The makeup of the microbiome -- the unique combination of microorganisms (mainly bacteria) known as the microbiota that inhabit the human body and are concentrated primarily in the gut -- has been implicated in a wide range of health concerns. This has motivated researchers around the world to develop analytical techniques to better understand the microbiome and its constituents and explore how they affect health and disease. The microbiome has been of particular interest to gastroenterologists in terms of how it relates to irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and other intestinal disorders.
The microbiota of a healthy individual provides protection from pathogenic organisms that commonly enter the body, such as through drinking contaminated water or eating contaminated food. Microbiota also stimulate the immune system, break down potentially toxic food compounds, and synthesize amino acids and certain vitamins, including vitamin K and the B vitamins (for example, the key enzymes needed to form vitamin B12 are only found in bacteria, not in plants or animals).
Genetics are a significant factor in what kinds of microbiota live in the colon, but environment and medication also play important roles. The merger of these factors is what creates a unique microbiome for each person. A high-fiber diet in particular affects the type and amount of microbiota in the intestines. Dietary fiber can only be broken down and fermented by enzymes from microbiota living in the colon. This fermentation results in the release of short-chain fatty acids, which in turn lower the pH of the colon and determine the type of microbiota present that can survive in this acidic environment. For instance, a lower pH helps limit the growth of certain harmful bacteria, such as Clostridium difficile. Current research is exploring the wide-ranging effects that these short-chain fatty acids have on health, including stimulating immune cell activity and regulating and maintaining normal blood levels of cholesterol and glucose.
Foods that support increased levels of these short-chain fatty acids are indigestible carbohydrates and fibers, such as inulin, resistant starches, gums, pectins, and fructooligosaccharides. These fibers are sometimes called prebiotics because they feed our beneficial microbiota. There are many healthful foods that naturally contain prebiotics, with the highest amounts found in raw garlic, onions, leeks, asparagus, Jerusalem artichokes, dandelion greens, bananas, and sea vegetables. However, most of these foods are also high in FODMAPs and can exacerbate symptoms of IBS, including gas and bloating.
If microbiota are so vital to our health, how can people with IBS ensure they have enough of them or have the right types without eating foods that may trigger their symptoms? Probiotics are supplement pills or capsules that contain live active bacteria that, according to the manufacturers, promote digestive health. The field of probiotics is a growing segment of the multi-billion dollar supplement industry, and it's evolving in tandem with rapidly emerging research.
It can be confusing for consumers to determine which probiotics may be helpful and which may be a waste of money. Consumers Health Report (CHR) -- a group of public health and nutrition professionals who conduct research through systematic scientific analysis to educate themselves and the public about the best health supplements on the market -- has written a thorough guide on this very topic. They cover almost everything you need to know in terms of what probiotics are, how they can support health, and which strains are best for which health conditions or symptoms. I hope you find this eye-opening report from CHR helpful and enlightening: What Are Probiotics? A Guide to Probiotic Foods, Supplements & Benefits.
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