how probiotics help immunity

I have been visiting my parents lately. Being older their immunity is of huge concern to me. So I asked them to start making the traditional Indian drink Kaanji at home (recipe below)

So how do ProBiotics help immunity? 
All our infections come from 2 main points :
1. Breathing
2. Eating
And the above 2 areas is where your immune system has to focus on.

When we take probiotics we help improve the "good bacteria" in our gut. This improves the gut lining quality. What this means is that your chances of getting sick from eating goes down. 

This takes pressure off your immune system. They say 80% of your immune system is in your gut. So when you take pressure off that part, it allows the immune system to focus on your breathing parts - your nose, your throat, your lungs.

This is how Probiotics help the immune system and I highly advise everyone to have good, homemade probiotics this time. Examples are : Sauerkraut, Kimchi, Kombucha and Kanji.

Other benefits we have seen from Kaanji is a reduction in dryness. So my Dad is having dry eyes and I hope this will reduce that. I have had post-menopausal women report benefits in dryness so I hope this will help my Dad.

Here is a link to a kaanji recipe https://youtu.be/1iuq6dhtrT8