The gut is the immune system’s first line of defense.
Here’s an interesting article on probiotics in today’s National Post (Canada).
According to the article,
the tissue in the gut linked to immune system functions constitutes 80% of the entire immune system in the body.
Of particular note is the author’s mention of research indicating the decrease in “transit time” for food passing through the gastrointestinal systems of elderly constipation sufferers when taking probiotic supplements.