Adequate and appropriate nutrition is vital for optimal functioning of all cells, including immune cells¹. Optimal nutrition helps immune cells initiate effective responses against pathogens, respond rapidly when needed and prevent chronic inflammation¹.

Certain micronutrients and dietary components play specific roles in developing and maintaining an effective immune system and reducing chronic inflammation¹.

Excessive intake of certain micronutrients can also impair immune responses, such as iron supplementation increasing morbidity and mortality in malaria-endemic regions¹.

The gut-associated lymphoid tissue (GALT) houses a majority of immune cells in the human body, under­scoring its significance in maintaining overall host health¹. The gut lumen contains the human gut microbiome, which provides antigens and signals that can interact with local and systemic immune cells¹. The composition of the gut microbiome changes throughout life in response to dietary factors and environmental influences like antibiotic use¹.

Several nutrients and dietary interventions have shown promising effects in improving gut health and reducing inflammation¹. The Mediterranean diet, characterized by consuming vegetables, fruits, nuts, legumes, fish, and healthy fats, has been associated with a lower risk of chronic diseases such as cardiovascular disease, cancer and Alzheimer’s disease¹. Fruits and vegetables contain bioactive compounds, including dietary polyphenols, that have immunomodulatory and anti-inflammatory properties¹.

Zinc is a cofactor in numerous proteins, and even a mild deficiency can impair both the adaptive and innate immune response. During sepsis, zinc homeostasis is disrupted, which has implications for therapeutic strategies in septic patients¹.

Selenium plays crucial functional, structural, and enzy­matic roles in various proteins, and maintaining optimal selenium status is vital for immune function and reducing the risk of chronic diseases such as cancer and cardiovascular disease¹.

Vitamin A plays a crucial role in regulating both innate and cell-mediated immunity². Its deficiency leads to increased susceptibility to infections and impaired immune function². Vitamin A deficiency affects cytokine release, antibody production and the function of various immune cells². Vitamin A promotes the expansion and differentiation of Th1 and Th2 cells, regulating the balance between proinflammatory and anti-inflammatory responses². Retinoic acid, a form of vitamin A, is involved in numerous biological activities and can impact intestinal inflammation and macrophage activity². Vitamin A administration has been beneficial in reducing mortality from diarrheal diseases and has shown potential antitumor effects in various cancers².

The B vitamins, including B1, B2, B3, and B12, play essential roles as co-enzymes in various metabolic path­ways and cellular functions². Vitamin B1 or thiamine, has antioxidant properties and can inhibit cytokine synthesis and antimicrobial oxidative reactions². It regulates immune metabolism by balancing glycolysis and the tricarboxylic acid cycle². Deficiency in vitamin B1 can lead to proinflammatory cytokine expression, neuro­inflammation and neuronal death². Thiamine has potential therapeutic applications in neurodegenerative diseases².

Riboflavin (vitamin B2) exhibits anti-inflammatory and antioxidant properties and activates mucosa-associated invariant T cells².

Vitamin B3 (niacin) functions as a precursor for nicotinamide adenine dinucleotide (NAD) and nico­tinamide adenine dinucleotide phosphate (NADP) cofactors involved in redox reactions, and it has anti-inflammatory effects through inhibition of the nuclear factor-kappa B pathway ².

Vitamin B12 (cobalamin) affects pro- and anti-infla­mmatory responses, and its deficiency is associated with altered immune cell populations, hyperhomocysteinemia, insulin resistance and potential links to certain cancers².

Vitamin C acts as an antioxidant, regulates immune functions and has anti-inflammatory properties². It can inhibit proinflammatory cytokines, enhance anti-inflammatory markers, modulate immune cell activity and potentially aid in the defense against microbial pathogens ².

Vitamin D exerts anti-inflammatory effects through its interaction with receptors and signaling pathways ². It can inhibit proinflammatory cytokines, regulate immune cell responses and contribute to the defense against infections². Additionally, vitamin D has been associated with anticancer effects, including apoptosis stimulation, suppression of cancer cell proliferation and inhibition of proinflammatory signaling pathways².

Arginine, an amino acid, is crucial to immune system function². It is involved in producing nitric oxide, which is important for macrophages in combating pathogens. They also play a role in the regulation of cytotoxicity by macrophages and have implications for pathogen recognition ². The enzyme arginase-1 (Arg-1) may be involved in reducing inflammation through its anti-inflammatory action².

Tryptophan is essential for the activity of the immune system². Tryptophan metabolism and its metabolites can influence immune signaling and metabolic pathways, and the balance between kynurenine and tryptophan can have anti-inflammatory effects². The kynurenine pathway regulates inflammation, mediated by enzymes such as indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase. The kynurenine/tryptophan ratio may be a marker for inflammation in various conditions ².

Glutamine, a nonessential amino acid, is an energy source and precursor for nucleotide synthesis, vital for rapidly dividing immune cells during immune responses¹. It plays a role in the functions of immune cells and is depleted in critical illness, highlighting the potential for clinical nutrition supplementation in critically ill patients¹.

Cholesterol plays a critical role in immune responses, particularly in the functionality of cellular membranes, especially the plasma membrane². It is essential for maintaining membrane integrity, fluidity and receptor arrangement. An imbalance in cholesterol levels can lead to the deposition of lipid plaques, triggering an inflammatory process ².

Omega-3 fatty acids eicosapentaenoic acids and doco­sahexaenoic acids are essential for promoting the resolution of inflammation, including in the respiratory tract³. Consuming an adequate amount of these fatty acids produces anti-inflammatory metabolites, which help alleviate inflammation³.

In conclusion, nutrition and immune function have a strong and dynamic relationship². Nutrients are crucial in modulating immune function through pro-inflammatory and anti-inflammatory effects ². Micro­nutrients such as vitamins A, B1, B2, B3, B12, C, and D; and minerals like zinc and selenium can influence both innate and adaptive immunity through genetic, biochemical, and signaling pathways². These nutrients can impact immune cells’ proliferation, cell division, mobilization, and overall physiology².

Furthermore, certain macronutrients like tryptophan, arginine, cholesterol, and polyunsaturated fatty acids have also been implicated in preventing and treating immune-related diseases².

1. Childs CE, Calder PC, Miles EA. Diet and immune function. Nutrients. 2019;11(8):1933.

2. Munteanu C, Schwartz B. The relationship between nutrition and the immune system. Front Nutr. 2022;9:1082500. 

3. Calder PC, Carr AC, Gombart AF, Eggersdorfer M. Optimal nutritional status for a well-functioning immune system is an important factor to protect against viral infections. Nutrients. 2020;12(4):1181.