Gut health = Gut diversity
The greater the gut diversity you have, the healthier you will be to fight off various attacks on your body. Having enough friendly gut flora reduces the incidence of allergies and autoimmune diseases plus restoring and balancing these flora in the gut can treat and reverse these conditions as well.
There are foods that can assist to increase your gut flora and boost your immune system. To name a few, various ferments like sauerkraut, kimchi, water kefir, kombucha, also medicinal mushrooms and herbs like oil of oregano, even apple cider vinegar and of course probiotics. Even vitamins like vitamin D can help balance microbes in the gut. All these will increase your gut flora and provide greater diversity to your gut garden.