For the professional sports person or amateur athlete, feeling unwell can reduce the ability to perform during training and competition, and can lead to poor recovery and poor performance. Ultimately, feeling chronically below par can affect the long term career.
There are numerous reasons for lowered immunity during training:
- repeated cycles of heavy exertion
- exposure to germs and bugs
- mental stress
- lack of sleep
- poor nutrition
- weight loss
Nutritional immunology is a rapidly growing area, and four key principles have emerged:
1. Almost all nutrients in the diet play a crucial role in immunity. Eating a wide variety of foods in your diet provides all these nutrients in most healthy adults, and mega doses of vitamin/mineral supplements do not “boost” immunity above normal levels. There may be one exception…..current research suggests that vitamin C when unwell can shorten the duration of the common cold.
2. Poor energy and nutrient intake can reduce the immunity and susceptibility to germs and bugs. Poor protein intake reduces immune function and strongly increases risk of various types of infections.
3. Some nutrients (glutamine, arginine, fatty acids, vitamin E) provide additional benefits to immunocompromised persons (e.g. the frail elderly) or patients who suffer from various infections. Currently there is a lack of evidence to support the use of these in preventing exercise-induced immune suppression and protection from infection.
4. Some supplements may prove useful in countering immune suppression for healthy adults during unusual mental and physical stress e.g. omega-3 fatty acids from fish oils reduce inflammatory responses.
Of the various nutritional countermeasures that have been evaluated so far, ingestion of carbohydrate before, during, and after prolonged or intense exertion has emerged as the most effective way to ensure less of a negative effect on the immune system. Athletes intent on reducing body fat by avoiding carbohydrates should be aware that this may impact on their immunity.
- Have a carbohydrate-based snack before you start high intensity training, particularly hard morning training. If you are unable to tolerate something before you start exercise, have a source of carbohydrate during the session such as a sports drink (6-8% carbohydrate)
- Have a carbohydrate & protein based snack shortly after training to start the recovery process. This is of particular importance for athletes training more than once a day with limited time to recover for the next session.
- Base meals around nutrient-rich carbohydrate-containing foods and fluids. Rice, pasta, bread, cereals, fruit, starchy vegetables and low-fat milk and yoghurt are nutrient-packed carbohydrate-containing choices. The aim is to match daily carbohydrate needs with an appropriate amount of carbohydrate-containing foods and fluids throughout the day.
Probiotics may benefit athletic performance indirectly by maintaining gut function and health, preventing the immunosuppressive effects of intense exercise, and reducing susceptibility to illness. Substantial evidence exists indicating that probiotics can reduce susceptibility to acute infectious diarrhoea (athletes may be particularly susceptible during foreign travel). Lactobacillus probiotics may also reduce coughs and cold incidence.
- Wash hands regularly, before meals, and after direct contact with potentially contagious people, public places and bathrooms.
- Use disposable paper towels and limit hand to mouth/nose contact when suffering from respiratory or gastrointestinal infection symptoms. Use alcohol-based hand-washing gel.
- Do not share drinking bottles, cups, towels, etc with other people.
A balanced and nutrient rich diet is fundamental to avoiding illness for those undergoing intense physical exercise. Current opinion is that athletes should invest in nutrient-rich foods and fluids that provide sufficient energy and a wide range of vitamins, minerals and other important chemicals, such as phytochemicals, found naturally in foods. When this is not possible the use of supplements such as multi vitamins, omega-3 fish oils, and probiotics may be advised.
A dietitian with experience in sports nutrition is ideally placed to advise on the specifics of food, fluid and supplements, taking in to account variables such as type, intensity, duration of exercise, time available for recovery between sessions and body composition goals during training and competition.