We all know this time of year with shorter, colder and darker days cold and flu season has officially started. Naturally you may turn to supplements to ensure you’re getting that higher dose of Vitamin D or boost your immune system with supportive herbs like Elderberry. However, understanding the connection between nutrition and immunity isn’t just about taking supplements when you feel that sore throat or fever coming on. It’s about recognizing that every meal you choose to eat either provides the raw materials your immune systems needs to function optimally or undermines your immune defences. What you decide to eat has a direct influence on your body’s ability to fight off illness, recover quickly from infections and maintain long term health.
How your Immune System Works
Before we dive into ways you can support your immune system, it’s helpful to understand a little bit about how your immune system actually works. Your immune system is your body’s natural defense system. Its purpose is to help fight infection and destroys microorganisms like bacteria, viruses, parasites, fungi or other things the body recognises as foreign and different from your own body’s healthy normal cells.
Your body has two different immune systems: the innate and adaptive immune system. Innate immunity is a non-specific response made up of the exterior barriers of your body which act as the first line of defence against pathogens-think skin, mucous membranes of the throat and gut and stomach acid. Your adaptive immune system is more targeted and also called acquired immunity. Your body develops protection to pathogens after an initial exposure, whether from the pathogen or a vaccine.
This complex system requires raw materials from your diet to specifically support growth, maintenance and accuracy of immune cell function. When your diet lacks the key nutrients needed for these immune cells to work properly, new cell growth may slow down, existing immune cells may be less effective and your body’s ability to mount an appropriate response reduces and worst-case scenario if conditions are right in the body (think high inflammation) the immune system can start to turn on itself, leading to autoimmune disease.
The Gut-Immune Connection
Did you know that more than 70% of your immune system is found within your gut and is largely controlled by the bacteria present in your gut microbiome? Your gastrointestinal tract is one of the main areas in the body that comes into frequent contact with foreign substances (ie food & microbes). This is why dietary inflammation plays such a key role in disease formation and poor immune health. Eating foods that are inflammatory or that your body is sensitive to leads to an overwhelmed and fatigued immune system which has less resources to fight infections like viruses or bacteria. To read more about reducing inflammation check out this blog post.
The Key Building Blocks of Immune Function
There are a few key nutrients your immune system needs to function properly. Supplementation can be helpful during an acute infection but eating a diet that provides these nutrients in adequate amounts is a good overall and long-term strategy. Let’s explore each in a bit more detail below:
- Protein: protein literally provides the structural foundation for your immune system. Antibodies, immune cell receptors and signaling molecules that coordinate immune responses are made up of protein. A lack of protein in the diet leads to the inability of your immune system to produce the required immune cells to function optimally.
Foods to Focus on: pasture raised & grass-fed meats, pasture raised poultry and eggs and wild caught fish, organic soy products. Plant based proteins are beneficial as well however do not provide all essential amino acids to support immune function most effectively. Plant proteins should be combined to ensure all essential amino acids are consumed such as paring plant proteins such as rice and beans, legumes and nuts/seeds and grains and nuts /seeds.
- Vitamin C: Vitamin C helps protect immune cells from oxidative stress. It’s an antioxidant which means it helps to neutralize the harmful compounds that result from inflammation and pathogens. Vitamin C also helps eliminate old immune cells and enhances immune cell function.
Foods to Focus on: guavas, kiwi, bell peppers, strawberries, oranges, papaya, broccoli, tomatoes, snow peas, kale.
Important to note: Vitamin C is highly sensitive to degradation and decreases rapidly after picking. In our Canadian winters, most fresh produce is being shipped far and by the time it gets to your table it’s been 1-2 weeks. Frozen sources may be a better alternative for Vitamin C during the winter months.
- Zinc: Zinc plays an important role in the development and function of immune cells and plays a key role in both innate and adaptive immunity.
Foods to Focus on: oysters, grass fed beef, chicken, organic tofu, pork chops, pumpkin seeds, lentils, gluten free oatmeal, shiitake mushrooms.
- Selenium: selenium is a potent antioxidant that strongly influence inflammation and immune responses and protect immune cells.
Foods to focus on: Brazil nuts, tuna, oysters, pork chops, grass fed beef, pasture raise chicken, organic tofu, shrimp, shiitake mushrooms.
- Pre & probiotics: A strong, diverse gut microbiome results from eating a variety of fermented foods and prebiotic containing foods. These bacteria positively influence your immune system by helping regulate the function of mucosal immune cells in the gut lining. They also help serve as a first line of defence competing with harmful bacteria and keep the balance of bacteria in your gut microbiome in check.
Foods to focus on: kimchi, kefir, sauerkraut, miso, beet kvass, fermented pickles. It’s also just as important to provide the right fibers these good bacteria need to survive. Prebiotic foods include garlic, onions, leeks, asparagus, oats, legumes, green banana.
I’m sure you’re thinking what about vitamin D? Vitamin D plays a role in immune system modulation and enhances the body’s ability to fight pathogens and we know that low vitamin D levels are linked to autoimmune diseases, inflammatory conditions and respiratory infections. Although there are some food sources of Vitamin D including fish, cremini mushrooms, pork chops and eggs, as Canadians we likely need additional supplementation, especially through the winter months. It’s best to test your levels with your doctor prior to supplementation.
Tying it all Together...
The key to not making this seem too overwhelming is to focus on eating a variety of plant foods. When you consistently purchase new and different meats, fruits, vegetables, fermented foods each week at the grocery store, your diet will provide the variety of immune building vitamins, minerals and phytonutrients it needs. Make it a goal every time you grocery shop to purchase at least 4-5 different plant foods than you purchased the week before. Eliminating processed foods and focusing on real, whole foods provides a variety of nutrients in combinations and forms that work synergistically in a way that supplements lack.
Every meal is an opportunity to strengthen your immune defenses. Eat real, whole foods, prioritize a variety of colourful foods and maintain consistency. The small incremental changes create the foundation for robust immune health not just during cold and flu season but throughout the rest of your life.