Dr Tamsin Lewis gives us the low-down on how to avoid colds this winter.

We’ve all been there. You wake up, feeling a bit groggy. Then the headache kicks in, your nose starts running and your muscles ache. Not only do you feel terrible but it also means you can’t do any exercise for days or even weeks.

That’s why your immune health should be a priority if you want to train consistently and get a head start on your race goals. It’s especially important for triathletes, since mild and moderate exercise boosts the immune system but anything over 90 minutes can negatively affect immune system function.

Every day you come into contact with thousands of different viruses and bacteria. Everything you touch, from a handrail on a bus to a bathroom door handle, will be covered in potentially harmful bugs. You touch things, and then touch your face. The bugs get into your body through mucosal surfaces – your nostrils, mouth or a break in the skin. Any invading bug will quickly be thwarted in its attempts to gain access by your white blood cells, which capture the bugs and kill them before they can replicate and enter your bloodstream. You also swallow vast numbers of bacteria and pathogens (potential disease-causing bugs) everyday, but most die in the saliva or acid environment of the stomach.

However, some bugs are stronger than others and have evolved ways to evade your immune response. These make you unwell, until your immune system adapts and finds out a way to kill the invader. Vomiting and diarrhoea are the result of a pathogen gaining access into your system as your body attempts to rid itself of the bug and its toxic products.


Travelling to new places increases our risk of developing an illness as our immune system is challenged by exposure to new bugs. Any shared environment also increases the risk of illness, as proximity to infected individuals is higher. Some people may carry pathogens and not be symptomatic. Coming into contact with them at a time when your immune system is compromised may cause you to become unwell.

Upper Respiratory Tract Infections (URTIs) are most common. An acute bout of heavy exercise induces immune system responses, similar to those induced by infection. While healthy, you will recover quickly from this, but in times of extra training or other stress, these responses persist and your chances of getting unwell are much higher if appropriate action is not taken.

Every year the cold and flu pathogens change and evolve and avoid our adaptive immune system, which recognises bugs that have previously attempted to attack us. This is why (unlike with chicken pox) you can repeatedly become infected and why we can’t vaccinate against common colds. Endurance exercise and training, if not properly managed, can weaken our immune system. The recruitment of white blood cells to fight off pathogens may be reduced, while elevated levels of stress hormones (especially cortisol) weaken the inflammatory component of the immune response and allow pathogen entry. Even if this doesn’t result in full-blown illness, once in our system bugs and their toxins cause inflammation and require energy, both physical and mental, to expunge from our bodies. This is energy which otherwise would be used for optimising our muscular and hormonal recovery and adaptation from training.


As a rule I do not usually advocate taking any supplements on a daily basis, all year round, as it is my personal belief that the body gets lazy at absorbing nutrients from food under such conditions. However, some of the suggestions below may help you if they are used in careful moderation and not to excess as then the benefits may be lost.

  • Vitamin C

Commonly heralded as a protective against colds. Large- scale scientific reviews suggest that taking daily Vitamin C is not recommended. However, it may be protective against developing URTI in times of heavy training or other physical and mental stress. Large doses, four to eight grams per day, are needed to reduce symptoms and duration of colds and flu.

  • Echinacea

Reduces symptom duration and incidence of colds in some regular users. Worth a try!

  • Antioxidant supplements

There’s no evidence that suggests that general supplementation with antioxidants boosts the immune system. In addition, it may prevent adaptation of muscles to training (by reducing the inflammation needed to stimulate muscles). Vitamin E may be harmful in excess and actually be pro-inflammatory. The exception is Quercetin (a flavanoid). Studies show promising immune- boosting effects – it may also boost mental stamina. Rich food sources include red onions, apples, blueberries, curly kale, hot peppers, tea and broccoli.

  • Glutamine (often found in recovery drinks)

Immune suppression and decreased glutamine levels have been found in athletes undergoing intense physical training. Supplementation before and after endurance races with glutamine seems to reduce URTI incidence in athletes.

  • Colostrum (the first milk a cow gives to its calf)

Contains multiple molecules that can influence how cells grow, function and repair themselves. A recent wide-scale review reports that taking colostrum improves resistance to infection and boosts immunity during times of strenuous training.

Studies also show it reduces incidence of GI distress experienced during exercise (especially in hot climates).

  • Probiotics

Studies show that daily probiotics – lactobacillus in particular – reduce URTI incidence in athletes.

  • Zinc

Taken in addition to Vitamin C at times of increased stress may boost immune system function (take with food).


  • Take anti-bacterial wipes with you on journeys. Wipe hand-rests. Avoid touching public toilet doors (use tissue).
  • Vaseline in nostrils may prevent bugs taking hold (I use it on flights).
  • Barrier sprays – Vicks First Defense helps some people.
  • Rinse your nose/gargle salt water if you feel the sniffles coming on.
  • Saunas and steam rooms raise body temperature and may help fight off illness. But keep hydrated.
  • Your mum was right – wrap up warm especially, your head and neck.
  • Take over-the-counter meds, but be sensible. No point suffering from a headache and sinus congestion if it can be helped.


  • Increased intensity of exercise
  • Increased duration of exercise
  • Sleep deprivation
  • Psychological stress – work/life/family
  • Nutrient poor diet – inadequate zinc/vitamin C/folate and healthy fats
  • Calorie restricted diets
  • Low body fat percentage
  • Frequent travel (increased exposure to new/unknown pathogens)
  • History of chronic disease – asthma, diabetes, heart disease etc
  • Not washing hands regularly and thoroughly, especially after using bathroom/using public transport
  • Heavy drinking sessions


  • Generally speaking if symptoms are above the neck (no chesty cough) and you have no fever, light exercise may help you get
    better quicker.
  • If light headed or resting heart rate raised by 10bpm take a day off.
  • Remember if you push on through, it is likely the illness will stick around for longer and your chances of re-infection are higher.