Gyms are a great place to get fit, but they're also a great place to get sick. Because intense exercise may temporarily lower immunity, you may be somewhat susceptible to catching a cold or flu.

An article in the International Journal of Sports Medicine reports that people who work out tend to have fewer germ-fighting resistance molecules in their saliva after working out than before they start. So, to help stave off sickness, always wash down machines and equipment before using it, assuming that the person who used it before you didn't. Also, try to keep your hands away from your face if possible, and wash them with soap and water before leaving the gym for the day.

As for immune-boosting foods, try to consume a diet rich in vitamin C, zinc, and garlic, as all have been shown to have some semblance of affect on preventing and/or reducing the duration of a cold.