The role of diet in maintaining overall health has long been recognised, but recent research has brought to light the significant impact nutrition has on the immune system. From keto diets to intermittent fasting, nutrition trends are everywhere, often claiming miraculous health benefits.
One area attracting particular attention is the connection between food and immunity. The foods we consume fuel our bodies and play a pivotal role in shaping immune responses, modulating inflammation, and influencing susceptibility to infections and diseases. It turns out that the relationship between diet and immune function is not just about folklore or trendy diets – it is a growing field of science, and researchers are uncovering some promising links between the two.
The connection between nutrition and immunity is not a contemporary concept. The Indian Ayurvedic system of medicine has long recognised the relationship between diet, lifestyle and health, advocating natural foods, herbs, and spices to strengthen immunity and promote overall wellness. Hippocrates, the progenitor of medicine, famously stated, “Let food be thy medicine.” For decades, practitioners have acknowledged that our dietary choices influence our health. However, it was not until the early 20th century that scientists commenced a more careful examination of these connections.
In 1912, Polish biochemist Casimir Funk posited that specific ailments, such as scurvy, were caused by the deficiency of essential nutrients he termed “vitamines.” This study was a significant milestone, as it revealed that nutrients are crucial in illness prevention and health maintenance. Advanced methods such as genomics and proteomics enable researchers to investigate how particular foods and dietary habits can enhance or impair our immune system.
The gut and immunity link
The enthusiasm regarding diet and immunity predominantly centres on the gut. The digestive system harbours trillions of bacteria, collectively referred to as the gut microbiome. These bacteria facilitate food decomposition, synthesise vitamins, and—most crucially for immunity—interact with human immune cells.
A balanced microbiome is essential for a robust immune system. Fibre-rich diets comprising fruits, vegetables, and whole grains support healthy bacteria, whereas diets abundant in processed foods and sugars can disrupt this equilibrium. Researchers are discovering that disturbances in the gut microbiota may be associated with inflammatory disorders and autoimmune diseases. A groundbreaking study published in Cell (2023) demonstrated how specific gut bacteria can influence the body’s ability to respond to vaccinations. Diets rich in fibre, prebiotics, and probiotics were shown to promote a healthier gut microbiome, which in turn bolstered immune function.
Fibre: Going beyond roughage
One of the most exciting developments in this field is the discovery of how dietary fibre—found in abundance in plants—can impact immune responses. Steven Van Dyken, an immunologist at the Washington University School of Medicine in St. Louis, Missouri, has been investigating how chitin, a fibre present in mushrooms, crustaceans, and insects, activates a form of immune response referred to as type 2 immunity. This response, generally triggered by allergies and parasites, also contributes to metabolic processes.
Van Dyken’s research on mice showed that chitin stimulated this immune response and affected metabolism. Mice consuming high-chitin diets exhibited notable alterations in their digestive systems and metabolic processes, indicating that adjusting fibre consumption may effectively manage obesity and associated conditions such as diabetes. This discovery paves the way for nutritional interventions for obesity-related diseases, utilising a straightforward approach.
High-fat diets compromise the immune system
Conversely, high-fat diets have been demonstrated to compromise the immune system in multiple ways. Obesity is recognised as impairing immune function, and the relationship between high-fat diets and immunological disturbance is evident.
High-fat diets can aggravate illnesses such as psoriasis, an autoimmune disorder characterised by the fast proliferation of skin cells, resulting in scaly areas. Researchers discovered that obese mice exhibited a reduced quantity of regulatory T cells in their epidermis, which are typically responsible for modulating inflammation. The mice exhibited more severe psoriatic symptoms compared to their slim counterparts.
This indicates that our dietary choices influence our waistlines and significantly impact immunological modulation, either exacerbating or mitigating chronic inflammatory disorders. Decreasing fat consumption may alleviate these immunological disturbances.
The potential of fasting
Although excessive consumption adversely impacts the immune system, what are the implications of reduced intake? Intermittent fasting, a regimen involving alternating times of consumption and abstention from food, has surged in popularity due to its prospective health advantages, and evidence suggests that fasting may also enhance immune function.
During fasting, immune cells known as monocytes, which usually circulate in the bloodstream to detect pathogens, withdraw to the bone marrow. This briefly alleviates inflammation, providing the body respite from the continuous activation of immunological responses. Nonetheless, the situation is not entirely favourable. Upon the cessation of fasting, the influx of monocytes into the bloodstream may provoke an inflammatory response, which can be detrimental in specific circumstances.
The intricate relationship that connects fasting, food, and immune function indicates that fasting may be a double-edged sword. Although it may provide short-term advantages, excessive or extended fasting could undermine the immune defence, especially when an individual is susceptible to illnesses.
Personalised nutrition
With the growing field of nutrigenomics, researchers are now exploring how individual genetic variations influence responses to certain nutrients. Personalised nutrition strategies, which take into account genetic makeup, lifestyle, and individual health conditions, are gaining momentum. Studies indicate that tailoring diets based on an individual’s unique biological markers could optimise immune function and reduce disease risk.
Researchers are examining how individual variances—such as genetics, microbiome makeup, and lifestyle—can affect the body’s response to certain diets.
A recent study by immunologist Yasmine Belkaid and physiologist Kevin Hall examined the impact of two distinct diets—ketogenic (high-fat, low-carbohydrate) and vegan (low-fat, plant-based)—on participants’ immune systems. During a four-week period, they observed that both diets induced significant alterations in immune cell populations and activity, albeit through distinct mechanisms. The ketogenic diet improved adaptive immunity, which is the body’s targeted reaction to specific infections, but the vegan diet augmented innate immunity, the body’s general and swift defence mechanism.
These findings indicate that various diets can uniquely influence our immune systems, and future dietary advice may become significantly more customised to individual requirements and health circumstances.
The connection between diet and immunity is undeniable. The foods we eat can either support a strong, balanced immune system or weaken it, leaving us more susceptible to infections and chronic diseases. As research continues to unravel the complex interplay between nutrition and immunity, one thing remains clear: a nutrient-rich, balanced diet is one of the most powerful tools we have to maintain optimal immune health.
As scientific advancements progress, it is plausible that physicians may recommend customised diets within the next decade to address immune-related disorders, including cancer and autoimmune diseases. In the future, nutrition recommendations may become as specific and individualised as pharmaceutical prescriptions, adapted to an individual’s own biology and health requirements
(Dr. Biju Dharmapalan, is Dean (Academic Affairs) at Garden City University, Bengaluru and Adjunct Faculty at National Institute of Advanced Studies, Bangalore. bijudharmapalan@gmail.com)
Published – November 14, 2024 06:00 pm IST
