When we hear about viruses and bacteria, we may think of runny noses and coughs. But the battleground for our immune system is not just in the nose and lungs. In fact, a whopping 80 percent of immune cells live in the gut. That’s not surprising, since it needs to be ready to spot germs every time we eat or drink.
The potentially harmful germs we swallow quickly enter a world chock full of other microbes. “We have many billions of
