Digestion is a complex process that our bodies carry out using a variety of chemicals. In this video, we're going to focus on the role of bacteria in digestion. Many different types of bacteria are found in the gut. In fact, scientists estimate that the gut contains between 300 and 1000 different types of bacteria. And the total number of bacteria in one person's gut could be anything between 100 and 1000 trillion. That's a lot of bacteria, so what are they doing inside our digestive system? The most common and important bacteria is the lactobacillus species which lives in our small intestine. When undigested, carbohydrates enter the intestines. Lactobacillus helps digest them, otherwise they would be lost from the body and unused. Lactobacillus also helps digest sugars found in dairy products. When lactobacillus bacteria anaerobically respire, they produce lactic acid as a waste product. Although lactic acid in our muscles hurt, lactic acid in our gut is actually very useful because it keeps the pH of our gut acidic, which means pathogen bacteria, so bad bacteria cannot thrive. This helps protect us from bacterial infections. Lactobacillus also helps prevent too much yeast growth in our guts, which if it spreads out to the rest of our body can cause yeast infections. Too many yeast cells can also cause problems with our digestive system. As well as aiding digestion, scientists have discovered that the bacteria in our guts can also influence our immune system, metabolism and the production of essential bio compounds. There's even research showing that some cardiovascular disease, diabetes, inflammatory bowel disease and obesity are associated with changes in our guts bacteria. But back to our gut bacteria and digestion. What happens if our doctor prescribes us antibiotics? Antibiotics work by killing bacteria or preventing them from reproducing. Does this harm our digestion and all the other wonderful things that gut bacteria do? Some antibiotics are targeted at specific types of bacteria, and so our doctors will try and target only the nasty pathogenic bacteria. However, often antibiotics will also kill our good, digestion bacteria too. But if you're ill and you need the antibiotics, then this is just a side effect that we have to handle. There are a few things we can try and do to help our good bacteria reestablish healthy gut populations. Probiotics are live bacteria and yeast that are found in some foods. It is thought that eating probiotics can help restore the natural balance of good bacteria in our guts that we lose from taking antibiotics. Only certain types of live bacteria make it through our acidic stomach and they need to be in very high doses. Prebiotics are essentially food for bacteria. They stimulate certain bacteria populations to multiply and survive in the gut. Probiotics can be found in these foods amongst many others. So while our bodies are brilliant at digesting food, it turns out they need a little help from friendly bacteria to get the job done, to catch any undigested food and to maintain a suitable pH that we stay healthy amongst many other great things.