Lemons are high in vitamin C, which is great for fighting colds. They?re high in potassium, which stimulates brain and nerve function. Potassium also helps control blood pressure. Ascorbic acid (vitamin C) found in lemons demonstrates anti-inflammatory effects, and is used as complementary support for asthma and other respiratory symptoms plus it enhances iron absorption in the body; iron plays an important role in immune function. Lemons also contain saponins, which show antimicrobial properties that may help keep cold and flu at bay. Lemons also reduce the amount of phlegm produced by the body.