Guavas are chock full of a number of nutrients, especially vitamic C, which give our immune systems a good boost. Vitamin C can help fight common bacterial and fungal infections. Guavas, which have four times more vitamin C than most citrus fruits, are a brilliant source of this nutrient. Guavas help maintain the sodium and potassium balance in the body. This in turn helps regulate the blood pressure, and keeps the heart healthy. The fruit is especially good for patients of hypertension or high blood pressure.