KSR: What are the key reasons for looking at micronutrients in terms of immune health?
ME: Balanced nutrition, which provides all the essential nutrients we need, is important to support an effective immune function. This is particularly relevant with the current situation regarding the spread of coronavirus infections; the immune system is the body’s first line of defence. A well-functioning immune system helps to reduce the risk of viral infections, its duration and severity.
Several vitamins and minerals play an important and complementary role in supporting the immune system — especially vitamins A, B6, B12, C, D, E and folate, and the minerals zinc, iron, selenium, magnesium and copper. A deficiency or marginal status in these micronutrients can negatively affect the immune function and decrease resistance to infections.
This is also recognised by the European Food Safety Authority (EFSA), as health claims have been granted for a number of these micronutrients supporting their contribution to the normal function of the immune system. Next to these micronutrients, omega-3 fatty acids also support an effective immune system, specifically by helping to resolve the inflammatory response.
For some of these micronutrients, an intake greater than the daily nutrient recommendations (RDA) is beneficial for optimal immune function. In addition, the requirements increase for certain micronutrients during periods of illness. A well-known example is vitamin C because levels in the body decrease during times of infection.
For a strong immune system, an intake of 200–500 mg per day is recommended for healthy people. This can be achieved by eating three oranges or two kiwi fruits every day or by taking a supplement. Vitamin C requirements change depending on health status, and an intake of 1–2 g per day is helpful for people who are sick.
Another example is vitamin D. Human studies have shown that a daily intake of 2000 international units (IU) is effective in reducing the risk of respiratory tract infections. In this case, supplementation is the only way to achieve this intake, as it is difficult to obtain this dose via the diet.
Supplementation with micronutrients and omega-3 fatty acids is, for these reasons, an effective and low-cost solution to support the optimal functioning of the immune system with the potential to reduce the risk of infection, including viral respiratory infections. Micronutrient supplements offer a safe option to complement the diet, eliminate micronutrient gaps and help to support the immune system.
Professor Manfred Eggersdorfer
Intakes above the daily nutrient recommendations, as mentioned, are within the recommended safety limits (upper limits) set by expert authorities, such as EFSA and the Institute of Medicine (IOM).
KSR: Although nutritional supplementation will not necessarily prevent infections or cure the disease, clinical data, although inconsistent, appears to support a potential for micronutrient supplementation to reduce the risk and/or severity of infections. Can you describe any examples?
ME: Vitamins and minerals collectively have a function within the innate and adaptive immune system. The innate immune system responds rapidly to infections. Vitamins support the development and maintenance of the physical barriers, are connected to the production and activity of antimicrobial proteins and are involved in the growth, differentiation and motility of innate cells. They are also involved in the killing activities of neutrophils and macrophages … and in the promotion of and recovery from inflammation.
The adaptive immune response acts within days of an infection occurring and builds up a specific response to one particular pathogen. It is long-lasting and enables the body to respond to repeated infections. Micronutrients support the adaptive immune response in several directions, including lymphocyte differentiation, the proliferation and cytokine production, the production of specific antibodies and the generation of memory cells.
The roles that vitamins C and D play in immunity are well elucidated:
- vitamin C supports the function of the epithelial barrier and the growth and function of the innate and adaptive immune cells
- neutrophil (white blood cells) migration to sites of infection
- killing of microbials
- production of specific antibodies.
Healthy neutrophils and macrophages contain concentrations of vitamin C that are 50–100 times higher than the concentration of vitamin C in the plasma. A healthy person produces about 100 billion neutrophils per day. When the immune system detects pathogens and acts to destroy the invaders, the need for vitamin C increases.
Many immune cells have vitamin D receptors that affect their function. Several recent meta-analyses have shown that vitamin D supplementation reduces the risk of respiratory tract infections. Like vitamin C, vitamin D has several functions in the immune system: it promotes the production of macrophages and increases the capacity to kill pathogens.
Vitamin D is also involved in the production of inflammatory cytokines. Furthermore, vitamin D metabolites regulate the production of specific antimicrobial proteins, which kill pathogens and thus help to reduce infections. This short overview indicates that vitamin C and D have multiple roles in the immune system and an optimal intake provides several benefits for individuals who are healthy or have an infection.
KSR: How can and should food/ingredient manufacturers help to declutter the science and claims related to nutrition and immune health?
ME: In a pandemic situation, as we are experiencing now with the coronavirus, the immune system is more important than ever before to reduce the risk of infections, as well as their duration and severity.
The science supporting why we need an optimal intake of vitamins and minerals is available; scientific experts engage, communicate and advocate the important role of micronutrients in building a strong immune system. Still, public awareness of the benefits of micronutrients for immune health must be increased.
Food and ingredient manufacturers, as well as authorities, have a responsibility to translate the science into solutions for consumers. Their engagement is important, as intake surveys indicate that there are certain population groups worldwide that do not meet the recommended levels of essential nutrients. This is true for developing countries, as well as for developed countries, such as the UK, Germany, France and the US, to mention a few.
Nutrients that are not consumed according to recommendations are vitamin A, vitamin E, vitamin C, vitamin D, vitamin B12, folate and some minerals, including zinc, iron and magnesium. For some of these nutrients up to 80–90% of certain populations do not achieve the adequate or optimal intake via the diet with their current lifestyle. Also, omega-3 fatty acid intake is low or very low in most countries and regions.
We have learned from the spread of coronavirus that elderly people in particular are at a higher risk of infection. We know that in the elderly the immune system is weaker and they also often have an inadequate intake of essential nutrients. Critical nutrients for the elderly are vitamin D, vitamin B12 and omega-3 fatty acids.
I believe there is a close link between nutrient intake and status, and the risk of viral infections. Preventive care must therefore be taken to support an optimal immune system. All these immune-boosting nutrients create promising opportunities for the development of innovative new health products. Food and ingredient manufacturers can develop products enriched with essential nutrients and use their health claims as a reference for their benefits.
KSR: It seems like a great time to promote a more holistic approach to both general and immune health to prevent future pandemics.
ME: A holistic approach to nutrition and immunity is the most promising way forward. In the situation of a pandemic spread of virus infections, public health practices — such as handwashing, wearing mouth masks and avoiding physical contact — in combination with supplementation with essential nutrients for a strong immune system can help to reduce the further spread and impact of infections.
Once the pandemic has passed, we can care for our body and long-term well-being by leading a healthy lifestyle. We can contribute to this through a balanced diet, combined with the use of fortified food products and/or supplements to fill nutritional gaps.
An optimal intake and status of the essential nutrients is the basis for good health and well-being, performance and healthy ageing. A holistic approach to nutrition and immunity will contribute to public health and limit the impact of seasonal and emerging viral infections on healthcare systems worldwide.