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Winter Immunity

Updated: Sep 29, 2021

Do you catch colds or flu easily? Even without COVID-19, it's just ‘that time of year’ for us to up-regulate our immune system to better protect ourselves from the bugs going around. Prevention may be easier than cure..


“The immune system is possibly the most complex system in the body. It is a well-orchestrated army that fights viruses and bacteria, clears out damaged tissue, destroys abnormal cells and helps us adapt to our environment.”

The immune system needs to be well nourished to function optimally. Poor diet, high physical and lifestyle stress can all take its toll. A weakened immune system can result in infection, and chronic infection can lead to further depletion of the immune system.

Innate and Acquired Immunity

The immune system is separated into two parts:

  1. Innate immunity – an immediate, indiscriminate, first line of defence against pathogens

  2. Acquired immunity – a slower, adapted and more specialised immunity that provides a second line of defence.

The organs of the immune system include the lymphatic vessels and organs (including the thymus, spleen, tonsils and lymph nodes), white blood cells (lymphocytes, neutrophils, basophils, eosinophils, etc), specialised cells (mast cells, macrophages etc) and specialised serum factors.

Supporting the Immune System

There is no magic pill that can support all aspects of the immune system. A comprehensive approach is necessary which includes a healthy lifestyle, balanced diet, moderate exercise, reduction or avoidance of toxins, stress management (which could include deep breathing and relaxation exercises) and a positive outlook. Appropriate nutritional and herbal supplementation can provide specific support when appropriate.

A list of lifestyle practices that is associated with natural killer cell activity includes [1]:

  • Not smoking

  • Increased intake of green vegetables

  • Regular meals

  • Maintaining proper body weight

  • Getting more than seven hours of sleep per night

  • Exercising regularly

  • A vegetarian diet

Dietary factors that depress immune function include nutrient deficiencies, excessive consumption of sugar, consumption of allergenic foods and high cholesterol levels in the blood. A whole-food diet rich in essential nutrients and antioxidants can help to enhance immune function.

Increase your antioxidants The antioxidant vitamins include vitamin A, C and E.

Most of us are aware of the importance of vitamin C in immunity. It has also been shown to have anti-viral and anti-bacterial effects [2].

It is a water-soluble nutrient that cannot be synthesized by humans so must be consumed regularly to maintain optimal levels. Vitamin C is quickly depleted during stress and in chronic disease [3].

Foods rich in vitamin C include bell peppers, parsley, broccoli, strawberreies brussel sprouts, papaya, kale, kiwi fruit citrus, cantaloupe and tomatoes.

Vitamin A also cannot be synthesized in the body and must be absorbed by the intestine from the diet. It is a very important nutrient to maintain the integrity of the body’s skin and lining of the gastrointestinal tract [4]. It also supports immune tolerance thus helping to prevent an over-active immune system resulting in allergies or possible auto-immunity.

Foods rich in vitamin A include carrots, kale, spinach, bell peppers, liver, sweet potatoes, winter squash, swiss chard, apricots, broccoli, tomatoes and asparagus.

Vitamin E interacts with vitamins A and C helping to scavenge free radicals. It is an important nutrient for the normal function of immune cells and can plan an important antioxidant role in cancer and heart disease [5].

Foods rich in vitamin E include sunflower seeds, swiss chard, almonds, spinach, collard greens, kale, papaya, olives, bell peppers, brussel sprouts, kiwi fruits, blueberries, tomatoes and broccoli [6].

Vitamin D is also a critical nutrient in optimal immunity

Don’t forget the zinc Any commentary on immunity has to include zinc as it serves a vital role in many immune system reactions. Zinc deficiency impairs overall immune function and resistance to infection [7]. It promotes the destruction of foreign pathogens, protects against free radical damage and is required for proper white blood cell function.

Foods rich in zinc include oysters, crimini mushrooms, spinach, grass-fed beef, lamb, summer squash, pumpkin seeds, venison, chard and shrimps.


1. Murray, M.T. and Pizzorno, J. 2012. The Encyclopedia of Natural Medicine Third Edition. New York: Atria Paperback 2. Hemilä H., Chalker E., and Douglas B. 2007. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. Issue 3. 3. Jacob, R. A. and Sotoudeh, G. 2002. Vitamin C Function and Status in Chronic Disease. Nutrition in Clinical Care, 5:66–74. 4. Mullin, G.E. 2011. Vitamin A and Immunity. Nutr Clin Pract. 26(4):495-496. 5. Pekmezci, D. 200. Vitamin E and immunity. In: Litwack, G., ed. 2011. Vitamins and the Immune System. Amsterdam: Elsevier. 6. Mateljan, G. 2007. The World’s Healthiest Foods. Seattle, WA: George Mateljan Foundation. 7. Fischer Walker, C. and Black, R.E. 2004. Zinc and the risk for infectious disease. Ann Rev of Nutr. 24:255-275.

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