Boosting your immune system in winter

As we delve into the depth of winter, with the long nights and the bitter cold, the chance of picking up colds or flu increases. The average adult gets sick two to four times per year with the majority of these illnesses occurring in the winter Months. For an endurance athlete losing even a couple of days to a cold can make the difference to a successful training plan. And when hard and intense exercise itself can suppress the proper functioning of the immune system, it becomes even more important for athletes to do what they can to protect and boost it. In this first instalment on the immune system and food I explain how the immune system works and what you should and should not do to protect it.

What is the Immune system?

The immune system is a clever network of organs, tissues and cells that work together to fight off harmful invaders such as bacteria, viruses, parasites and fungi. It has two main defence mechanisms: the innate and the adaptive systems.

Initially, you have your mucosal membrane, your first line of defence also called your innate immune system, found in your nose, eyes, mouth and gut. This protective coating is brimming with white blood cells to fight of invaders before they even enter into your body. However, if this defensive coating becomes weakened through a previous attack or through poor diet and lifestyle choices it can become compromised by an attacking germ can break through and enter into your body.

If an invading germ does manages to penetrate into your blood stream then the second defensive system, your adaptive immune system, is called into action. This part of your immune system is also comprised of white blood cells called lymphocytes (the two main classes are called T cells & B cells). However where it differs from your innate immune system is that it highly specific, reacting to an individual pathogen, creating unique antibodies that will attack the same invader if it ever enters the blood stream again. Like an elephant, the adaptive immune system never forgets and will always know how to destroy an invader it has developed antibodies to. This is the reason you cannot catch the same cold twice!  

How to boost your immune system

Luckily for endurance athletes there are some very simple do’s and don’ts that can help to enhance our immune system to protect us from winter colds:


  • Relax: Take time out of your day to rest up and relax as the stress hormone cortisol has a huge negative impact on the immune system.
  • Sleep: Get a good night’s sleep as the body repairs during our sleeping hours. An endurance athlete should aim for a minimum of 8 hours per night.
  • Wash your hands: Wash your hands before eating as this helps to destroy the germs even before they reach your body.
  • Catch the sun: Get out in the midday sun as during the shortened winter days it is difficult to keep up our Vitamin D levels, vital for healthy immune function. Getting 20 minutes of midday sun exposure helps to manage levels until the longer days arrive.
  • Change it up: Eat a wide variety of fruits and vegetables. The more different colours the better!
  • Stock up: Eat foods with immune boosting vitamins and minerals: vitamin B6, B12, C, D & E, zinc, iron and beta-carotene.


  • Eat sugar: Research has shown that eating even as little as half a teaspoon of sugar negatively impacts our immune system through putting certain white blood cells called neutrophils into a sugar induced coma.
  • Drink alcohol (or at least drink in moderation): Alcohol’s major metabolite, acetaldehyde, can impair the ciliary function in the lungs, making them more prone to bacterial and viral invasion.
  • Eat a high fat diet: Research has shown that a diet high saturated or trans fat alter the cell structure of T cells negatively impacting their function.
  • Train to Excess: Over training suppresses the immune system through the release of the stress hormone cortisol. Therefore, if you feel a cold brewing ease off the intense training for a day or two.
  • Smoke: The nicotine in both traditional cigarettes and e-cigarettes increases the stress hormone cortisol while lowering B-cell formation and T-cell activity.

 Next month we will look in detail at some of our favourite ingredients that  maximises the functioning of the immune system.

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