Crowdsourcing help needed: how many microbes are brought into human GI tract via food? #microbiome

Quick but somewhat complex question here that came up at a recent meeting I went to - someone wanted to know:

How many microbes come into the human GI tract from outside sources (e.g., food)?

Other related questions:

• How many cells /day?
• How many are alive?
• How many kinds come in?
• How much flow through is there vs. digestion vs. colonization?

Note - I know there have been many studies of pathogens on food and how they get into the GI tract, but what about non pathogens?

Any references or #s would be very helpful.

Thanks