How to boost your immune system through diet

September 22, 2014 , ,

Do you get sick often? Your immune system may be to blame.

There are many factors that influence your immune system, such as your stress levels, age, diet, etc. Among all these factors, your diet plays a huge role because immunity is a complex system that requires all the nutrients to function optimally.

In order to function properly, the immune system needs essential nutrients as well as non-essential phytochemicals (see box). Even a small deficiency of certain nutrients can affect immune responses. The main nutrients to monitor are zinc, selenium, iron, copper, vitamins A, C, E, and folic acid.

What are phytochemicals?

Phytochemicals are natural compounds found in plants. All fruits and vegetables and many grains contain phytochemicals. They give colour to fruits and vegetables. Some phytochemicals act as antioxidants. Here are some types of phytochemicals: carotenoids (beta-carotene, lycopene and lutein), flavonoids, isoflavones, etc. Phytochemicals may help reduce the risk of cancer, but we still know very little about their activities and protective effects.

Source: Canadian Cancer Society

A balanced diet also has a positive effect on the circulatory system, which the immune system depends upon. The skin and membranes that form openings in the body (nose, eyes, respiratory system and digestive system) are the first lines of defense.

Principles to boost your immune system:

  • Fill your plate with fruits and vegetables

Vitamins (especially A and C) and phytochemicals act as antioxidants that promote immune functions.

Goals: Eat 5 to 10 servings a day and choose at least 2 different colours at each meal to maximize the variety of vitamins, minerals and antioxidants.

Mixed Lettuce Salad with Grapefruit

  • Choose lean proteins

Proteins are made of amino acids, which are part of every cell structure in the body, including those that nourish the immune system. Insufficient protein intake will result in decreased production of white blood cells (immune system cells).

Goals: Consume 0.8 to 1 gram of protein per kg of weight. For example, a woman weighing 132 pounds (60 kg) should consume 48 to 60 grams of protein a day. Opt for protein sources that are low in saturated fats like fish, poultry, lean meat, eggs, legumes, nuts and seeds.

  • Control the amount and quality of fat

While a high-fat diet reduces the function of T lymphocytes (a type of immune system cell), lowering the fat intake on the other hand stimulates the production of these cells.

Goals: Limit fat intake to 30% of the energy consumed. The intake of saturated fat should not exceed 5 to 10% of the energy consumed. The remaining 20 to 25% of fat should come from the following sources of unsaturated fats: canola and olive oil, avocados, nuts and seeds.

So a person whose energy needs are 1,800 kcal per day should consume around 60 grams of total fat a day, including 20 grams maximum of saturated fat.

  • Drink tea

Green tea contains antioxidants called catechins. These could have a positive effect on the lymphocyte response in addition to having anti-inflammatory properties.

Goal: Drink 1 cup of green tea a day. Let it brew for about 3 minutes.

  • Maintain energy balance

Consuming too few calories will lower the production of immune cells and it could also lead to a risk of long-term nutritional deficiencies. The system is weakened as a result. On the other hand, consuming excess calories will result in an overproduction of certain hormone-like substances, which will reduce the production of immune cells. So basically the amount of calories you consume should correspond to your needs. To estimate your energy needs, see the Health Canada table.


  • Curb sugar intake

If our sugar intake is very high and sugar replaces nutritious food, we aren’t likely to meet our daily nutritional needs. This will bring down our immunity. So the consumption of added sugars should be limited.

  • Supplements

Vitamin D could have a regulatory effect on the immune system. It is easy to meet our vitamin D requirements during summer, as our own body produces it when exposed to the sun. But in winter, it’s usually much harder to produce this vitamin naturally in the northern latitudes. So we should consume vitamin D-rich foods such as certain fatty fish (salmon, tuna, sardines) and fortified foods. In some cases, it may even be necessary to take supplements. The vitamin D requirement for people below 70 years is 600 IU, and 800 IU for those above 70 years.

Try our Marinated Swordfish with Marjoram recipe, which is an excellent source of vitamin D.

  • Improve your bacterial flora: the difference between prebiotics and probiotics

Prebiotics: Non-digestible carbohydrates that stimulate immunity by changing the composition and activity of bacterial flora.

Goal: Regularly consume whole grains, bananas, onions, garlic and artichokes.

Probiotics: Beneficial bacteria that protect and stimulate the production of immune cells in the digestive tract besides having anti-inflammatory properties.

Goal: Eat yogurt and kefir that contain the “active culture” seal on a daily basis.

  • Maintain proper hydration

Optimal hydration promotes the absorption of nutrients.

Goal: Drink 1.5 to 2 litres of water per day.

  • Exercise

Physical activity has a positive effect on weight and helps reduce cholesterol and triglyceride levels. High cholesterol and triglyceride levels prevent immune cells from functioning properly.

In conclusion

Start changing by focusing on a diet with plenty of vegetables and eat fruits for dessert and snacks. Remember to also pay attention to a variety of colours. Should you catch infections regularly, it would be advisable to do a blood test and nutritional evaluation first before taking supplements.


Marie-Maxime Bergeron
Changing eating habits gradually and adapting to the needs of my clients is the cornerstone of my approach. Eating well for fun and for health is the goal and everything begins with a return to simplicity in our habits. I am a nutritionist and have offered counselling in nutrition for 10 years.

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