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Keeping Your Immune System Strong to Fight Off Viruses

Samara Felesky-Hunt, B.Sc., R.D. Registered Dietitian and Nutritionist practicing in Calgary, Alberta.

Question: How can I keep my immune system strong to fight off viruses and flu?

What makes up the immune system?

The immune system is a complex system made up of bone marrow, thymus, spleen and lymph nodes. The immune system produces and sends white blood cells throughout the body to fight off infectious agents. It is designed to defend our bodies from the bacteria, microbes, viruses and toxins that we encounter daily.

Your skin is your first defence against bacteria that is trying to weaken your immune system. Skin forms a wall against bacteria and alerts your white blood cells that an infection is coming. Most infectious agents get inside the body when they are inhaled, or swallowed.

Factors That Can Weaken Your Immune System

There are many factors that can weaken your immune system such as aging, poor nutrition, and an unhealthy lifestyle. Natural aging causes a variety of changes in our bodies including a slowing down of the immune system. As well, as we get older our body’s ability to absorb nutrients maybe affected. The vitamins and minerals our bodies need to keep the immune system strong may not be absorbed as quickly or can even be depleted.

The immune system needs a variety of vitamins and minerals to stay strong. Poor nutrition can weaken the ability of the immune system to fight off infectious agents and enable the production of free radicals, which can lead to serious illness such as heart disease. Not getting enough vitamin C for instance can weaken the body’s ability to fight off infection. Eating too much sugar can compromise the ability of white blood cells to kill germs.

Stress, lack of sleep, rest or physical activity can take its toll on the immune system. When our bodies are stressed, they release a substance called cortisol. The release of cortisol slows the immune system and weakens its ability to fight off infectious agents. Lack of physical activity can also weaken the immune system which is why staying active is so important.

Nutrients that can contribute to a Healthy Immune System

Eating a well-balanced diet ensures that your body gets everything it needs to maintain a healthy immune system. The nutrient chart below highlights 10 nutrients your body’s needs and how they benefit your immune health.


Dietary Source


Vitamin C

Citrus fruits, leafy vegetables, melons, potatoes, red peppers, broccoli

Powerful antioxidant, protects against damage from free radicals and helps the body resist infection.


Meat, fish, poultry, eggs, dairy products, legumes, whole grains

Helps to maintain a healthy nervous system. Stimulates antibody response.

Vitamin D

Sunlight, fortified milk, eggs, fish liver oils, meat

Helps in the absorption of calcium and phosphorus, plus the normal development and maintenance of bones and teeth. Supports immune function.

Vitamin E

Wheat germ, peanuts, almonds, sunflower seeds, vegetable oils

An antioxidant, destroyer of free radicals. It can also improve immune function in the elderly. It may fight toxins from cigarette smoke and other pollutants.

Vitamin A & Beta-Carotene

Yellow, red and orange fruits and vegetables or dark green vegetables

Helps prevent night blindness and other eye problems, skin disorders, colds, flu, and infections


Red meats, whole grains, oysters, shellfish, dairy products

Essential for growth and development. Increases the production of white blood cells that fight infection and heals wounds.


Tuna, red snapper, shrimp, seafood, poultry & meat, Brazil nuts

A powerful antioxidant that helps reduce the risk of certain cancers and heart disease


Mushrooms, breads, cereals, beans, peas, lentils, potatoes, sunflower seeds, nuts

Maintains energy levels by promoting iron absorption

Helps to protect against heart disease & strokes

Good for healthy bones


Meat, fish, poultry, whole grains, enriched breads, breakfast cereals

Prevents iron-deficiency anaemia, maintains energy levels

Promotes resistance to infection and disease

Promotes growth

Stimulates the appetite

Folic Acid

Green leafy vegetables, nuts, asparagus, bananas

Lowers the risk of heart disease and stroke

Generates red blood cells

Helps wounds heal

Builds muscle

Eating 5 to 10 servings of fruit and vegetables can help you meet your daily requirements of vitamin C, vitamin A, beta-carotene and folic acid. Moving over to whole grains versus refined grains will pump your diet with more B-vitamins, iron and zinc. Consuming lean protein choices such as egg whites, lean cuts of red meats, poultry, fish, nuts, seeds and legumes will add selenium, copper, iron and zinc without adding saturated fats. Consuming 2 to 4 servings of milk products will help you meet your daily requirement of vitamin D. And, you can get all the vitamin E you need by eating more nuts, seeds and leafy greens.

5 Lifestyle Tips That Can Help Strengthen the Immune System

  1. Eat a balanced diet and don’t skip meals. Eat vegetables and fruits between meals.
  2. Include immune-boosting nutrients each day. Incorporate them into your daily meals.
  3. Stay active – An active lifestyle can help keep your body strong so you can fight off infectious agents is easier.
  4. Get plenty of sleep and rest. Your body rejuvenates when it is at rest.
  5. Drink plenty of water. Fluids help flush out bacteria and viruses from your body.
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