70% of the immune system is located in the gut, where diverse bacteria is best. You likely know that what you eat can affect your weight and energy level throughout the day. But you might not realize the extent to which diet affects the immune system.
“Seventy percent of the immune system is located in the gut,” says David Heber, MD, PhD, professor emeritus of medicine at UCLA Health. “Nutrition is a key modulator of immune function.”
https://connect.uclahealth.org/2021/03/19/want-to-boost-immunity-look-to-the-gut/#:~:text=70% of the immune system,diet affects the immune system.