Digestive tract is like a second brain

I have a cold, cough, runny nose, muscles are a bit sore and when I coughed, I noticed that my lungs felt not as elastic as usual, but soft like a sponge or marshmallow.

I had already drunk a large dose of orange juice flavored with vitamin C early in the morning to treat my cold, so my brain must have been working particularly well at that time. After thinking about it for a while, I connected the elasticity of the lungs to yeast and through it to the intestines.

Digestion is a very important thing for human well-being, and it is said that the digestive tract is like a second brain.

The intestines normally contain yeast along with other microbes,
perhaps it had appeared a little too much due to the consumption of sweet and carbohydrate-rich substances, in the summer.

I thought about it and ended up doing a yeast removal 
which Google also says the following:

Diet:
Reduce sugar, yeast, dairy products and grain products from your diet.
Favour fibre-rich vegetables and products containing probiotics.
Probiotics:
Foods: Fermented milk products (buttermilk, yoghurt), sauerkraut, kimchi, kombucha.
Long-term use of probiotics, such as lactic acid bacteria,
can help balance the gut microbiota and reduce yeast growth.
Stress management:
Ensure adequate rest and stress management, as stress can affect gut balance and yeast growth.

Conclusions:
A well-functioning digestive system probably also helps the immune system function well.