Eating for immunity support
28 Jun 2020
Contribution by Amanda Bunn (@amandabunn)
Amanda Bunn is a New Zealand-based coach with The Method Now. In her “spare time”, she’s an emergency department doctor, CrossFit athlete, gym owner and coach. Here’s Amanda’s best advice on eating foods to support your immune system.
The body is full of biochemical defence systems that modulate our immune systems and make us more resilient against disease. By stimulating and upregulating some of these physiological factors, we can support the healthy function of our immune system.
Fruit and vegetables contain substances called phytonutrients, which, along with a host of other beneficial properties, enhance immunity – so the very best thing you can do to support your immunity is eat a diet rich in a variety of fruits and vegetables. All the colours offer different benefits and some even work synergistically to have a more powerful effect - so aim to eat the colours of the rainbow every day.
Fibre is also a key part or your immunity arsenal. It helps keep your gut lining and microbiome healthy, which is has been linked extensively to a stronger and more adaptable immune system. Foods high in fibre include:
All fruit & veg, especially beetroot, spinach, broccoli, kale, tomatoes, avocado, carrots, brussel sprouts, artichoke and sweet potato with the skin on.
Berries (raspberries top this list, but all berries are good) and fruit with pulp - oranges, lemon, apple, banana.
Legumes – black beans beat everything else for fibre content, as well as lentils and chickpeas.
Almonds, walnuts, pecans or hazelnuts (all with the skin on).
The top three micronutrients to support immune function are: Vitamin D3, Vitamin C, and Zinc. It can be difficult to consume these in high quantities, so high quality supplementation can be beneficial.
Vitamin D is critical for health. Virtually every cell in the body has a vitamin D receptor, which, when bound to vitamin D, can influence the expression of more than 200 genes. It has a significant role in regulating immune function. There are two types of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). D2 is made naturally by plants and D3 is the form your body naturally produces when it’s exposed to sunlight.
The easiest way to naturally boost vitamin D production is through exposure to sunlight; it’s recommended to aim for around 20 minutes of direct safe sun exposure per day. (There is a caveat to this through UV exposure and skin cancer, so you only want to be in sun exposure when the UV index is below 3. There is an app called UVIMate, which gives you real time information on the UV index in your area and thus if it is okay to be out in direct light.) Typically speaking exposure in the morning or later afternoon/early evening is best – early morning exposure has the added benefit of help with your circadian rhythm and sleep.
Top foods for vitamin D are: Fatty fish (i.e. tuna, salmon, sardines and mackerel), whole eggs, beef liver and cod liver oil.
Vitamin C is an antioxidant that animals produce in response to stress. Humans lost the ability to do this during our evolution and now have to obtain it from our diet. Vitamin C's role in immunity is related to glutathione, the body’s main antioxidant defence mechanism, which is produced in the liver. It protects against free radicals and helps to eliminate toxins. This is by far more powerful than antioxidant supplements or vitamins because the body will self-regulate glutathione’s role in the immune system.
Foods high in vitamin C include: Guava, capsicum (red and yellow), broccoli, cauliflower, kiwifruit, strawberries, tomatoes, sweet potato, kale and brussel sprouts.
Zinc is used for the function of more than 300 enzymes and more than 1,000 transcription factors (proteins that regulate the function of genes) in humans. It also plays an important role as a structural agent of proteins and cell membranes preventing oxidative stress. It promotes hormone production and immunity, as well as fighting against infections.
Top food sources of zinc include: Grass-fed red meat, shellfish (in particular oysters, crab, mussels and prawns/shrimp), pumpkin seeds, cashew nuts, cheddar cheese and dark chocolate (80%+).
It’s important that your immune system is supported by a healthy, balanced diet, as well as two other key factors:
Prioritise getting enough sleep. Sleep supports your natural killer cells and forms part of your initial immune response.
Managing stress as much as possible. Self-isolation is a great time to learn new stress-management techniques, such as meditation or breathwork. Stress plays a huge role in compromising the immune system, so if you’re someone who suffers from a lot of stress and anxiety, you might also notice you’re more susceptible to getting sick.