Because ROS are chemically unstable, they readily react with nearby structures such as cell membranes, proteins, and DNA. When their production outpaces the body’s antioxidant defences, a state known as oxidative stress develops. Oxidative stress can activate inflammatory signalling pathways inside cells, including one called nuclear factor kappa B (NF-κB), which increases the production of pro-inflammatory cytokines. Over time, this contributes to a sustained inflammatory environment that may lower the threshold for immune-driven conditions such as eczema to flare.

This is especially important for individuals with eczema whose immune systems are already primed toward inflammatory signalling. When metabolic stress elevates systemic inflammation, it can strengthen type 2 immune signalling in the skin. This leads to increased production of cytokines such as IL-4 and IL-13, which drive itch and inflammation and reduce filaggrin production, further weakening the skin barrier. In this way, repeated metabolic stress as a result of eating a poor diet may indirectly worsen barrier integrity and flare severity.

Ultra-Processed Foods and Barrier Function

Ultra-processed foods are industrial formulations made from refined ingredients and combined with additives such as emulsifiers, stabilisers, artificial flavourings, and preservatives. Unlike minimally processed foods, they are typically low in fibre and micronutrients while being engineered for convenience, shelf life, and hyper-palatability. They are often rapidly digested and energy-dense, which can encourage frequent blood sugar spikes and overconsumption.

Large epidemiological studies have consistently found that higher consumption of ultra-processed foods is associated with elevated inflammatory markers, including C-reactive protein (CRP), a protein produced by the liver in response to systemic inflammation. Although observational data cannot prove causation, controlled studies have demonstrated that ultra-processed diets can induce measurable changes including altered insulin sensitivity and inflammatory signalling even when calorie intake is matched to minimally processed diets. This suggests that food quality, not just quantity, influences inflammatory biology.

One proposed mechanism centres on the gut barrier. Certain additives, particularly emulsifiers used to improve texture and prolong shelf life, have been shown to alter the gut microbiome and interfere with tight junction proteins that maintain the intestinal wall. When these junctions are disrupted, the gut lining becomes more permeable, allowing bacterial fragments such as lipopolysaccharides (LPS) to enter the blood stream. LPS acts as a potent immune stimulus, triggering the release of inflammatory cytokines in a process described as metabolic endotoxemia.

For someone with eczema, this low-grade systemic immune activation may be significant. If inflammatory signals are already elevated due to gut barrier disruption, the immune system may be more easily pushed toward further activation in the skin. Increased gut permeability can reinforce the same inflammatory cycle seen in eczema: greater barrier disruption leads to heightened immune signalling, which further reduces filaggrin and weakens the skin’s ability to hold moisture and protect against irritants, ultimately keeping the inflammatory cycle going.

Fibre, the Microbiome, and Short-Chain Fatty Acids

One of the clearest links between diet and inflammation is dietary fibre intake. Fibre, found in vegetables, legumes, whole grains, nuts, and seeds, cannot be broken down by human digestive enzymes. Instead of being absorbed in the small intestine, it travels to the colon, where it becomes fuel for specific bacteria that live there. When these bacteria ferment fibre, they produce short-chain fatty acids (SCFAs), including butyrate, acetate, and propionate. These compounds are not insignificant by-products; they act as important signalling molecules that influence both gut health and immune regulation.

Butyrate serves as a primary energy source for the cells lining the colon and helps maintain the tight junctions that hold those cells together. By supporting these structural connections, it strengthens the gut barrier and reduces the likelihood that microbial fragments pass into circulation. SCFAs also shape immune behaviour more directly. They promote the development of regulatory T cells (Tregs), which function as the immune system’s braking system, preventing excessive or misdirected inflammatory responses. When fibre intake is sufficient and SCFA production is strong, immune signalling tends to remain more balanced and restrained.

But when fibre intake falls short and SCFA production drops, immune regulation becomes less steady. In people with eczema, whose immune systems are already prone to overreacting, this can tilt the balance further toward inflammation. The skin barrier may then struggle to recover fully between exposures, allowing irritation and flares to persist more easily.

Fatty Acid Balance and Inflammatory Mediators

Both omega-6 and omega-3 fatty acids are essential polyunsaturated fats, meaning they cannot be produced by the body and must be obtained through diet. Once consumed, they are incorporated into cell membranes and used to produce signalling molecules that regulate inflammation, blood flow, and immune activity. As mentioned at the start, inflammation itself is not harmful – it is a necessary part of healing and defence. However, the types of fats we eat can influence how strongly (or how calmly) inflammatory pathways are activated and how efficiently they are resolved. 

Omega-6 fats are found in high amounts in industrial seed oils such as soybean, corn, sunflower, safflower, and cottonseed oil. These oils became widely used after the Second World War and are now common ingredients in processed foods, ready meals, snack foods, baked goods, fried foods, fast food, margarine, and many restaurant meals. As consumption of ultra-processed foods increased, so too did overall omega-6 intake. 

Omega-3 fats are found in oily fish such as salmon, sardines, mackerel, and anchovies, as well as in flaxseeds, chia seeds, walnuts, and algae-based foods. While omega-6 fats can be converted into compounds that promote inflammation when required, omega-3 fats give rise to molecules that help dampen and resolve inflammation once a response has occurred. Both fats are necessary, but modern diets tend to contain far more omega-6 than omega-3.

Growing research suggests that this imbalance may have meaningful consequences. When omega-6 intake consistently outweighs omega-3 intake, the body may favour the production of pro-inflammatory signalling molecules over inflammation-resolving ones. Over time, this can contribute to a state of low-grade, sustained inflammation rather than a tightly regulated inflammatory response that switches off efficiently. Reducing reliance on foods high in industrial seed oils while increasing intake of omega-3-rich foods may help restore a more balanced ratio. By shifting that balance, the body may be better able to regulate inflammatory responses rather than remaining in a persistently reactive state.

Micronutrients, Polyphenols, and Oxidative Stress

Inflammatory signalling is also shaped by micronutrients; the vitamins and minerals the body requires in smaller amounts in order to function properly. Nutrients such as magnesium, zinc, selenium, and vitamin D play important roles in immune regulation:

  • Magnesium is involved in hundreds of enzymatic reactions throughout the body, including processes that regulate inflammatory responses. Adequate magnesium levels help keep immune signalling proportionate rather than excessive.
  • Zinc supports the development and function of immune cells and helps maintain the integrity of epithelial barriers (protective cell linings such as the skin and gut), which are critical for preventing unwanted substances from triggering immune activation.
  • Selenium contributes to antioxidant defence systems by supporting enzymes that neutralise reactive oxygen species, thereby limiting oxidative stress and the inflammatory signalling it can provoke.
  • Vitamin D influences how immune cells respond to both genuine threats and harmless environmental stimuli, helping to guide the immune system toward a more balanced and controlled reaction.

Beyond vitamins and minerals, plant foods provide compounds known as polyphenols. These are naturally occurring chemicals found in berries, leafy greens, herbs, spices, tea, coffee, and dark chocolate. Polyphenols act as antioxidants, meaning they help neutralise reactive oxygen species; unstable molecules produced during metabolism and inflammation that can damage cells if left unchecked. By reducing oxidative stress and influencing inflammatory signalling pathways, polyphenols contribute to a more regulated immune environment.

Diets rich in colourful, minimally processed plant foods tend to supply a broad spectrum of these micronutrients and plant compounds. When dietary variety is limited, particularly in patterns dominated by refined or ultra-processed foods, intake of these protective compounds often falls. Increasing plant diversity in the diet does more than improve nutrient intake; it supports antioxidant defences, helps regulate immune responses, and contributes to a more stable internal environment in which inflammation is less likely to become chronic.

Stress, Lifestyle, and Immune Reactivity

Diet isn’t the only factor that influences inflammation. The immune system also responds to the overall environment we create through our daily habits. Chronic stress, for example, alters cortisol rhythms and affects how immune cells communicate. In short bursts, stress hormones are adaptive and protective. But when stress becomes persistent, cortisol signalling can become dysregulated, disrupting normal immune balance. Stress also influences digestive rhythm and gut function, affecting how quickly food moves through the gut and altering the microbiome. Over time, this can shift the body into a pro-inflammatory state.

Sleep plays an equally important role in immune regulation. During deep sleep, the body carries out much of its repair and regulatory work, including recalibrating immune activity. When sleep is shortened or fragmented, this restorative process is interrupted. Studies show that even short-term sleep deprivation can increase circulating inflammatory markers such as interleukin-6 (IL-6) and C-reactive protein (CRP). Persistent sleep disruption may therefore create a background of low-grade inflammation that the body struggles to fully resolve. The immune system becomes more easily activated and slower to return to baseline.

A lack of physical activity can further compound these effects. Regular movement improves insulin sensitivity, supports healthy circulation, and helps regulate inflammatory signalling. By contrast, prolonged sedentary behaviour is associated with metabolic changes that favour chronic, low-level inflammation. When stress, sleep disruption, and inactivity occur alongside poor dietary patterns, their effects do not remain isolated. They overlap and reinforce one another, gradually shifting the body toward a more reactive physiological state in which inflammatory responses are triggered more readily and settle more slowly.

What a Lower-Inflammatory Pattern Means for Eczema

Diets associated with lower inflammation focus on plant diversity, fibre intake, omega-3–rich foods, minimally processed ingredients, and stable blood sugar regulation. These elements work together rather than independently. A fibre-rich diet supports the production of short-chain fatty acids in the gut, which help maintain barrier integrity and promote regulatory immune activity. Omega-3 fats contribute to the resolution of inflammation rather than its persistence. Minimally processed foods reduce exposure to additives and excessive Omega-6 intake that may disturb gut and metabolic balance. Stable blood sugar patterns reduce oxidative stress and limit unnecessary activation of inflammatory pathways.

For individuals with eczema, this broader inflammatory environment matters. When systemic inflammation is elevated, immune signalling may already be primed toward reactivity. In that context, relatively minor triggers, such as environmental irritants entering through a disrupted skin barrier, may provoke stronger and longer-lasting inflammatory responses. A lower-inflammatory dietary pattern does not directly “repair” the skin, but it may reduce the background immune activation that makes flares more likely to escalate.

It is important to approach this realistically. Eczema remains multifactorial, involving genetic susceptibility, structural barrier proteins such as filaggrin, immune dysregulation, environmental exposures, and stress. However, diet influences several of the upstream systems that shape overall immune tone, including gut barrier integrity, microbial composition, oxidative stress levels, and fatty acid balance. In many individuals, modifying these inputs through a healthy diet may reduce the likelihood and intensity of eczema flares, and prevent its persistence.

More on this topic

Understanding the Gut-Skin axis​

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The effect of & Nutrition on Inflammation

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