Foods that increase the immune system

Nutrition has an impact on the immune system.

The balance of the microbiota (the community of microorganisms that colonise the human body), especially the intestinal microbiota, is crucial for the immune system.

A proper diet can favourably influence both the production of molecules with anti-inflammatory activity by bacterial flora, and the proliferation of valuable resident microorganisms, to the detriment of other potentially harmful ones.

To support the immune system, it’s useful to start with a varied and balanced diet as part of a healthy lifestyle.

Following a balanced and varied diet, with the right ratio of macronutrients (proteins, fats and carbohydrates) is important for wellbeing. A protein-deficient diet is known to be associated with an increased risk of infection. Some amino acids (the ‘building blocks’ of which proteins are composed) are used as a source of energy by the cells in the immune system, regulate the expression of genes that modulate the immune response, are involved in the production of molecules that participate in the immune response, or serve to activate substances necessary for an efficient immune response.

Fats also play their part. Saturated fats (typical of foods of animal origin such as meat, eggs and milk) and so-called trans or hydrogenated fats (found in many industrial foods and also responsible for the increase in cholesterol) are associated with inflammation, while the consumption of unsaturated fats (found in vegetables and fish) is correlated with a reduction in inflammation.

Finally, carbohydrate sources can also influence inflammatory processes. Excessive consumption of refined carbohydrates, characterised by a high glycaemic index (therefore able to raise blood sugar levels very quickly), has been associated with the elevation of the inflammatory state, while the consumption of foods with a low glycaemic index (such as fruits, vegetables, nuts, seeds and whole grains) does not trigger an inflammatory response.

A high calorie intake, an excess of added sugars, the scarcity of fibre and the preferential consumption of fats with an inflammatory effect can become a non-negligible risk factor for the incidence of various diseases.

Particular molecules with antioxidant action present in various vegetables and fruit are allies of the immune system. The best known is vitamin C, a micronutrient important for the health of the body’s barriers (such as the skin), normal functioning of the immune system, and protection of cells from oxidation damage.

Other vitamins important for normal immune system function are:

• Vitamin A, which is also useful for maintaining normal skin and mucous membranes and for the process of cell specialisation
• B vitamins, in particular vitamin B6, folic acid and vitamin B12
• Vitamin D, which is also important for the absorption of calcium and phosphorus and for maintaining normal bones and teeth

Various minerals can also act as antioxidants and/or ensure the proper functioning of the immune system, which requires an adequate intake of iron, zinc, selenium and copper.

Other allies are prebiotics, substances that contribute to the balance of intestinal flora. The best known of these are dietary fibres, which act as a nutrient for the bacterial flora, promoting the growth of bacteria allied to health (such as bifidobacteria and lactobacilli), reducing the growth of pathogens and improving the intestinal barrier and the degree of inflammation thanks to the production of short-chain fatty acids resulting from their bacterial fermentation.

Probiotics (also called live milk enzymes) are microorganisms which, if they survive the passage through the gastric environment and reach the intestine in sufficient quantity, are able to exert beneficial actions on the organism, favouring, in particular, the balance of the intestinal flora.

Are there any foods that are helpful in a diet that can contribute to normal immune function?

Among the protein foods, those of animal origin with a high biological value are preferable, such as eggs, fish and lean meats (for example chicken).

Fish can also be useful as a source of omega-3, polyunsaturated fatty acids with anti-inflammatory activity.

The consumption of fruit and vegetables, especially seasonal ones, is also associated with a reduction in the levels of inflammation in the body; this positive effect is added to the benefit derived from the intake of vitamins, minerals, fibre and other molecules with antioxidant action (such as polyphenols and flavonoids), as well as a reduced calorie content of the food.

The benefits of animal-derived foods should not, however, be underestimated. Cheeses, for example, in addition to calcium, also contain other micronutrients that are valuable for the immune system. In particular, several cheeses are rich in vitamin A, which is also found in carrots, apricots, parsley, rocket, basil, tomatoes, yellow squash, radish, mango, peaches, spinach and peppers, liver and eggs.

Vitamin B6 is found in garlic, artichokes, radish, pistachios, lamb and some cheeses; folic acid is found in green leafy vegetables (such as broccoli, chard and spinach), legumes and eggs, while vitamin B12 is found in meat, offal, eggs, milk and dairy products and seafood.

Vitamin C is abundant in citrus fruits (such as oranges and lemons), berries, kiwis, peppers, parsley, rocket, broccoli, cabbage and cauliflower, lettuce, tomatoes, and also among spices, particularly chilli peppers.

Food sources of vitamin D are, however, limited: fatty fish (salmon, tuna, swordfish, herring, mackerel, sardines), eggs, milk and dairy products, mushrooms and cocoa beans.

Radish, spinach, chicory, olives, squash flowers, legumes, oatmeal, meat, eggs and dried fruit are rich in iron.

Selenium is found in fish (tuna, sardines, sole, cod), in seafood and shellfish (clams, mussels and shrimps), in meat (lamb, beef) and beans.

Zinc is abundant in meats, fish and cheeses.

Copper is very common in food.

The amounts of nutrients to be taken to meet the body’s needs are usually provided by a varied diet.

Finally, fibre is present in legumes, whole grains and their derivatives.

In most cases, following a diet that is as varied as possible, rich in fruits and vegetables and balanced, allows you to assimilate nutrients and substances useful for the immune system.

In the presence of specific deficiencies, it may, however, be useful to take, on the advice of the doctor, food supplements.

One deficiency that is becoming more prevalent in Western populations, especially of advanced age, is vitamin D deficiency.