Dietary Defenses and Nutrition for Immunity

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Nutrition has a significant impact on immunity throughout the lifespan. In the womb, a child acquires passive immunity by getting antibodies through the placenta and, after birth, through nursing (Lokossou et al. 2022). Throughout the rest of a person’s life, dietary choices will continue to strongly influence various functions of the immune system, such as innate and adaptive responses (Tourkochristou, Triantos & Mouzaki 2021). (See “Innate, Adaptive and Inflammatory Systems: An Overview,” below, for more on these key terms.)

Adequate nutrition will fortify the body’s epithelial (barrier) membranes with trained immune cells, hold microbes and pathogens at harbors, and identify and eliminate abnormal tissue growths, or neoplasms.

Fitting diet and nutrition for immunity should contain foods and other active substances that are known to stimulate and balance immune responses. What follows is a discussion of several specific diets and nutrient powerhouses that offer immune-friendly effects.

Diets and Nutrition for Immunity

Unbalanced diets may have negative, undesirable effects on immunity. For example, the high incidence of immune-related disorders in Western countries is often linked to high calorie intake, excessive carbohydrates and saturated fats, and lack of fibers in the diet. However, several diets are considered to be very beneficial for the immune system.

The Mediterranean Diet

The Mediterranean diet, one of the most immune-friendly regimes, is defined by the high intake of plant-originated foods; a balanced consumption of dairy products, eggs and sea foods; and a limited intake of red meat and sweets. This diet provides a healthy omega-6 to omega-3 ratio, with omega-3 fats coming from fish and vegetables (such as green vegetables), as well as seeds and nuts (Casas, Sacanella & Estruch 2014).

Healthy and anti-aging properties of the Mediterranean diet might be related to its immunoregulatory and antiinflammatory effects, which are mediated by isoflavones, vitamins, minerals and omega-3 fatty acids (Di Danielle et al. 2017). Omega-3 fatty acids decrease inflammation by suppressing migration of white blood cells, their adhesion to the walls of blood vessels, and the release of pro-inflammatory (inflammation-promoting) molecules (Calder 2017).

Furthermore, extra virgin olive oil, one of the key components of the Mediterranean diet, contains large quantities of polyphenols known to quench inflammation due to their antioxidant and anti-inflammatory powers (Bonaccio et al. 2017).

See “Gut Microbiota and the Mediterranean Diet,”  below, for how this nutritional approach may indirectly improve immunity.

The Ketogenic Diet

The ketogenic diet, which is characterized by low carbohydrate intake and high fat consumption, has been a part of several therapeutic strategies. This diet increases the intake of fatty acids and stimulates production of ketone bodies, which act as both a fuel source and immunoregulatory molecules.

For instance, ketone bodies show the capacity to decrease inflammation and therefore have a therapeutic potential for preventing and curing allergies and autoimmune disorders (Ang et al. 2020). In addition, a ketogenic diet may help to fight infections. In fact, there is evidence that it activates a specific subtype of lymphocytes in the lungs and thus strengthens protective immunity against the flu virus (Goldberg et al. 2019). On the other hand, a high-carbohydrate diet may stimulate immune cells in patients with inflammation and autoimmunity (Zhang et al. 2019).

Calorie-Restricted Diets

Although the effects of caloric restriction on the immune system have not been studied extensively, it is well known that obesity is a strong trigger of inflammation (Zhang et al. 2019). Currently available data points out that reduced food intake can regulate immune processes. For example, a moderate food restriction has been shown to activate T lymphocytes, which protect against infection and autoimmune inflammation (Ahmed et al. 2009; Okawa, Nagai & Hase 2021). In addition, calorie restriction may stimulate antitumor immunity (Pistollato et al. 2021). Furthermore, limiting calorie intake may help rejuvenate the immune system, as calorie restriction delays T lymphocyte deterioration in studies using nonhuman primates (Messaoudi et al. 2006).

One caveat: Despite the obvious benefits of moderate calorie restriction for the immune system, undernutrition may cause a severe immunodeficiency by suppressing the growth of immune cells, the production of antibodies and the process of phagocytosis, whereby cells engulf and digest other cells, including pathogens (Alwarawrah, Kiernan & MacIver 2018).

See also: Immunity: A Trend Worth Supporting

Individual Substances in Nutrition for Immunity

Surprisingly, the effects of spices are not limited to gustatory and olfactory pleasures: Our immunity can in fact be “spiced up” by their nutrients.

Spices, vitamins and minerals are among the powerhouses within nutrition for immunity.

Superior Spices

Spices were consumed by humans for centuries and deserve the close attention of dietitians and nutritionists. Surprisingly, the effects of spices are not limited to gustatory and olfactory pleasures: Our immunity can in fact be “spiced up” by their nutrients. For instance: Garlic can regulate immune homeostasis by activating immune cells and regulating the production of bioactive molecules (Melguizo-Rodriguez et al. 2022).

Ginger, another phytonutrient, acts as an antioxidant and anti-inflammatory nutrient and therefore can potentially be used for inflammatory disorders.

Curcumin, a yellow-hued spice obtained from Curcuma longa (turmeric) plants, has been found to suppress pro-
inflammatory T lymphocytes and the production of pro-inflammatory molecules (Tripathy et al. 2021).

Vivid Vitamins

In the kaleidoscope of immunoregulatory molecules, vitamins have a vital place, as vitamin deficiencies in plasma concentrations can dramatically suppress the immune functions (Djukic et al. 2014). Multiple nutritional and clinical studies have identified vitamins that may boost the defense mechanisms of the human body. Among them:

Vitamin A. Vitamin A is found in both fruits and vegetables and regulates both innate and adaptive immunity (Stephensen 2001). Carrots, mangoes, spinach, apricots, sweet potatoes and squash provide the best supply of vitamin A (Huang et al. 2018).

Vitamin C. Powerful antioxidant and immunostimulatory functions characterize vitamin C, which is present in many fruits and veggies (Carr & Maggini 2017). Some of the highest stores are found in citrus fruits, kiwifruit, strawberries, tomatoes and white potatoes, as well as in crucifers like broccoli, cauliflower, cabbage and Brussels sprouts (HSPH 2020).

Vitamin D. Interestingly, vitamin D possesses both immunostimulatory and immunosuppressive effects (Athanassiou, Mavragani & Koutsilieris 2022). In addition, vitamin D blocks inflammatory pathways and therefore prevents inflammation (Trochoutsou et al. 2015). Specific sources include cod liver oil, fish (salmon, swordfish, tuna, sardines), D-fortified juices and milks, fortified cereals, egg yolks and beef liver (HSPH 2022).

Vitamin E. Green leafy vegetables and dried fruits are a source of vitamin E, which stimulates immune responses and decreases infections in the elderly (Reider et al. 2020).

Remarkable Minerals

The supply of minerals is highly valuable for the functioning of both the innate and adaptive immune system, including antimicrobial defense mechanisms and the long-term balance of pro- and anti-inflammatory regulation. In particular, lack of copper, iron, magnesium, selenium and zinc in the diet may diminish the immune response.

Copper. Small quantities of copper are needed for many physiological functions, and balancing copper in the body helps to enrich immune responses. In line with this, copper deficiency appears if the daily intake falls below 0.8 mg/day and causes reduced antibody production and cellular immunity. The most significant sources of copper are liver, shellfish, nuts, vegetables and mushrooms (Altarelli et al. 2019).

Iron. The most common nutrient deficiency is iron-deficiency anemia, which affects approximately 25% of the world’s population and is caused by an insufficient supply of iron (Coad & Conlon 2011). Deficiency of this mineral impairs proliferation of B lymphocytes, decreases antibody production and inhibits function of the T lymphocytes (Mullick et al. 2006; Jiang et al. 2019). Iron supports the development and functions of both red and white blood cells. Meat, fish, chicken, seafood, legumes, eggs and vegetables can be named among the top food sources of iron (Beck et al. 2021).

Magnesium. Magnesium regulates many functions of the immune system, such as innate and adaptive immune responses and inflammation. For instance, by affecting macrophages, the key cells of the innate immune system, magnesium supplementation decreases production of pro-inflammatory molecules and therefore suppresses inflammation (Sugimoto et al. 2012). As to the adaptive immune system, magnesium directly influences the growth and differentiation of the lymphocytes (Feske, Skolnik & Prakriya 2012). Good sources of magnesium include spinach, oats, nuts, potatoes and lentils (Volpe 2013).

Selenium. Sufficient selenium is required for the immune system, as proteins containing selenium also regulate inflammatory responses (Huang, Rose & Hoffman 2012). Oats, wheat, brown rice, sunflower seeds, nuts and mushrooms are the foods that are especially rich in selenium. In addition, meat, tuna, salmon and shellfish are selenium-enriched foods of animal origin (Kieliszek 2019).

Zinc. The protective function of zinc as an anti-inflammatory microelement has been extensively documented (Planeta Keep 2022). Zinc is directly involved in the maintenance of both the innate and the adaptive immunity. As a result, having an adequate supply of zinc may shield people from viral infections by preventing viruses from entering their tissues and growing in their cells (Read et al. 2019). Among plant foods, wild rice, pasta, oats, chickpeas and spinach are especially rich in zinc. In ad-
dition, oysters and dairy products are good sources of zinc (Murphy, Willis & Watt 1975).

See also: Helping Clients Enjoy the Taste and Culture of Food

Can Diets Prevent and Cure?

Can a diet have both preventive and therapeutic effects for immune-mediated diseases, such as allergies and autoimmunity? Based on the latest research, the answer is yes. Here are a few specific examples.

Allergies. Multiple studies have shown that a healthy diet helps prevent allergic reactions in infancy. Both increased nutritional diversity and allergen diversity during the first year of life correlate with the diminished risk of food allergies over the first 10 years of a child’s life (Venter et al. 2020a).

Autoimmune disorders. Plant-based nutrition for immunity, such as Mediterranean and vegetarian diets, provides anti-inflammatory nutrients, which might protect against autoimmunity (Estruch 2010). For instance, quercetin, found in onions and garlic, shows potent anti-inflammatory and antioxidant effects (Azeem et al. 2022).

Furthermore, antioxidant vitamins A, D and E might be helpful in suppressing autoimmune reactions. Clinical studies have found a link between vitamin D deficiency and the development of autoimmune diseases (Athanassiou, Mavragani & Koutsilieris 2022).

Viral infections and infectious diseases. Nutritional activation of the immune system might be beneficial for prevention and, perhaps, treatment of viral infections (Calder et al. 2020). Primarily, fruits and vegetables provide a plethora of vitamins, minerals and other active nutrients, which give our immune system the strength to resist microbial infections.

Also, antimicrobial activity of different plants and herbs, such as garlic, ginger and black pepper, might be beneficial for prevention of infectious diseases via activation of the immune cells (Singh et al. 2021).

See also: The Food-Inflammation Connection

Connecting the Dots in Nutrition for Immunity

Additional studies are required to understand the effects of various diets and nutrients on the immune system and allow disease-specific dietary strategies to be developed with high certainty. Still, overall, the close connection between nutrition and immunity provides an exceptional possibility to create individual therapeutic approaches to prevent and cure immune, infectious and other diseases.

Healthy and immune-friendly diet plans and individual active substances, such as spices, vitamins and minerals, may ameliorate inflammation and positively modify the immune status. While more research is needed, today’s findings provide fitness and nutrition professionals with yet another set of benefits to help them encourage healthier eating among clients.