Immunity under control: The best vitamins and supplements for staying healthy

How vitamins help boost immunity

Vitamins are essential micronutrients that cannot be synthesized endogenously or are synthesized in insufficient amounts, so the main source is the diet. They support many body functions, including optimal functioning of the immune system. There are several 'immune vitamins' that play a specific role in the body's defense:

• Vitamin C: stimulates the production of leukocytes in the blood and influences the level of antibodies produced by B lymphocytes
• Vitamin D: Regulates the immune response and helps activate T cells, which are essential for defense against infection.
• Vitamin A: Maintains healthy mucous membranes, which are the first line of defense against pathogens.
• Vitamin E: Acts as a powerful antioxidant, protecting immune cells from oxidative damage.
• Vitamin B6: Supports the production of antibodies and other essential components of the immune system.

Best vitamins for the immune system

Next, we'll detail the best vitamins for the immune system, as well as some information on food sources and recommended dosages.

Vitamin C

Benefits and natural sources

Vitamin C, also known as ascorbic acid, is probably the best-known vitamin for immune defense. During infections and stress, serum vitamin C concentration and leukocytes drop rapidly. This vitamin plays a crucial role in increasing the production of white blood cells, which are essential for fighting infection. Vitamin C also contributes to the function of phagocytes, cells that engulf and destroy pathogens. Vitamin C is also a powerful antioxidant, working against the oxidative stress that occurs during infection and inflammation.

Natural sources of vitamin C include:

• Citrus: oranges, lemons, grapefruit
• Other fruits: kiwi, strawberries, guava, papaya
• Vegetables: bell peppers, broccoli, Brussels sprouts

Recommended daily intake

The recommended daily intake of vitamin C varies according to age, sex and other individual factors but is generally 90 mg/day for adult men and 75 mg/day for adult women. During infections or for smokers, in whom there is greater oxidative stress, the dose may be increased by 35 mg/day or more, as recommended by a doctor.

Vitamin D

Benefits and natural sources

Vitamin D is a fat-soluble vitamin essential for the activation of T cells and macrophages, which detect and destroy pathogens. Vitamin D deficiency has been associated with an increased risk of viral or bacterial respiratory infections, and adequate supplementation can reduce their frequency and severity. People with low vitamin D levels (<30 ng/mL) were found to be more likely to report a recent upper respiratory tract infection than those with sufficient levels.

Natural sources of vitamin D include:

• Endogen, through sun exposure: the main way the body makes vitamin D
• Oily fish: salmon, mackerel, sardines, tuna
• Fortified dairy: milk, yogurt, cheese
• Egg yolk
• Mushrooms

Recommended daily allowance

The recommended daily dose of vitamin D varies, but for most adults it is 600 IU (international units) or 15 µg per day. In severe deficiencies, a doctor may recommend higher doses for a short period of time.

Vitamin A

Benefits and natural sources

Vitamin A or retinol is an antioxidant vitamin important for maintaining the health and integrity of the mucous membranes, which form a physical barrier against pathogens. Vitamin A also plays an important role in the production and function of B and T lymphocytes in the blood and is involved in antibody production, influencing both cellular and humoral immunity.

Natural sources of vitamin A include:

• Orange and yellow vegetables: carrots, pumpkin, sweet potatoes
• Fruits: mango, apricots, melon, grapefruit
• Animal products: liver, eggs, fortified milk, salmon

Recommended daily intake

The recommended daily intake of vitamin A for adults is about 700 μg for women and 900 μg for men. Vitamin A requirements are higher during pregnancy and breastfeeding. It is important not to exceed the recommended daily allowance as vitamin A is fat-soluble and can become toxic in large amounts.

Vitamin E

Benefits and natural sources

Vitamin E is a powerful antioxidant that protects immune cells from the effects of oxidative stress. It also contributes to immunity by modulating the function of T lymphocytes, macrophages and NK cells. It is especially effective in alleviating the deterioration of the immune and inflammatory response that occurs with advancing age.

Natural sources of vitamin E include:

• Nuts and seeds: almonds, sunflower seeds, walnuts, pine buds
• Vegetable oils: olive oil, sunflower oil
• Green vegetables: spinach, broccoli, asparagus
• Fruits: avocado, mango

Recommended daily intake

The recommended daily dose of vitamin E is about 15 mg for adults. In case of supplementation, it is important not to exceed the recommended dose as high doses may interfere with blood clotting.

Vitamin B6

Benefits and natural sources

VitaminB6 is a water-soluble vitamin involved in both cellular and humoral immunity. It influences the production of antibodies and other essential components of the immune system. Vitamin B6 deficiency has been shown to impair immune function, for example by impairing the differentiation and maturation of T cells involved in cell-mediated immunity.

Natural sources of vitamin B6 are a wide variety of foods and include:

• Animal products: chicken, beef, beef, tuna, salmon, eggs, milk
• Vegetables: potatoes, spinach, carrots,
• Legumes: chickpeas, peas
• Fruit: bananas, avocado

Recommended daily intake

The recommended daily intake of vitamin B6 is about 1.3 mg for adults. The daily requirement of vitamin B6 is higher in pregnancy and breastfeeding due to increased needs, reaching 1.9-2 mg.

Other essential supplements for immunity

Zinc

Benefits and natural sources

Zinc is an essential mineral for the functioning of the immune system and people with zinc deficiency have increased susceptibility to infections. Involved in cell division and DNA replication, zinc influences most of the key mediators of immunity, such as neutrophils, macrophages, NK cells, T and B lymphocytes. Studies of daily zinc intake in children have shown that zinc reduces the incidence of acute lower respiratory tract infections by 45%.

Zinc also has antioxidant properties that help stabilize cell membranes and protect the body against reactive oxygen species.

Natural sources of zinc include:

• Seafood: oysters, crab, lobster
• Meat: beef, pork, chicken
• Legumes: chickpeas, beans, lentils
• Nuts and seeds: pumpkin seeds, cashew, hemp seeds

Recommended daily intake

The recommended daily dose of zinc for adults is about 11 mg for men and 8 mg for women. During infections or to support immune function, doses may be higher, but it is important not to exceed 40 mg per day to avoid toxicity.

Selenium

Benefits and natural sources

Selenium is another essential mineral for immunity, with a role in protecting cells against oxidative stress and regulating immunity. Adequate selenium levels are important both for initiating the immune response and for regulating excessive immune responses and chronic inflammation. Selenium deficiency has a negative impact on immune cells during their activation, differentiation and proliferation.

Selenium also helps maintain normal thyroid function, which is involved in metabolism and immunity.

Natural sources of selenium include:

• Brazil nuts: the richest source of selenium.
• Fish and seafood: tuna, sardines, shrimps
• Meat and offal: liver, kidney, beef
• Wholegrain cereals: brown rice, wheat, oats

Recommended daily intake

The recommended daily intake of selenium for adults is about 55 μg. In case of supplementation, it is important not to exceed 400 μg per day to prevent toxicity.

Probiotics

Benefits and natural sources

Probiotics are beneficial bacteria that can interact with intestinal immune cells and the gut microbiome, modulating immune function. Probiotics can stimulate cytokine production with activation of regulatory T cells, which maintain immune homeostasis in the gut lining.

A healthy gut with a well-balanced microbiome is essential for strong immunity, as most immune cells are found in the digestive tract. The gut is constantly exposed to new antigens and immune stimuli from food, but also from gut pathogens.

Natural sources of probiotics include:

• Fermented products: yogurt, kefir, kimchi, sauerkraut
• Probiotic supplements: capsules, tablets, powders

Recommended daily dose

The recommended daily dose of probiotics varies depending on the bacterial strain and the product used. It is important to follow the instructions on the product label and consult a doctor or nutritionist for specific recommendations.

How to incorporate immune-boosting vitamins into your diet

Foods rich in vitamins and minerals

Including a wide variety of vitamin and mineral-rich foods in your daily diet is essential for maintaining a strong immune system. Here are some examples of foods that can be incorporated into your diet:

• Fresh fruits and vegetables: citrus fruits, berries, green leafy vegetables, bell peppers, broccoli
• Lean meat and fish: chicken, turkey, salmon, tuna
• Dairy: fortified milk, yogurt, cheese
• Nuts and seeds: almonds, brazil nuts, sunflower seeds, hemp seeds
• Whole grains: brown rice, quinoa, oats

Tips for proper supplementation

To get the most from your immunity supplements, it's important to follow a few tips:

• Consult a specialist: Before starting any new supplement, it is recommended that you consult a doctor or nutrition specialist to determine the correct dosage and need for the supplement, based on blood tests and individual factors.
• Following the recommended dose: Always follow the directions on the product label and avoid overdose.
• Integrating supplements into your daily routine: It is important to take supplements consistently every day for them to be effective
• Combining with food: Vitamins A, D, E and K are fat-soluble and are better absorbed when consumed with foods high in healthy fats.

Avoiding overdose

Overdose of vitamins and minerals can have adverse health effects. For example, high doses of vitamin A can cause liver toxicity, excess vitamin D can lead to hypercalcemia, and excess zinc can cause gastrointestinal disorders.

Compared with water-soluble vitamins (vitamin C, B-complex vitamins), the risk of overdose is higher for fat-soluble vitamins (vitamins A, D, E, K) because they have a lower rate of elimination and a greater propensity to accumulate in the body.

To avoid overdosage, it is important to follow the recommended doses for a limited period of time, preferably as advised by a specialist, and to avoid excessive consumption of supplements, with food being the primary source.

Always consider all the micronutrient sources you use (diet, multivitamins and minerals, separate vitamins) as they may overlap and increase the risk of overdose.