Probiotics are live bacteria which do seem to have various beneficial effects as they transit through the gut, though for the most part they don't actually colonise the gut.
Prebiotics are food for colonic bacteria, components of food we eat which we can't digest but our gut bacteria can.
Probiotics can be very useful but prebiotics provide the foundation for a healthy gut microbiota.
Here is a series of articles on prebiotics which gather together a lot of valuable info in one place
1,
2,
3,
4,
5.
Note this was written for essentially healthy people. A lot of us have found that we are very sensitive to pre and probiotics so the usual cautions apply. Start low and go slow when experimenting with any of these.
The place to start is diet, ensuring you include as wide a range of prebiotic rich foods as possible. There is discussion of this in the articles. You could then consider boosting this with some concentrated fibre sources. Look for a range of different types but start with just one at a time in very small amounts to gauge your own reaction. Again the articles canvass some of these.
I try to take several different types daily, varying these from day to day. I think it is better to take smaller amounts of several different types rather than a large amount of one or two, more like what happens when we eat a varied diet. I also favour relatively unprocessed products rather than some of the artificial laboratory creations (though I do take a little of one of these, benefibre, as a starch substitute since I don't eat much in my diet), again more like normal eating.
Here are a few notes I made on the prebiotics which I most often take. They are by no means complete but give an idea of range of types.
aloe vera inner leaf predominantly acetylated glucomannan
benefibre is hydrolysed wheat dextrin (RS4)
acacia gum is predominantly arabinogalactan
baobab powder is a source of pectin, polyglucuronic-galacturonic, polyphenols and other fibres
larch is a source of arabinogalactans - good for bifido - reduces NH3
psyllium is a source of arabinoxylans
raw potato starch is a source of RS2 - increases butyrate, acetate, propionate production in vivo
Artinia is a source of insoluble β1-4 N-acetyl D-glucosamine chitin-glucan - liked by Roseburia and other cluster XIVa
PGX is a source of glucomannan, glucomannan/glucuronate; mannuronic/guluronic acids
Fucoidin is predominantly sulfated polyfucose
Mushrooms are a source of polymers of N-acetylglucosmine (chitin), βglucans and mannans
fructans (inulin/FOS) enhance Ca uptake in gut; feed bifido
Pectins increase acetate production in vivo; apple pectin good for
Faecalibacterium