In general, the immune system is suppressed by intensive training, with many parameters being reduced or disturbed during the hours following a work-out. This may place athletes at risk of succumbing to an infectious illness during this time. Many nutrients or dietary factors have been proposed as an aid to the immune system – for example, vitamins C and E, glutamine, zinc and most recently probiotics – but none of these have proved to provide universal protection. The most recent evidence points to carbohydrate as one of the most promising nutritional immune protectors. Ensuring adequate carbohydrate stores before exercise and consuming carbohydrate during and/or after a prolonged or high-intensity work-out has been shown to reduce the disturbance to immune system markers. The carbohydrate reduces the stress hormone response to exercise, thus minimising its effect on the immune system, as well as also supplying glucose to fuel the activity of many of the immune system white cells.