The fact that there are many health benefits of lemons is a bonus. The little lemon has big antibacterial, antiviral, and immune-boosting powers and are often used as a weight loss aid (lemon juice is a digestive aid and liver cleanser). Lemons contain many substances--notably citric acid, calcium, magnesium, vitamin C, bioflavonoids, pectin, and limonene--that promote immunity and fight infection.
Bet you didn't know that the Ancient Egyptians believed that eating lemons and drinking lemon juice was an effective protection against a variety of poisons.