What to Eat to Keep Your Immune System Fit

We all know the old saying, “You are what you eat.” But in these times of uncertainty, it may be more true than we realized: Yes, it is possible to support the immune system with nutrients and thus make it “fit” against infections.

“Immuno-nutrition” – i.e. strengthening the immune system by supplying it with certain nutrients – is an active field of medicine applied primarily in the setting of intensive care.  But in fact, it can also used in immunology, helping to prevent diseases and strengthen the body resistance in dealing with them. Research at the Department of Immunology and Pathophysiology from Medical University Graz has shown the role nutrition plays and how an optimal combination can support the immune system even in phases of viral infections.

And for those who are planning their Osterjause – this year at home – can also take heart:

Regional specialties such as horseradish, beetle beans and (Styrian) pumpkin seed oil are power boosters for the immune system, alongside other regional dishes.

Know Your Nutritional Status

As with many things in life, balance is crucial in nutrition, as the function of immune cells and metabolism are closely linked. “Changes in nutritional status have effects on hormones and the function of immune cells,” says Sandra Holasek, from the Otto Lowei Research Centre and the Med Uni Graz. “In civilized society, however, we often find a deficiency of micronutrients – the so-called ‘hidden hunger’ – despite an oversupply of food,” adds her colleague Sonja Lackner, “And body mass in particular has immunological significance.”

This matters in Austria where more than 41% of the population are overweight or obese. According to the latest Austrian Nutritional Breakdown, large parts of the population do not meet nutritional recommendations. Especially important micronutrients are often undersupplied, such as β-carotene, vitamin D, vitamin E, vitamin B2 and vitamins B6, B12, vitamin C, iron and folic acid. So, what to do?

What to cook today?

Here’s a handy guide of what immune functions these nutrients have and which foods can provide them.

Polyphenols and carotenoids

These two nutrient groups have a strong influence on the distribution of body fat and contribute significantly to immune coordination.  

The following foods are ideal suppliers:

Apples, dark berries, spices (e.g. cinnamon, caraway, rosemary, thyme), dark chocolate/cocoa powder, asparagus, carrots, onion, spinach, kale, legumes (peas, beetle beans, lentils), nuts (walnuts, hazelnuts, almonds), chestnuts

Iron

Iron plays a major role how your immune response can perform. For example, an iron deficiency leads to a change in the number of T-lymphocytes (helper cells).

The following foods are rich in iron:

pork liver, rump steak, sesame seed/oil, pumpkin seeds, amaranth, beans, lentils, linseed, oats, spinach

Zinc

A zinc deficiency also affects the T cells in the immune system. Zinc remains stable during chemical processes in the body and is an essential component of antioxidative enzymes.

The following foods are good sources of zinc:

Lamb, pork liver, beef shoulder, pumpkin seeds, sesame seed/oil, oats, lentils, hard cheese

Selenium

Selenium is a component of antioxidative enzymes and protects the immune cells from oxidative stress.

Valuable selenium suppliers are:

Egg yolks, whole grain wheat cereals, sesame seeds/oil, peanuts, fish

Vitamin A

Especially in the regeneration of skin and mucous membranes, vitamin A plays a vital role and thus supports our body’s natural barrier against the penetration of viruses. It also plays an essential role in the intestinal immune defense.

The following foods are rich in vitamin A:

pork/beef liver, carrots, sweet potatoes, spinach, melons, red peppers

Vitamin D

Vitamin D controls a number of physiological functions related to the immune system. Even in countries with many hours of sunshine, a vitamin D deficiency can be observed, which is why a diet rich in vitamin D is becoming the focus of attention of the medical community.

Supporting these are:

Mackerel, salmon trout, rainbow trout, eel, herring, salmon, mushrooms

Vitamin E

Vitamin E is a strong fat-soluble antioxidant and thus also acts as cell protection in immune reactions. It is also crucial for the functionality of proteins and fatty acids, as well as for the production of antibodies.

Important sources of vitamin E:

Wheat germ oil, sunflower oil, rapeseed oil, olive oil, Styrian pumpkin seed oil, hazelnuts, almonds, kale, chickpeas

Vitamin C

One of the most important water-soluble antioxidants is vitamin C. It plays a major role in redox cell signaling, an important regulatory mechanism of the immune system. Smokers in particular, have a need for up to 50% extra vitamin C than non-smokers.

The following foods provide a particularly large amount of vitamin C:

paprika, black currant, kale, broccoli, kiwi, oranges, sea buckthorn, horseradish

B Vitamins

This vitamin group plays an important role in our energy metabolism and cell structure. B vitamins also ensure that the immune cells are well supplied and can regenerate. B vitamins are mainly found in animal foods, which is why vegetarians are more likely to suffer from a vitamin B deficiency.

These foods are rich in vitamin B:

B12: beef liver, clams, tuna, mackerel, herring, rainbow trout, nori seaweed, shoulder of beef, eggs, milk, cheese

Folic acid: spinach, beef liver, beans, sprouts, chickpeas, quinoa, strawberries, sunflower seeds, egg yolk

B6: beef liver, wild salmon, chicken breast, potatoes, bananas, tuna, Chinese cabbage, pistachios, amaranth, sunflower seeds, lentils

Mahlzeit

A balanced diet can help our immune system battle viral infections and diseases. “The spectrum of action of the individual nutrients makes a diverse choice of food necessary,” says Holasek.  “A plant-based diet of [mostly] fresh foods and a moderate proportion of high-quality animal products fulfills these criteria,” concludes Lackner. The Austrian food pyramid also offers practical instructions.

Other lifestyle factors influence our immune system: Exercise, stress, restful sleep, and associated factors like over- or underweight, smoking, alcohol and general health all affect individual immune functions.

So, get ready for your Osterjause with eggs, horseradish, salad and meat – while planning in all those other lovely things listed above that can help us all stay healthy.

With thanks to:

Assoz.-Prof.ⁱⁿ PDⁱⁿ Dr.ⁱⁿ Sandra Holasek
MMag.^a Dr.ⁱⁿ Sonja Lackner
Lehrstuhl für Immunologie und Pathophysiologie
Otto Loewi Forschungszentrum
Medizinische Universität Graz