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How diet can support your immune system

During times of illness or flu season, people often turn to supplements, natural health-care products, or increase their intake of specific foods to boost their immune system. From high doses of vitamin C, to adding honey in tea, there are a variety of marketed products and trends that promise increased immunity. However, our immune systems are very complex, and a lot of factors contribute to the strength of that system. No one food or nutrition is the answer, but there are diet and lifestyle behaviors that can help support your individual immune system.

A look into the immune system

Our immune system protects our bodies from invaders such as bacteria, viruses, and toxins. Our first line of defense is the innate immune system. This includes barriers such as the skin, mucous membranes, stomach acid, enzymes, and cells to fight off harmful germs, parasites or cells (ie. cancer). From the moment you are born, your innate immune system is active. Our acquired immune system learns to recognize foreign substances and is responsible for creating antibodies and immune cells to attack invaders. Immunizations train the system to create antibodies to protect from these harmful invaders.1

What factors decrease the immune system?

  1. Lifestyle factors such as poor diet, lack of sleep, and stress

  2. Chronic disease (such as uncontrolled diabetes, cancer, gastrointestinal conditions, and HIV)

  3. Environmental toxins (ie. air pollution, smoking, alcohol)

  4. Aging

Actionable nutrition & lifestyle goals to support the immune system

Having a balanced nourishing diet supports all cells, not only immune cells. There are no quick fixes or specific foods that offer specific protection, but certain behaviours and patterns can help prepare your body for invaders and inflammation in the body.2

  1. Limit ultra-processed foods (ie. soda, candies, cold cuts, fast food, packaged cookies, cakes and salty snacks)

  2. Limit refined sugars (sweetened beverages, flavored yogurts, high sugar cereals, granola and bars, candy and baked goods). Aim for 10g or less of sugar per serving for yogurt, cereals and cereal bars.

  3. Consistent sleep schedule with 7-9 hrs of sleep per night

  4. Staying regularly active 

  5. Foods rich in the following nutrients: vitamin A, C, E, D, zinc, selenium, iron, and protein

Nutrient and Food sources

Protein: Seafood, lean meat, poultry, eggs, beans and peas, soy products and unsalted nuts and seeds.
Iron: Lean meat, chicken, turkey, fish/seafood, tofu, legumes, nuts/seeds (ie.pumpkin seeds, hemp hearts, almonds), leafy greens, oatmeal.
Vitamin C: Citrus fruits such as oranges, grapefruit and tangerines, or red bell pepper, papaya, strawberries, spinach, kale, brussels sprouts.
Vitamin A: Carrots, sweet potatoes, pumpkin, butternut squash, dark leafy greens.
Vitamin E: Almonds, peanut butter, sunflower seeds or oil, hazelnuts.
Vitamin D: Food sources are limited but some can be found in fatty fish such as salmon, mackerel, tuna, sardines. Supplement with 1000 IU/day of vitamin D3 daily, especially in winter months.
Zinc: Lean meat, poultry, seafood, dairy products, whole grains, beans, seeds and nuts.
Selenium: Seafood, lean meat, poultry, tuna, eggs, whole grains, brazil nuts (limit to 1-3 per day to avoid toxicity), cottage cheese.


When the cold weather hits, many people turn to natural health products such as Echinacea, ginseng, etc. and vitamin/mineral supplements. Remember, just because something is labelled “natural”, doesn’t always mean it’s safe. There are still risks of overdoses and negative side effects or drug interactions. It’s best to first check with a healthcare professional before starting a new supplement. For example, both zinc and selenium can be toxic in high doses, and taking more than 2000 mg of vitamin C per day can have side effects like diarrhea.3

The microbiome and immunity

The gut is very complex and the bacteria in it can have a large impact on health. The microbiome is the collection of bacteria in the gut and researchers are studying a wide range of effects it may have on the body, including immunity. In fact, 70-80% of our immunity is in the gut.4 The gut microbiota and immune system are intricately related. When your gut is out of balance, your whole body can be affected. Reducing ultra-processed foods, and incorporating more pre and probiotic rich foods can support a more efficient gut microbiome.2

Prebiotics: Fibrous foods that provide food for probiotics and promote growth and activity of beneficial bacteria in our guts. 

  • Beans and legumes

  • Raw garlic and onions

  • Asparagus

  • Jerusalem artichoke

  • Under-ripe bananas

  • Tomatoes

  • Whole grains

  • Chicory

Probiotics: Live microorganisms that support the microbiome. These are found naturally in fermented foods such as:

  • Kefir

  • Yogurt

  • Kombucha

  • Tempeh

  • Sauerkraut

  • Kimchi

  • Or can also be taken via probiotic supplementation (speak to your dietitian or doctor first) 

Bottom line

Overall, there is still more research to be done to determine how diet may help or harm the immune system, but there is a clear connection between dietary choices and overall health. A diet rich in whole foods such as vegetables, fruits, nuts/seeds, legumes, and lean proteins, and low in ultra-processed foods can help prevent chronic disease and support a healthy immune system.

 A Preventive Health Assessment at TELUS Health Care Centres provides a snapshot of your overall health through a series of diagnostic testing and 1:1 conversations with healthcare providers, including a registered dietitian. Virtual appointments with registered dietitians are also available through TELUS Health Virtual Care


  1. The immune system. Johns Hopkins Medicine. (n.d.). Retrieved April 5, 2022, from

  2. Nutrition and immunity. The Nutrition Source. (2021, January 27). Retrieved April 5, 2022, from

  3. Get the facts on the immune system - unlock food. (n.d.). Retrieved April 5, 2022, from

  4. How your gut affects your immune system: A symbiotic relationship. GilbertLab. (2021, June 8). Retrieved April 5, 2022, from

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