sIgA - means Secratory IgA. It is an antibody. See geeky stuff below. It's 'secreted' by immune cells in your intestines and other areas - hence the term secretary before it. Your body is extremely busy secreting these molecules every day.
No offence towards your naturopath, but I highly doubt there is going to be an issue with sIgA in your body. There is only a small amount in your blood anyway <-- well small in relation to other antibodies. However in your intestines it is a whole other story. Again, see geeky stuff below
Even just in our intestines alone; simply to protect us from oral antigens (bacteria etc) that we swallow on our food or breathe in and swallow in our mucus/spit we have about
2x10^10 or 20,000,000,000 cells (so multi billions of B-cells) that secrete IgA (antibody) or "flags". And every single day these B-cells secrete between 5 and 15 grams of secretory IgA in our mucus. So that's ~6 x10^23 IgA molecules per gram.... so the amount of sIgA were secrete daily in our intestines alone to protect us from what we eat, swallow, and what reside within us is an amount or number that is so high and so large it's hard to even count or grasp...
Math wise it's this ( I think it's correct) but a math person might want to double check as I hate math:
So every single day in our intestines we secrete 600,000,000,000,000,000,000,000 molecules of secretory IgA per gram x (times) between 5-15 grams secreted each day.
Multiply the above number by 15 (for 15 grams) and this tells us the cells of our intestines alone, every single day secrete up to 9,000,000,000,000,000,000,000,000 secretory IgA molecules simply to protect us from the bacteria in and entering our guts...