Introduction

Inflammation is a physiological response of the immune system to injury, infection, or irritants, facilitating healing in the acute phase. However, chronic persistent inflammation, a hallmark of autoimmune and rheumatic diseases, leads to progressive damage of tissues and organs. In recent years, the interaction between diet, nutrition, and inflammation has gained significant attention. Dietary factors act as important modifiable cofactors, alongside genetic and environmental influences, in the pathophysiology of chronic inflammatory diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis, gout, etc.

Diet as a Modulator of Inflammation

Diet influences inflammatory pathways in two opposing ways.

1. Nutrition as a Friend (Anti-inflammatory Role): Certain nutrients and dietary patterns exert anti-inflammatory and immunomodulatory effects, contributing to disease prevention and control.
2. Nutrition as a Foe (Pro-inflammatory Role): Conversely, unhealthy dietary components promote oxidative stress, immune activation, and chronic inflammation, exacerbating disease processes.
3. Disease-Related Malnutrition (DRM): Chronic inflammation contributes to anorexia, increased muscle catabolism, and Insulin resistance. These collectively result in Disease-Related Malnutrition (DRM), which further worsens clinical outcomes in rheumatic diseases.

Key Anti-inflammatory Dietary Components

1. Dietary Fibersare known for their anti-inflammatory properties. Non-digestible carbohydrates in fibers are fermented by gut microbiota → Short-chain fatty acids (SCFAs) → Acetyl-CoA production > Inhibition of NF-κB+ leading to decreased proinflammatory cytokines. Additionally, fiber-rich diets are associated with high polyphenol intake, complex carbohydrates, and improved gut microbiome composition.

1. Polyphenolsare a heterogeneous group of plant-derived bioactive compounds like flavonoids, lignans, and stilbenes with antioxidant / anti-inflammatory effects. They also cause modulation of gut microbiota and reduce iNOS and COX-2 activity.

3. Omega-3 Fatty Acids– Polyunsaturated fatty acids (PUFAs), especially omega-3 fatty acids, are among the most extensively studied anti-inflammatory nutrients. Humans cannot synthesize them and must be obtained through diet. Examples are EPA (Eicosapentaenoic acid), DHA (Docosahexaenoic acid) and main sources are fatty fish (salmon, mackerel, tuna), nuts (walnuts, almonds), and plant sources (precursors). The effects of omega-6 fatty acids remain controversial, and it is advisable to have foods with a high omega 3/omega 6 fatty acid ratio.

Common food sources with the above anti-inflammatory components are green tea (EGCG – epigallocatechin gallate), fruits (berries, cherries, mango), vegetables (green leafy vegetables, tomato – lycopene), black coffee, and dark chocolate.

Common Pro-inflammatory Dietary Components 

1. Refined Sugars– Regular consumption of food with high refined sugars (processed foods stripped of their natural fibers) causes a rapid glycemic spike and formation of advanced glycation end Products (AGEs) and leads to oxidative stress, cellular damage, and inflammation.
2. Trans Fatty Acids– Found in partially hydrogenated oils, have strong pro-inflammatory effects and lead to ↑ Reactive oxygen species (ROS), cell membrane damage, altered intracellular signalling, and promotion of inflammatory pathways.

3. Saturated Fatty Acids– Role is less clearly defined. Potentially pro-inflammatory effect via oxidative stress pathways.

Common pro-inflammatory foods are refined white bread, pastries, deep-fried foods, sugar-sweetened beverages, red meat, and processed foods.

Dietary Patterns and Inflammation

There is no single “ideal” anti-inflammatory diet. However, several dietary patterns show consistent anti-inflammatory benefits:

1. Mediterranean Diet (MD): It is a predominantly plant-based diet characterized by high intake of fruits, vegetables, legumes, olive oil, with moderate consumption of fish and dairy products. It has strong anti-inflammatory effects backed by solid research over many years.
2. DASH Diet: Emphasises fruits, vegetables, and low sodium. Beneficial in metabolic and inflammatory states.
3. Paleolithic Diet: Focuses on whole, unprocessed foods with emerging evidence in inflammatory modulation.

Obesity and Inflammation

Obesity is characterized by excess fat accumulation caused by dietary caloric surplus, among other causes. Adipose tissue acts as an endocrine organ to release Inflammatory mediators like TNF-α, IL-6, and adipokines, leading to chronic low-grade inflammation. It also promotes autoimmunity by ↓ Regulatory T cells (Treg) and↑ B-cell activation. Also, pro-inflammatory cytokines → proteolysis→ Loss of muscle mass leads to sarcopenic obesity. It is one of the key risk factors implicated in the pathogenesis and perpetuation of inflammation in RA/OA/Psoriasis /PsA. 

Clinical Implications in Rheumatic Diseases

In Rheumatology, dietary influences have been explored mainly in Rheumatoid arthritis (RA), Systemic lupus erythematosus (SLE), Psoriasis, Gout, and Osteoarthritis (OA). However, only a limited number of rheumatic diseases have been systematically studied in relation to diet. Many of the above-mentioned dietary components are found to have a role in modulating disease activity in RA/SLE, although multicentric randomised controlled studies with clear outcomes are lacking. A balanced diet can help preserve the body’s homeostasis, increase periods of remission, and improve physical and mental well being /quality of life. It is wise to remember that after the disease onset, dietary interventions act as adjunct therapy (complementary) and not as a replacement for pharmacological treatment in the control of inflammation.

Conclusion

Diet plays a critical and modifiable role in the regulation of inflammation and the pathogenesis of rheumatic diseases. While certain dietary components exhibit protective anti-inflammatory effects, others contribute to disease exacerbation/perpetuation. Adopting a balanced, nutrient-rich dietary pattern—such as the Mediterranean diet—may help in reducing systemic inflammation and improving clinical outcomes. Future research should focus on disease-specific dietary strategies and personalized nutrition approaches in rheumatology.

Suggested reading: 

1) Stumpf F, Keller B, Gressies C, Schuetz P. Inflammation and Nutrition: Friend or Foe? Nutrients. 2023 Feb 25;15(5):1159

2) Gioia C, Lucchino B, Tarsitano MG, Iannuccelli C, Di Franco M. Dietary Habits and Nutrition in Rheumatoid Arthritis: Can Diet Influence Disease Development and Clinical Manifestations? Nutrients. 2020 May 18;12(5):1456.

3) Constantin MM, Nita IE, Olteanu R, Constantin T, Bucur S, Matei C, Raducan A. Significance and impact of dietary factors on systemic lupus erythematosus pathogenesis. Exp Ther Med. 2019 Feb;17(2):1085-1090.