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Health Tips & Advice

Nutrition Strategies to Strengthen Your Immune System

By Leslie Beck, RD, Director of Food and Nutrition, Medcan

Small changes to your diet can lead to improved overall health.

Many people make dietary adjustments for a variety of reasons: to lower blood pressure or sugar, to manage digestive issues, to lose weight or to boost energy, for example. But there’s another reason to improve your diet: bolstering immune health to increase your body’s resistance to illness. Eating a healthy diet is an essential strategy since a well-functioning immune system relies on a steady stream of nutrients.

What is the immune system?

The immune system is a complex network of cells and tissues throughout the body that constantly work together to defend against infection from harmful bacteria and viruses. We have two types of immunity: innate and adaptive. Innate immunity is your body’s first line of defense; it’s comprised of protective barriers like your skin, the lining of your intestinal tract, stomach acid and immune cells. Adaptive immunity is the system that learns to recognize a harmful microbe so, the next time it enters your body, your immune cells can quickly destroy it.

Older age, environmental toxins (e.g., pollution, smoking, alcohol), chronic stress, lack of sleep, excess weight, a sedentary lifestyle and poor diet can weaken the immune system.

Immune-supporting nutrients

When it comes to diet, a number of nutrients play a central role in maintaining a strong immune system—for its everyday functioning and for escalating its activity to fight infection. Here are a few of the key players.

Protein-rich foods supply the body with amino acids, which are used to make many different immune compounds. They also deliver other immune-supportive nutrients such as zinc, selenium and omega-3 fatty acids. Include a good source of protein at each meal (e.g., fish, chicken, eggs, beans and lentils, tofu, yogurt).

Vitamin A reinforces our body’s barriers against invasion from pathogens by maintaining healthy epithelial tissue, which forms the skin and the lining of the respiratory, urinary and digestive tracts. Vitamin A is also needed to generate antibodies, immune cells that neutralize pathogens.

Preformed vitamin A is found in milk, yogurt, cheese, herring, salmon, tuna and liver. Beta-carotene – plentiful in sweet potato, carrots, butternut squash, spinach, kale, broccoli, red and yellow peppers, Swiss chard, mango, cantaloupe and dried apricots – is converted to vitamin A in the body.

Vitamin C is an antioxidant that protects immune cells from damage caused by free radicals, unstable oxygen compounds that are generated during the body’s immune response. Vitamin C may also increase the production of immune cells that engulf and kill pathogens.

The best food sources include citrus fruit, kiwifruit, strawberries, mango, cantaloupe, pineapple, red and green bell peppers, broccoli, cauliflower, Brussels sprouts, cabbage and tomato juice. Include at least two vitamin C-rich foods in your daily diet. To supplement with vitamin C, take 500 mg once or twice daily.

Vitamin D has many effects on immune cells, including dampening inflammation and helping synthesize proteins that fight bacteria. A vitamin D deficiency has been linked to a higher risk of upper respiratory tract infections.

Since we don’t get enough sun to produce adequate vitamin D in our skin during the winter months—and very few foods contain the nutrient—a daily vitamin D3 supplement of 1000 or 2000 IU is recommended to achieve a sufficient vitamin D status. Some people, however, will need a higher dose.

Zinc is required for the growth and development of immune cells and it’s also used to synthesize antibodies. Excellent sources include oysters, beef, crab, pork, chicken, pumpkin seeds, cashews, chickpeas, yogurt, milk and fortified breakfast cereals.

If you supplement, do not exceed a total daily zinc intake of 40 mg from supplements and diet combined. Consequences of excess zinc include impaired immune function, reduced levels of HDL (“good”) cholesterol, loss of appetite, diarrhea, headaches and abdominal pain.

Other immune-supportive nutrients include folate, vitamin E, selenium and omega-3 fatty acids.

The gut-immune connection

Your gut microbiome, the active microbial community that lives inside your large intestine, plays a major role immune function. In fact, most of our immune cells—70%—are found in the gut. Our diet is considered the most powerful tool that can alter the composition and activity of the gut microbiome.

To build a robust microbiome, include prebiotic foods in your daily diet. Prebiotics act like fertilizers, nourishing your gut microbes; they include asparagus, bananas, Jerusalem artichokes, jicama, rye, barley, kefir, leeks, onions, garlic and chicory root.

Adding immune-friendly foods to your daily diet can do more that help shield your body from infection. These nutrient-packed whole foods that can also help improve your overall health and wellbeing. Start by making one dietary change to your diet each week—such as including vitamin C-packed strawberries or mango to your breakfast smoothie or snacking on zinc-rich pumpkin seeds—and then build on that.

To book a nutrition appointment, contact nutrition@medcan.com or 416-862-1553. Follow Medcan Director of Food and Nutrition Leslie Beck on Twitter @LeslieBeckRD.

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