Gut health and its impact on immunity
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The fact that gut health has a profound effect on the immune system is a surprise to many people, though scientists have known that the microbes in the intestines affect health since at least 1907. They’re still discovering new things about the often complex relationship between gut flora and the GI tract. Between 70 and 80 percent of the immune cells in the human body are found in the gastrointestinal system. Here’s how these trillions of cells in the gut microbiome work.
What makes up the gut microbes
The microbes that live in your gut include different types of bacteria, including Bifidobacterium, Bacteroides and Lactobacillus. There are also fungi such as Saccharomyces, Penicillium and Candida. The gut even holds beneficial viruses. These viruses eat harmful bacteria and even beneficial bacteria if they become too numerous. Their goal, basically, is to keep the population of bacteria in check. Viruses also support the immune system and support gut balance after a course of antibiotics.
Gut bacteria trains the immune system
Good bacteria actually train the immune cells in the lining of the gut. They do this by helping the body digest dietary fiber that the body can’t break down on its own. This produces short-chain fatty acids, or SCFAs. These molecules help lower inflammation and influence the actions of helper T cells, white blood cells that release cytokines that tell other immune cells to destroy pathogens. However, the release of too many cytokines can themselves cause illness. SCFAs keep helper cells from going overboard.
The bacteria also have molecules on their surfaces that lock onto receptors found on the gut’s immune cells. When this happens, it activates genes that prevent "cytokine storms" and keep down swelling.
Gut flora keep toxins out of the blood
The gut flora help keep the gut barrier strong by preventing pathogens from invading the bloodstream. This is because they take up so much space in the GI tract that they block germs. There’s even something called “leaky gut,” where the small intestine lacks these barriers that block bits of food, pathogens and other debris from getting into the blood and causing illness.
Supporting the gut microbiome
Supporting your gut health is easy and even delicious. The secret is making sure you get enough dietary fiber in your diet. Probiotics are also important.
What dietary fiber does
As discussed, dietary fiber produces short-chain fatty acids as bacteria ferment it. Good sources of fiber are beans, oats, brown rice, apples, broccoli and leafy greens such as kale. Seeds and nuts also contain good amounts of dietary fiber.
Prebiotics vs probiotics
Prebiotics are another name for dietary fiber. Your body can’t break this fiber down by itself but relies on the bacteria in your lower gut to do this. Probiotics are yeast and live bacteria such as Lactobacillus. They’re famously found in fermented foods such as yogurt and kimchi as well as dietary supplements.
