Our immune system is essential for our adaptability and survival. This complex and integrated system protects us from attack by the invisible sea of bacteria, viruses and toxins that exists in our everyday environment and safeguards us against many chronic diseases, asthma, and food allergies. Nutrition is vital to building and supporting a strong immune system, something we want to maintain in optimal condition during the COVID-19 pandemic.
How nutrition supports optimal immune function
The immune system is supported by nutrients, which are required at each stage of an immune response. Consumption of a traditional diet rich in vegetables, fruits, whole grains, beans, nuts, seeds, fatty fish and olive oil is an effective way to enhance immunity. A steady stream of nutrients supports many important immune-related functions. For example:
- Proteins provide the building blocks for the immune system, and glutamine, a major fuel source for immune cells.
- Healthy fats dampen inflammation and help absorb fat-soluble vitamins.
- Carbohydrates help minimize the risk of upper respiratory tract infections after prolonged, intense exercise.
Plant foods are rich in phytochemicals, which help us stay healthy. Most phytochemicals act as antioxidants, protecting the body against damage from free radicals. Other phytochemicals display antibacterial or antiviral function, and many help increase the number and strength of immune cells. Thousands of phytochemicals are found in foods we routinely eat, including those commonly associated with immunity, such as olive oil, natural cocoa, green tea, red wine, and turmeric. While some phytochemicals have funky names like ellagic acid, found in raspberries, and glucosinolates, found in Brussels sprouts, they are widely distributed in plants and are responsible for the variety of different colours, flavours, and aromas we enjoy.
Unfortunately, nearly half of the calories in the typical Canadian diet come from ultra-processed foods, including fast food, processed meats, candy, pop, and ice cream, which contain excess sugar and animal fats. In addition to promoting high rates of obesity, these inflammatory-type diets also suppress immunity.
What about the use of supplements to bridge nutritional gaps?
While taking a pill may seem appealing in terms of convenience, no single nutrient or herbal supplement is up to the momentous task of providing complete nutritional benefits. Many nutrients, including iron, copper, selenium, zinc, and folic acid, as well as vitamins A, B, C, D and E are important to support our bodies. Filling in nutritional gaps with supplements only makes sense when you try to eat a balanced diet and still can’t meet the recommended amounts of essential nutrients. Many people often fall short on essential nutrients. Many factors may contribute to nutritional deficiencies, including:
- Lifestyle factors (e.g., excess alcohol, restrictive diets, stress)
- Malabsorptive conditions (e.g., Crohn’s disease)
- Medications (e.g., antibiotics, antacids)
When it comes to optimal nutrition, it’s often a balance between too little and too much. While even relatively mild deficiency states (e.g., zinc) can impair immune function, mega doses are not the answer. Taking high doses of vitamin C to reduce the frequency of respiratory tract infections or vitamin B12 to treat a deficiency is not necessarily problematic, as excess amounts are eliminated. However, over-supplementing with iron can lead to the overgrowth of bacteria, and excess zinc or copper can impair immune function. Whole foods are the way to go, as they provide nutrition beyond the sum of their nutrient parts and limit the potential for excess.
A supplement worth considering is vitamin D. Taking vitamin D supplements is beneficial, because it can be challenging to naturally obtain from diet and sunshine alone—especially if you’re trying to avoid the sun due to health concerns.
Your gut and the immune system
While nutrients and phytochemicals support immunity, there is approximately 4,000 square feet of real estate in our digestive tract that warrants attention. The gut provides a physical barrier to pathogens and contains a mucus lining that can trap pathogens. In addition, stomach acid and intestinal enzymes destroy pathogens. The gut is home to more than 70% of the body’s immune cells along with trillions of resident microbes that make up what’s called the microbiota. During the first three years of life, gut microbes teach our immune system how to behave, and they subsequently help maintain a balanced immune system throughout our lives. Some key factors that support a healthy gut and the body’s natural defenses include good hydration, moderate alcohol intake, and a diet rich in prebiotics and probiotics.
Prebiotics are non-digestible soluble fibres that feed gut microbes and are found in various foods, including avocados, asparagus, bananas, radicchios, leeks, garlic, and inulin, as well as potatoes and beans that have been cooked and cooled. Some of these fibres are fermented by friendly bacteria in the large intestine to short-chain fatty acids, which fuel cells in the gut and protect the digestive tract from harmful bacteria. As a bonus, fibre can also help remove toxins from the body.
Probiotics are live microbes that stimulate production of immune cells. They help fight colds, flus and infections and also stimulate production of antibodies that neutralize pathogens such as bacteria and viruses. Probiotics also compete for nutrients that are in limited supply and occupy space that may have otherwise been taken up by pathogenic organisms. While probiotics are available as supplements, they can also be obtained from fermented foods that have not been heat treated, such as kimchi, sauerkraut, miso, yogurt, and many cheeses.
8 nutritional strategies to help support your immune system:
- Feast on a variety of fibre-rich plant foods, especially colourful fruits and vegetables
- Ditch processed inflammatory “food-like” products
- Incorporate healthy fats such as olive oil, nuts, seeds and fatty fish into meals and snacks
- Drink lots of water, moderate alcohol consumption, and think twice about reaching for that pop or energy drink
- Avoid restrictive diets if you can
- Eat until you are 80% full—well nourished, yet not overfed
- Enjoy prebiotic- and probiotic-rich foods
- When food alone can’t offer enough nutrition, consider tailored nutrient supplementation with your doctor and dietitian.
For more information on nutrition and your immune system, speak with your Copeman registered dietitian.