Questions and answers about nutrition, immune system and the coronavirus

In the current pandemic, we observe a growing interest in the topic of immunity and health. At the same time, there has been a lot of misinformation surrounding nutrition, immune system and COVID-19. Currently, there is no scientifically proven evidence that any specific food or supplement will prevent infection with COVID-19/Coronavirus. Nevertheless, healthy nutrition remains one of the keys for sustaining immune health. In search of scientifically sound assessments, we spoke with nutritionist and epidemiologist Dr. Krasimira Aleksandrova.

Does what we eat and drink affect our immune system?

There is no doubt that our nutrition and lifestyle play an important role in determining our overall health, including sustaining a balanced immune status. What we eat and drink is essential to support the functions of immune cells allowing them to promote effective responses against pathogens. The immune system demands energy and nutrients obtained from diet and many specific nutrients have specific roles in the immune system development and maintenance. Insufficient and excessive intake of certain nutrients can lead to impairment of immune function and its capacity to respond against infections. That’s why a well-balanced diet is so important to prevent and reduce chronic inflammation that bear multiple health-deleterious consequences to the human organism. It is not important that you beware only specific foods or nutrients, but following an overall healthy dietary pattern based on variety of fresh fruits and vegetables, fermented foods (e.g., yoghurt), nuts and seeds and whole-grain cereals. In the last years, interesting findings in the gut health and its role in the immune balance have emerged. That has been suggested that around 70% of our immune system is regulated in our gut. Good gut bacteria can be favorably influenced if we eat plenty of fibrous and pre-biotic foods such as bananas, flax seeds and yoghurt rich in Lactobacillus and Bifidobacteria. On the other hand, scientific research has shown that excess intakes of high ultra-processed food rich in sugar, fats and salt plus many industrial ingredients, such as modified starches and color additives have been associated with higher level of inflammation and dysfunctional immunity. Along with good nutrition, we should not forget that the formula of good health is not complete without regular physical activity and sufficient sleeping hours.
At DIfE, we have conducted various studies all suggesting that following an overall healthy diet and lifestyle can prevent age-related diseases 1. One potential explanation behind these observed positive influences could be the role of nutritional and lifestyle factors in supporting the maintenance of a balanced immune status throughout human lifespan.

Are there indications of the relationship between nutritional factors and inflammation /immune response which we should take into account in the current pandemic?

A well-functioning immune system is crucial in the battle against COVID-19, especially because there is still no vaccine or antiviral drugs against this new virus. Nutrition could be one of the keys each of us holds to sustain balanced immune health in the current pandemic. However, this should be done based on cautious interpretation of scientific research and not based on common knowledge only. In the internet numerous myths about ‘miraculous’ foods, drinks and supplements that help to protect against COVID-19 have emerged. To date, no specific medication, herbal product or substance has been scientifically approved to either protect or fight against this virus. Attempting to boost one’s immune system is not advantageous to health and can even lead to overactivated immune system and adverse health outcomes. People may also erroneously feel protected from coronavirus and become less careful about keeping good hygiene and following strictly epidemiological measures. One should be particularly careful, when buying ‘immune stimulators’ such as supplements, additives, or any medicinal product without doctor’s consultation.

So far, a body of scientific evidence from animal and human studies suggested that immune system could be most beneficially influenced by a diet rich in antioxidant nutrients and specific minerals. Various micronutrients were particularly shown to influence the immune health such as the vitamins A, D, C, E, B6, B12 and folate and the minerals copper, iron, zinc and selenium. Among these, vitamin C, vitamin D and zinc were shown to have most significant and convincingly reported immune-balancing properties. In many instances – particularly for younger people - the intake of additional vitamins, minerals and trace elements may be superfluous. Having a balanced diet rich in fresh fruits and vegetables and regular outdoor physical activity, would be usually sufficient to provide our bodies with all the essential nutrients. Outdoor physical activity could especially relevant for people in Germany, because vitamin D deficiency is common in the European region, especially in older people. A diverse and well-balanced diet rich in colored fruits and vegetables together with practicing other healthy lifestyle behavior, such as moderate outdoor exercise supports a healthy immune function. Our research at DIfE also showed that plant-based nutrition has anti-inflammatory properties, especially diets high in whole grains, fruits, vegetables, nuts and olive oil (Mediterranean-style diet)2. Moreover, plant-based foods contain other important compounds such as polyphenols, which we also found to be associated with lower inflammation levels 3. The German Society for Nutrition (DGE) recommends a wholesome diet with predominantly plant-based foods4.

Overall, diet alone cannot replace epidemiologic and hygienic recommendations like social distancing and regular hand washing. However, the recommendation for healthy nutrition and lifestyle is of utmost importance to keep our immune systems in the right balance before, during and after COVID-19 infection.

How does age affect our immune system?

As newborns, our immune systems are immature and we rely on immunity transferred from mother’s breast milk. As bacteria and viruses invade our organism, our immunity gradually matures and strengthens. When we get older, our immune system is well prepared to fight known pathogens, but its ability to fight new infections such as the novel COVID-19 virus substantially decreases with advanced age. With age occurs a decline in immune function, known as immunosenescence, due to the deterioration of both the acquired and innate immune systems. Therefore, elderly people are at significantly higher risk of severe disease upon COVID-19 infection. Chronic inflammation or inflammaging is characteristic of ageing and important risk factor for age-related chronic diseases like cardiovascular diseases or cancer. The immune system comprises a complex interplay between a variety of molecules, cells, tissues and organs that are ready to be activated when needed in the right proportion in order to not damage the human body. Both suppressed and activated immunity is dangerous for health and therefore it is important to keep immune system in balance. Key factors for this are, as already mentioned, a healthy diet together with other beneficial lifestyle factors such as sufficient sleep, exercise and stress reduction. The International Society for Immunonutrition generally recommends elderly people to increase their intake of zinc, vitamin E, C and D. But without doctor’s consultation people should be careful with these supplements.

At DIfE, we are actively working to get more insights on this important topic. Our group is especially interested to unveil important links between nutrition, immunity and ageing, specially to understand whether innate and acquired immunity may be influenced by human nutrition particularly in aged populations and to suggest nutritional strategies that may also have the potential of lowering the risk and severity of diseases.

1 Aleksandrova, K et al, BMC Medicine, 2014 and Ford, E et al, JAMA Internal Medicine, 2009
2 Eichelmann, F et al, Obesity Reviews, 2016
3 Harms, L et al, British Journal of Nutrition, 2020
4 10 Regeln der DGE


This term refers to the permanently increased release of cytokines in advanced age. Immune cells released cytokines as part of the immune response. As a rule, these pro-inflammatory messengers are only formed as a reaction to a stimulus and then degraded again. During chronic inflammatory diseases, however, permanently elevated cytokine levels may also occur. The chronic inflammations caused by inflammaging are suspected of promoting the aging process and associated diseases such as cardiovascular diseases and cancer.