Foods and Nutrients That Support Your Immune System
Updated: Oct 19
Your immune system is a complex network of cells, tissues and organs that helps protect your body against infections. Good nutrition is one of the foundations of normal immune function, and several vitamins and minerals play essential roles in this process.
No single food can prevent you from getting sick, and eating more of a particular nutrient does not necessarily improve immunity if you already get enough. However, a varied diet can help you meet your nutritional needs and reduce the risk of deficiencies that may impair immune function.
In this article, I explore the key nutrients involved in immune health, the foods that provide them, and what the evidence tells us about supplements.
The aim is not to find a miracle food, but to build everyday eating habits that support your health over time.
1. How does nutrition affect your immune system?
Your immune system relies on many different nutrients to function properly. Some help maintain the physical barriers that protect your body, such as your skin and the lining of your digestive tract. Others support the development and activity of immune cells, the production of antibodies, cell repair and the regulation of inflammation.
Both insufficient and excessive intake of certain nutrients can be harmful. For example, deficiencies in vitamin C, vitamin D, zinc and other essential nutrients can impair aspects of immune function. However, taking high doses of these nutrients does not automatically make your immune system more effective.
The most reliable starting point is a varied, balanced diet that provides enough energy, protein, vitamins, minerals, fibre and other beneficial food components.
2. Essential vitamins for immune function
Vitamin C: More than citrus fruit
Vitamin C is an antioxidant that supports normal immune function, helps protect cells from oxidative damage and contributes to collagen formation. Collagen is important for the structure and integrity of skin and other tissues that help form protective barriers against pathogens.
Good food sources include:
Citrus fruits, such as oranges and grapefruit
Berries (such as black currants, strawberries, sea buckthorn)
Kiwifruit
Papaya, pineapple
Red and green peppers
Broccoli, Brussels sprouts and cabbage
Potatoes and other vegetables
You do not need to rely on oranges alone. Peppers, kiwifruit, berries and many vegetables can also provide substantial amounts of vitamin C.
Vitamin C is sensitive to heat and can be lost into cooking water. However, this does not mean that vegetables should always be eaten raw. Including both raw and cooked vegetables in your diet is a sensible approach. Steaming, shorter cooking times and using cooking water in soups can help retain more of the vitamin.
Do vitamin C supplements prevent colds?
Regular vitamin C supplementation does not appear to prevent colds in the general population, although it may modestly shorten their duration. Starting supplements only after cold symptoms begin has not consistently been shown to help.
For most people, eating vitamin C-rich foods regularly is a good foundation.
Vitamin D: Important for immune regulation
Vitamin D contributes to normal immune function and is also essential for maintaining healthy bones and muscles. The body can produce vitamin D when skin is exposed to ultraviolet B radiation, but production depends on factors such as season, latitude, skin pigmentation and time spent outdoors.
In Estonia, sunlight is insufficient for reliable vitamin D production during much of the autumn and winter, making dietary intake and, where appropriate, supplementation particularly relevant.
Food sources include:
Fatty fish, such as salmon, herring and sardines
Egg yolks
Some mushrooms exposed to ultraviolet light
Foods fortified with vitamin D, where available
Only a limited number of foods naturally provide substantial amounts of vitamin D.
Vitamin D deficiency can impair normal immune function. However, research into whether supplements prevent respiratory infections has produced mixed results, and supplementation is not a substitute for appropriate medical care.
Consider national recommendations, individual risk factors and professional advice when deciding whether supplementation is appropriate. Avoid taking high doses without a clear reason, as excessive vitamin D can be toxic.
Vitamin D3 does not routinely need to be combined with vitamin K2. There is insufficient evidence that everyone taking vitamin D requires additional K2.
Vitamin A: Supporting protective barriers
Vitamin A is important for the maintenance of skin and the lining of the respiratory and digestive tracts. It also contributes to the normal development and function of immune cells.
Food sources include:
Carrots, pumpkin and sweet potatoes
Spinach, kale and other dark green vegetables
Eggs and dairy products
Liver, which contains substantial amounts of preformed vitamin A
Orange and dark green vegetables contain carotenoids, some of which the body can convert into vitamin A. Absorption of carotenoids can be improved by eating these foods with a source of fat.
Liver is a concentrated source of vitamin A, but it should not be eaten frequently or in large amounts without considering total intake. Excessive preformed vitamin A can be harmful, and liver should be avoided during pregnancy because of its high vitamin A content.
Vitamin E: Protecting cells
Vitamin E is an antioxidant that helps protect cell membranes from oxidative damage and contributes to normal immune function.
Food sources include:
Almonds and hazelnuts
Sunflower seeds
Vegetable oils, such as sunflower oil
Avocados
Some green vegetables (cooked spinach, cooked turnip greens)
Nuts and seeds are useful additions to a varied diet because they also provide unsaturated fats, fibre and other nutrients. There is generally no need to take high-dose vitamin E supplements for immune support if your diet provides enough.
Vitamins B6, B12 and folate
Several B vitamins are involved in processes necessary for normal immune cell development and function.
Vitamin B6 supports protein metabolism and many biochemical reactions. Vitamin B12 and folate are essential for DNA synthesis and the formation of blood cells, among other functions.
Food sources include:
Vitamin B6: poultry, fish, potatoes, bananas, chickpeas and other legumes.
Vitamin B12: fish, meat, eggs and dairy products, as well as fortified foods and appropriate supplements.
Folate: leafy green vegetables, beans, lentils, peas and broccoli.
People following a vegan diet need a reliable source of vitamin B12, usually through fortified foods or supplementation. Vitamin B12 deficiency can develop gradually, so relying on symptoms alone to identify it is not advisable.
3. Essential minerals for immune health
Zinc: Supporting immune cells
Zinc is involved in the development and function of immune cells, wound healing, DNA synthesis and many other processes.
Food sources include:
Meat and seafood
Dairy products
Beans, chickpeas and lentils
Pumpkin seeds and other nuts and seeds
Whole grains
Zinc from animal foods is generally more readily absorbed than zinc from many plant foods. Phytates in whole grains, legumes, nuts and seeds can reduce zinc absorption, but these foods still contribute valuable amounts of zinc and other nutrients.
Soaking, sprouting, fermenting and cooking can reduce phytate levels to varying degrees. However, you do not need to soak every nut, seed or legume to maintain a healthy diet.
Zinc deficiency can impair immune function, but taking excessive amounts of zinc can also cause harm. High intakes over time can interfere with copper absorption and may themselves impair immune function.
Zinc lozenges have shown some potential to shorten the duration of a common cold in certain circumstances, but results vary depending on the formulation and how they are used. They are not a general recommendation for daily prevention.
Selenium: Essential in small amounts
Selenium is needed for the activity of several enzymes involved in antioxidant defence, thyroid function and immune regulation.
Food sources include:
Fish and seafood
Eggs
Meat and poultry
Dairy products
Whole grains
Brazil nuts
Selenium content in plant foods can vary considerably depending on the selenium content of the soil in which they were grown. Brazil nuts can contain very high and highly variable amounts, so eating a fixed number every day is not a reliable way to control selenium intake.
Both deficiency and excess can be harmful. A varied diet is generally preferable to routine high-dose selenium supplementation unless a specific need has been identified.
Iron: Supporting oxygen transport and immune function
Iron is essential for haemoglobin, which transports oxygen in the blood. It is also involved in cellular energy production and normal immune function.
Food sources include:
Meat and seafood
Lentils, beans and chickpeas
Tofu
Pumpkin seeds
Iron-fortified cereals
Green leafy vegetables (like spinach)
Iron from meat and seafood is generally more readily absorbed than non-heme iron from plant foods. Eating plant sources of iron alongside vitamin C-rich foods can improve the absorption of non-heme iron.
For example, add peppers or berries to a meal containing lentils or beans.
Iron deficiency can affect health and should be investigated when suspected. However, iron supplements should not be taken simply to boost immunity. Excess iron can be harmful, so supplementation should be guided by an appropriate assessment.
Other minerals worth remembering
Copper, iodine and magnesium also contribute to normal body function, including processes relevant to immunity. Their roles are part of a much broader network of biological processes rather than a direct way to prevent infections.
A varied diet containing vegetables, fruit, whole grains, legumes, nuts, seeds, fish, eggs and other suitable protein sources can help provide these minerals.
4. Protein: Building blocks for immune function
Protein provides amino acids needed to build and repair body tissues and produce many of the molecules involved in immune responses, including antibodies.
Eating too little protein or not getting enough overall energy can compromise health, particularly in people who are older, unwell, recovering from surgery or experiencing malnutrition.
Good protein sources include:
Fish and seafood
Eggs and dairy products
Poultry and other meats
Beans, lentils and chickpeas
Tofu, tempeh and other soy foods
Nuts, seeds and whole grains, which also contribute protein
You do not need to necessarily eat animal products to obtain sufficient protein. A well-planned plant-based diet can meet protein needs by including a variety of protein-rich foods throughout the day.
The goal is to meet your individual needs consistently, rather than consuming unusually large amounts of protein in the hope of strengthening immunity.
5. Gut health, fibre and fermented foods
Your digestive tract is an important part of your body's defence system. The gut lining forms a barrier, while immune cells and the gut microbiome interact in complex ways that researchers are continuing to investigate.
The gut microbiome refers to the community of microorganisms living in the digestive tract. Diet is one of several factors that influence its composition and activity.
Many gut microorganisms use dietary fibre as a source of energy. Some fermentable fibres are converted into short-chain fatty acids, which play roles in maintaining gut barrier function and regulating immune activity.
Good sources of fibre include:
Vegetables and fruit
Oats, rye and other whole grains
Beans, peas and lentils
Nuts and seeds
Aim to include a variety of these foods regularly. Increase fibre gradually if you are not used to eating much of it, and drink enough fluid to support normal digestion.
Fermented foods
Foods such as kefir, yoghurt containing live cultures, sauerkraut, kimchi, miso and tempeh can add variety to the diet. Some contain live microorganisms, although the types and amounts vary between products.
Fermented foods are not probiotics in the strict scientific sense. The term probiotic refers to live microorganisms that have demonstrated a health benefit when consumed in adequate amounts.
Research into fermented foods and the microbiome is promising, but the effects depend on the food, microorganisms, person and health outcome being studied. It would be an overstatement to say that eating fermented foods guarantees stronger immunity or prevents infections.
Choose fermented foods that you enjoy and tolerate, and include them regularly as part of an overall varied diet.
6. Do immune-support supplements work?
Supplements can be useful when they help correct a nutrient deficiency, meet increased requirements or address a recognised risk of inadequate intake. They are not automatically beneficial for everyone and since they are not regulated like medicine, quality is very important.
The evidence varies by nutrient and health outcome:
Vitamin C: Regular supplementation may modestly shorten colds but does not reliably prevent them in the general population.
Vitamin D: Essential for normal immune function, but evidence that supplementation prevents respiratory infections is mixed. Correcting deficiency remains important.
Zinc: Certain lozenge formulations may shorten a cold when used early, but evidence is variable and high intakes can cause adverse effects.
Selenium: Essential for normal function, but there is insufficient evidence to recommend routine supplementation to prevent infections in people who already obtain enough.
Herbal products and other supplements: Evidence differs considerably between products and preparations. Laboratory findings do not necessarily translate into benefits in people.
More is not always better. Excessive intake of some vitamins and minerals can be toxic, and supplements may interact with medications.
Be particularly cautious with high-dose vitamin A, vitamin D, zinc, selenium and iron. If you suspect a deficiency or are considering supplementation because of a health concern, discuss the most appropriate approach with a healthcare professional.
7. What does an immune-supportive diet look like in practice?
Rather than focusing on a short list of special foods, aim to build a varied eating pattern that regularly provides the nutrients your body needs.
A practical approach is to:
Include vegetables and fruit of different colours every day.
Choose whole grains such as oats, rye bread and barley regularly.
Eat beans, lentils or other legumes frequently.
Include suitable protein sources at meals.
Add nuts and seeds in portions that suit your needs.
Eat fish regularly if it fits your dietary preferences.
Include sources of calcium and vitamin B12 appropriate to your diet.
Use a variety of oils and other sources of unsaturated fats.
Drink enough fluid to meet your needs.
You do not need to eat every food listed in this article every day. What matters is the overall pattern over time, together with adequate energy intake and sufficient variety.
For further guidance, see the Estonian national dietary recommendations at Toitumine.ee.
I have also created downloadable resources on all vitamins and minerals our body needs, which foods contain them and also what are the signs of deficiency. Go to my Resources page to download these one-pagers.
The bottom line
A healthy immune system depends on many interacting factors, and nutrition is one important part of the picture. Vitamins, minerals, protein and other nutrients help your immune system function normally, but no individual food or supplement can guarantee protection against infection.
The most useful starting point is a varied diet that provides enough energy and essential nutrients. Supplements can be appropriate in specific circumstances, particularly when a deficiency or increased need has been identified, but taking high doses without a clear reason is not a reliable shortcut to better health.
Focus on consistency rather than perfection. A variety of vegetables, fruit, whole grains, legumes, nuts, seeds and suitable protein sources can help you meet your nutritional needs and support your health over time.
For more on the wider picture, read my companion article: How to Support Your Immune System: 7 Evidence-Based Habits.
Sources and further reading
National Institutes of Health, Office of Dietary Supplements. Dietary Supplements for Immune Function and Infectious Diseases — Consumer Fact Sheet.
National Institutes of Health, Office of Dietary Supplements. Dietary Supplements for Immune Function and Infectious Diseases — Health Professional Fact Sheet.
Harvard T.H. Chan School of Public Health, The Nutrition Source. Nutrition and Immunity.
Tervise Arengu Instituut. Toitumine.ee — Estonian nutrition recommendations and practical guidance.
If you are looking for support improving your diet and health, please do contact me for nutrition counselling and health coaching at info@katrinpeo.com.