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Nutrition guide to Fight Illness

A change of temperature, the clocks have “sprung” forward, your training is becoming a bit more intense. How can you improve immunity from illnesses?




Our body equilibrium will be under a bit of stress with all the changes going on at the moment. It has had almost 6 months of hard, long winter sessions in the cold and dark. We need to protect our bodies from the extra stress with increased training intensity and the changeable weather we normally experience at this time of year.


Supporting Immunity

The immune system has evolved to protect us against the numerous foreign bodies such as viruses, bacteria and parasites that attack our bodies on a day-to-day basis. The defence mechanism involves many different cell types and chemical messengers and its effectiveness can be influenced by a variety of factors including alcohol consumption, psychological stress, strenuous exercise, nutritional status, age, gut flora and genetics. Fighting Illness with a Healthy Gut


Strenuous Exercise

It is important when undertaking a heavy schedule of training to ensure that a good healthy balanced diet is consumed to provide sufficient nutrients to support the immune system. It’s also important to include some regular recovery time during the week as well as getting adequate sleep. This will help counteract any potential immunosuppressive effects that a heavy training schedule may have. 

Other precautions that can be taken to prevent picking up viruses include:

  • Regularly washing hands after touching surfaces frequently handled by the public - Creating healthy habits
  • Avoiding hand to eye or hand to mouth contact to prevent transferring microbes to these vulnerable areas.
  • Keep your dinking bottle clean by sterilising it regularly and not sharing drinks bottles.



Nutritional deficiencies can impair immune function and evidence shows that the prevalence or severity of many infections is increased by specific deficiencies. However, excessive intakes of individual micronutrients can also impair immune function. 

The macronutrients protein, carbohydrate and fat all play a role in maintaining immune system function. Inadequate protein intake can lead to impairment of cell replication and protein synthesis necessary for the production of key immune cells (white blood cells) and soluble factors (chemical messenger proteins, which transmit messages between cells). 

Carbohydrate is an important fuel source for immune cells. In addition to this, it is also well accepted that exercising in a carbohydrate depleted state will increase stress hormone production which in turn will suppress immune function. 

So its important to ensure a good carbohydrate intake when training regularly and to use a carbohydrate containing drink (ie sports drink providing 30-60g carbohydrate per hour) during prolonged exercise to prevent blood glucose levels dropping too low. 

Dehydration is also associated with increased stress hormone response, which will in turn adversely affect immune function, so in addition to the performance effects, this is another good reason for keeping hydrated. Drinking fluids during exercise will also prevent getting a dry mouth by maintaining saliva secretion. This is important because saliva contains proteins with anti-microbial properties which help prevent the entry of microbes into the body via the mouth. Re-hydration strategies

Both high fat and low fat diets may compromise immune function. An intake of approximately 20% energy from fat is the recommendation for athletes and active people which avoids either extreme. Moderate amounts of omega-3 fats - found in oily fish (salmon, fresh tuna, mackerel, trout, sardine …) linseeds, rapeseed oil, walnuts and omega-3 enriched eggs – may be beneficial to immune function as they suppress the production of substances called prostaglandins. Which may have immunosuppressive effects. Good fats; Bad fats





Vitamins and minerals

Several vitamins and minerals are important for normal immune function including A, E, C, B12, B6, folic acid, zinc, iron, selenium and copper.


Vitamin C

Vitamin C is concentrated in white cells and the adrenal gland and is necessary foe a wide range of functions related to the production of stress hormones. The recommended nutrient intake (RNI) for vitamin C is 40mg per day in the UK.

A Cochrane review showed that taking 200mg of vitamin C per day had no effect on the incidence of the common cold in the ordinary population but for those people exposed to short periods of extreme physical or cold stress or both (ie marathon runners, skiers …) the incidents was halved. The duration and severity of cold symptoms were reduced slightly with vitamin C supplementation.

It should be noted that doses if vitamin C in excess of 100mg per day can cause gastrointestinal side effects. 

It is possible to have an adequate intake of vitamin C from your diet to support the immune function as it is found in virtually all fruit and vegetables. Especially good sources are sweet peppers, broccoli, watercress, tomatoes, blackcurrants, kiwi, citrus fruits, strawberries, and mango. The content of vitamin C in foods will decrease during transport, processing, storage, cooking, bruising, and cutting. 

To obtain as much vitamin C as possible from your food;

  • Eat fresh fruit and vegetables within a few days of buying to preserve as much of the vitamin as possible
  • Store in a cool, dark, dry place and be aware that cooking reduces the vitamin C content by approximately 50%
  • Stir fry, microwave or steam to retain more of the nutrient than boiling. Cook for the shortest time possible
  • Prepare vegetables just before cooking, do not slice finely and leave the skin on where possible
  • Eat vegetables straight away once cooked as keeping them warm could reduce the vitamin C content by about 25%


If you feel you are unable to get sufficient vitamin C from your diet then seek professional help from a registered dietitian or nutritionist before taking vitamin supplements. This is required to assess whether a vitamin supplement is actually manufactured with robust quality control procedures in place is sourced.



Zinc is a component of over 200 key enzymes involved in the synthesis of proteins and genetic material, energy metabolism, and immune system function. Good sources of zinc in the diet include meat, poultry, shellfish, dairy products, nuts, pulses and wholegrain. 

The recommended nutrient intake for zinc is 9.5mg per day for men and 7mg per day for women. The studies looking at zinc supplementation for the common cold show mixed results. In the studies that do show a beneficial effect on reduction of symptoms duration and/or severity, it has been emphasised that zinc must be taken within 24 hours of onset of symptoms to be of any benefit. 

High intakes of supplemental zinc can affect the absorption of copper, iron and manganese and can cause abdominal pain and nausea and the safe upper level is set by the FSA as 25mg per day. A good diet can provide sufficient zinc for most individuals, but again any concern regarding intake should be discussed with a qualified professional.



During the times of year when your body will be susceptible to illness it is important to include good food sources in your diet of the key nutrients involved in supporting immune function.



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