Infectious agents are all around us, whether or not you succumb to them is determined not only by your exposure but also by your balance of bacteria. This is because beneficial bacteria both consume the nutrients that would otherwise feed the bad guys and also block the receptor sites that harmful bacteria have to latch on to cause infection, by, for example, entering the bloodstream.

The main reason probiotics protect us is that they also produce substances such as lactic acid and hydrogen peroxide, which stop the harmful bacteria from growing. They are then called nature’s antibiotics.