December 28

Training, nutrition and illness

We know that exercise has huge benefits to health, but how does that translate to illness and our ability to avoid cold, flu, infections, and dare I say it… COVID.

Here’s what you need to know.

First off, importantly, we know that being generally fit and active leads to a stronger immune system than we see in people who are sedentary, and moderate amounts of exercise can have huge benefits all round. Why then, does it always seem that illness is suspiciously common in athletes- those at the top of the tree for fitness?


Training, dieting and immune function

Importantly, when it comes to fighting off illness, more exercise is certainly not always better. In fact, after intense, long duration (90 minutes plus) training sessions, immune function will often be reduced. The risk here is that this may present an opportunity for virus’ and other infections to take hold. Another key consideration is that if we push too far for too long, this reduced function of the immune system (along with other factors associated with overtraining) can become a chronic condition, leading to an increased risk of illness, amongst other negative consequences!

Other factors can heavily influence immune function too, including overall stress. This includes typical life stressors, both psychological and emotional, and also physical stress. This is one reason why over longer periods of time, dieting can also suppress immune function through various mechanisms, including chronically elevated stress hormones and nutrient deficiencies. So, although maintaining a healthy weight is important for health, chasing bodyweight with extreme training and nutrition strategies can be a dangerous tactic.

Although a cold, flu, infection, and other illnesses may appear less serious in fit, healthy individuals such as athletes, at best, they can be costly with missed training sessions, reduced performance, and generally slowing down progress! At worst, this suppression of the immune system can lead to both a higher frequency and higher severity of illnesses than would be otherwise expected.

So what can we do to minimise the risk?


Tips to optimise immune function:

There’s a number of things we can do to make sure our immune system isn’t being suppressed unnecessarily through sub-optimal training and nutritional practices.

  • Monitor training load, and be mindful of frequent, intense, long duration training sessions: Can you get training benefits with another approach?
  • Ensure adequate macronutrient intake, particularly Carbohydrate intake to match usage on longer duration training sessions, adequate protein for recovery and appropriate intakes of PUFA’s- particularly omega 3’s.
  • Eat your 5 a day…. the benefits of actual fruit and veg can be far more powerful than supplements alone.
  • Ensure adequate micronutrient intake through a balanced diet, and include a high quality multivitamin/ multimineral supplement (unless advised otherwise, be mindful of high dose supplementation of specific micronutrients.
  • Supplement with vitamin D3 if deficient (there’s a good chance living in the UK, that you are)
  • Consider supplementing with probiotics.
  • Avoid binge drinking

Once you’re doing this, other supplements and methods may come into play, but the above will help to optimise immune function alongside an intensive training plan.


Tips for minimising risk of infection:

Remember, we get ill for a number of reasons, and it’s generally about more than just the immune system. In general, illness risk is a product of amount of exposure to potential illness combined with immune function. The above helps to ensure a strong immune system, but this can only go so far. So what can we do to minimise potential exposure to harmful illnesses?

  • Allow plenty of time (1-2 days minimum) between long duration, intense training sessions.
  • Avoid sessions over 90 minutes where possible.
  • Even when increasing overall training load, keep easy days easy! Do not underestimate the benefit of easy sessions!
  • Avoid rapid weight loss
  • Prioritise sleep
  • Avoid contact with those showing signs of infection, and wear a face mask where appropriate
  • Be mindful of contact with young children who may carry more infectious agents than adults. Also be mindful of contact with animals due to the risk of exposure to infectious agents.
  • Good personal and oral hygiene is a must, including hand washing, regular showers, hand gels, etc.
  • Do not share cutlery, cups, drinks bottles etc
  • maintain hydration during and around exercise
  • Manage other stressors as much as possible: physical, psychological and emotional. Be mindful that when life stress is high, training stress may need to reduce. The same goes for “nutritional stress factors”, where avoiding dieting during these periods and aiming for an energy matched, high quality nutritional intake may be key.
  • Consider vaccination where relevant

We can’t completely eradicate the risk of illness, but all of these methods will help to keep the risk relatively low. This can mean more time to train, better recovery, and more progress.


Hope this helps!

If you want personal support to help you to get results in a FAST and SUSTAINABLE manner, contact us now. For more information on this topic, take a look at the book sport nutrition by Jeukendrup and Gleeson, Chapter 13, nutrition and immune function in athletes.

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Josh Kennedy MSc, ASCC, CSCS

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