Adequate intake of the body's essential nutrients, like vitamins, minerals, protein, and fat, will help stave off the illness. It is important to understand that it is not necessary to go to the other extreme by consuming huge amounts of these vitamins and minerals. First of all, this could lead to toxicity in certain vitamins and minerals. Secondly, the body can only use so much of any particular vitamin or mineral. By providing the body its essential building blocks, you enable the immune system to build its defenses to protect against the most vicious of cold and flu viruses.
Regular exercise is also an important factor but for different reasons than diet and sleep.
The primary role of exercise in a planned prevention program is to promote circulation of the immune system's components throughout the body. With increased blood flow throughout the body, the immune system has a greater chance of finding illness and dealing with it rather than just waiting for the illness to spread before beginning to mount its defense. This potentially will allow your immune system to be more efficient in eliminating unwanted guests and reduce the chance that you would get sick in the first place. During times of stress, your body mobilizes its forces to protect against illness and any other threat to your well-being. This physiological response serves its purpose well but when experienced chronically it can be extremely detrimental.