What are the 5 nutrients to strengthen the immune system? How can you boost your immune system by following these recommendations? Vitamin C, vitamin D, zinc, selenium, and beta-glucans are key nutrients to support a normal function of the immune system
The immune system
The immune system is our body’s main defence barrier against infections. It is made up of different cells and organs that work together to protect us from viruses, bacteria and other pathogens.
Nutrients to strengthen the immune system
Nutrients such as vitamins C and D, minerals such as zinc and selenium, and beta-glucans support the proper functioning of the immune system.
However, a significant percentage of the population in Europe does not meet the recommended intakes for these vitamins and minerals.
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin with strong antioxidant activity. It protects our body’s cells from oxidative stress, contributes to the normal functioning of the immune system, acts as a cofactor in collagen synthesis, and improves iron absorption in the intestine.
Vitamin C helps to strengthen the immune system.
According to a review article, vitamin C improves the epithelial and endothelial barriers’ integrity, stimulates the immune response, and reduces the incidence of colds and pneumonia in people who engage in strenuous physical activity.
Vitamin C concentrations in plasma and white blood cells decline rapidly in the event of infection and stress. Therefore, vitamin C supplementation may help shorten the duration of colds and reduce their symptoms.
What foods contain vitamin C?
Vitamin C is found in citrus fruits, strawberries, kiwi fruit, papaya, cabbage, and peppers. It is very sensitive to heat and is destroyed during cooking. It is, therefore, preferable to eat these foods raw.
Vitamin D acts both on innate immunity by stimulating the production of antimicrobial peptides and adaptive immunity by regulating cytokines and antibodies’ production.
Adequate vitamin D levels are associated with a strengthened immune system and decreased viral and bacterial infections.
In a meta-analysis of over 11,000 patients, vitamin D supplementation has been shown to reduce the risk of respiratory tract infections. The best results were found with daily or weekly supplementation compared to monthly boluses, with vitamin D3 being more effective than D2.
According to recently published articles, the anti-inflammatory mechanisms of vitamin D may be relevant for viral infection in the same way as other viral respiratory diseases.
Achieving optimal vitamin D levels through supplementation could strengthen the immune system.
What are the main sources of vitamin D?
Vitamin D is a fat-soluble vitamin found in few foods, with fatty fish being the main dietary source.
It can be synthesised endogenously through the action of sunlight on our skin, but it is currently the most important vitamin deficiency in many countries. Therefore, it is necessary to evaluate its supplementation both to reach sufficient levels and maintain them.
Zinc is considered an essential nutrient to support the normal functioning of the immune system, particularly for cells that mediate innate and adaptive responses. It protects against oxidative stress, contributes to the integrity of hair, skin and nails, and is essential for maintaining a sense of taste.
The deficiency is associated with complications in wound healing and reduced immune response.
Where is zinc found?
Zinc is present in meats, eggs, seafood and, to a lesser extent, in whole grains and legumes.
Phytates (a form of phosphorus storage) in dietary fibre can inhibit its absorption.
Selenium contributes to a normal immune system, the proper functioning of the thyroid gland, spermatogenesis, and hair and nails maintenance. It performs several biological functions in selenoproteins, a group of enzymes dependent on this mineral.
It has an antioxidant action acting in synergy with vitamins C and E, regenerate them from their oxidised forms, and promote maximum antioxidant protection. Selenium deficiency has been associated with weakened immunity.
Where is selenium found?
In food, selenium is found in red meat, offals, seafood, fatty fish, eggs, whole grains, Brazil nuts and garlic. The amount present in plant foods varies according to the selenium content of the soil in which the plants are grown. Unfortunately, soils are becoming increasingly depleted in selenium in Europe.
There are different ways of providing selenium through dietary supplements. Organic forms provide a more effective increase in blood selenium than inorganic forms. Among the organic forms, selenium-enriched yeast provides selenomethionine which is better absorbed in our body.
Beta-glucans are a type of dietary fibre (polysaccharides) found in cereals, algae, mushrooms and yeast. They are made up of long chains of polysaccharides with different structures and properties depending on their origin. The beta-1,3/1,6-glucans of fungi and yeasts have the highest immunomodulatory activity.
They act by improving the innate immune system’s response and balancing the adaptive response.
The synergy between beta-glucans and vitamin C
Beta-glucans have a strong synergy with vitamin C to strengthen the immune response.
In a randomised clinical trial of 175 children over 12 months, 100 mg of beta-glucans and 100 mg of vitamin C were administered compared to vitamin C alone. The beta-glucan group had more children free of respiratory infection than the placebo group and significantly reduced influenza incidence.
It has also been shown in clinical studies that beta-glucan supplementation can reduce markers of inflammation after intense and prolonged exercise.
Author: Anna Paré Vidal
Avery JC, Hoffmann PR. Selenium, Selenoproteins, and Immunity. Nutrients. 2018 Sep 1;10(9):1203.
Bonaventura et al. Zinc and its role in immunity and inflammation. Autoimmun Rev. 2015 Apr;14(4):277-85.
Brenner H, Holleczek B, Schöttker B. Vitamin D Insufficiency and Deficiency and Mortality from Respiratory Diseases in a Cohort of Older Adults: Potential for Limiting the Death Toll during and beyond the COVID-19 Pandemic? Nutrients. 2020 Aug 18;12(8):2488.
Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017 Nov 3;9(11):1211.
Charoenngam N, Holick MF. Immunologic effects of vitamin D on human health and disease. Nutrients. 2020 Jul 15;12(7):2097.
De Marco, Calder PC, Roche HM. Beta-1,3/1,6-Glucans and Immunity: State of the Art and Future Directions. Mol Nutr Food Res. 2020.
Harbige L, Calder P, Marcos A, Dardenne M, Perdigón G, Perez-Cano F, Savino W, Slobodianik N, Solano L, Valdes R. ISIN position statement on nutrition, immunity and COVID-19. International Society for Immunonutrition (ISIN). Board members (March 2020).
Ilie et al. The role of vitamin D in the prevention of coronavirus disease 2019 infection and mortality. Aging Clin Exp Res. 2020 Jul;32(7):1195-1198.
Kaufman et al. SARS-CoV-2 positivity rates associates with circulating 25-hydroxyvitamin D levels. PloS One. 2020 Sep 17;15(9):e0239252.
San Mauro-Martín, Garicano-Vilar E. Papel de la vitamina C y los beta-glucanos sobre el sistema inmunitario: revisión. Rev Esp Nutr Hum Diet. 2015;19(4):238-245.
Skalny et al. Zinc and respiratory tract infections: Perspectives for COVID-19 (Review). Int J Mol Med. 2020 Jul;46(1):17-26.